AKS Racing

Got no response in C4 Tech / Performance, so I thought I would post here.

Prior to my latest combo, the car ran with the factory fuel filter, return filter, and 85-91 regulator (just had larger diameter, 3/8" fuel lines). Two complete identical fuel systems. When the motor was shut down, the injectors would maybe bleed 4-5 lbs of pressure overnight.

The new combo includes the same intake pump, same booster pump, same injectors, but different regulator (supplied with TPIS Mini Ram, think LT1 style), fuel filter (Aeroquip -12AN unit), no return fuel filter, and all 1/2" fuel lines. Upon shut down, the pressure will drop by approx. 10 lbs pressure within 20 mins, and will drop to 5psi overnight.

Was there some sort of check valve in the old fuel filter, or return filter? If not maybe the regulator is allowing the pressure to bleed back to the tank, whereas the old regulator did not allow this.

This is annoying, when the car has not been driven in a few days, as the psi will be at zero when initially cranking. After the first energize, no cranking, the pressure jumps to 10 psi. Wait 30 secs, re-enegize, psi jumps to 35 psi. Wait 30 secs, crank motor, fires right up, psi steady at 40 psi. It does not appear that the injectors are leaking at all, they didn't in the previous combo either.

Anyone experienced this? Anyone with aftermarket fuel system set-up? BTW, the secondary system (fuel for N2O system) maintains pressure as it has done in the past. No components were changed on the secondary fuel system.

Thanks in advance,
Aaron

clem zahrobsky

is not the check valve in the pump?

torquejunky

Probably the regulator leaking but it could be the check valve in the pump. You can check to see which it is by pinching the return line and then the supply line to see which way the pressure is bleeding off. If neither stops the pressure from bleeding off you have a leaky injector(s).

AKS Racing

I think it must be the regulator. I guess I will pull the connector from the FMU and see if there is a slow flow in the return line (after the regulator) to determine if this is indeed the problem. Bottom line, the pumps are the same, the injectors are the same, but the reg is different. Leads me to believe this is where I should concentrate my efforts first.

Will post once I find the problem.

Thanks,
Aaron

gcrouse

Sounds normal to me. If I haven't driven mine in a few days, it will read 0psi for just a moment when the ignition comes on; but the fuel pump primes for 3-4 seconds and it goes 12-25-37-48 psi real quick. Is yours priming? Are you giving it a few seconds or going straight from OFF->START?

Note the fuel pump is on for priming before start; off during cranking; on again once oil pressure rises above 7psi or so.

Monty

Sounds normal to me. Actually, in my opinion, I wouldn't want it to maintain pressure indefinitely. Seems to me that's asking for trouble, and probably increases the possiblity of leakage. It's a safety feature.

I run two Aeromotive "1100hp" fuel pumps, controlled by Aeromotives Fuel Pump Controller. It's plumbed from the tank to the Aeromotive AFPR via -10 Aeroquip hose, etc.

As far as I know, the aftermarket fuel pumps don't have a check valve like the OEM intank fuel pumps. When you initially turn the key to or past run, your ECM or fuel pump controller should prime the fuel pump and get it up to normal pressure, whatever your AFPR is set at. By design, most ECM's/Fuel Pump controllers will prime the pump fro 5-10 seconds if you only turn the ignition to RUN or it doesn't recieve a signal from the Tach/Distributor. This is also a safety feature. If it receives a signal from the Tach/Distributor, it will continue to operate and maintain pressure.

My fuel pressure falls to 0 almost immediately. It did with my Accel/DFI controlled system using a single Aeromotive "1100hp" pump with the same -10 feed/-08 return system with a TPIS conventional rail mounted AFPR, and it does now with my dual Aeromotve pump system with remote mount Aeromotive AFPR.

AKS Racing

I think the real issue is that the system only primes for approx. 3 sec, allowing the pressure to rise to maybe 10-15 psi. This is not enough to fire the engine. So I wait for 30 secs to let the computer time out, then it will proime again for 3 secs, raising the pressure to about 35-38 psi. The motor will crank and then fire after a couple of turns, or if I prime a third time, the engine will fire immediately.

This is quite annoying waiting in between the 3 seperate priming sessions. Total start time 1 1/2 mins. This is a pain. It never had this issue before. I still maintain a check valve in the feed side, and the reg should control on the return. I believe the factory system is designed to bleed psi to zero after 24-36 hrs (to the tank). I think I am compounding my issue with the 1/2" lines from the tank, large Aeromotive filters, ect.

TPIS has informed me that the reg can be tested, but I must pull it and send to them, they will return it, if it tests OK, or replace it if it is defective.

Thanks for the assistance.

Aaron