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Axl67

1989 Jeep YJ Wrangler 2.5L With No Spark

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Hello, can anyone please help me figure out why my jeep has no spark. The first 2 weeks after i bought it I had no issues. Then one day I turn the key and it wouldn't start. It'll crank but no spark. I unplugged the sparkplug cable that goes from the distributor cap to the coil only to fibnd no spark. I changed the Ignition Module, along with the Coil but still no spark. The frustrating part about it, is that the jeep can go days without any issues. it'll start up and run prfectly fine. But on the days I needed the most...It won't start. I have the jeep towed home twice in the last 3 weeks. Once the tow truck driver leaves I'll turn the key and it starts right up.

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Ax161...Welcome to the forums.  When the 2.5L runs right, everything is good?  This sounds like the crankshaft position sensor (CPS) not getting a consistent reference signal during cranking.  Whether or not you have rear main seal oil seepage, the CPS picks up oil and debris over time.  Often the device is not defective, just dirty. 

 

The CPS is at the back of the engine on the converter housing or bellhousing.  When you're looking forward, the CPS bolts into position around 11 o'clock.  Remove the CPS without damaging the plastic wire connector.  Clean the CPS with electrical contact cleaner and test the ohms-resistance, moving the wires gently to be sure there is not a wire open.  The test is across the "A" and "B" terminals at the CPS connector.  The test is supposed to be run with the engine hot, although this gets difficult in terms of burning yourself, so be very careful.  With the CPS connector plug disconnected and your ohmmeter leads between the "A" and "B" terminals, you should get a reading of 200 +/- 75 ohms.

 

In addition to the ohms resistance reading, you need a clean CPS probe.  Try this and see if that's the fix.  If not, we'll take it to the next step. 

 

Another general problem area is poor or oxidized wire grounds.  In particular, the engine to body and engine to frame and battery grounds must not be oxidized or loose.  This turns up a lot with the early YJ Wrangler 2.5L.  Check the ground attachment screws for oxidation and resistance.

 

Moses

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