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CherokeeManatee
April 27th, 2012, 20:39
I've put off starting a new thread but am unsure where to go from here.

1993 4.0 Manual

It ran fine one day and the next it did not start.

-I have fuel pressure as shown by the fuel gauge and the fuel rail squirts when I depress the nozzle.
-I have a spark at the spark plugs (test 2 of them and both sparked when cranked) - Didn't look at the color so I may have to do that again.
-Inspected all the wires I could find and didn't find any in horrible condition.
-Fuses all checked out in the engine bay.
-After sitting for a while and lots of cranks my battery is low. 12.5V sitting and 11.3V cranking.



When I turn my key 1 click before cranking I hear the normal clicking and slight whine of what I think is the fuel pump getting ready. Whatever that noise is, it is normal.

At the advice of two friends and many threads here I replaced the CPS without any results.

My next step is to jump the vehicle since I think it doesn't have enough juice to start.

Any advice?

Keithmania
April 27th, 2012, 22:15
I have come across similar issues in the past. Could be your battery, but I'd also check your grounds, XJ's aren't known to have the best grounding system in the auto world. Might also consider your TPS as well.

GrimmJeeper
April 28th, 2012, 12:26
x2 on grounds, most likely culprit is the one on the passenger side of the block by the oil filter. take it off, clean the stud off good with a wire brush and sand the terminals on the ground wire and the surface on the block clean.

birchlakeXJ
April 28th, 2012, 14:20
1. Spark color matters. Check it again. You must have a strong, BLUE, snapping spark. Yellow/orange/white indicates a weak spark (usually a bad ignition coil).

2. You need 31 psi for the engine to start. The only accurate way of determining if you have that is with a fuel pressure gauge. Can't tell that by watching it while depressing the schrader valve.

3. If spark is good (and only if) try introducing a small amount of gas into the intake...or a shot of starting fluid. If the engine starts and runs for a few seconds with this technique, you have isolated a "fuel delivery problem".

4. Best to get a battery charger on your battery for an extended period of time before trying to start. If you have a weak battery and the engine won't fire because of it, you can easily flood the engine and that just makes troubleshooting your original problem that much more difficult.

CherokeeManatee
May 1st, 2012, 03:05
Thanks for the input guys!

I got a hold of a battery charger. My next step will be to fully charge my battery, check the color of the spark, shoot some starter fluid in the intake.

I'll report back with results.

CherokeeManatee
May 1st, 2012, 19:33
x2 on grounds, most likely culprit is the one on the passenger side of the block by the oil filter. take it off, clean the stud off good with a wire brush and sand the terminals on the ground wire and the surface on the block clean.

Would a bad ground cause the vehicle to not start one day after it was working the previous one?

Just finished messing with the jeep:
Battery is good.

Starter fluid had no effect so I guess it's not a fuel issue.

Spark plug had a blue->white with a reddish hue spark coming from it...I'm not too good at telling the color on these things.

Here's what the plug looks like:
http://i293.photobucket.com/albums/mm76/sirlaughalot146/4x4/Jeep/Misc%20Parts/6fce7d73.jpg

old_man
May 2nd, 2012, 06:10
The plug isn't horrible but could use a hotter heat range or maybe you do a lot of short trips. The discoloration could be cause by running cold or crappy gas.

Personally I would throw in a cheap set of Champions (thats what the 4.0L's seem to like). The plugs are not what is causing your problem from what I see, but the plugs will pay for them selves because they are so cheap.

After cranking do you smell any gas smell if you sniff the tailpipe? You should. If not I would be concerned about a loss of injector drive. It comes directly from the ecu but don't jump on the ecu too quick as there are common problems in the wiring. See if you can snag a noid light to check out the injector.

CherokeeManatee
May 12th, 2012, 14:24
Noid light tested - injector flashes each turnover (as I think it should).

Smell of gas at tailpipe.

CherokeeManatee
May 16th, 2012, 18:44
Ok I'm at a loss at where to go from here. A recap of what I have done:

Fuel:
-Gas at tailpipe.
-Noid light flashing when cranking. Used a GM PFI noid light.
-Starting fluid in intake produces no change in cranking sound.
-Removed spark plugs and aired engine for a day to evaporate any leftover fuel.

Electric:
-Spark at all plugs.
-Found 1 rusted/corroded wire and distributor point - replaced wires, cap, and rotor.
-Applied Dielectric grease to numerous connections in the engine bay.
-Replaced CPS.
-Checked all fuses (found out that my horn one is blown!) and switched around relays - all good.

The only ground I can find is the one near the oil filter - it looks OK (not great) but can this prevent the engine from starting?

Friend mentioned the timing chain may have jumped a tooth or something. My distributor spins (looked at it while engine cranked) but is this something I should consider or diagnose further?

What other sensors should I look at? Anything I should recheck?

Thank you all for your help!

birchlakeXJ
May 17th, 2012, 04:07
Did you test your ignition coil yet? Gotta do that. Marginal spark is often caused by a failing coil.

Flyfisher
May 17th, 2012, 11:44
Three essentials for engine to run, spark, fuel, and compression. Seems you've got spark and fuel, have you checked compression?

It may seem odd, but a badly flooded engine can wash the cylinder walls and leave a lot of gas in the oil pan. The gas prevents the oil from assisting with good compression. Check the oil dip-stick for a gas smell. If you smell gas in the oil, an oil change might just fix your no-start problem.

Don't laugh, I've seen it work on several occasions. Putting a little oil directly in the cylinder (via spark plug hole) will also boost the compression.

Worth a try, and cheaper than throwing parts at it.

CherokeeManatee
May 29th, 2012, 19:49
Turns out it's the ignition coil! I tested all the plugs except this one. Thank you all for your help.