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Ignition Switch [message #350887] Mon, 23 December 2019 19:05 Go to next message
Melbo is currently offline  Melbo   United States
Messages: 144
Registered: August 2018
Location: Albuquerque NM
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Senior Member
I bought my '73 GMC without ever trying to start it. It was parked and trying to start it was not going to do me any favors. I knew it was going to be a project. I had it towed to a storage facility. I checked to see if the onan was going to work and it was. I did the fuel system from back to front. Time for the 455 to be checked out. I pulled the fuel pump and figured out that I need to change the timing chain and gears. I changed the oil and filter. Put oil in all eight cylinders. Using a breaker bar rotated it to #1 TDC. Pulled the dizzy and pressurized the oil system. Time for a compression check. Put a battery in then put the key in the key slot and the buzzer came on. Turned the key and it didn't feel right and nothing happened. When I let go it didn't spring back like I am used to. I tried it a couple of times and it just did not seem right and nothing -- I mean nothing from the starter. I tried it with jumpers and got the same. I checked the voltage at the primary wires at the starter and it was only 6 volts. I pulled the starter and it did nothing on the bench. So I pulled the alternator and took both the alternator and starter to my rebuilder. My question is are the ignition switches common to replace and if that is necessary are there other issues I should check as I am going through this. I just want to cover the stuff that will give me problems later on while I am into the middle of this.

TIA

Melbo


Albuquerque NM Bus Conversion 1978 MCI 1973 GMC
Re: [GMCnet] Ignition Switch [message #350889 is a reply to message #350887] Mon, 23 December 2019 19:20 Go to previous messageGo to next message
jimk is currently offline  jimk   United States
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Registered: July 2006
Location: Belmont, CA
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Senior Member
I think your jumping around too much.
First, see if the dash livens up.
Ifit does not, testing the starter is not the answer and dont wast your
time or money on an alternator.
Call me before you wast your time and funds (800) 752-7502 and ask for me.

On Mon, Dec 23, 2019 at 5:05 PM melmull--- via Gmclist <
gmclist@list.gmcnet.org> wrote:

> I bought my '73 GMC without ever trying to start it. It was parked and
> trying to start it was not going to do me any favors. I knew it was going
> to
> be a project. I had it towed to a storage facility. I checked to see if
> the onan was going to work and it was. I did the fuel system from back to
> front. Time for the 455 to be checked out. I pulled the fuel pump and
> figured out that I need to change the timing chain and gears. I changed the
> oil
> and filter. Put oil in all eight cylinders. Using a breaker bar rotated it
> to #1 TDC. Pulled the dizzy and pressurized the oil system. Time for a
> compression check. Put a battery in then put the key in the key slot and
> the buzzer came on. Turned the key and it didn't feel right and nothing
> happened. When I let go it didn't spring back like I am used to. I tried
> it a couple of times and it just did not seem right and nothing -- I mean
> nothing from the starter. I tried it with jumpers and got the same. I
> checked the voltage at the primary wires at the starter and it was only 6
> volts. I pulled the starter and it did nothing on the bench. So I pulled
> the alternator and took both the alternator and starter to my rebuilder. My
> question is are the ignition switches common to replace and if that is
> necessary are there other issues I should check as I am going through
> this. I
> just want to cover the stuff that will give me problems later on while I
> am into the middle of this.
>
> TIA
>
> Melbo
> --
> Albuquerque NM Bus Conversion 1978 MCI 1973 GMC
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmcrvparts.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
Re: [GMCnet] Ignition Switch [message #350900 is a reply to message #350889] Mon, 23 December 2019 23:47 Go to previous messageGo to next message
Melbo is currently offline  Melbo   United States
Messages: 144
Registered: August 2018
Location: Albuquerque NM
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Senior Member
Jim

