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New engine, started initially, now won't.

X

xj2win

NAXJA Forum User
Location
MonTana
Working on a 92 Xj with 4.0 and 5 speed.
Like the title says, my old engine was experiencing a massive amount of blowby so I bit the bullet and bought a new one. Got everything reinstalled, timed it, and fired her up. It started right away and I hopped out to look over the engine bay. In total it idled for about ten seconds and then died. I let it sit a few minutes and started it again, gave it gas this time and kept it at 3000 rpm. Ran for about 30 seconds and started smoking out of the engine bay quite a bit. I shut it off, and haven't been able to get it to start again. I checked the distributor - there is spark. Checked the fuel rail - there is pressure. I did a WOT test to try and get it to start and it wouldn't. Any other ideas what it could be? Crank position sensor? I also did a voltmeter test on the #1 injector, and it was receiving 5.xx volts, I figured that would be plenty for injector pulse.

In hopes of eliminating some canditdates, here's all the new stuff that went in with the engine:
-coolant and oil pressure sensors (did cluster swap also)
-thermostat
-cap, rotor, plugs, wires
-fuel filter and fuel pump
 
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Whenever I change a engine and have problems, the first thing I do is go over the procedure agian and check everything, becuse I will after it fires and runs anyways. It sounds like crank sensor to me as well, although I've never had a crank sensor problem in a Jeep, many people have.
 
It's easy to damage a crank sensor when you install a motor, now I know that you said that you have spark and injector pulse so that means that the sensor is operating, but if the sensor bracket is bent it will thow it out of alignment and screw everything up. Just shine a bright light down there and see if it looks even the slightest bit damaged.
 
The sensor is a magnetic pickup, and the flexplate has a ring behind the teeth with notches in it. 3 long notches and many many short notches. This ring passes by the sensor telling the computer where the engine is positioned (long notches) and how fast the engine is running (short notches)
 
Well thanks, I'll go pick up a CPS tomorrow and hope that it runs. This project is getting more expensive by the day!
Also, I tried to do the CEL jump with a bulb I tested to make sure it was good, but no codes came up. Does the CEL typically come on when the key is in the accessory position before startup? I can't get mine to come on at all. :dunno:
 
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I agree with the advice to go over everything again, especially everything electrical. Are you certain all the injector connectors are in the correct order? All sensor connectors AND GROUNDS connected correctly and tight? All vacuum lines connected to right spots? Have you tested your IAC and TPS to make sure they are working correctly?

Where was the smoke coming from and what color? I consider it normal for some smoking from the engine bay after I've done serious work, as there is usually some oil on the exhaust manifold that needs to burn off.
 
Definitly check the CPS, even if your is ok it doesnt hurt to have a trail spare. IAC, (idle air controler) i would check that clean it and check it again. if you were getting that kind of blow by it is probably full of crud.
 
Going to go test and clean the IAC and TPS. I was under the impression that it would not give spark at all if the CPS is bad. The smoke was white, from near the manifold seal near the #6 cylinder. Checked the gasket and it was tight, it is possible that the manifold got cracked from pulling it out of the way when installing the engine. The engine had good vaccuum, and I'm confident all the lines and electrical connections are correct, I diagramed them all when taking it apart and have re-checked them several times over. It was a low-optioned sport, so there isn't much to check.
 
Just to update this, I cleaned and tested all the sensors on the intake manifold, got a fuel pressure gauge to make sure there was enough pressure, and everything seemed ok. Finally ended up resetting the timing, moving it forward one tooth on the dizzy and it ran. Seemed to have trouble starting, so I pulled the engine control fuses and am letting it sit to hopefully reset the ECU so it can re-learn the new engine when I start it tomorrow. I guess the computer was able to compensate the fuel and injector pulses to keep it running for a little while before.

I'll post up some pics when I get them uploaded later this week.
 
Had to fix a squeaky idler pulley bearing and it won't start again, no spark now. :bawl::bawl::bawl:
The guys at NAPA are getting to know me pretty well. :banghead:
 
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