Starting Problems -
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post #1 of 5 Old 08-19-2005, 09:16 AM Thread Starter
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1997 TJ Wrangler 
Join Date: Jan 2005
Location: Guston
Posts: 469
Starting Problems

I'm going to also post this in the Cherokee forum.

My son has a 90 Comanche with the 4.0.
4X4 auto. Long Bed.

Here is the problem.

Last weekend, it would not start.
Turned over just fine. Good battery, but; wouldn't fire.

My first thought was fuel. It had gas. Then I thought fuel pump.
Poured some gas in the throttle body, and nothing. Not firing at all.

I pulled the coil wire from the distributor and did the screw driver test.
No spark.

Pulled the wire from the coil and put it back on. Then it fired.

Ran good for 2 days. Then same thing. He got it started again.
Then 2 more days it did it again. This time, pulling the wire and replacing didn't seem to do it. It finally started, but; after several minutes of screwing with it.

The spark plug wires aren't that old, so I don't think it is the coil wire.
I'm going to put a new one on anyway just to be sure.
If it isn't that what do you think?

Coil? Ignition module? Any other ideas?



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post #2 of 5 Old 08-19-2005, 07:49 PM
Ed in North Ga
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1989 MJ Comanche 
Join Date: Mar 2005
Location: Hiawassee GA.
Posts: 707
usually its the CPS-the crankshaft position sensor, that gives people fits when they have a no start condition. Cute little sensor, mounted on the bellhouseing that tells the computer that the engine "is indeed turning over, add spark".

One of the funny tests/fixes people use, is to unplug it, and then plug it right back in- the theroy behind it is spooky- the sensor is a glorified hall effect style magnet- it sits in relation to the flywheels ring-flywheel turns, magnet senses the gaps in the ring, computer gets the OK to fire the plugs. When the sensor "magicly dies", it, in theroy, lose`s its magnatisim...unplugging, then replugging the connector supposedly wakes it back up....and signals a trip to the autoparts store for 2 new for the glove box, one for the bellhouseing....because there aint no autoparts store around when you only have one...and its bad.....and its snowing....and dark.

Your situation sounds like that....but without testing it, theres no real way to know for sure. You need a good OHMS/Volt meter- they should come stock with the renix jeeps(87-91) because you can test 99% of everything with one-

I`d go by the numbers-even if yours seems like its in a different area, since its more than likely ignition related-
test the CPS, the TPS- check to see if it has a functioning NSS-(nuteral safty switch-)- followed by the ignition box under hood, then on the lower column. The TPS isnt really a factor in starting, but i dont know if a bad one would kill the spark or not. The ignition dosent really go through it, as much as it uses it after the fact.

Once you own a renix for some time, you get to know these areas like second nature- when something go`s wrong, you`ll already know what areas to start testing- thats what makes the renix jeeps so good in my opinion-their easy to test and check once you know the tricks. Its not something super complicated like the newer jeeps with OBD11(and above) supercomputers , nor an old jeep that you need a carburator degree to get to run because the jets are off a hair, and the condensor looks like a roasted mashmellow. You`ll not have to take a renix into the stealership like a new jeep...the sensors are basicly dumb, the code storage is minimal at best, and when things go wrong, you can fix them.

side suggestion- he`s got a 90? check the fuel injectors for leaks- its about time for that to start. Check ALLDATA for the recalls, because I know hes got a few comeing to him if someone else hasent done them yet. Go ahead and put aside money for a new fuelpump if its the original-and a radiator, but think about converting to the open style...

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1989 Jeep MJ- 200,000- 28mpg. If its a Renix, its all good. 1989 XJ (sold) 310,000- 29mpg. Renix. See the pattern?
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post #3 of 5 Old 08-24-2005, 05:57 AM Thread Starter
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Location: Guston
Posts: 469
CPS was the problem.


by the way, what's a renix?
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post #4 of 5 Old 08-11-2012, 07:42 PM
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1987 MJ Comanche 
Join Date: Jul 2012
Location: Harlan
Posts: 168
Reniex refers to the fuel injection system used on the jeep cherokees/comanches 87-90.
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post #5 of 5 Old 08-12-2012, 07:04 AM Thread Starter
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I did get that figured out about 6-7 years ago.
This is a very old post.

90 MJ 4.0 4X4 5sp LB Pioneer Big Ton.
Truck contains parts from 3 MJs, 2 XJs, 1 TJ and a dishwasher.

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Wifes: 97 TJ 2.5 4X4 5sp 31's stock. . . Slow but; reliable.
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