Thank you for your response. I try to do things one at a time. My question now is does the 455 stay and is capable of good service OR does it come out and go to my engine guy for a rebuild. AND if he tells me it isn't viable time for a crate engine. That is kind of the heart of the vehicle portion of the GMC in my opinion. I understand that one pays the money and take the chance. The dash in the gmc is trashed. I am not sure why or how and it really doesn't make a difference to me now because that will be a project all by itself. What exactly would I look for to "light up" on the dash? The starter being non functional makes it impossible to do a compression test. Once the starter works I really don't need the key switch operational to do the compression test. I was kind of curious if that is a common item that fails and how it fails. If it can be revived or it needs to be replaced. I guess I can just leave it until it becomes a real issue and I can see that as I proceed I am going to have some major ones. Thanks again for the response.

Melbo


Albuquerque NM Bus Conversion 1978 MCI 1973 GMC
Re: [GMCnet] Ignition Switch [message #350904 is a reply to message #350900] Tue, 24 December 2019 02:04 Go to previous messageGo to next message
Ken Burton is currently offline  Ken Burton   United States
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
Senior Member
First the answer to your ignitions switch, if needed. It is a common item and available from multiple vendors including Jim K. or Auto zone. It is simple to change mounted on the lower steering column. Also the neutral safety switch is down there too.

Following Jim K's recommendation, Before you start throwing parts at it, you need to follow a systematic approach to your problem and prove the item is bad before replacing it. Start with the cranking battery voltage readings under no load and when the key is turned to start. If it is good, then clean battery cables and read the voltage to the starter and starter solenoid when the key is turned. ONLY if both are good should the starter be removed. A reading of 6 volts says you have a bad battery or bad connection before the starter.

I would not consider working on the 455 before I got it running to see if there is really a problem.

Jim K. or any of us will help you if you are willing to shoot each issue one at a time.


Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
Re: [GMCnet] Ignition Switch [message #350905 is a reply to message #350904] Tue, 24 December 2019 05:56 Go to previous messageGo to next message
Bruce Hart is currently offline  Bruce Hart   United States
Messages: 1501
Registered: October 2011
Location: La Grange, Wyoming
Karma: 5
Senior Member
You don't need the key switch to crank over the engine. Install a remote
switch to crank the engine.
Gene Fisher has a good write up on starting issues:
http://www.gmcmhphotos.com/photos/gmc-cranking-improve-for-free/p34368-bad-battery-connections.html

On Tue, Dec 24, 2019 at 1:05 AM Ken Burton via Gmclist <
gmclist@list.gmcnet.org> wrote:

> First the answer to your ignitions switch, if needed. It is a common item
> and available from multiple vendors including Jim K. or Auto zone. It is
> simple to change mounted on the lower steering column. Also the neutral
> safety switch is down there too.
>
> Following Jim K's recommendation, Before you start throwing parts at it,
> you need to follow a systematic approach to your problem and prove the item
> is bad before replacing it. Start with the cranking battery voltage
> readings under no load and when the key is turned to start. If it is good,
> then
> clean battery cables and read the voltage to the starter and starter
> solenoid when the key is turned. ONLY if both are good should the starter
> be
> removed. A reading of 6 volts says you have a bad battery or bad
> connection before the starter.
>
> I would not consider working on the 455 before I got it running to see if
> there is really a problem.
>
> Jim K. or any of us will help you if you are willing to shoot each issue
> one at a time.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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>


--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class
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Bruce Hart 1976 Palm Beach 1977 28' Kingsley La Grange, Wyoming
Re: Ignition Switch [message #350907 is a reply to message #350887] Tue, 24 December 2019 08:18 Go to previous messageGo to next message
JohnL455 is currently offline  JohnL455   United States
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Registered: October 2006
Location: Woodstock, IL
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Senior Member
You can't evaluate the engine until it runs!
Your 6 V reading at the starter tells me you have a meter, but makes no sense and you don't tell us what you are metering across. First confirm the meter. On 20 VDC scale You should have about 12.6 across the battery of a good vehicle. Then start the vehicle and you should have about 14 Volts or more iif vehicle is cold. Now you know the meter works. Start by metering across you engine battery. You should see that 12.6. Below that charge the battery and report back. Below about 12.4 the battery is very discharged and may not crank. Another no cost test is to turn on the headlights. If they dim out when you try to crank, you have a bad battery or bad connection on the cables. If they stay bright then you have a bad starter, bad ign switch or bad NSS or bad connections to them.


