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Model:Wrangler YJ



I want to thank anyone in advance for any help you can give me in diagnosing the problem with my jeep, here is what I have

1991 Jeep Wrangler YJ
6 cyl 4.0L HO, fuel injected
196,000 miles

between this breakdown and the last one a month ago (it was the distributor, stator bracket was loose and elongated)between the problem before and trying to figure out this problem I have replaced:
MAP sensor,
02 sensor,
MAT sensor,
TPS sensor,
AIS motor,
Crank position sensor
Fuel and air filters,
Timing chain gears/sprockets.
I have also:
ē cleaned all terminals and plugs on wiring harnesses under the hood and put dialectic grease on the terminals before reattaching
ē tested all the fuel injectors, all 6 injectors are 14.2 to 14.4 ohms and when cranked I am getting around 5 volts to each one.

The jeep showed no problem when I parked it after work, First thing the morning it didnít want to start, didnít notice anything wrong when I parked it the day before. My gas gage is not accurate so I thought it might have been out. Put a gallon of gas in and after a few seconds cranking it started.

Drove it to the gas station and filled it up, it started right up.
I dove it for about a mile or so, stopping at 2 lights, at the second light it was idling a bit rough and at the 3 light it stalled.
It would crank great, but nothing. Had it towed home

Opened the hood and discovered that one screw on the distributor cap hade loosened up and the cap had raised up on the right side about a half inch or so, took off the cap and inspected it and the rotor, both looked ok so I put it back together, tried to start it, cranked but no start. Figuring it could be the cap or rotor I replaced them with new, same, crank but no start, slight smell of fuel under hood

I did the key diagnostic test and pulled no codes, now or throughout the process of trying to repair it

At this point I checked fuel pump and have 38 pounds pressure at the rail, also checked for spark from coil and spark plugs and have good spark from both. All the vacuum hoses are in place and good. I rotated the engine at the camshaft to TDC and looked where rotor lined up, the rotor as right at the trailing edge of the cylinder 1 post on cap. Fig 1

Fig1 - can post

from what I read in the factory service manual and from the jeep forum lists when the timing chain and sprockets reach this age and mileage it is possible that the chain can stretch enough to jump a tooth, I figured with the distributor cap loose this could be the problem so I opened up the timing cover and the timing chain was stretched beyond the specs for replacing and the bench marks on the sprockets were not quite lined up at TDC, fig 2

fig 2 - can post

I changed the chain and sprockets and all went smoothly, got it all back together and the rotor centered on the cylinder 1 position on the distributor, fig 3

Fig 3 - can post

Thinking the problem was solved I put everything back together and after a few attempts still no start, the next morning I tried again and I did get one small POP from the engine and smoke came from the intake manifold in the first attempt but nothing but crank after that. I tried spraying starter fluid into throttle body and the best I can get is a single backfire out of the intake.

The base ignition is not adjustable; distributor has a mounting tab and canít be rotated. The engine controller/computer board controls the timing so I tried repositioning the distributor back one and two notches in the cam gear to retard the spark but no help.

at this point I thought it might be the signal sync generator or the distributor and since I just changed them last month I took it in and exchanged it, installed the new one, no help.

As an added problem that may or may not be related my transmission now has a slow steady leak now for about 2 days

I have spark at the plugs, fuel at the rail and cranks like nobodies business but it wonít kick over.
Thanks for taking the time to read this, I am ready to pull out what remaining hair out of my head, any help in where to look next would be greatly appreciated



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