95 jeep yj hard start

loosecannon

New member
So, my brother in laws jeep is starting rough. If you cycle the fuel pump 2 or 3 times it fires right up... If it sits for more than a few hours, it starts hard again.my first guess would have been a fuel pressure regulator, but after I changed it out, I let it sit over night it started hard again. My next guess would be a fault in the fuel pump. Any suggestions? I'd rather get any input/info that I possibly can..before I blindly have him throw any more money and parts at it! Thank you and keep on Jeepin on!
 

Did you figure this one out? I would have thought the fuel pump as we'll.
 
X2 ( well 3 , actually) on the electric fuel pump. If the filter is not clogged or water logged then a pressure test consisting if cranking pressure and running pressure will need to be performed. You'll want to compare running pressure with fuel,pressure regulator line on and off while running to see PSI difference. Can't get to my books now for specs as my library is constantly being moved from one place to another while interior home work is being done but that's obtainable on line so not to worry. I could say that if your not getting a consistant reading in every attempt to,start the engine , the pump is bad or there is a leak in line or in the tank sending unit connections . I cannot remember if the YJ 's sending unit is easily accessible as is the XJ but if so and you want to take a peek at the rubber hose that connects the electric pump to the sending units metal pressure line for a,rupture , I'd say go,for it. But if you've got to drop the tank , you'll want to be sure the pump,is bad before going through all this labor. If it's the original pump with high mileage and much driving below a quarter tank and lack of filter changes , it may be on its way.
See if auto zone can rent you a fuel pressure tester and try getting readings. Whether a 2.5 or 4.0 , the reading is taken from the Schrader valve on the fuel rail so not a huge hassle of pluming in test adapters like a throttle body . Look for consistency in psi in several,starts/ cranking and psi readings running with/without fuel,pressure regulator line on. Cranking psi should get up,close to running ( 40 psi or so ) but the first reading is what tells how good or bad the pressure is when key turned on and cranking begins. If pressure builds in steps then a restriction( clogged filter), leak or outright bad pump is probable. Let's check this before we start pointing at crank or cam position sensors first. But from your post , priming with the key sounds like fuel pump problems. Please post back when able.
 
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Ok, so after weeks of digging..and traveling up and down every avenue. We (my brother in law and I) caved and brought the jeep to someone..who called someone that is a Chrysler guy. Turns out it was a bad ECM, signal problem I guess. It also turns out that there are none available anywhere! He ended up having to send the computer to Florida to be rebuilt...turnaround time was about three weeks. I will post up more details after I talk to the man in person. I want to thank everyone who took the time to help with the process of elimination though. Every little bit helped!
 

Wow! I'm just seeing this. Both YJ and TJ experience this issue. Typically it is the drain back valve in the pump that fails. The valve does not let the fuel in the lines drain back into he tank. When it fails and it does drain back you end up turning the key on for five sec 2x before starting so the pump primes the system. You can do this until you need to change the pump.

Have you searched the forum or other forums prior to taking it to a dealer or shop? The fix even if you feel it is above your ability you go in with more knowledge.

PCM is a rare failure and there are some tests to verify.

I hope it all works out for you. Post up what you did so far and what you found. Describe symptoms as best as you could.
 
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