John Lebetski
Woodstock, IL
77 Eleganza II
Re: Ignition Switch [message #350916 is a reply to message #350907] Tue, 24 December 2019 15:57 Go to previous messageGo to next message
Melbo is currently offline  Melbo   United States
Messages: 144
Registered: August 2018
Location: Albuquerque NM
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Senior Member
I agree with Bruce and I can operate the starer and do the compression test with or without the ignition switch working properly however I was asking ahead. According to the flow chart on page 388 of the 73-74 maintenance manual I was supposed to "remove starter for repair" I did jump ahead with the meter. The second flow chart shows a meter reading of 7 volts as the break off point. My starter is in for the rebuild. My more direct question was when my meter reads 6 volts -- with the break off point being 7 volts it appears from the instructions that you are testing the starter switch contacts. I could however be mistaken with that assumption.

I guess I should have been more detailed in my question and the process I am going through.

Thanks for the help with this.

Melbo


Albuquerque NM Bus Conversion 1978 MCI 1973 GMC
Re: [GMCnet] Ignition Switch [message #350920 is a reply to message #350916] Wed, 25 December 2019 06:31 Go to previous messageGo to next message
Rich Kinas is currently offline  Rich Kinas   United States
Messages: 113
Registered: July 2019
Karma: 1
Senior Member
Starter troubleshooting can always be fun. And while the manual is very
helpful, unless you thoroughly understand why the manual is having you take
some specific action, the results can be very confusing. The nominal
voltage of the battery is 12 volts, and with small loads will remain 12
volts during operation of said small loads. The starter is not a small load
it is very large in fact. For large loads the battery voltage drops when
providing power for these loads. The troubleshooting charts are trying to
determine if the condition of the battery is poor enough that it cannot be
put back in service with the ability to maintain an acceptable supply
voltage under heavy load. I always keep a new fully charged battery
(condition known and monitored) in my shop just for
troubleshooting.purposes, I replace the battery of the circuit being tested
with this good battery, If things work, get a new battery, if not something
else is really broken and a fresh good battery will take all that voltage
guess work out of the equation.

Merry Christmas one and all!




On Tue, Dec 24, 2019 at 4:58 PM melmull--- via Gmclist <
gmclist@list.gmcnet.org> wrote:

> I agree with Bruce and I can operate the starer and do the compression
> test with or without the ignition switch working properly however I was
> asking
> ahead. According to the flow chart on page 388 of the 73-74 maintenance
> manual I was supposed to "remove starter for repair" I did jump ahead with
> the meter. The second flow chart shows a meter reading of 7 volts as the
> break off point. My starter is in for the rebuild. My more direct question
> was when my meter reads 6 volts -- with the break off point being 7 volts
> it appears from the instructions that you are testing the starter switch
> contacts. I could however be mistaken with that assumption.
>
> I guess I should have been more detailed in my question and the process I
> am going through.
>
> Thanks for the help with this.
>
> Melbo
> --
> Albuquerque NM Bus Conversion 1978 MCI 1973 GMC
>
> _______________________________________________
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> Unsubscribe or Change List Options:
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Rich Kinas 1976 Elaganza II Orlando, FL
Re: Ignition Switch [message #350923 is a reply to message #350887] Wed, 25 December 2019 10:25 Go to previous messageGo to next message
jhbridges is currently offline  jhbridges   United States
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Registered: May 2011
Location: Braselton ga
Karma: -74
Senior Member
Your switch problems point to a problem with either the (cast) gear or the action rod itself, based on "It doesn't feel right". However, I side with the suggestions above. Take both battery cables off and shine them and the posts. If they are 'get by' cables (with the clamps secured to the cables with a piece of metal and two bolts) remove them and save them with your other copper to recycle and buy proper cables/ Before you connect the new ground cable, Remove EVERY heavy duty cable, shine it and its connection, and return it. Reroute them such that the positive cable goes directly to the starter solenoid and another comes from the solenoid up to the battery paralleling switch, i.e. no connections in the cable from the battery post to the starter solenoid post. This give the least drop to the starter.

