Tuning Aeromotive Return Style Fuel System. How do I keep the fuel pump on when crank

[vcious04]

Alright, Ive been fighting with this modern transplant into a 69 camaro. The issues I am having is keeping fuel pressure in the system while cranking. From what I understand is this particular aeromitive design does not hold fuel pressure in the system at all.

I am using a 99 M6 Trans Am PCM. Initial key on pump primes, have fuel pressure while it primes but goes to zero. Is there a calibration in HPTuners that allows me to keep the pump running while cranking? Ive looked at the cranking fuel area of the tune but have never modified before in that area.

Thanks guys!

[DSteck]

This sounds more like a wiring issue.

[vcious04]

This system does use an aeromotive controller that has a fuel trigger (supplied by PCM) to turn on the pump. I know the main issues is the boost reference regulator is designed to not hold fuel pressure. I don't care for it and if you obviously hookup a direct source to the fuel pump it will stay on and keep pressure at the rails, fires right up with no issues. I've thought about hooking up a relay to the "Crank" portion on the ignition switch that will allow the pump to run 100% when cranking only. BUT.... Bacially all I am asking/trying to correct is if HPTuners has a setting that will allow me to keep the fuel pump on when cranking.

[jimmyblue]

Does this pump have a checkvalve? Or the regulator,
an excessive leakage below crackpoint? Do you know what
is allowing rail pressure to bleed in such short time?

[sdobart]

The Aeromotive regulators don't have check-valves because they hinder performance - because of that they bleed pressure almost instantly. The fuel pump prime-time is hard coded in LS1 PCMs. I do believe you can change it in the LS2 PCMs though. You need to use switched +12v from the main relay or a similar source instead of the fuel pump trigger from the PCM in order to make your fuel pump run constantly. I suppose you could also T/wire in a switch that would temporarily apply power to the fuel pump during cranking, then you could shut it off after, and the PCM would continue sending 12v to the pump.

edit: Using a SPDT relay like blownbluez06 suggests below is an even better idea.

[blownbluez06]

You could use a SPDT relay off the wire that is hot during start (usually 10ga yellow or purple on is the GM standard color). Tap the starter solenoid wire anywhere you choose, find the fuel pump feed wire. You can go between the PCM and relay if you choose. You just need to know which end is the source and which is the load after cutting the wire. If you're putting the relay in line on the pump side of the other relay, do not chinch out. Buy a good, brand name, high current relay. Potter Brumfield or Tyco/Bosch. I've had too many cheap chinese relays fail, even when running half their current load rating and it would suck to save 5.00 on a relay and have it cost you a 300.00 tow home or worse.
Back to the wiring part. You're going to cut the wire path and close that path back using the N.C. (normally closed) relay contacts from your new relay, putting the load end of your circuit on pin 30. Run appropriate gauged/fused 12v to pin 87 and ground to pin 85. Run your hot-while-starting wire to pin 86. When you go to start the vehicle, you lose power from the original relay, the new relay opens the circuit and sends 12v down the line toward the pump or relay. I took the time to draw you diagrams for each scenario and prefer interrupting between the PCM and relay. See attached. hot-while-starting-1.jpghot-while-starting-2.jpghot-while-starting-3.jpg

[blownbluez06]

Here's diagrams I drew of the other scenario, which I prefer. hot-while-starting-4.jpghot-while-starting-5.jpghot-while-starting-6.jpg

[sarg]

I just plumbed in a check valve.

[Chevy406]

Adding a way to correct fuel pump prime while cranking when you have an Aeromotive fuel pump controller. I had the same problem as the original poster. I found an article that included troubleshooting guidelines. In my case there was a voltage pressure drop in my IGN+ trigger to the FPSC (fuel pump speed controller). The Aeromotive FPSC requires more than 9.5v to operate. I corrected this by adding a relay in the IGN+ circuit. Now my fuel pump will prime for the initial 2 seconds like normal and then the pump will kick back ON during cranking like it is supposed to. Maybe this update will help someone else in the future.

Credit to this fix goes to this website:
http://www.verociousmotorsports.com/...bleshooting#q3

Clyde