1992 4.0L cherokee turns over but will not start?? - JeepForum.com
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Unread 01-13-2008, 05:26 AM   #1
spanish_lad
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1992 4.0L cherokee turns over but will not start??

hi all, i'm new here, bought a cherokee limited 4.0L a little while ago and its been sweet.. till last week.

mum drove it down to a friends house in the country, they went out to the shops in the friends car, came back and she started it up.. it ran fine for a minute or so at idle...then cut out... and now it wont start again??

i've tried jump starting it, it spins fine but wont fire.. so i started to investigate - it seems there is no spark at the distributer? i've checked a few things out, looks at a few plugs etc, check connections...i really cant see anything wrong with it?

anyone got any ideas? someone said it could be something to do with the relays - i've swapped the auto shut down relay with one of the others so its not that. the fuel pump comes on when you turn the key to acc, theres fuel at the rail...

what could of failed like this to make it not start again?

everyone i talk to says its gonna be the crank position sensor, but i was told to test this it would show a dead short at the connector plug on top of the engine, and it does. could it still be broken?

please guys, looking through the forum you seem to know what you are talking about.. this is a daily driver not a toy and we are stuck without it

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Unread 01-13-2008, 06:33 AM   #2
balloo93
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Does the fuel pump prime?
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Unread 01-13-2008, 06:42 AM   #3
tjwalker
It's the crank sensor!
 
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How did you determine that there is no spark?

I'm not sure if this is the spec. for all years on the crank sensor, but the spec. I've seen says you should see 200 ohms, plus or minus 75 ohms. Without the crank reference signal, your XJ will not start.

Also related to a no start, no spark condition could be the camshaft position sensor (also sometimes referred to as the pickup coil or stator) which is located inside of the distributor. And don't forget the coil itself and coil wire. There is a spec for coil resistances and you can check them with a meter which it sounds like you have. Replace distributor cap and rotor if you haven't done so recently.

Some things to think about. Good luck and post back what you find!
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Unread 01-13-2008, 01:53 PM   #4
spanish_lad
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baloo93
Quote:
Originally Posted by spanish_lad

anyone got any ideas? someone said it could be something to do with the relays - i've swapped the auto shut down relay with one of the others so its not that. the fuel pump comes on when you turn the key to acc, theres fuel at the rail...
tjwalker i pulled a plug lead and put a spare plug into it (new) laid it on the block (somwhere earthed) and there was no spark what so ever. that right isn't it?

mums been without a car now i've cliped the exaust on something and battered the engine mounts on my coupe, i need to sort this

i heard something about the cps, and as well about the computer having some random screws touching the board so it shorts - it was on ask.com i think.
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Unread 01-13-2008, 01:57 PM   #5
spanish_lad
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Quote:
Originally Posted by tjwalker
Also related to a no start, no spark condition could be the camshaft position sensor (also sometimes referred to as the pickup coil or stator) which is located inside of the distributor. And don't forget the coil itself and coil wire. There is a spec for coil resistances and you can check them with a meter which it sounds like you have. Replace distributor cap and rotor if you haven't done so recently.
er.. isn't the cps on the crank / gearbox / engine ?
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Unread 01-13-2008, 05:11 PM   #6
tjwalker
It's the crank sensor!
 
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The way you tested for spark should be fine.

Crankshaft position sensor is located on the bellhousing, drivers side I believe. Use the SEARCH function with the term CPS* (needs to be 4 characters) to get more information on testing/replacement. You really do need to check out the resistance of your crank sensor as it is probably the single most common sensor failure on the XJ.

Good luck....!
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Unread 01-13-2008, 08:27 PM   #7
spanish_lad
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i believe that to test the cps it should have a dead short over pins one and three, which mine does, indicating that it is fuctioning correctly? assuming i'm testing the correct plug? i think i am, back of the engine bay, on top of the inlet manifold, behind the throtle position sensor?

not been able to go down to the car today (its parked up 10 miles away ) i dont want to go in and blindly replace parts that dont need replacing !

is there anything else that can cause cutting out / non starting apart from the cps? i'd like to iliminate things as i go, if i can.

