Ignition Coil?

When a coil go bad, does the engine shut down without a warning?
My XJ stopped yesterday as sudden as if the ignition is turned off. I was at about 45 MPH. I cannot get it to restart.

I threw parts at it, parts I had on the self, Crankshaft, and Camshaft sensors, but I do not have a coil. I also tried a known good PCM. Checked ignition and wire connectivity. Every thing look good except it have no spark. It have plenty of power to the coil and plenty of fuel but no spark.

What other things should I look at? I have a PC based manual but it do not give coil testing procedures.

The last time that happened to me the shaft in the distributor had gotten so loose the rotor shattered on one of the distributor cap contacts.

8Mud said:

The last time that happened to me the shaft in the distributor had gotten so loose the rotor shattered on one of the distributor cap contacts.

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I did check that when I was in the distributor to replace the sensor in there. it did feel good and rotated when I cranked the engine.
My 1994 XJ broke the roll pin in the distributor once.

How did you check for spark?

You can use an ohm meter to test the coil. The primary circuit should have a resistance reading of about 1 ohm. The secondary should be somewhere between 11,000 and 15,000 ohms. Also check each circuit to ground. That should be infinite (open).

techno1154 said:

When a coil go bad, does the engine shut down without a warning?

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Yes. That is exactly how mine failed.

However, fuel was still being delivered. I was on the freeway when it happened and had just climbed a pass. The raw fuel being dumped on the hot cat didn't work out particularly well for the cat.

Saudade said:

How did you check for spark?

You can use an ohm meter to test the coil. The primary circuit should have a resistance reading of about 1 ohm. The secondary should be somewhere between 11,000 and 15,000 ohms. Also check each circuit to ground. That should be infinite (open).

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Between the primary/s it is 1.6 ohms. Primaries to secondary is open.

Anak said:

Yes. That is exactly how mine failed.

However, fuel was still being delivered. I was on the freeway when it happened and had just climbed a pass. The raw fuel being dumped on the hot cat didn't work out particularly well for the cat.

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Was yours also the coil?

This is the first time troubleshooting electrical on a computer controlled vehicle. There are no codes to read. The manual reference a DRB scan tool. This is not readily available. One test referenced in the manual is to check for positive voltage at the coil connector while turning over the engine with the starter. While doing so, the voltage dropped to less than 1 volt. May be a PCM issue. however, a known good PCM does exactly the same thing.

I am going to the local store to get a coil especially because I do not have one in my spares inventory.

The coil plus comes from the ASD relay. The coil negative goes to the PCM and is triggered to ground.
Disconnect the coil, test the plus while cranking, if the voltage drops significantly you have an issue upstream from the coil. If it drops significantly connected on the plus side while cranking, you likely have a partial short in the coil.
Did you test the plus, minus, and high voltage side of the coil to ground?

8Mud said:

The coil plus comes from the ASD relay. The coil negative goes to the PCM and is triggered to ground.
Disconnect the coil, test the plus while cranking, if the voltage drops significantly you have an issue upstream from the coil. If it drops significantly connected on the plus side while cranking, you likely have a partial short in the coil.
Did you test the plus, minus, and high voltage side of the coil to ground?

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I did test with the coil removed positive to negative, positive to output, positive to coil body. Then I did the same tests with the negative input. The only reading was between the primary (pos and neg) input. Tis was done wit the VOA meter leads attached to the positive in the connector and the negative to the battery.

Yes, I do agree the issue is before the coil. I disconnected all sensors including the injectors and cranked the engine and the voltage dropped to less tan 1 volt when the engine is turning then returned to 12.6 when I released the key. I think I need to start looking at the positive input to the PCM or maybe the wire from the PCM to the coil.

techno1154 said:

Was yours also the coil?

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Yes.

After reading all of the comments no one mentioned CPS, for craps and giggles try unplugging and cleaning the contacts for the CPS with electronic cleaner, and adding dielectric grease, or if you don’t want to go through the trouble, unplug CPS use a multimeter while cranking to see if it’s outputting any voltage.


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azzy89 said:

After reading all of the comments no one mentioned CPS, for craps and giggles try unplugging and cleaning the contacts for the CPS with electronic cleaner, and adding dielectric grease, or if you don’t want to go through the trouble, unplug CPS use a multimeter while cranking to see if it’s outputting any voltage.


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He said he changed the CPS in his OP.

Saudade said:

He said he changed the CPS in his OP.

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Good catch, my bad, still good to check cause all the new CPS s are made in China, unless you wait a year or two for Nick Risley (REM guy) to come up with a solution to that issue. Also good idea to back probe the connector on the harness side to make sure it is actually receiving that signal.


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I had a coil issue with my first '98 XJ. I bought it and it didn't run. I tired to test stuff. I think I did check the coil. Finally, I just put a new coil from NAPA. Then it ran. Had an issue with my present '98, after wheeling. I did have an MDS coil on it. Probably had it for 5 years. It did have a spark when I took one of the grounds off. I replaced the coil and the alternator. Then it ran.
Now on my 2000. I bought it non running. I replaced about everything. Sensors, fuel pump, swapped the coil rail. I tried to check volts and ohms. Then I got some NOID lights to check the injectors. I had replaced the originals with 12 holes. The originals looked bad, rusty and cracked cases. The NOID light would light up after I turned the key, then retracts it. Just a flash. A guy at work said it might be the ignition electrical block. I bought one from NAPA, and after a few tries, it ran.
Also, I had a Gremlin that the coil would a act up intermittently. I took it to a shop, and when I drove it home, it ran great. Next morning, it would not start. Guy down the road, took his multimeter, a few measurements, said coil was bad. Replaced the coil and it ran.

Is the coil made by Magnetti/Marelli?
If so, replace it.

cruiser54 said:

Is the coil made by Magnetti/Marelli?
If so, replace it.

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I am not sure who made the coil. I did see signs of arching on at least tree pins in connector 100 which have all the engine controls running through it including the coil ground wire. I will try to get a good harness from the Pick and Pull and splice it in.

I will also get a new coil while I am at it. It may take a few weeks because my job is a 100% travel job even though I am at home most weekends. Not having the XJ cost me a 2018 Corolla for my commute. Well, it is better than the XJ on
gas.

Well, I was pressed for time so I parked the XJ and bought a Corolla to get to work.

Saturday I had some time with it and got it running. I am not sure what fixed it but it runs. I replaced the coil and cleaned the contacts at the ECM. Now, I move on to other things.

There was a coolant leak at the water pump bolts so I removed the pump to replace the gasket. The valve cover gasket leaks. The old XJ recently start scent marking its territory so it is a good time to fix that. Lastly, the timing chain is stretched. I knew that a long time but could not afford to take the XJ apart. Now I do and need to order a timing chain set.

Who carries good timing chain sets today?

as far as parts goes, it's a crap shoot. Look at country of origin in the description or on the box.

Melling appears to be manufactured in USA.

Cloyes, I couldn't find info on, usually if they don't
say, they're made offshore...