Fuel pump will not prime but engine runs

[stitch]

Engine runs flawlessly. No stutters, dying, or other issues related to fuel delivery.

Problem is to start the car I have to keep the starter going for almost 5 full seconds. This is unconditional (same when hot/cold etc.).
I do NOT hear the fuel pump prime when I put the key in.
I can hear gas trickle back into the tank when the car is off.

Checked the fuel pump relay by swapping it out with a known good relay — no change.
Checked every fuse in both boxes just to be sure — all good.

This is a weird one because it *seems* like the pump itself is working just fine.
Keep in mind that I have a set of aftermarket Clegg injectors to go with my 4.6 conversion.

Any suggestion would be helpful.

 

[TJ Jim]

Regulator leaks

 

[5632]

Turn the key on and off several times then start.

 

[TJ4Jim]

Your fuel system is draining back either due to the regulator or internal fuel pump check valve. If it starts at all then your pump is trying to prime (2 seconds only) but 2 seconds isn't enough so try what 5632 suggested several time before cranking. Then shop for a fuel pump or replacement regulator if you want to try that.

​

 

[stitch]

Turn the key on and off several times then start.

This makes no change.

 

[stitch]

Your fuel system is draining back either due to the regulator or internal fuel pump check valve. If it starts at all then your pump is trying to prime (2 seconds only) but 2 seconds isn't enough so try what 5632 suggested several time before cranking. Then shop for a fuel pump or replacement regulator if you want to try that.

​

From reading about similar problems all day it sounds like I'm in the market for a new pump. Probably the check valve in the pump, not the regulator.
Just wanted to make sure I don't have any ghosts in my machine because I can't hear the pump prime at all — dead silent with the key in.

 

[TJ Jim]

From reading about similar problems all day it sounds like I'm in the market for a new pump. Probably the check valve in the pump, not the regulator.
Just wanted to make sure I don't have any ghosts in my machine because I can't hear the pump prime at all — dead silent with the key in.

I believe the check valve is part of the regulator. You can buy that part separately if you wanna cheap out and risk the pump failing next.

 

[stitch]

I believe the check valve is part of the regulator. You can buy that part separately if you wanna cheap out and risk the pump failing next.

Interesting... I'll double check. I've already bought a new pump (pretty sure the current one is stock so it's a good idea to replace it anyway), but I'll see if the problem persists and replace the regulator if that's the case.

 

[Jerry Bransford]

Sounds more like it's caused by the check valve Inside the fuel pressure regulator.

 

[TJ4Jim]

I believe the check valve is part of the regulator. You can buy that part separately if you wanna cheap out and risk the pump failing next.

The check valve is part of the fuel pump and regulators job is to bypasses any overpressure to maintain rail pressure. If it fails it's bypassing to much fuel and it's draining back. There is no specific check valve in the regulator it only acts as one when maintaining proper operational fuel pressure.

 

[TJ4Jim]

From reading about similar problems all day it sounds like I'm in the market for a new pump. Probably the check valve in the pump, not the regulator.
Just wanted to make sure I don't have any ghosts in my machine because I can't hear the pump prime at all — dead silent with the key in.

You really can only hear it prime if you listen closely near the rear driver side tire.

 

[stitch]

Sounds more like it's caused by the check valve Inside the fuel pressure regulator.

Decided to buy both and see which one fixes the issue... I'll swap them one at a time to figure out what the problem was for sure and post back here when I do.

 

[JeepGirl1013]

I just got an OEM pump off dead jeep for $32!

 

[TJ4Jim]

I just got an OEM pump off dead jeep for $32!

If you know anyone with a small motorcycle jack they are great tool for dropping our tanks.

 

[stitch]

If you know anyone with a small motorcycle jack they are great tool for dropping our tanks.

View attachment 498213

I actually do. I'll borrow it for this job. Thanks for the tip.

 

[stitch]

Check valve in the regulator or pump (whichever one, I replaced both) was absolutely the problem. New pump and regulator are installed and work perfectly. Thanks for the help guys.