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Old January 23rd, 2022, 09:06
Lost_Wrench Lost_Wrench is offline
NAXJA Forum User
Join Date: Dec 2020
Location: CO
Posts: 86
Re: Fuel Pump Check Valve or leaky Injectors?

UPDATE: Well I'm back to the drawing board. I replaced the head gasket, it took me 14 hours by myself and that was the first one I've ever done so all in all not too bad just time consuming. My old head gasket didn't look bad meaning there were no holes or blemishes that I could see. After putting back together it still ran bad. Long cranking times to start, rough low idle at first, and backfiring. Having a brand new clean exhaust manifold gasket made one thing apparent right away. Fuel was completely filling up cylinder 2. I watched as it slowly became more saturated in front of my eyes. Apparently what I thought was white smoke and condensation coming out of the tailpipe was actually straight gas coming out of the tailpipe. So I switched out that injector with one of the old Chrysler Mopar injectors and the idle immediately improved and sounded normal at 800 rpm. I took it for a test drive and after being sluggish at first it ran great, had plenty of power and was running fine even up to 75 mon, but upon restarting I've got the same old symptoms of long cranking stumbling and backfiring. I did notice that my oil pressure is higher now according to the gauge, I'm not sure if that's a result of the new head gasket improving compression or if I need a new sending unit for some reason even though it was not touched during the head gasket install. It goes all the way to 80 psi at WOT whereas before it maybe went to 60 at WOT. Now for those of you who warned or advised against cheap injectors, please tell me what good injectors are. I replaced my original Chrysler Injectors with cheap Bosch injectors, then went to much more expensive USA made Standard injectors of which at least one was stuck open right out of the box I learned. Should i order a set directly from mopar next? Also, after researching I think my fuel pressure is in question and my fuel pump may be faulty as well. I was getting 28-30 psi on the fuel gauge while idling. But turning the key to "on" only made the gauge jump to maybe 2 psi for a second or two and then drop to zero. So it seems a check valve is faulty since the rail isn't staying primed, or I have 1 or more stuck open injectors. I've still read conflicting information regarding the correct fuel pressure for a '96. I don't have a pressure regulator on my fuel rail so it's on the pump assembly. Apparently these are supposed to have 39-49 psi, while the ones with the regulator have 31 psi and both types were made in 1996. There are a lot of things I could have done different or better to this point but I'm still at a loss for the most part.
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