Stephen68

Hey guys, take a look at the video in the link and give me some feedback on what you think may be the problem....Many thanks!

Injuneer

Not conclusive.

Could be - 1) check valve in pump; 2) fuel pressure regulator; 3) leaking injector(s); 4) leaking fuel line, including the flex line in the tank.

4th Gen LT1 F-body Tech Articles

Stephen68

Fred, thank you sir. Here is what i have tested...The fuel pressure regulator is a new Aeromotive 13106 and i have set the proper pressure and checked it for leaks, zero. I inspected the fuel lines under the hood for any leaks and there were none. I pulled the fuel rail up and primed the system and no leaks there either. As for the flex line in the tank i think i am just going to install a new Delphi OEM pump since i need to remove the old pump anyways...Your thoughts sir?

Injuneer

Did you check the fuel pressure regulator vacuum line for wet fuel?

The other possible problem with the pressure regulator is allowing fuel to leak into the return line, not shutting off fully when the pressure drops to 40psi. That is hard to check. Rob/Shoebox has a method, but as he cautions, could damage the nylon fuel line.

Stephen68

Fred, yes sir, i did check the FPR vacuum line and it is bone dry...I have a new OEM pump coming and i will report back with an update...Thank you again Sir!

Stephen68

Ok, new Delphi fuel pump installed. Now when key is on but not running i get almost 50psi but as soon as the pump kicks off it starts dropping...not instantly like last time but very quickly....within say 30 seconds now. Also, while running it will hold 47 psi and if i remove the vacuum line from the FPR it goes up to a little better than 50psi. Think im going to put my factory FPR back on....

Injuneer

Were you not able to adjust the pressure down to 43.5 psi at idle, without the vacuum line hooked up?

Stephen68

Fred, in all honesty i didnt know to do it with the vacuum line off...Is this what i should do before swapping out the FPR? Thanks!

PS...Should the car be operating temp before adjusting?

Stephen68

Fred, does this sound correct to you sir, its straight from Aeromotives web site:

"6.) I’ve installed my new Aeromotive bypass regulator. Fuel pressure seems to adjust fine and holds great when the engine is running, but when I shut the engine off, pressure drops quickly to zero. Shouldn’t the pressure hold like it did with a stock regulator?
No, Aeromotive EFI bypass regulators may not seal perfectly when the pump is off. They are engineered for the highest possible performance when the engine is running. OEM regulators must hold pressure for 30-minutes after shut-down to pass EPA emissions standards. At Aeromotive we know our customers priority is to have the best possible flow and pressure control when the engine is running and we don’t compromise this standard to force the regulator to seal when the engine is off. If extended crank or hard-start becomes a concern, first allow the pump to run and prime as long as possible after turning the key to the run position, then start cranking the engine, just before the pump shuts off. If the priming cycle is too short to allow the engine to start easily with this approach, extend the priming cycle in the ECU if programmable, or ad a timer board or momentary button to the fuel pump run circuit."

Stephen68

Update, adjusted the Aeromotive FPR to 43.5 with no vacuum line while idling...Attached the Vacuum line back up and now it idles 39.5 steady.....

Injuneer

Not all FPR's hold pressure. My Weldon outboard regulator doesn't. Apparently the Aeromotive does not either.

You pressure sounds correct.

Stephen68

Turns out the diaphragm in the Aeromotive was bad. Reinstalled the OEM FPR and now all checks out fine....Thanks!

Injuneer

Another strike against the Aeromotive LT1 AFPR. When problems with this unit surfaced more than 15 years ago, Aeromotive claimed it was due to changes in the formulation of pump gasoline, damaging the internals. If you somehow received a very old unit out of stock, might explain it. Or did you possibly buy the unit that was advertised in the Marketplace "Parts For Sale" listing a few months back?

Even after Aeromotive indicated they revised the materials to match updated fuel formulations, failures kept occurring. When I pointed this out on this site, Aeromotive sent someone to join up and discredit me. Their position was that their failure statistics showed that the unit was not unreliable. But for 15 years there have been numerous verified failure reports (like yours) of their LT1 AFPR, but few, if any, regarding the stock FPR. And there are far more people still using their stock units, than people who have opted for the Aeromotive unit.

Note - I am not faulting Aeromotive in general. I know they make many excellent fuel handling products that are at the top of their class. That's why the situation with the LT1 AFPR is so puzzling.

sscott

Question, if I go back to the stock FPR can I still use my Autometer fuel pressure gage, I think the diaphragm in my AFPR is going south and I don't think I have the need for an adjustable one for the $$$$$ they want for one.