Home » Public Forums » GMCnet » Remove or not remove (Electric fuel pump)
| Remove or not remove [message #358451] |
Wed, 09 September 2020 12:42  |
thigh19
Messages: 92
Registered: July 2019
Location: Vancouver Wa
Karma: 1
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A friend of mine, pretty good mechanic, cautioned me on adding an electric fuel pump and not removing the mechanical fuel pump. Said that if the diaphragm in the mechanical should rupture, could fill up the engine with fuel. Makes sense, has anyone experienced this?
Thanx
Thom High
Vancouver Washington
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| Re: Remove or not remove [message #358452 is a reply to message #358451] |
Wed, 09 September 2020 14:01  |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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It can rupture. But if you have a new mechanical fuel pump. Chances of that are very very slim.
Mechanical pump is extremely reliable and almost never fail. Especially if not 45 years old.
Electric pumps are very failure prone.
I would only remove the mechanical pump if you intend to only use the electric pump. For me, i ran the mechanical pump almost exclusively and only switched on the aux electric pump rarely when vapor lock was a possibility.
I am now running efi and no mechanical pump. But I have 2 electric pumps. So if one quits i am not stuck.
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] Remove or not remove [message #358454 is a reply to message #358452] |
Wed, 09 September 2020 14:52 |
Len Novak
Messages: 676
Registered: February 2004
Location: Las Vegas, NV
Karma: -3
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I start the coach after running the electric pump. The only time I turn it
on is if suspect vapor lock.
On Wed, Sep 9, 2020 at 12:02 PM Jon Roche via Gmclist <
gmclist@list.gmcnet.org> wrote:
> It can rupture. But if you have a new mechanical fuel pump. Chances of
> that are very very slim.
>
> Mechanical pump is extremely reliable and almost never fail. Especially
> if not 45 years old.
>
> Electric pumps are very failure prone.
>
> I would only remove the mechanical pump if you intend to only use the
> electric pump. For me, i ran the mechanical pump almost exclusively and
> only
> switched on the aux electric pump rarely when vapor lock was a
> possibility.
>
> I am now running efi and no mechanical pump. But I have 2 electric
> pumps. So if one quits i am not stuck.
> --
> Jon Roche
> 75 palm beach
> EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
> St. Cloud, MN
> http://lqqkatjon.blogspot.com/
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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--
*Len and Pat Novak*
*1978 GMC Kingsley*
*The Beast II with dash lights that work and labels you can see!*
*Las Vegas, NV* new email: B52sRule@Gmail.com
http://www.gmcmhphotos.com/photos/showgallery.php?cat=4375
www.bdub.net/novak/
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Len and Pat Novak
1978 GMC Kingsley
The Beast II with dash lights that work and labels you can see!
Las Vegas, NV new email: B52sRule@Gmail.com
http://www.gmcmhphotos.com/photos/showgallery.php?cat=4375
www.bdub.net/novak/
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| Re: [GMCnet] Remove or not remove [message #358455 is a reply to message #358454] |
Wed, 09 September 2020 15:56 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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John is right on.
I suggest only using the Aux electric only for starting and during vapor
loc situations.
Keep in ming the rotary pumps will require a bypass valve.
On Wed, Sep 9, 2020 at 12:53 PM Len Len via Gmclist
wrote:
> I start the coach after running the electric pump. The only time I turn it
> on is if suspect vapor lock.
>
> On Wed, Sep 9, 2020 at 12:02 PM Jon Roche via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> It can rupture. But if you have a new mechanical fuel pump. Chances
> of
>> that are very very slim.
>>
>> Mechanical pump is extremely reliable and almost never fail. Especially
>> if not 45 years old.
>>
>> Electric pumps are very failure prone.
>>
>> I would only remove the mechanical pump if you intend to only use the
>> electric pump. For me, i ran the mechanical pump almost exclusively
> and
>> only
>> switched on the aux electric pump rarely when vapor lock was a
>> possibility.
>>
>> I am now running efi and no mechanical pump. But I have 2 electric
>> pumps. So if one quits i am not stuck.
>> --
>> Jon Roche
>> 75 palm beach
>> EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
>> St. Cloud, MN
>> http://lqqkatjon.blogspot.com/
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>
>
> --
>
> *Len and Pat Novak*
>
> *1978 GMC Kingsley*
>
> *The Beast II with dash lights that work and labels you can see!*
>
> *Las Vegas, NV* new email: B52sRule@Gmail.com
>
> http://www.gmcmhphotos.com/photos/showgallery.php?cat=4375
>
>
>
> www.bdub.net/novak/
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Remove or not remove [message #358459 is a reply to message #358454] |
Wed, 09 September 2020 18:00 |
tmaki
Messages: 200
Registered: September 2005
Karma: 0
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Senior Member |
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[Somehow I sent the draft to myself, but not the list...sorry for the double post, if so.][
Yes. Just getting over it.
I can't comment on the specific cause, because I don't know for sure. My GMC has had an electric pump for the 21 years I've owned it, and who knows how long before that. Has always worked as intended and with no worries.
Never had a problem until just a few months ago. I should have known better, but I cheaped out when I saw a fuel leak from the mechanical pump. The leak was from a hole on the side of the pump, at what appeared to the the pivot point of the pump arm. Instead of replacing the pump (the "cheap out" part of the story), I removed the pump, tapped out the hole and plugged it with a short piece (@ 1/4" long) of threaded stock JB-welded into place. That took care of the leak.
All was well when I ran the engine -- UNTIL -- I started noticing a "miss" and rougher-than-usual idling. Fearing it might be time for a new timing chain/gear-ectomy, I sort of let it go until I figured I could get to that project. On subsequent startings, I noticed more idling deterioration and almost no acceleration, but a LOT of white/gray smoke out the exhaust with a really bad smell.
In an effort to verify my "timing problem", I lined up the timing mark and the distributor #1. Following the t-shooting chart, I determined that timing was spot on -- no chain looseness, no tooth skip -- exactly on spec.
I'll skip over the "yada, yada, yada" part, but suffice it to say that I pulled the oil pan plug and drained out 2-1/2 gallons of liquid from the pan. Terrible color, worse smell. That was my clue. The electric pump was filling the oil pan with gas. No wonder my carburetor seemed to never get primed.
After doing two complete oil and filter changes (with a few minutes of idling to circulate between changes), and installation of a new mechanical fuel pump, I now have my smooth 455 back. It's taken a few runnings to get rid of the smoke, but it has now subsided, and things are back to normal for an engine with 113,000 miles. All the "clacking" is gone, and I get good revving. I haven't taken it out on the road yet, but I'm confident that all will be well.
If you notice a change in the way your electric pump sounds, that's a sign.
If you check your oil, and the indication on the stick is above the FULL mark, that's a sign. (My dipstick tube is broken off behind the manifold.)
If your engine all of a sudden starts to "miss" and belch out foul smoke, that's a sign.
If you don't do anything about it, (as Bill Engvall would say) "Here's your sign!"
Hope this helps.
Toby Maki
73 Glacier 230
Riverside, CA
-----Original Message-----
> From: Thom High via Gmclist
> Sent: Sep 9, 2020 10:42 AM
> To: gmclist@list.gmcnet.org
> Cc: Thom High
> Subject: [GMCnet] Remove or not remove
>
> A friend of mine, pretty good mechanic, cautioned me on adding an electric fuel pump and not removing the mechanical fuel pump. Said that if the
> diaphragm in the mechanical should rupture, could fill up the engine with fuel. Makes sense, has anyone experienced this?
> Thanx
> Thom High
> Vancouver Washington
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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