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Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
I bought a cheap test kit at Harbor Freight. For my purpose of diagnosing a bad cylinder, it should be good enough. It's not like we're trying to differentiate between 2 or 3 psi, we're going from 152 PSI down to 89 psi. I will see if my local auto parts store has one to rent and test Cylinder #6 again. But for all intended purposes I'm pretty sure my Cylinder 6 is bad.
Also wanted to know what a general price of a valve job would be.
I've bought a TON of stuff from HFT. Some stuff is OK, other stuff I've thrown out before I even used it (like the "titanium" drill set).
Anyway, the 41 PSI fuel pressure at idle may be accurate (or not). I'd get the loaner kit from AZ to confirm that before I started shooting the parts cannon at the fuel pump.
Well cylinder #6 with low 89psi compression is a no brainer but I think I've ruled out all other
possible causes for the multiple cylinder misfire other then the low fuel delivery. What else
could it be?
Have you looked at the Distributor Switchplate/ camshaft position sensor?
Everybody always forgets this little guy. Do not get lost in the weeds troubleshoot one issue at a time. You obviously have a compression issue on cylinder #6, the fuel pressure is a little low but I do not believe it is low enough to cause a misfire on every cylinder. Look at the camshaft position sensor on the distributor., also pull the distributor out and look for a worn gear.
Y'know, all these $20-$60 dollar things are going to add up, as well as time spent. You may want to go and just yank the head and try to figure out the compression problem. If it's a ring or piston problem (valves and gasket look good), and a used engine is an option you're going to get all those parts anyway.
Using a multimeter on the "voltage" setting, hook one lead of the multimeter to the positive (NOT negative) battery terminal and test both pins of the removed injector plug with the other lead while the engine is running. One wire from injector is at 13V, and the PCM periodically shorts the other injector wire to ground to open the solenoid. So on the multimeter (relative to the positive battery voltage), one pin should read at 0V and the other should read a little under 2V. For more info see https://www.cherokeeforum.com/f2/how...cm-95-a-248325.
Can you explain this a little gooder? No matter how many times I read it in my mind the multimeter and the PCM, respectively, both get smoked (although admittedly, most of my neurons, at this point in my life, are smoked). TIA.
I found this for if you were wanting to try and thoroughly test to verify if your Jeeps fuel pressure is really too low.. to see the psi under load.
(copy and pasted): -test fuel pressure at idle with the fpr vacuum hose connected, then disconnect the vacuum hose and hold your finger over it to stop the vacuum leak (still idling) and look at the fuel pressure now. remember both numbers. the higher number (vacuum hose removed) is the one you use to compare to stock spec. -now connect the vacuum hose again and find a way to mount the pressure guage somewhere it can be seen while driving. like remove the hood and stick it in the wiper if it's long enough, or something similar. the more throttle you give it, the higher the pressure should get, and vice versa. basically, you're looking for a drop in pressure as rpms climb. ie: cruise at like 15-20mpg, lock the tranny to 2nd gear, give it heavy throttle and watch the guage; fuel pressure should be near that high number from idle with vacuum removed, and should stay at that pressure all the way to redline. full throttle should be exactly the same pressure as that high pressure at idle, again, all the way to redline. if the pressure drops off at any point as rpms climb, especially if it's a considerable amount, fuel pump is shot.and fyi, a fuel pump can be darn near 90% shot and still provide perfect test results doing the idling test, because idle uses near zero fuel volume, like 99.9% of the fuel the pump is pushing will be just going straight back to the tank. (end copy and paste)
You could ignore that part of the procedure above pertaining to removing the vacuum line.. if you do this test for the psi while driving under a load, since the regulator is not controlled by vacuum.
I have been driving it regularly and have gone through several tanks of gas on a 30 day temp tag.
I have decided to yank the head and get it re-valved at a local machine shop for $200. while that's
being done I;m going to pull the distributer and elvaluate. I defentally have to get the compression
on #6 fixed first. Once back together, I continue to troubleshoot the rest of it. Ill be taking the head
off this weekend and off the the shop on Monday. I'll look at the lower end once I have it apart. I'll
keep everyone informed.
I pulled the head and dropped it off at the shop Tuesday evening. They are going to X-Ray it for cracks and inspect it for warpage before they rebuild it. I should have it back by the end of the week. After I get it back together, I'll continue troubleshooting the multiple Cylinder Missfire problem. With cylinder #6 low compression and misfire out of the way I'll see where I stand.
Well just got the news back from the Machine Shop that the 4.0 head in 96 XJ that I sent out is cracked at cylinder number 6 causing the misfire. Now I'm on the hunt for a new head. Anyone have anything available?
10-14-2019, 04:09 AM
