Fuel system electrical - stupid design

[x2xtreme360]

My fuel pressure is literally dropping almost instantly too. I turn off the car, pop the hood, and my gauge on the rail reads around 5psi.

[GTOJOE]

Try the fuel pump resistor bypass and see if it then primes. It's a 5 min job and 100% reverseable if it makes no difference.

Stealth 316 - Fuel Pump Relay/Resistor Bypass

[x2xtreme360]

My resistor has always been bypassed. Pump hotwired.

[stealthee]

Even if you make it prime you are only masking a current problem.

With it starting to bleed off badly as soon as you changed the sender then it sounds to me like you don't have a good seal somewhere.

[x2xtreme360]

I agree, Stealthee. I've never been a fan of doing one thing to cover up another.

With that being said, I re-tightened the fuel sender earlier today, just to be sure. I haven't really tested it further because I had to get ready for work. I still need to figure out what the culprit is.

My initial statement though, on the priming, is why I'm a little angry. Why they wouldn't make the system prime is beyond me.

[GTOJOE]

next solution then is to wire up the hotwired pump so that the relay is getting power when the key is in the ON position. Just means either running new wires to the pump relay or cutting the origional fuel pump wires [as they are now the power for the relay] and splicing them into the ignition switch etc.

Edit: note on above 2 posts. Even with the stock FPR you will get bleeding. Cannot be avoided. Just a better FPR will take longer to bleed out.

[x2xtreme360]

If I ever set it up to prime, I would do it right. I would never want the pump to be working in the ON position all the time. It's pretty loud.

[stealthee]

I agree, Stealthee. I've never been a fan of doing one thing to cover up another.

With that being said, I re-tightened the fuel sender earlier today, just to be sure. I haven't really tested it further because I had to get ready for work. I still need to figure out what the culprit is.

My initial statement though, on the priming, is why I'm a little angry. Why they wouldn't make the system prime is beyond me.

Because its not needed. The system is designed to remain primed with fuel pressure and ready to fire.

[stealthee]

If I ever set it up to prime, I would do it right. I would never want the pump to be working in the ON position all the time. It's pretty loud.

It really wouldnt be that hard to wire it to prime. When I lost power to my fuel pump I did a fuel pump hotwire as a temp fix and got two of the wires to the relay mixed up. I started the car and about 3 seconds later it shut off because the pump shut off.

[Gearheadvr4]

If I'm not mistaken the stock setup does prime with the key on. When you go aftermarket and bypass everything with a hotwire maybe you lose that? The MFI sends power for fuel pump but maybe it goes to the resistor first since it gas two voltage levels depending on load. I haven't looked at the service manual for a while...

Sounds to me like the aftermarket FPR and walbro is bleeding off the pressure. I had a similar setup as you but mine always held great. Btw, do you have your fuel vapor canister removed? If yes then did you cap the lines running into the engine bay? You will lose pressure and dump fuel vapor into the engine bay if you didnt cap them.