--johnny


Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons. Braselton, Ga. I forgive them all, save those who hurt the dogs. They must answer to me in hell
Re: Ignition Switch [message #350924 is a reply to message #350887] Wed, 25 December 2019 10:31 Go to previous messageGo to next message
jhbridges is currently offline  jhbridges   United States
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Registered: May 2011
Location: Braselton ga
Karma: -74
Senior Member
While I'm sure it happens, I've never had a starter on anything with bad or broken internal wiring. Not to say it doesn't happen, only that it never happened to me. My problems with starters have been worn brushes, worn front bushings, failed solenoid connections, arced and cruddy slip rings and rear bearings, pretty much in that order. Rear bearings are like throwout bearings... I've replaced a lot that were probably OK, but weighing the cost of the part against the pain in the ass factor of replacing it says put another one in while it's apart.

--johnny


Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons. Braselton, Ga. I forgive them all, save those who hurt the dogs. They must answer to me in hell
Re: [GMCnet] Ignition Switch [message #350926 is a reply to message #350924] Wed, 25 December 2019 11:20 Go to previous messageGo to next message
James Hupy is currently offline  James Hupy   United States
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Registered: May 2010
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Senior Member
Low voltage. Hmmm, what could that possibly be? CHECK VOLTAGE AT THE
BATTERY POSTS FIRST. Then, the isolator top and bottom lugs. If they are
not the same, remove all your cables and make the connections BRIGHT AND
SHINY, like the Christmas star. THEN, check the voltage at the starter.
Jim Hupy
Salem, Oregon

On Wed, Dec 25, 2019, 8:32 AM Johnny Bridges via Gmclist <
gmclist@list.gmcnet.org> wrote:

> While I'm sure it happens, I've never had a starter on anything with bad
> or broken internal wiring. Not to say it doesn't happen, only that it never
> happened to me. My problems with starters have been worn brushes, worn
> front bushings, failed solenoid connections, arced and cruddy slip rings and
> rear bearings, pretty much in that order. Rear bearings are like throwout
> bearings... I've replaced a lot that were probably OK, but weighing the
> cost of the part against the pain in the ass factor of replacing it says
> put another one in while it's apart.
>
> --johnny
> --
> Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
> Braselton, Ga.
> I forgive them all, save those who hurt the dogs. They must answer to me
> in hell
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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Re: [GMCnet] Ignition Switch [message #350931 is a reply to message #350926] Wed, 25 December 2019 12:28 Go to previous messageGo to next message
Melbo is currently offline  Melbo   United States
Messages: 144
Registered: August 2018
Location: Albuquerque NM
Karma: 0
Senior Member
Jim

Thank you for your response. When I see your posts I read them carefully. I am working on the learning curve here. Disconnecting and dropping a starter is pretty simple and when it is bench tested with a fully charged battery and nothing happens my best judgement is take it to the rebuilder. The shop that does my starters also does my alternators so I figured lets do a little preventative maintenance and took them both in. With them enjoying the holiday season it could be a spell before I get them back. No problem I will do some following up of other portions of the start circuit so when I get the starter back I will be sure that any voltage drop should be within tolerable ranges. I was just struck with the 7 volt reference in the flow chart on the starter circuit. I only had 6.2 volts. The flow chart took me the same place BUT I was curious if the start switch could be the culprit. By the time I get the starter back I will have a better understanding of the start circuit how to proceed.

