[rock141b]

Hi to everyone, I posted a problem I have with my 91 silverado 305sbc it just died going thru the parking lot. Turned key on and no noise from the old fuel pump and none from the injectors as I cranked it over. Sooo while thinking what I was going to do 75 miles from home and about 20 mins later I turned the key on and the pump started working and the truck started and I drove home no problem.
So now about a week later I went to the dump and it died as I was leaving, so I had AAA tow it home. Again after the tow home and 30 mins later turned key on and the pump started working and the truck started right up. I did all the checks and removed the fuel pump relay while the truck was runing and the truck kept on running, did all the rest of the fuel system checks and everything checked out. So why would the pump work after 20 or 30 mins of being turned off, any suggestions, thanks.

 

[98Hotrod98]

Did the motor stumble for a bit then die, or was it like a light switch and just died?
After it died, would the motor turn over?


Have you been having idle issues or acceleration issues recently?

 

[rock141b]

Hi no just slowly quit, when I turned on the key no fuel pump noise, after about 30mins pump started to work and truck started. When I tried to start it after it quit the motor turned over no problem, after a time pump started to work again and it started right up, engine idles smooth and runs fine just quits after a time when just idling then no fuel until about 30 mins later then starts up.

 

[98Hotrod98]

I know the crankshaft position sensor can cause similar behavior, i've had a few of them go out over the years on different vehicles. Normally they throw codes, but not always( jeep ).

 

[rock141b]

Thanks everything like that checked out, I think it might be a intermittent fuel pump thanks for your imput.

 

[DIGS16]

what about possible vapor lock? that would kinda make sense

 

[tbplus10]

You'll never vapor lock a vehicle with injectors because it pushes the fuel instead of pulling like older carburated vehicles.

 

[silveradotrailblazer]

I think, the key word here is think, I saw on this site where the TBI trucks had fuel pump ground issues. I THINK.

 

[stephan]

X2, yep some do STB, & I keep coming back to what the op said about not hearing the fuel pump when he turned the key back on. Also pumps from that vintage suffer from heat stroke lol.

Rock, I don't know where you live & what your climate is right now, but was it hot the day this happened? The FIs return unused (non injected) fuel to the tank in a never ending continuous loop & all the fuel that's returned has been preheated by engine heat. Too much heat & it will kill the pump, & the fact that you said that a half hour later it fired right up tells me this might be the problem (half hour later the fuel & the pump have cooled down enough to run again) Check your ground like STB said & if it's in order, I would suspect a tired pump that is suffering from high electrical resistance due to heat. One thing you can do to test this is to always keep your fuel tank as full as possible because it has more cold mass to counteract the pre-heated fuel that is returning, & will keep the pump cooler.

 

[DIGS16]

You'll never vapor lock a vehicle with injectors because it pushes the fuel instead of pulling like older carburated vehicles.

well he said its a '91, i dont know if they came with fuel injectors back then or not, just an idea

 

[stephan]

Yep they had them Digs. TBI throttle body injection with two injectors shooting into a throttle body that looked suspiciously like a warmed over carbuerator from China or Russia They ran on 12 psi & never vapor locked, but the injectors did seem to to leak a little when they were sitting & would cause the engine to act flooded when restarting.

 

[DIGS16]

learn something everyday lol

 

[tbplus10]

looked suspiciously like a warmed over carbuerator from China or Russia

They werent from China? :shocked: You do learn something everyday.

 

[stephan]

LOL just messin around Tim. They were manufactured in the U.S. by Rochester, but they're just such an odd piece, that I've just never accepted them as high grade American technology.

 

[rock141b]

Truck slowly died

Hey guys thanks for the suggestions, here is what I did. I bought a new fuel pump motor and a new fuel pump relay (cheap insurance) and installed them both.
NOW I'm having a small problem when starting the truck, it seems to crank for about 5/7 seconds and have to give a little throddle before it starts. Before replacing the pump etc. it started right up bamb!! with no problem, so what the heck do you think is causing this hick-up injectors dirty or ?? thanks again, this is a great sight with great people helping other car/truck guys!

 

[tbplus10]

LOL just messin around Tim. They were manufactured in the U.S. by Rochester, but they're just such an odd piece, that I've just never accepted them as high grade American technology.

Actually I was messing with you because I felt the same way, they always looked like a cheesy aftermarket add-on someone bought from a magazine add that claimed it would increase mileage by a 1000 mpg.