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Unread 02-28-2012, 05:51 PM   #1
Digger02
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1990 Jeep Cherokee Problem

ok i have a 1990 jeep cherokee that i cant get to start. It has spark and pulse to the injectors. Theres pressure at the fuel rail. It acts like it will start but it doesnt. Also it fowls the plugs and puffs white smoke at im trying to start it. Any help would be appreciated im at the point of total frustration. Thanks in advance for the help.

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Unread 02-28-2012, 06:13 PM   #2
tjwalker
It's the crank sensor!
 
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1. Is the spark a snapping BLUE spark? Yellow/white/orange indicates a weak spark, which will not be strong enough to start the engine. Usual suspect here is the ignition coil. Your coil can be tested for both primary and secondary resistances with a meter and a manual.

2. If spark checks out (and only IF) introduce a small splash of fuel into the intake or a short shot of starting fluid. If it starts and runs for a short time, you have confirmed a fuel delivery problem. For a 1990, you need 31 psi to start and run the engine. Use a fuel pressure gauge if there is any question.

3. What is the status of tuneup hardware? Importance of this absolutely cannot be overstated. Fresh Champion copper plugs gapped to .035, new plug wires, distributor cap, rotor, fuel filter.

4. Still stuck.....run a compression test on all cylinders. You should have 120-150 psi, with no more than a 30 psi variation between cylinders.

5. Here is a link to an article that shows you how to test many things on the RENIX. Should be a bookmark for all RENIX owners.

http://www.lunghd.com/Tech_Articles/...iagnostics.htm
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Unread 02-29-2012, 07:18 AM   #3
cruiser54
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Aside from what Mr Walker says, check the plastic line that runs from your throttle body to the MAP sensor located on the firewall. No cracks, melted spots, poor rubber connections at either end.
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Unread 02-29-2012, 08:54 AM   #4
Digger02
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ok will try those tonight thanks again guys.
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Unread 03-01-2012, 03:58 PM   #5
Digger02
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OK i tried ether and still wont start. Has a nice blue spark. Have to get a new compression tester the one i have is old. Im still baffled it feels like it has good compression. Could it be the ecm?
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Unread 03-01-2012, 04:48 PM   #6
cruiser54
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Quote:
Originally Posted by Digger02 View Post
OK i tried ether and still wont start. Has a nice blue spark. Have to get a new compression tester the one i have is old. Im still baffled it feels like it has good compression. Could it be the ecm?
ECM is telling it to spark and ether should be ignited by that spark. Not the ECM.
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Unread 03-01-2012, 05:22 PM   #7
Digger02
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ok update got it start. Just unbolted the distributor and advanced the timing. Started. Then put it back in normal position. And it started again. But kicker is it runs real rough. and when it tries to start i can see the distributor wiggling. Kinda wierd. Any ideas on why it runs rough. maybe injectors?
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Unread 03-01-2012, 06:01 PM   #8
tjwalker
It's the crank sensor!
 
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Shouldn't have to do that to start the engine. With the "play" you mention, it might be time to find a salvage yard distributor to see if that resolves your issue.
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Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
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Unread 03-01-2012, 06:41 PM   #9
cruiser54
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Quote:
Originally Posted by Digger02 View Post
ok update got it start. Just unbolted the distributor and advanced the timing. Started. Then put it back in normal position. And it started again. But kicker is it runs real rough. and when it tries to start i can see the distributor wiggling. Kinda wierd. Any ideas on why it runs rough. maybe injectors?
Take care of that distributor before proceeding any further.
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Unread 03-05-2012, 06:05 PM   #10
Digger02
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ok got the distributor issue fixed but now i have a new problem. when i put it in reverse or drive in 2wd mode i get nothing but when i shift into 4wd it will move forward and backward. but when i put it back into 2wd it will not move either way. also it grinds really loud for a second when i shift into park. any help is appreciated. thanks in advance.
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Unread 03-06-2012, 03:30 PM   #11
cruiser54
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You're in neutral in the transfer case when 2wd is indicated. Adjust the linkage.
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