RENIX = Trash

[Djmack]

Sorry if I offended anyone.

Anyway, I'm currently deployed right now. I dont know if any of you remember me saying at SierraFest last year that i have a 1990 White XJ. Well, it's sitting right now waiting for me to get back and do something with it.

The problem: Currently i have swapped CPS(Crank pos. Sensor) plugs, wires, Ign. Coil, and resealed the entire top end (Head gasket, valve cover gasket, exh/int gasket). After resealing it, i went to start it up, It took a second to play with the adjustment of the distributor, but it started and ran with out flaw. (Note: I did all the work to clean the grime and grease off. The last owner did not maintain it.) So, i got all excited, decided it was late and just cleaned up to finish putting everything together the next day. Next day rolls around, I was curious if what i did continued to work. So, i went in to start the jeep. It turned the engine with either no fuel or no spark. If i remember correctly, both were intermittent at any time.

So, im just sitting here in the desert trying to figure out cheap ways to fix it. Could it be the computer? Could the CPS be 1/100 of 1mm off? I have removed and refreshed all ground and Positive connections to the block, body, starter, etc.

The interior has been gutted and cleaned from top to bottom. It is a bone stock cherokee, and im just trying to get it running right and sell it. This would be an awesome daily driver with new shocks and brakes.

Help me yall.

 

[Mike1331]

So it cranks but no start?

In this order i would;

check fuel pressure at rail

check spark at each wire with a spark tester or unscrew and ground plug while cranking

check resistances of cps tps cam sensor at dizzy while both cranking and non cranking with ig. on.

 

[SacXJguy]

Just throwing out a random Idea, If theres no crank, Maybe your NSS crapped out? If that isnt the issue its good to clean it anyways. Try starting it in neutral, also check to see if your reverse lights come on. You could have a gunked NSS. It's easy to open and clean.

 

[5-90]

So you have crank, but no start, right? (It's an important distinction.)

There was a TSB out about a weak CKP signal getting back to the ECU - the fix was to wire it directly. Does anyone here have a copy?

I don't recall if the CKP output can be read with a DMM, so no advice there. If the CKP is off slightly in one direction or the other on the bracket, that just plays with timing. If the CKP is out along its axis (flying height changed,) that can affect signal - I'm not sure what the actual flying height of the CKP tip is.

Extremely Stupid Question(tm) - You didn't use an HO CKP and adapt it, did you? That won't work - the two sensors work on different principles...

 

[Bigbadduck]

You can use a ddm to check a ckp, a cold engine you should have anywhere between 222 and 285 ohms. Also when when cranking the engine you should a voltage output over 4 vdc. But that doesn't should like your problem, you possible have a ground issue. Check your ground from battery to engin block at oil dipstick mounting bolt and then from valve cover to firewall. Check out cruisers54 thread on renix ground refreshing I think this will take care of your issue.

 

[moparmansfield]

I had a similar issue in my 89 mj. A wire came loose in that stupid fuse or relay box on the left side of the motor. I'd get ahold of a wiring diagram and check those out

 

[Djmack]

Re: Re: RENIX = Trash

You can use a ddm to check a ckp, a cold engine you should have anywhere between 222 and 285 ohms. Also when when cranking the engine you should a voltage output over 4 vdc. But that doesn't should like your problem, you possible have a ground issue. Check your ground from battery to engin block at oil dipstick mounting bolt and then from valve cover to firewall. Check out cruisers54 thread on renix ground refreshing I think this will take care of your issue.

As previously stated, ALL ground connections have been cleaned, cleaned and cleaned.

 

[Djmack]

Re: Re: RENIX = Trash

So you have crank, but no start, right? (It's an important distinction.)

There was a TSB out about a weak CKP signal getting back to the ECU - the fix was to wire it directly. Does anyone here have a copy?

I don't recall if the CKP output can be read with a DMM, so no advice there. If the CKP is off slightly in one direction or the other on the bracket, that just plays with timing. If the CKP is out along its axis (flying height changed,) that can affect signal - I'm not sure what the actual flying height of the CKP tip is.

Extremely Stupid Question(tm) - You didn't use an HO CKP and adapt it, did you? That won't work - the two sensors work on different principles...

To confirm, I have crank, intermittent start. Some days it will start, most days it won't. And yes it is the proper CPS.

When it does start and run, it seems to do so flawlessly. I'm at a loss. Maybe the sensor gap is just a hair farther than it wants.