Stock 305 TPI. If I floor it, it pulls pretty strong to about 4000 rpm. Then it dies and the rpms start to fall and it'll just stay at about 3000 rpm and wont go any further.

I have already replaced all of the injectors, fuel filter, cap, rotor, plugs, module, coil, and wires. I just replaced the fuel pump as well (because the old one was loud and I thought that might have been the problem). I put a Walbro pump in and now, 200 miles later, that has gotten super loud too.


I'd welcome any input on what to look for.

 

Timing or valve float !

 

This or fuel issue ... or possibly an extreme air flow restriction ?

 

That's reminds me of a old post were a guy with tpi maf did engine work and had a rich condition and his engine wouldn't rev. He put duct tape over his tb and forgot about it lmao

 

ok. got more info. Just hooked up a fuel pressure gauge. with key on and engine off it goes to 40psi and immediately drops to 30 and holds steady. start the car and its at about 30. I can drive around for a little while and everything is fine. once I drive for about 20 miles and floor it the fuel pressure will go to 0 and the car stumbles and starts to die. let of the gas and the fuel press climbs to between 20 and 30 and the car picks back up again; though still not running right at this point.
I have a brand spanking new Walbro 255 pump, new ac delco fuel filter, new fuel sending unit, and just had the fuel tank cleaned by a professional.
Would a bad fuel press regulator give these symptoms? If so, I would think it would do it all the time, not just when the car heats up; that's why I haven't replaced it. (oh, and the fuel pump is somewhat quiet for the first couple of minutes and then starts to get crazy loud)

 

The noise of the fuel pump can be caused bye cavitation or its going bad. When the engine is warm prime the fuel system and pinch off the return crossover line that goes from the block to the frame rail. If the pressure rapidly drops the fuel pump or dampener is your issue.

 

ok, key on engine off...do I pinch the line during the 2 seconds the pump is running?

 

The engine doesnt have to be running , just turn the key on and do the 2 second prime. Turn the key off wait for a few seconds them pinch off the return line. You can identify it bye following the hardline out of the regulator body or visually it is the skinnier 5/16th hardline. small vice grips with small pieces of wood like a paint stir stick between the jaws to help protect the hose from being damaged. Watch the fuel pressure it should hold for atleast 5-10 min. If it bleeds off there is only a few places the fuel can go, through the injectors but you would be running super rich all the time. Back through the pump or out a damaged pulsator dampener or out the vacuum reference line of the regulator but than again you would be running rich all the time and have evidence of fuel in the vacuum line.

 

went back out to do what you said. turned the key on, pump was quiet (like it normally should be) ... pressure went to 20. then to 0. turned key on and off again; same thing. now the pump will run and produce pressure but it will not hold any pressure. if I start the car it will start but fuel press holds at 20. if I remove the vacuum line going to the regulator there is no change in pressure. if I pinch off the return line while it is running the press shoots up over 60 (then I let off so it doesn't go too high). I do not see any leaks and did not smell fuel in the fpr vac line.
in absence of anything else (no leaks, new pump, new filter, etc...)im thinking I had a bad fpr. the only things that don't make sense is that at first it had to get hot before I had a problem and now I have a different set of problems than I had before. i am wondering if a bad regulator could have caused damage to my new pump?

 

It sounds like the fpr spring is weak, diaphragm is distorted from being old or the tip is not sealing on thee regulator body.the pump is working hard if it shoots up to 60psi or more but it could be failing when the pump has ran for awhile. Wish I could give more advice.

 

I really appreciate the help you have given me. Thanks! I made a new post with the new symptoms to see what I might have missed.





te=Tuned Performance;5712126]It sounds like the fpr spring is weak, diaphragm is distorted from being old or the tip is not sealing on thee regulator body.the pump is working hard if it shoots up to 60psi or more but it could be failing when the pump has ran for awhile. Wish I could give more advice.[/quote]