keith95jr

i have a 95 camaro thats losing alot of fuel pressure underload. its a 383 and im using the 255 walbro pump with an aeromotive regulator 36 lbs injectors. fuel filter is brand new. when the car primes it tacks just about 60 psi, running at idle about 42ish,if i rev it at idle it drops down to mid to high 30s. driving around the block it holds decent pressure. but as i go up quickly in rpms it drops down to 20ish or below. im scared to WOT it as may guess is that the needle will find 0 pretty fast. if someone could point mein the right direction as maybe i hooked something up wrong or maybe a faulty part? thanks

Pullngz

Are these all new parts?

Or was the car running fine and this just started happening?

Mike

keith95jr

its basicaly a fresh build but its been a long fresh build LOL.it also has a basic mail order tune ( enough to get it running) i know it will need a real tune.

Pullngz

At this point it could be anything, the pump, the regulator, or leaky injectors. Check out "shbox" website he has a lot of info on how to check everything out on his how to's page.

4th Gen LT1 F-Body Tech Aids

Mike

keith95jr

thanks ill check it out

Pullngz

No problem man, post what is was, when you get it figured out.

Mike

Injuneer

The Aeromotive LT1 fuel pressure regulators are known for a high failure rate. The fact that it primes to 60psi is indicating a problem, if you didn't set the AFPR that high.

Do not attempt to take it to max load. At 20psi your 36#/HR injectors can only supply 24.4#/HR. It's going to run seriously lean.

What is the fuel pressure regulator set to? Is that the pressure you told the tuner you planned to run?

What are using to read the fuel pressure - a mechanical gauge or an electronic gauge with the sensor hooked to the Schrader valve?

keith95jr

when i set the pressure i started the car checked the pressure, shut the car off made adjustment, and continued to do this untili got the 42 at idle. as for the tuner i just told him what i was running and let him do his job, so i figured it would be the same psi but since your asking i guess i could be wrong

keith95jr

the gauge is machanical hooked to the schrader valve

Injuneer

You don't need to shut the engine down to adjust the fuel pressure. You can adjust with the engine running, while watching the gauge. But you do have to pull the vacuum line off before you set it. Plug the vacuum line to prevent a vacuum leak. Then set it at 43.5psi. That is what GM fuel injectors are flow rated at. If you are running Ford injectors they are flow rated at a lower pressure, so they will flow about 5% more at 43.5psi. The tuner should have asked for the brand of the injectors and the pressure you set your system at.

When you reattach the vacuum line, the pressure will drop proportional to intake manifold vacuum. With a stock cam you will typically see an 8psi drop. With a more aggressive cam you might only see a 4psi drop. When the engine is idling, if you suddenly open the throttle to rev it up, the pressure should increase, because the manifold vacuum will drop.

keith95jr

thanks for the help guys but i think i just found my problem or atleast most of my problem, i used to have 36lb injectors. over the winter i had ordered and installed new injectors and the new injectors are 42lb. i was getting fustrated with other parts of this build and wasnt even thinking about the change in injector size.