Gmc nonstart

[alwalk63]

I have a gmc class c rv with 400ci engine, it can usually by started in spring after priming the carb. This year, nope. It will catch, burn the fuel and stall out.
I replaced the fuel pump, still no fuel. Replacing sending unjt was suggested but i also undertand the rod the activates the fuel pump can wear. I would think checking this would make more sense than dropping the fuel tank.
Would it be possible to diagnose this by attaching fuel line to pump and inserting into gas can and on the line coming out of the fuel pump feed into another can to see if its drawing gas

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[grcauto]

Does the accelerator pump throw fuel?
Year might help.

 

[alwalk63]

Sorry thought I included year. It's a 78.

No when pumping accelerator no fuel comes through the fuel lines.

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[billr]

"Would it be possible to diagnose this by attaching fuel line to pump and inserting into gas can and on the line coming out of the fuel pump feed into another can to see if its drawing gas"

Yes, do that. It should spurt out a bit of fuel for every two revolutions that the engine is cranked. After checking for flow, put a pressure gauge into that line (plugging it up). Pressure with no flow should be about 5 psi.

 

[alwalk63]

Okay thanks.

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[grcauto]

Probably the diaphragm is leaky.

 

[JackC]

Probably the diaphragm is leaky.

Sounds very logical on that 1978 vehicle.

 

[bp042665]

i have done a fuel pump where the push rod will drop and new pump wont pump fuel to carb

 

[billr]

Good point! It has been so long, I forgot you have to hold that rod up carefully while slipping the pump arm in under it. A very thick grease will also hold the rod up long enough for you to get the pump in.

 

[alwalk63]

I had thought of the rod not being in place properly, i had a mechanic replace the fuel pump. That was the other issueninwas hoping tonekiminate by testing the fuel pump in this ,manner

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