91 yj driving me crazy

The first thing you should do is buy a code reader like you said. If the computer isn't bad, it will usually tell you what sensor is bad or if there is another problem. I had a similiar problem as you, and it turned out to be the CPS sensor. The only way I was able to determine this was with a code reader. But that isn't your problem because you are getting spark. Buy the code reader before you spend any more money..

-Brent Bogrees '89 YJ 4.0L w/ 33" BFG MT's '94 XJ 4.0L w/ 31" BFG AT's

You said there's a spark, but what you measured was that there's enought pulse in the plug wire to trigger your strobe gun, right? I had a bad coil once (full of water, actually). The pulse was strong enough to trigger my strobe, but not enough to create the spark at the plus that I needed. Unscrew some plugs, lay them to ground and observe the spark. Just a thought... Good luck!

-Kris

snipped-for-privacy@osu.edu (Brent Bogrees) wrote in news: snipped-for-privacy@posting.google.com:

You don't need a code reader on a '91. Turn the ignition on and off three times in rapid succession and the codes will blink out with a pause between each digit. the last code, indicating end of codes is 5-5.

crank sensor??

(CPS) Crankshaft Position Sensor, which counts the flywheel teeth and is mounted on the bell housing...... Just my thoughts, as mentioned in a previous post.

Paul in VA

mike did pass the time by typing:

You have fuel and spark, with those the engine has to start or at least make noise unless the timing is way off.

I think 8 degreed before TDC is where your timing should be. Sure the distributor is indexed properly and the plug wires are going to the correct cylinders?

look at this articles...

ok i checked the cps, it read around 260 ohms the spec is 200 + or -

however i think i need to read that article about 50 times, it seems to be a bit over my head...

my motor is what he refers to as a 'traditional engine', it still has a distributor cap/rotor for the spark, but uses a cps for injector timing... and it seems that the relation between the 2 may be off, or the ECM is processing the readings from the sensor wrong... i do have an extra distributor cap i could make a window in, but im not really sure how to get them back into sync

Thanks for the link serg i think this might be it.., if you could explain the article a little that would be awesome :-)

Thanks, Mike

Did you change the timing chain as a result of something or did this happen after the change?

Could be you now have more than one issue....

Mike

mike wrote:

I had starting problems when I first got my 91 YJ this time last year and it came to be multiple problems.

First crank no spark- changed CPS rig started OK for 3 days.

Again crank no spark-cleaned all grounds especially ground at back on engine to firewall-ground wire was in peices-started ok that day

Again crank no spark- Distrubutor pick up coil? Tried to remove dist broke a bolt and pushed to my local garage for a re-man dist. When I got her back replaced wires plugs and coil- fine starting for a few days

Again crank this time WITH SPARK . Did not have a fuel pressure tester, noticed the vacuum line to the fuel pressure regulator was worn and cracked. Repalced vacum line and fuel pressure regulator did fuel filter as well- Jeep started and ran OK a few days

Again crank with spark-replaced all relays as rig has 120,000 and it was time anyway-for this as well as most of the above. New relays did not help.

Noticed that when I bang on the gas tank rig would start so had mechanic replace fuel pump-rig started and ran fine for two weeks then no start again with spark.

Loose ground by e-brake cable was the cause, I think of all no fuel no start problems. By working on the rig I must have shook the ground wire so she would start. Still have not found which wire put do do know that when the rig wont start now I release the e-brake and she fires right up

Purpose of my post is that you may have more than one thing gone wrong.

ok i got the dash to come back, i inspected all the fuses in the under dash panel and they all looked visually good so i decided to test their resitance anyway... i found that almost all the fuses had a layer of corrosion over their blades, i cleand them with some sandpaper and walla, now i can read my codes....

12 Battery or computer recently disconnected

11 No ignition reference signal detected during cranking (bad Hall effect) OR timing belt skipped one or more teeth; OR loss of either camshaft or crankshaft position sensor. Can cause the engine to stop working entirely with no limp-home mode.

# 55 is end of codes - it's normal. Before you call your dealer or mechanic, consider that the blink-spacing is not always perfectly uniform, so if you see 23 23, it's probably just a single 55. (Codes are not repeated.) # 33 is normal on earlier models if you don't have air conditioning.

ok so 12 i know, and mine is a 91 with no ac so 33 is ok as well

so 11 is the culprit

i just changed the timing chain so i know its not that

the cps is reading the correct ohm value (i measured a new one at the parts store with the same ohm meter)

the cam position sensor when looked up i can't find anything, there is a distributor on this motor which leads me to think that i can adjust the timing like on old v-8s by twisting the distributor counter clockwise to advance and clockwise to retard...

one of serg's postings seems to be the answer although like i said i dont have a simutech or really fully understand it...

i am going to trace the wires from the cam positon sensor to the ecm to make sure a wire isnt failing, there is also a set of wires leading back to the distributor to a harness that may be the 'cam position sensor' i will also trace those wires back

like i said earlier the timing is now at 0 degrees, an earlier post referenced 8 degrees advance so if the wires are good leading to the ecm i am guessing to twist the distributor - is this the right thing to do?

also 11 can mean 'bad hall effect' what does that mean? i looked up hall effect and it has to do with voltage generated on a perpendicutlar wire running through windings that have a current flowing through them - is that correct and how does it relate and more importantly how do i get a good hall effect

Thanks, Mike

mike did pass the time by typing:

Your CPS sensor is a "hall effect" sensor. It can go bad if the sensor is contaminated by metal filings sticking to it. You can see it better on ABS sensors as the fuzzies that stick to them.

This is for the 93ZJ but might help.

Inside the distributor there is a pickup coil and wheel that is used to define the #1 cylinder compression position - the CPS goes around twice for on revolution of the distributor/cam so this is used to completely define the engine position to the computer. On early 4.0 engines there was a problem with the wires breaking where they exit the distributor and I've had the cam position sensor go bad on other engines.

One common problem with the CPS is that the connector up on the firewall gets cruddy and gets to be intermittent - clean that sucker really well then use some dielectric grease to seal out moisture. The CPS is a Hall Effect switch so the fact that it has a resistance doesn't really mean that it is switching. You can check it with a fast ohmmeter (analog, digital is usually too slow) by passing a magnet or just a sizable hunk of metal over the pickup, but by then you have it out anyway. If you replace it, I highly recommend the dealer part - the price is usually pretty close and the quality is much better than the cheap (not inexpensive, just cheap) replacement parts.

Ok, let me see if I got this right...

You have dirty fuses so your dash quit on you. This caused a no spark situation by shutting down the computer.

You then started changing things like the timing chain for some reason?

Now you have the dash and spark working but something is 'off'.

I would be double checking the timing chain.

Mike

mike wrote: