I recently picked up this '90 XJ 4.0L as a driveway plow/bush truck and it ran fine aside from an oil pressure issue. I pulled the dizzy to check the oil pump, and reinstalled it. After reinstall, it ran like crap so I figured the distributor must be a tooth off and I'd just reset it. I fixed the oil pressure issue but now it won't run.

I took the dizzy out and put in back in about 10 times and it won't run on its own at all after the second removal. I tried setting it a tooth forward, a tooth back, 180 out and completely reset the timing by setting #1 @ TDC on compression, aligning the timing mark to 0* and setting the dizzy rotor exactly at #1 with the cap more than a few times.

It WILL NOT run by itself, however, if I spray a ton of throttle body cleaner down the intake, it'll run great til it runs out of TB cleaner. The timing mark location looks good when cranking with a timing light and the spark plugs will arc to the block.

I originally got the truck because of a leaky injector causing that owner to think he had a head gasket problem, so I suspected a fuel pressure problem (eventhough it ran great before dizzy removal). I took out all the injectors, cleaned them, cycled them in cleaner and o-ringed them. They all audibly open and shut as commanded.

No apparent leaks, and if you cycle the fuel pump with the schrader open it sprays good. If you cycle the key a couple times and open the schrader, pressurized fuel comes out. I plan on getting a gauge on it tonight to test fuel pressure, but I'm just having a hard time believing it's a total fuel pressure problem when it won't even sputter on its own fuel.

As I just got this truck, I'm not familiar with all it's systems. How is cam position determined and how are the injectors fired? If I screwed up my injector timing by messing with the dizzy, how can I reset this?

Any other suggestions? Any help is appreciated as I have way too much time invested into this beater truck.

 

clean the connector on the dist plug that connect to the module in the dist

 

I'll double check for bent or loose pins in that connector. Does the distributor have a sensor that tells the injectors to fire?

 

Yes, the Cam Positioning Sensor.

 

Is the cam sensor under the rotor? Any idea how it works or how it is timed?

 

That would be it, and honestly I have no idea I have never replaced one yet.

 

it send a signal to the ecm when the injectors should fire the litte rond pc break the contacts when it turns sending the signal

 

I'll have a look at the cam sensor as well to ensure all looks good. What kind of signal does it send so I can check for it?

If there are no apparent connector concerns and circuitry checks out, I'll try swapping with a known good dizzy after making sure fuel pressure is good. I think my buddy has an extra distributor.

Thanks for the info guys. It's hard to find in what limited publications are available. Any additional input is welcome as you guys are much more familiar with this motor than I am.

 

Fuel pressure is 40 psi cranking, so that looks good. I had a look at the sensor under the rotor, looks like a stander hall effect sensor.

The dizzy 3 wire connector pins look good and fits seem fine. The 3 wires, black, violet and grey/black from the dizzy sensor connector have 1 ohm resistance throughout the harness.

Does anyone have wiring diagrams for these? I'm trtying to think of anything else as the only thing messed with was the distributor. At somewhat of a loss right now til I can find a known good distributor or some good diagrams.

 

Just following up on this with the fix information. Believe it or not, it was bad gas.

After verifying many times the ignition timing was correct, fuel pressure good, compression good, and injectors firing in the correct sequence, there was nothing left in the engine bay to test. The thing ran great on throttle body cleaner so all that was left was fuel.

I drained the tank and the stuff that came out wouldn't even burn. The truck ran good before I messed with it but didn't after diagnosing a bit. Maybe there was water in the very bottom of the tank. New gas in the tank and it runs great.