HI I swapped in a 350 carb into my 89 camaro v-6 car. I was told if I cut the power to the electric pump that it wouldn't affect my car. Well we have put a new mechanical fuel pump on the my 350 with a new intake and carb both edelbrock.we have replaced the cap, rotor ,wires, plugs, coil, and the the wiring harness on my hei distributor.it doesn't cut out in stop and go traffic its only when I am on the highway and only after about 8-9 minutes but until then it runs great. It is really starting to confuse me. But after it dies it will start right back up and go for another few minutes and does it again.

 

anyone?

 

Could be the modulae in the distributor breaking down...or could be vaporlocking.

Or could be something else

Did you use a return line to the tank for the new pump?

 

no the mechanical pump only has one line into it and no return line. Yeah we just got back from autozone to have it tested and guess what It was bad. Thanks for your help.

 

well that didn't stop the problem. I noticed something else it also does it when the temperature reaches the 190 range. This is really confusing me here. I don't know what it can be.

 

anyone?

 

can anyone help..

 

Assume you meant you had the module tested? I so, when you put the new one back in, did you use the grease under it? The Dielectric grease acts as an insultaor for the module from heat.

Other thing I'd suggest if you think it's fuel, is look for a 3port pump and let the unused fuel return to the tank, keeps the fuel cooler and eliminates vaporlock (if that's what you have).

You might try posting a different question for more info...such as "Anyone use a fuelpump without a return line without problems?"

 

I don't know what to do anymore.

 

Can you clarify the last post? Exactly what was it that tested bad? The fuel pump?

If so, you might want to perform a fuel flow test. This would require a separate fuel supply to the carb, and a running test to measure the time required to deliver one gallon of fuel to a container. A good pump should be able to deliver a gallon of fuel in less than 120 seconds. If the system cannot do that with a new pump, you may have a restriction in the pickup line (like the electric pump, strainer, kinked hose, etc.).

 

Yeah I had the module tested and it is was bad so we got a new one but it didn't stop the problem. The fuel pump is good. Its changed up on me now. It can run in town at around 200 degrees and run like new but at 175 degress and driving down the highway I can make it almost a mile and it will start to try to die but then i shut it off for about 30 seconds and it starts like new and runs good for another mile or so and does it again. I can stomp on it full throttle when it is around 165 degrees and it won't even hesitate it takes off like lightening so if there was something in the fuel line wouldn't it affect it when you are at WOT.

 

So then the eletric fuel pump is still in the tank? This may not be an ideal test buy I have actually taken an intank pump for an 87 IROC and tried to both blow through, an suck throug it. I was not very successful. I could make a little air go through it, but it was very difficult. I suspect your mechanical fuel pump is having the same delima.

I suspect your mechanical pump is able to supply enough fuel for low rpm driving and short bursts at WOT because it is able to keep the float bowl full enough to handle the needs. But after driving at higher rpms on the highway for a while the bowl empties and it can't keep up.

I would like to believe the intank fuel pumps would let fuel pass through without restriction but I don't think it is the case. If someone else has experienced otherwise I would like to know because I'm about to have to do the same thing on my brother's 91 RS this weekend.

This is all assuming the intank pump is still in there.

 

we still have the in tank pump still in there

 

Then you really should perform the flow test on your pump.

 

I used the following procedure for perform a complete "fuel delivery" test:

1.- Fuel presure test.
2.- Fuel volume (flow) test.
3.- Feeling the Engine power under driving and accelerating conditions in the street/highway.
4.- Number 3 again, but in limp home mode (without PROM).


Others ideas?



Denis V.

 

You really should take the electric one out and use a mechanical fuel pump pickup. The flow will be too restricted for the mechanical pump with the other one still attached. The only thing that does help when using a one line mechanical instead of the stock one with the return line is to drill a small hole in the gas cap to let the fuel tank vent. That's all. I have had no problems with the one hose pump, but my car was also an originally carbureted car and had a mechanical pump to beggin with.

 

THANK YOU VERY MUCH. I really apprieciate it.

 

Originally posted by TA5LiterHO
You really should take the electric one out and use a mechanical fuel pump pickup.




Do you mean the pump pick up in the tank because we took the electric pump out and now the pickup is to up to high and I don't know what to do about it. If I need one where can I get one.

 

You probably don't need to drill a hole in your fuel cap. It should already have a vent and surge valve in it, plus the EVAP system controls tank pressure and allows venting. Many early ThirdGens came with a mechanical fuel pump and NO hole in the fuel filler cap.

As for the fuel pickup, you can replace teh entire assembly with a pickup for a mechanical pump, or install a tube and pickup screen adapter in place of the electric pump.

Frankly, if you're going to the trouble of removing the tank to remove the pump, you might just want to install a new electric pump and use a three-line pressure regulator to control output pressure.

And even before that, I'd check for fuel starvation by performing the flow test. You might not even have a problem with the fuel delivery, and could be barking up the wrong tree.