yes, i do have a electrical tester, i'm a spark (domestic electrician by trade, well, apprentice, but i still have all the tools :lol: )
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Unread 01-13-2008, 09:59 PM   #8
von_marko
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I have a 1990 4.0 limited with 340,000 miles on original engine. Since I bought it new in 1990, I've had several "turns but won't start" problems. All with different fixes.
1. The Crankshaft position sensor. It is the 4 pin connector at the back of the intake manifold. There are only 2 wires leaving the connector that go down toward the bell housing. Check these 2 wires with an ohm meter, reagrdless of what pin numbers you have been told. There should be about 200 ohms on a cold engine.
2. Bad wires at the ignition switch on the steering columb. Turn key to "ON" position and stick a flat tip screwdriver into the.... nevermind, to hard to explain.
3. Alternator - Remember the battery is for turning the starter only, not running the engine. Stick a test light or DC Voltmeter in the alternator output wire while someone tries to start the engine.
4. My 1990 model has a ignition control module that sits directly under the coil.
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Unread 01-14-2008, 04:37 AM   #9
spanish_lad
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so von_marko, are you saying that you have had four seperate instances of "non-starting cherokee syndrome" and its been 4 seperate problems?

blimey, theres more to check than originally i'd thought.

how can i test numbers 2, 3 and 4 ?

bad wires, i'd guess remove the steering column housing and give the wiring a wiggle while trying to start it?

alternator, what voltage should it be putting out? as you say stick a test bulb, i'm assuming "any" voltage is good?

how can i test the ignition control module? should there be a certain voltage coming out of it?
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Unread 01-14-2008, 07:58 AM   #10
tjwalker
It's the crank sensor!
 
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Don't waste any more time before checking the CPS at it's source location on the bellhousing! If you're trying to intercept it, you could be missing a wiring problem. No shortcuts here. Gotta get underneath. From your posts, it sounds like this has not been done. Look for 200 ohms plus minus 75. You are really spinning your wheels until you eliminate this sensor as a possibility.

There are two camps of XJ owners. Owners that have had the crank sensor fail and owners that are GOING to have the crank sensor fail!

The crank sensor is located on the upper flange of the transmission bellhousing at the rear of the engine on the Drivers side. Held on by two Hex Head bolts and it is easy to see from underneath, but a little tricky to get a wrench on it. A long extension and a Flex/U-Joint type socket works if you need to replace.

Other possibilities:
*Your camshaft position sensor located inside the distributor
*Distributor cap or rotor (just replace them, they are CHEAP)
*Your coil (check resistances primary/secondary)
*Your coil wire

These are some common reasons for Jeep crank but no start IMHO.
If you are an electrician and therefore know your way around a meter, then you should be able to eliminate the crank sensor, wires and coil as suspects in a few minutes.
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Unread 01-14-2008, 09:50 AM   #11
spanish_lad
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ok then, sounds like a plan. i was going to change leads, dizzy cap and rotor as a matter of course, so i'll probably do that and then change the cps as well.

sounds like these crank position sensors are a right pain in the ***. i have been under the car and it is a nightmare to get to - my coupe is a transverse engine and you can unplug the sensor with one hand while holding the bonnet open with the other lol

ok, so onto my next question. where do i source "cheaper" parts from. not cheap as in bargin basement but over here a set of leads is $35, is that about the same as the usa? not sure about the cap and rotor prices yet.

and i have been looking for a cps as well online, the ONLY one i have found, for the same year as mine is $95, second hand!! surely they cant be that expensive?
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Unread 01-14-2008, 10:32 AM   #12
tjwalker
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Wires cap and rotor first sounds reasonable as it sounds like your XJ might need them anyways.

Yea, the crank sensor isn't exactly easy to navigate but you can do it. As far as sourcing parts, I can't help you much on that as I generally don't order them. $35 for wires is not a bad price. I have my own source who gets me all my Jeep parts at his cost. He is a good friend who has saved me some pretty big coin along the way.

If you find that you need to buy a crank sensor, DON'T buy a second hand sensor! That's like buying used underwear which isn't exactly a good idea, agreed? I personally like OEM sensors; they may cost a bit more but cost is only one part of the equation. In the U.S, I think Cherokee crank sensors are maybe around $100 U.S. give or take a bit.

Post back what you find out!
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Unread 01-14-2008, 01:45 PM   #13
collkid
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CPS CPS CPS CPS CPS


Yeah there like $70
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Unread 01-15-2008, 01:02 AM   #14
spanish_lad
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out of interest..

how long is the "centre pin" of the distributer cap? ie: how far does it go down into the distrubuter? only reason i ask...every other one i have done, the pin is about a half inch long, and sprung. the one in the cherokee cap is only about 1/8th" long, and solid.

could be something as silly as the cap is not touching the rotor !
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Unread 01-15-2008, 11:23 AM   #15
spanish_lad
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ordered a new rotor, cap, and leads, and a cps today..

the rotor and cap are pennies..

the leads, like i said, are $35...

the cps is $42 !!

ok, so it is going to be non-oem, and perhaps not as "good" as a jeep unit, but if i change it and it gets the jeep going, fine. if i change it and its not that, i'll have a spare

we shall see on the distributor tomorrow
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