Thanks again for the response

Melbo

Johnny

Upgrading the cables is definitely in the master plan. I have the first year model that was set up for three batteries -- one for the onan -- one for the house system -- one for the start battery. I will be running a "00" pair of welding cables to the onan to eliminate that battery and will be replacing all the large cables at the battery compartment (if you really can call it that) once I determine how many feet and number of connectors I need from the electric supply house. Until I'm at that stage (which would have to include the house systems) I usually check for voltage drop (loaded and unloaded) to see if I need to bypass something for better results.

Melbo


Albuquerque NM Bus Conversion 1978 MCI 1973 GMC
Re: Ignition Switch [message #350934 is a reply to message #350887] Wed, 25 December 2019 12:52 Go to previous messageGo to next message
Matt Colie is currently offline  Matt Colie   United States
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Location: S.E. Michigan
Karma: 7
Senior Member
Melbo,
The 10MT starter is in actual fact, too robust. In service it will keep trying to work when it should have called quits long before. If you have a good shop handy, support them.

You don't need 00 to crank the onan. But a better answermight be to make the systems with the house bank behind the apu to do both the house and apu start. Then you can also put in the slide tray so that they are easily maintained.

Our 23 does not give us that option.

Matt at the daughter's and dabbing at phone screen


Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
Re: Ignition Switch [message #350936 is a reply to message #350934] Wed, 25 December 2019 13:18 Go to previous messageGo to next message
Melbo is currently offline  Melbo   United States
Messages: 144
Registered: August 2018
Location: Albuquerque NM
Karma: 0
Senior Member
Matt

I am used to 24 volt house and start systems from the bus conversion I did. The voltage drop is hard on starters and that is the main function of the cables to the onan. "00" welding cable is very flexible and I would put it in a conduit (flexible or rigid to be determined) and it is only rated for 175 amps. I am not sure the amp draw for starting the onan but I would guess it to be over 125 and "0" is only rated for 150 amps so I could be approaching my max draw. One size up while you are doing it is easier than redoing it later IMHO. I like working with the "00" better than the "0000". I still have a collection of sets of "0000" cable from different battery sets I have had and removed. I kind of like your idea of the batteries in the back. The 455 starter could max out the "00" cables I would think. Don't those starters draw over 200 amps. Well all this is to be determined at a later time. I like the multiple "P" expressions.

Proper Prior Planning Prevents Piss Poor Performance.

One step at a time and thanks for the help

Melbo


Albuquerque NM Bus Conversion 1978 MCI 1973 GMC
Re: [GMCnet] Ignition Switch [message #350950 is a reply to message #350936] Wed, 25 December 2019 16:16 Go to previous messageGo to next message
k2gkk is currently offline  k2gkk   United States
Messages: 4452
Registered: November 2009
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Senior Member
I would not worry about the cable to the Onan starter. All that genset needs is a decent motorcycle battery for its starting purpose.

Starter for the 455 or 403 is a whole different matter, though.
D C "Mac" Macdonald
Amateur Radio K2GKK​
Since 30 November '53​
USAF and FAA, Retired​
Member GMCMI & Classics​
Oklahoma City, OK​
"The Money Pit"​
TZE166V101966​
'76 ex-Palm Beach​
k2gkk + hotmail dot com

________________________________
From: Gmclist on behalf of melmull--- via Gmclist
Sent: Wednesday, December 25, 2019 13:18
To: gmclist@list.gmcnet.org
Cc: melmull@gmail.com
Subject: Re: [GMCnet] Ignition Switch

Matt

I am used to 24 volt house and start systems from the bus conversion I did. The voltage drop is hard on starters and that is the main function of the
cables to the onan. "00" welding cable is very flexible and I would put it in a conduit (flexible or rigid to be determined) and it is only rated for
175 amps. I am not sure the amp draw for starting the onan but I would guess it to be over 125 and "0" is only rated for 150 amps so I could be
approaching my max draw. One size up while you are doing it is easier than redoing it later IMHO. I like working with the "00" better than the
"0000". I still have a collection of sets of "0000" cable from different battery sets I have had and removed. I kind of like your idea of the
batteries in the back. The 455 starter could max out the "00" cables I would think. Don't those starters draw over 200 amps. Well all this is to be
determined at a later time. I like the multiple "P" expressions.

