cranks, starts, dies

87 MJ, 4.0, AW4, RENIX, 135k miles, beater pickup

Basically it starts fine and idles for about 3 seconds then dies. Then it won't start again until I wait a long time (like the next day). But... If I start it up and rev it to around 2-3k, it will stay running just fine until it goes back to idle, then it dies. It seems like an electrical cut off in that it just cuts out, no sputter or anything.

Once it dies after the first start, it won't start again for at least 1/2 hour, probably more (I give up and try again the next day), it just cranks.

Fuel pressure is good (checked w/gauge)
No ballast resistor that I can find
Pulled the idle air controller and cleaned it off w/solvent
haven't checked battery voltage, but it seems to crank fine
It sat for about 3 weeks in Dec w/o being started, in the freezing cold

Not sure if it has anything to do with it, but in here in CT most/all gas is now E10; my first thought was the fuel filter was clogged. But the fuel pressure is fine.

Any thoughts before I start throwing parts at it? I am thinking ASD relay (or whatever its called), coil, ecu, ???

And yes I searched first, and read a bunch of posts with similar, but not exact symptoms.

Thanks

There should be a ballst resistor, it should be on the drivers side inner fender. White plastic piece with one wire going in, one wire going out. If you find it jump a wire over it and see if it will run, if it does replace it. Have the battery load tested, it can have enough volts to crank it, but not keep it running.

Check your battery voltage. my jeep would crank all day but it would not idle. I load tested my battery and found it would drop to 6 volts at half the load it was rated for. The engine managment sytems usually require 8 volts to run.

Yup, ballast resistor (you DO have one) and weak battery are suspect. Verify those two things first.

First thing I would do with ANY RENIX rig is take the 2 wires off the balast resistor and splice them together. That thing is a waste of time. Its just there because the yuppies who bought XJ's back in the day didnt want to hear the fuel pump.

Had the same issue with my '89 4.0. I had been tinkering on the acc. wiring the previous day and had bumped one of the connectors on my ballast resistor just enough to make it look like it was connected, but wasn't. As soon as I found and fixed it, it ran perfect.

ok I looked again and I can't find anything looking like the ballast on the driver side inner fender. There's just a relay I think for EGR. Anyway I just pulled the battery, and will get it tested tomorrow. Before I pulled it, I tried starting it w/jumper cables attached to my running XJ. My thinking (maybe wrong) is that if its the MJ battery, attaching it to the good XJ would get around that. Solid cranking, but no start at all. So I tried again w/o the jumpers, still no start. So now its a "cranks, no start". Hopefully just the battery, but we'll see...

does it have spark? - how about throwing the battery from the running vehicle in it quick and give it a try - I bet the cps is bad - anyone second that notion?

Battery checked out ok. Still can't find the ballast resistor, I had read that some 87's didn't have one, it was installed as a recall. Anyone have a photo of where it should be?

Anyway I can hear the fuel pump running, have fuel pressure during the crank that holds steady after cranking stops, plus I can smell gas after cranking for a bit. I'm guessing no spark but I'll have to check that next. Its probably time for the part replacement game to begin... So I'll start with the CPS - bought one today from Pepboys - $30. Will try to get it swaped out soon, after I check for spark. Any other thoughts??

ok I started to swap out the cps and realized how much of a PITA it is. So i decided to check it w/the multi meter first before i got too far. It reads 180+/- ohms across the 2 leads, which I believe is in spec.

So my question is - can a cps be in spec (200 +/- 50 ohms per the RENIX manual), and be bad? I don't want to go thru the hassle of pulling it out if I dont need to.

oh, and since I cleaned the idle air valve and put it back, it doesnt start at all. Just cranks...

1987 MJ RENIX

also just to eliminate things:

I assume if I have pressure on the fuel rail, its not the fuel pump, pump relay, or other such things, correct?

Ok, battery is fully charged and load test is passed.

Have you renewed all the B+ connections and all of the grounds, including those at the back of the head and the dipstick tube?

Do you have spark?

no spark. still checking connections...

If you have renewed all of the battery connections and grounds, and no spark, I would replace the CPS even if it tests good. Sometimes they test good but are too weak to trigger due to the gap between the CPS and the flywheel/flexplate.

Finally got some good weather to work on this some more. So for anyone still keeping score:

Swapped the CPS, still nothing. Next I tried swapping out the coil/ignition controller unit, and it started right up, idled no problem, and seems to be fine now.

dont know if yours has an alarm, but on my 92 if the battery died or got disconnected mine would do the same exact thing. the problem was the alarm. i would have to close all the doors, lock it with the key, then unlock it and it would start right up after that.