Starts then quits after a few

88 MJ 4.0(stroked to 4.6) AW4

Driving home from work the other day and she up and quits on me. Restarted and idled for about 20seconds then quits. I had this problem before but it cleared up.

I thought it was the fuel pump/filters so I replaced the pump, intank filter and external filter. Still starts and idles for about 30 seconds then dies even if I try to coax it along with the pedal.

Replaced my vacuum hoses because they needed it and thought that might help the vacuum on the fuel regualtor but some thing as before.

I am leaning toward the fuel regulator but not sure how to test it or check it.

Any other suggestions?

there should be a schrader valve on the fuel rail just past the pressure reg. get a fuel pressure gage and screw onto it, (the valve looks like a tire valve) start it up, i think the pressure should be around 35 to 40 psi

update:

got a fuel pressure gauge from Napa, put on fuel rail and turned on ignition but did not start it. gauge - 0 psi

started it and it fires right up and gauge reads 20 and slowly falls back to zero and engine quits.

When I replaced the pump I found the power wire was warn by the driveshaft rubbing on it( just ran Johnson Valley so I flexed it quite a bit). So I cut the bad section out and spliced it together, tested it and had 12 volts out to the pump.

shouldn't the fuel pump come on when the key is on?

how can it start with no fuel pressure?

what else should I check?

thanks

You should be able to hear the fuel pump. Mine is a stock in tank and it is plenty loud when I turn the switch on.

Yes, you should be able to hear the fuel pump with the engine running. And as I recall, for the first few seconds after you turn the key to the on position, as well. Perhaps it's your fuel pump relay or maybe the ballast? resistor over on the driver's side fender well... close to the front of the vehicle. That resistor should have two wires coming out of it and maybe the resistor is shot or the wires are not making good contact... just a thought. Good luck, Rick

Well after reading my FSM's( should've done this first ) it states power for the fuel pump comes from the starting relay on startup but through the fuel pump relay after that. Swapped my fuel pump relay with the one next to it( O2 heater?) and whadda ya know - varooom! fired right up and stayed running. Damn, all that work and it was a simple relay problem.

Next time read your FSM's!! and check the simple stuff first!!:twak:

for anyone seaching on this subject - the fuel pressure gauge I got at Napa was about $50.00, forgot what brand but its made for the schrader vavle connection and has a bleeder hose also.

go to Napa for your fuel pump relays - the store closest to me didn't even have to look in the book/computer, just pulled it out of box behind the counter.

Checkers sells a Bosch fuel pump but it does not fit exactly, you have to play with the adapters that are included. When putting the lock ring back on after you have installed the fuel pump, use a long screwdriver/prybar to squash the new o-ring a little so you can get the lock ring started.

RTFM is always a good thing.

Nice Catch.