Home » Public Forums » GMCnet » [GMCnet] Ignition switch drama
| [GMCnet] Ignition switch drama [message #365266] |
Tue, 06 July 2021 13:56  |
David Simpson
Messages: 4
Registered: June 2020
Karma: 0
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Junior Member |
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I have an occasional but potentially traumatizing problem when starting
the engine.
Normal behavior is; insert and turn the key to the start position,
starter rapidly goes "ur ur ur ur ur ur" (phonetic sound of starter),
engine fires, key released immediately and it returns to run position,
starter disengages, no more "ur ur ur... " Everything is fine and away I go.
But sometimes, I get this abnormal behavior; turn the key to start
position, starter goes "ur ur ur ur ur ur" engine does not start, key
released and it returns to the run position BUT the starter continues to
go "ur ur ur ur ur ur ur ur"! Mercifully the engine does not start
though it tries to cough. I flip key back and forth between Start, Run,
Off, and even Accessory while starter continues to go "ur ur ur ur ur
ur". I grab something to tap the ignition switch with, "ur ur ur ur"
continues. Finally and unexpectedly, after resorting to repeatedly
trying every position the key can be turned to, turning the key to the
Off position has the desired effect and the starter takes a break. I'm
at a gas station, or a rest area or a camp ground and I want to get
going, but do I try it again? Eventually I muster the courage and try
it again. Thankfully I get normal behavior and I am on the road again.
I cannot find any reference to this problem in the GMCMI Magazine
technical articles nor in the GMCMI forum archives. All I have learned
is that the ignition key rotates the tumbler that moves a rod (up or
down - not sure which way) parallel to the steering column which engages
the switch which in turn engages the starter.
Is it a mechanical failure soon to strand me? Is it a simple magic lock
lubricant I need to buy and inject? Is it an adjustment of the start
switch I need to make? Is it something a locksmith should be consulted
on? (When it happens I fear the engine will catch and fling the starter
motor off doing nasty damage, thus the potential trauma.) Any similar
experiences and/or suggestions from anyone?
Dave Simpson
1975 26' Transmode - Upfitted by Norris
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| Re: [GMCnet] Ignition switch drama [message #365267 is a reply to message #365266] |
Tue, 06 July 2021 14:23  |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Senior Member |
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I would suggest 2 things.
1. replace the ignition switch, not that expensive, part stores will have one in stock, and it is very easy to change. It is located on drive side of steering column just about where the lower dash ends. There is just a couple screws, electrical connector, and a rod. The rod is what the tumbler operates to activate the actual switch.
2., and what I think is more likely, time to pull the starter and have it rebuilt. chances are you have a sticky solenoid. this is not a terrible job, if you pull up on to a curb with the driver side tire, you can usually crawl under to pull it out on the road if you don't have a jack, or ramps. just make sure you battery cables are disconnected when messing with the starter.
you are probably close to being stuck on the road with a problem.... I would fix sooner then later.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: [GMCnet] Ignition switch drama [message #365268 is a reply to message #365266] |
Tue, 06 July 2021 14:27 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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First you need to diagnose if it is the starter or the ignition switch/key and rack system. The switch could be ending the 12V start signal when you turn the key to run as it should, but starter contactor sticking. I would wire a test light up to the start terminal wire up to where I could see it Disconnect at starter and alligator clip and tape. The light should 100% track what your doing up top. I don’t have the schematic open, but If you just connect without disconnecting from starter the hold-in winding may light the light and mislead you. Once the test shows the switch is good, replace starter. If switch bad, replace or adjust switch and mechanism.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Ignition switch drama [message #365270 is a reply to message #365266] |
Tue, 06 July 2021 16:55 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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David,
Unlike the others, none of which are bad places to try, I will add another thing to the mix.
I don't believe it is in the starter proper or the solenoid because I can't come up with a failure scenario that fits. It could be a sticking solenoid, but that is a failure I have never seen and only heard of once in 50+ years. I have seen them stick so as to fail to engage.
It could easily be that the ignition switch down on the column is either worn out or vastly out of adjustment, but that does not work with the "it works right sometimes". If it is really badly worn, it could fit but I have never seen one that worn out. Both are available from Standard US 95 for a non-tilt column and US 105 for the tilt column.
I have a last place to look that is very likely, but more of a pain in the column than the others. The lock cylinder engages a rack and pinion set to move the switch. This is such a common mode failure that the replacement set is available on a hook at most store front parts stores. It is less than 15$us and is a Dorman Kit 83211. You will also need to borrow that store's steering wheel puller kit and the GM lock plate depressor so you can get at the stuff in the column that is below that. It is not a hard or a long job, but getting the snap ring up the steering shaft is always a primary pain. Do not mix the old and the new parts.
If you add a geographic note to your sigfile, you might discover that you have so local old friends that you need to meet.
Matt
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
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| Re: [GMCnet] Ignition switch drama [message #365271 is a reply to message #365270] |
Tue, 06 July 2021 17:37 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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I vote for starter solenoid sticking and failing to retract occasionally. It could also be the bendix gear that the solenoid moves into the flywheel teeth. On aircraft starters this is a common failure because of it's constant exposure to 100 mph wind, rain, and snow. Because of this we are on a 50 hour preventative maintenance lubricating schedule. We are suppose to lube it ever 50 hours with spray silicone.
