| [GMCnet] Re: Issue with rough idle and stalling with electric fuel pump [message #364931 is a reply to message #364923] |
Wed, 23 June 2021 11:59   |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma:
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Senior Member |
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Tom,
If possible, you need to put a fuel pressure gauge at the inlet to the card
to check the output pressure of the electric pump, 'cause it sure sounds
like the carb's float is being "sunk" (overpowered) by that pressure,
causing you to have an over-rich idle mixture.
JMHO,
Ken H.
On Wed, Jun 23, 2021 at 12:24 PM Tom Lins wrote:
> I have what to me is a strange issue that I don't understand.
> I am hoping someone has run into this before or has some things I can
> check.
>
> Just got the coach out of the storage area and brought it to the house for
> some cleaning in anticipation on takeing some short trips.
> It had been sitting for 8 months or so with fuel stabilizer and an almost
> full tank.
> It was running a little rough so I changed the plugs (NGK) and wires.
> It ran noticeably better so I called it a day after doing some cleaning.
> Next day I went out to drive it back to the storage yard and during
> warming it up it started to run very rough and stall.
>
> Some background:
> I replaced the failed isolater with a yandina combiner last week and
> during troubleshooting I got a 20v reading on the center post of the
> isolater.
> I do not have a mechanical fuel pump only a Carter electric pump. That was
> done by one of the PO's
> The carb is a rebuilt I got from JimK just before the Pandemic when I had
> 2 FITech EFI's go belly up in 2019.
> So this carb has not been run more than 500 miles.
>
> Right now when I start it and warm it up it runs rough like it is missing
> unless I turn off the the electric fuel pump (there is a switch on the
> dash)
> When I turn off the electric pump after 5 to 7 seconds the idle smooths
> out at about 900 rpm.
> When I turn on the fuel pump after 5 t0 10 seconds it starts running rough
> and will stall if I do not touch the gas pedal.
> I have also noticed that when I turn on the pump the volt meter on the
> dash drops from about 14 to about 13.
>
>
> --
> Tom Lins
> St Augustine, FL
> 77 GM Rear Twin, Dry Bath, 455, Aluminum Radiator Quad-Bag Suspension
> Solar Panel
> Manuals on DVD
> YOUTUBE Channel: GMC Dealer Training Tapes
> http://www.bdub.net/tomlins/
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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