Proper Prior Planning Prevents Piss Poor Performance.

One step at a time and thanks for the help

Melbo
--
Albuquerque NM Bus Conversion 1978 MCI 1973 GMC

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Re: Ignition Switch [message #350952 is a reply to message #350887] Wed, 25 December 2019 16:50 Go to previous messageGo to next message
jhbridges is currently offline  jhbridges   United States
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
Senior Member
If it was me, first up is a working chassis electrical system with proper cabling, cranking the coach and charging its battery. We used the same Onans, rated 7KW in promotional vehicles the uprate due to better manifolding and better cooling where space wasn't a concern. Since they ran several times a week, a separate battery and the genset stock worked just fine and kept us out of the vehicle 12V supply. In RV use, unless you're a lot more diligent than I about keeping a maintenance charger on the battery, you're better off modifying the genset and using the house battery(s) in the coach. Disconnect the Onan charging system.

---johnny


Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons. Braselton, Ga. I forgive them all, save those who hurt the dogs. They must answer to me in hell
Re: Ignition Switch [message #350953 is a reply to message #350952] Wed, 25 December 2019 17:08 Go to previous messageGo to next message
Melbo is currently offline  Melbo   United States
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Registered: August 2018
Location: Albuquerque NM
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Senior Member
Johnny

That has been done. I have no electric power where I store and work on the coach so I got the onan up and running first. Then I refurbed the tanks so I would have a good fuel supply. Now I am trying to determine if the 455 stays in or gets removed. One step at a time and I keep reading manuals and this board and upgrade suggestions and ideas that show up. It is a project in the works and this board and the people who post here have already saved me a lot of work and wasted time and I appreciate it.

I have a wish list but everything in sequence.

Just My Way

Thank you

Melbo


Albuquerque NM Bus Conversion 1978 MCI 1973 GMC
Re: Ignition Switch [message #350955 is a reply to message #350953] Wed, 25 December 2019 19:34 Go to previous messageGo to next message
Matt Colie is currently offline  Matt Colie   United States
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Registered: March 2007
Location: S.E. Michigan
Karma: 7
Senior Member
Melbo wrote on Wed, 25 December 2019 18:08
Johnny

That has been done. I have no electric power where I store and work on the coach so I got the onan up and running first. Then I refurbed the tanks so I would have a good fuel supply. Now I am trying to determine if the 455 stays in or gets removed. One step at a time and I keep reading manuals and this board and upgrade suggestions and ideas that show up. It is a project in the works and this board and the people who post here have already saved me a lot of work and wasted time and I appreciate it.

I have a wish list but everything in sequence.

Just My Way

Thank you

Melbo
Melbo,

I like the way you think, and the fact that you are capable is refreshing. (Go read some other RV sites!!)

Now, I start my Onan with a little garden tractor battery. (A motorcycle battery was more expensive.) I think I measured the cranking current at about 85amps. Then again, it is a BF and not an NH.

I really do suggest that you look at the arrangement of the house electrics in the later coaches. As said, the house battery in the front of the early coaches seriously sucks. I don't have much choice as I don't have the space in the rear for a house bank.

I have to admit that the three battery arrangement has been good to me. Before we had the real battery monitor, we killed the house bank with some carelessness (and electric refrigeration) and accidental left the marker lights on over night. This no real issue as the Onan saved the day.

As to removing the 455. The only reasonable replacement is the Cadillac 500. The Oldsmobile rear face of block and the need to pass the drive axle under the crankshaft make this a very serious issue. The only other thing I would consider would be a Dave Lenzi installed 8.1L. That is something for Dave to do because he is a confirmed wizard of GMC.

Matt - have a real keyboard now that I am home from Christmas dinner with the daughter and family.


Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
Re: [GMCnet] Ignition Switch [message #350999 is a reply to message #350931] Sat, 28 December 2019 07:47 Go to previous messageGo to next message
Ken Henderson is currently offline  Ken Henderson   United States
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
Senior Member
Melmull,

You've asked at least a couple of times whether the starter switch could be
the cause of your low starter voltage. Despite all the good information
that's been provided, no one has explicitly answered that important
question. My answer is NO. The only function of the starter switch is to
provide current to the solenoid on the top of the starter. When activated,
that solenoid closes its internal, very large, contacts between the battery
cable and the starter's field and armature windings. When you measure the
voltage at the starter's battery terminal, you're measuring before those
contacts and excluding all sources of voltage drop except the intervening
cable, connections, and the battery itself. So, there's no obvious way for
the starter switch to cause low voltage at the starter.

HTH,

Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL,
Manny Brakes & 1-Ton, Troy-Bilt APU, etc., etc., etc.
www.gmcwipersetc.com


On Wed, Dec 25, 2019 at 1:29 PM melmull--- via Gmclist <
gmclist@list.gmcnet.org> wrote:

> Jim
>
> Thank you for your response. When I see your posts I read them
> carefully. I am working on the learning curve here. Disconnecting and
> dropping a
> starter is pretty simple and when it is bench tested with a fully charged
> battery and nothing happens my best judgement is take it to the rebuilder.
> The shop that does my starters also does my alternators so I figured lets
> do a little preventative maintenance and took them both in. With them
> enjoying the holiday season it could be a spell before I get them back.
> No problem I will do some following up of other portions of the start
> circuit
> so when I get the starter back I will be sure that any voltage drop should
> be within tolerable ranges. I was just struck with the 7 volt reference in
> the flow chart on the starter circuit. I only had 6.2 volts. The flow
> chart took me the same place BUT I was curious if the start switch could be
> the culprit. By the time I get the starter back I will have a better
> understanding of the start circuit how to proceed.
>
> Thanks again for the response
>
> Melbo
>
> Johnny
>
> Upgrading the cables is definitely in the master plan. I have the first
> year model that was set up for three batteries -- one for the onan -- one
> for
> the house system -- one for the start battery. I will be running a "00"
> pair of welding cables to the onan to eliminate that battery and will be
> replacing all the large cables at the battery compartment (if you really
> can call it that) once I determine how many feet and number of connectors I
> need from the electric supply house. Until I'm at that stage (which would
> have to include the house systems) I usually check for voltage drop (loaded
> and unloaded) to see if I need to bypass something for better results.
>
> Melbo
> --
> Albuquerque NM Bus Conversion 1978 MCI 1973 GMC
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
Re: Ignition Switch [message #351001 is a reply to message #350887] Sat, 28 December 2019 09:39 Go to previous messageGo to previous message
jhbridges is currently offline  jhbridges   United States
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
Senior Member
What KenH said. However, it is possible for the contacts inside the solenoid to degrade. Put your meter on the 1 or 2 volt scale, negative on the large bolt strapped to the solenoid and positive on the large bolt the battery cable connects to. Crank, and see what the drop is. Or quick and dirty, take a (sacrifice-able) screwdriver and short the two large bolt terminals on the solenoid together. This bypasses the solenoid contacts.
The above being said, I'd still look for a bad connection in the heavy battery cables, INCLUDING the ground cable to the engine block. If they're all tight and shiny and the screwdriver trick doesn't get a start, and there's 12V at the solenoid, now you're justified in removing the starter. Which if you do, simply renew the front bushing and rear bearing and brushes, and clean up the armature and undercut the mica between contacts on the armature just a bit with a piece of fine tooth hacksaw blade. Score the side of the case into both the rear and nose pieces so it goes back together in the same orientation it came apart. Stoddard solvent (mineral spirits) and a brush will clean it up before reassembly.

--johnny


Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons. Braselton, Ga. I forgive them all, save those who hurt the dogs. They must answer to me in hell

[Updated on: Sat, 28 December 2019 09:41]

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