The Diagnosis
Ah my sweet sweet summer project, what a project you have become. Today I change, test and re-test everything. Maybe this post should be called “The do-over” because I put so many of the old “known good” parts back on trying to track down an unusual problem. As an old painter I know once said:”You know we did it right ’cause we had to do it twice”. This is the Free Model T.
The symptoms: a high rev bog and a long crank time to start. The jeep idled great and revved and drove well but the exact instant I hit 3500 RPM it would bog all the way down to idle. The idle was fine but it stalled if I touched the throttle. If I turned off and restarted it, the Jeep would run great- until I hit 3500 rpm again.
The first thing I did was check for flash codes by quickly cycling the key on-off-on-off-on (as a 1995 model this jeep is OBD 1). The only code was for the front 3 fuel injectors. Easy! I had already reconditioned and tested the old injectors so I checked for proper fuel pressure and installed the old injectors.
Nope. Same problem.
I suspected I may have messed up the idle air control motor so I checked that and the manifold absolute pressure sensor next by swapping for the good ones on Patient Wife’s jeep. Thanks wife.
Nope.
Maybe it was a clogged catalytic converter, ruined o2 sensor or fouled plugs from burning off the assembly lube. I checked exhaust pressure at the o2 bung (only .5 psi) and looked at the plugs. I ran it with the o2 sensor unplugged in case it was shorted.
Nope
Shorted air temp sensor? Coolant temp sensor? Bad coil? Messed up crank position sensor? Cam sensor?
No, no, no, no, no.
Timing? Hmmmm.
This distributor has an allignment hole through the rotor and into the body.
It was extremely close but not perfect. Because the distributor can only be installed in one position and cannot be rotated I figured I had it in the best spot. If I changed the distributor 1 tooth clockwise or counter it was way off. After carefully studying the position of the 13 teeth on the drive gear in relation to the roll pin holding it on I hypothesized that the gear was installed 180 degrees out.
Look how the splines line up differently with each side of the roll pin.
Could it be? Could my brand new
distributor have been assembled incorrectly? I would have checked it against the old part except I removed the gear to turn it into an engine oil priming tool in my Last post!
I ran to the O’reilly and checked the 2 they had in stock for allignment. The new one they had was the same as mine. The remanufactured one was opposite AND had marking compound on the gear and body showing me that someone had taken proper alignment into consideration. I was sure now the gear was the issue.
I took my already-clearcoated part back home, pressed out the roll pin, spun the gear and put everything back together. The allignment hole was now PERFECT. I reinstalled all the new parts that I had removed during the testing and hit the freeway where my hapless herp-a-derp-Jerp promptly bucked a couple times and died. Praise God for AAA.
My first tow in YEARS. The next day I shot some starting fluid down the intake and cranked it. Nothing. If it was a fuel issue the engine would have started momentarily. I tested for spark and had none. I assumed the crank sensor had bitten the dust because they’re a common failure item on these and I had loaned it to a friend to help diagnose HIS jeep. Also I had to notch it slightly to get it installed because my resin filled motor mount mad the engine sit slightly higher.
If it were indeed the crank sensor I would have no spark but also no injector pulse. I don’t have a noid light set so I tested for power and ground signal to the injectors with a test light. I did have injector pulse so I went to the coil. I checked all the connections and the jeep started but if I even breathed on the alternator/coil wiring harness it would stall. After peeling back the loom and seeing the condition of the harness I pulled the whole thing out.
After cutting, soldering, shrink tubing and fixing some plug-in connectors I tested all the wires with my trusty meter and reinstalled the harness. After a bit of wiggling I discovered that the jeep would stall only when pushing straight down on the coil plug-in. I pulled that plug apart one last time and gave the female contacts a tiny crimp. Problem solved. No amount of wiggling stalls the motor now which is good because this jeep is going to see A LOT
of bumps.
Until next time Rustlovers: have a bumpy ride.