Pull the starter and then pull the solenoid off of the starter. Clean every thing up, lube it, and reinstall. If I am wrong you are only out of a couple of hours and out no parts money.
Disconnect the starting battery before working on the starter.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
[Updated on: Tue, 06 July 2021 17:44] Report message to a moderator |
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| [GMCnet] Re: Ignition switch drama [message #365274 is a reply to message #365266] |
Tue, 06 July 2021 19:23 |
Dave Stragand
Messages: 307
Registered: October 2017
Karma: 0
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Senior Member |
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It sounds like the solenoid to me. When you turn the key, power is supplied to an electromagnet in the solenoid, which pulls a plunger forward. As the plunger moves forward, it slides the starter's gear out to engage with the flywheel. When the plunger is fully forward and the gear fully engaged, the plunger hits a button/switch that engages the starter motor to start cranking.
If that button stays pushed in (like with a sticking solenoid), the starter will spin regardless of whether or not the key is turned and the solenoid is energized. The vibration of the starter and/or toggling that electromagnet on and off may be freeing the plunger it enough to have it eventually stop. If the engine starts to run, it usually will kick out the starter gear thus pushing back the solenoid as well (but not always).
Replacement solenoids are available as an individual unit, but usually it's best to R&R the whole starter if you're going through the effort anyway.
-Dave
1978 Transmode near Pittsburgh
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1978 Transmode (403)
Pittsburgh, PA
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| [GMCnet] Re: Ignition switch drama [message #365275 is a reply to message #365274] |
Tue, 06 July 2021 18:12 |
Dave Stragand
Messages: 307
Registered: October 2017
Karma: 0
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Senior Member |
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It sounds like the solenoid to me. When you turn the key, power is supplied to an electromagnet in the solenoid, which pulls a plunger forward. As the plunger moves forward, it slides the starter's gear out to engage with the flywheel. When the plunger is fully forward and the gear fully engaged, the plunger hits a button/switch that engages the starter motor to start cranking.
If that button stays pushed in (like with a sticking solenoid), the starter will spin regardless of whether or not the key is turned and the solenoid is energized. The vibration of the starter and/or toggling that electromagnet on and off may be freeing the plunger it enough to have it eventually stop. If the engine starts to run, it usually will kick out the starter gear thus pushing back the solenoid as well (but not always).
Replacement solenoids are available as an individual unit, but usually it's best to R&R the whole starter if you're going through the effort anyway.
-Dave
1978 Transmode near Pittsburgh
-----Original Message-----
From: David
Sent: Tuesday, July 06, 2021 2:56 PM
To: gmclist@list.gmcnet.org
Subject: [GMCnet] Ignition switch drama
I have an occasional but potentially traumatizing problem when starting the engine.
Normal behavior is; insert and turn the key to the start position, starter rapidly goes "ur ur ur ur ur ur" (phonetic sound of starter), engine fires, key released immediately and it returns to run position, starter disengages, no more "ur ur ur... " Everything is fine and away I go.
But sometimes, I get this abnormal behavior; turn the key to start position, starter goes "ur ur ur ur ur ur" engine does not start, key released and it returns to the run position BUT the starter continues to go "ur ur ur ur ur ur ur ur"! Mercifully the engine does not start though it tries to cough. I flip key back and forth between Start, Run, Off, and even Accessory while starter continues to go "ur ur ur ur ur ur". I grab something to tap the ignition switch with, "ur ur ur ur"
continues. Finally and unexpectedly, after resorting to repeatedly trying every position the key can be turned to, turning the key to the Off position has the desired effect and the starter takes a break. I'm at a gas station, or a rest area or a camp ground and I want to get going, but do I try it again? Eventually I muster the courage and try it again. Thankfully I get normal behavior and I am on the road again.
I cannot find any reference to this problem in the GMCMI Magazine technical articles nor in the GMCMI forum archives. All I have learned is that the ignition key rotates the tumbler that moves a rod (up or down - not sure which way) parallel to the steering column which engages the switch which in turn engages the starter.
Is it a mechanical failure soon to strand me? Is it a simple magic lock lubricant I need to buy and inject? Is it an adjustment of the start switch I need to make? Is it something a locksmith should be consulted on? (When it happens I fear the engine will catch and fling the starter motor off doing nasty damage, thus the potential trauma.) Any similar experiences and/or suggestions from anyone?
Dave Simpson
1975 26' Transmode - Upfitted by Norris
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
1978 Transmode (403)
Pittsburgh, PA
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| Re: [GMCnet] Ignition switch drama [message #365278 is a reply to message #365266] |
Wed, 07 July 2021 07:19 |
kingd
Messages: 592
Registered: June 2004
Karma: 2
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Senior Member |
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Note to DAVE SIMPSON. I don't think anyone who replied said the actual electrical switch is not part of the "switch" that the key goes into. A GMC motorhome electrical ignition switch is remotely activated by a ROD along side and down the steering column. The actual electrical switch is NOT by the key but it is down the column. This switch can get out of adjustment. I would suggest that you also determine if that actual switch is being operated correctly.
DAVE KING
lurker, wannabe
Toronto, Ontario, Canada
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