Faulty new Delphi fuel pump or something else?

[02FRTJ]

Background: OEM fuel pump went out on my 2002 TJ 4.0. It wouldn't hold enough pressure to keep the Jeep running. And when turned off, the pressure would rapidly fall to 0 PSI. Replaced it with a new Delphi fuel pump and upon first ignition turn on with the new pump, it took 4 on/off cycles for the pump to build all the way to ~40 PSI. Didn't think much of it since the fuel lines had been disconnected and it was a brand new pump. It cranked right up and ran fine.

Fast forward a few days, with the Jeep still sitting in the garage, I go back out and throw the pressure gauge on the fuel rail just to see if it had dropped at all. Reading 0 PSI. Figured I probably had some leakage from old injectors. So I turn the ignition on and I didn't hear the pump and the pressure stayed at 0. After a dozen on/off cycles of the ignition, the pump finally turned on and I got a few PSI. Did it again and gained more PSI. It took a handful of on/off of the ignition to build up to ~40 PSI.

So, a couple of questions...

1) Should the short 2-second priming cycle of the pump bring the PSI up higher than ~10 PSI at a time when starting from 0?

2) While I wait for it to act up again so I can get a volt meter on the pump to see if it is even getting power, what else do I need to be on the lookout for?

 

[macleanflood]

PSI should be around 48 psi after priming. My Jeep has run on as little as 28.

Might want to replace the o-rings on your injectors if you think they're suspect.

I put a Brute Power on my 97. Almost cheapest pump I could get on Rock Auto. It's doing great.

-Mac

 

[02FRTJ]

Can the pump go from 0 to full PSI in one 2-second priming cycle? Or does it need multiple priming cycles to get up to full PSI like I am witnessing?

Trying to figure out if that is normal behavior or not.

 

[macleanflood]

Usually 2-3. Pressure gauge will answer that question better.

-Mac

 

[02FRTJ]

Update:

Let it sit a couple of days and went out to check it this afternoon. Pressure had fallen to 20 PSI but immediately primed to 40+ PSI on first try. I bled the pressure off down to 0 to see how many key cycles it would take to prime up to 40+ PSI and it did it on the first try. So that was good.

However, upon cranking, the pressure gauge was going crazy between 52 and 62 PSI while running. It was flicking back and forth so fast you couldn't see the needle. Just she faint shade of it. Turned it on and off a half dozen times and bled the pressure off and it kept doing it. So either Autozone's rental gauge has gone bad or the new fuel pump and/or regulator is acting up.

Probably just going to take Summit Racing up on their free replacement and throw another new pump in.

 

[UND_Sioux]

Update:

Let it sit a couple of days and went out to check it this afternoon. Pressure had fallen to 20 PSI but immediately primed to 40+ PSI on first try. I bled the pressure off down to 0 to see how many key cycles it would take to prime up to 40+ PSI and it did it on the first try. So that was good.

However, upon cranking, the pressure gauge was going crazy between 52 and 62 PSI while running. It was flicking back and forth so fast you couldn't see the needle. Just she faint shade of it. Turned it on and off a half dozen times and bled the pressure off and it kept doing it. So either Autozone's rental gauge has gone bad or the new fuel pump and/or regulator is acting up.

Probably just going to take Summit Racing up on their free replacement and throw another new pump in.

I had just asked a similar question. I also installed a Delphi when I had the tank out last year. Replaced a perfectly good Mopar (which I kept) due to my incorrect thought that I didn't want to replace it in the near future. Turns out the Delphi check valve didn't hold pressure at all. Zero PSI within seconds of turning off the engine. I'm throwing my Delphi in the trash.