Fuel pump not priming, but Jeep still runs (eventually)

[JoshNZ]

My Jeep seems to be going through tough times at the moment.

The current issue is the fuel pump, it use to prime very audibly (no carpet or rear seats)

Now I’m not hearing it at all, and the thing won’t fire, just turns over. After that, if I turn the ignition off, then on and try to start it, it fires right up.
Doesn’t seem to suffer while driving, (although I’m not pushing it at all)

If it’s recently shut off, still warm etc, it’ll fire up right away, but stutter and lose rpm (like it’s got no fuel) turn it off and on again at it purrs again...

it’s only done about 90,000 miles. But does spend most it’s time in the NZ bush and beach. Lots of water (fresh), sand and mud.

I’m thinking new fuel pump and change the fuel filters.

Any other thoughts or suggestions?
It’s had an ignition issue recently, some issues in the pcm wiring.

 

[Jerry Bransford]

That's not a fuel filter issue, it just sounds like the check valve in the fuel pump has failed. If it was me I'd replace the fuel pump itself with a Bosch replacement which is available on Amazon and www.rockauto.com. Don't cheap out with a store brand, Spectra, or Airtex.

 

[JoshNZ]

Yep, I'll grab a Bosch replacement. Fuel filter was a while I'm there thing/don't know when it was last changed kind of thing.

Check valve explain the lack of easy starting, but not why it doesn't seem to prime with the key on at all?
If the check valve has failed, shouldn't I be able to prime it by cycling the key a few times? Then it should fire right up?

I guess if the valves completely failed, there's a lot of air in the system that needs to be bled out. I'll try a longer crank this afternoon and see if it eventually fires.

I also love to over think things, spend too long trying to determine the why, assume the worse, and then find its the simple obvious part.. I'll order a fuel pump now.

 

[Russ Mullen]

I had exactly the same problem (seemed like check valve), so I just replaced the pump. Problem solved.

My guess is that the priming process was designed on the assumption that the check valve was working. In other words, it's designed to make up for a slight loss in pressure, and not to re-pressurize the entire line from 0.