I have a 1987 Jaguar XJ6 that stopped running while I was driving down the freeway at about 65 miles an hour. It was like someone turned off the key. Appears to be some kind of an electrical problem and I have no idea where to begin. Has anyone ever heard of this happening? Any suggestions as to what it may be?

Sincerely
Scott Miles

 

Well it's a 30 year old Jaguar...to be expected. That said check the basics, fuel pump, ingition, fuses. See if it will run on starting fluid with the key on? If so you've got an fuel supply problem. If not check the fuel system.

 

As ISC says it could be anything. You just have to pick a place to begin and keep going.

If you want to make a *guess* I'd go with the ignition module (AC Delco D1906). It resides inside the amplifier which is bolted to the front of the intake manifold---black box about 4" square.

This might help

ENGINE CRANKS BUT WON'T START

Cheers
DD

 

[QUOTE=Doug;1498340] If you want to make a *guess* I'd go with the ignition module.


You can start your diagnosis before the car rolls to a stop. If the tachometer dead drops to zero while driving you lost ignition. If the tach still shows RPM while coasting to a stop .. you lost fuel (or injector pulse). Also.. when you crank over to start, the tach will "quiver" while cranking indicating an ignition pulse (and a good module).

 

Agree, it seems that ignition diagnostics are easier than fueling issues.


I've two favorites:


1. Jump 12v battery to coil + and crank.


2. Attach a strobe timing light to the coil to distributor HT lead and crank.


Carl

 

Carl:

Thanks for the advice. I have 9.6 volts to the coil when I crank, but there is no spark at all. I had the coil tested and checked okay. I will try battery direct to coil to see if that works.

Thanks
Scott

 

Carl:

Tried battery direct to coil and still no spark. I do not have a strobe to give the other a try.

 

Frank:

I cannot get the tach to quiver. Does that mean the ignition module is bad.

Thanks
Scott

 

The test assumes a fully charged battery

1) Measure voltage at coil "+" terminal with key "on". It should be within
one volt of battery voltage. If not suspect a problem with the wiring to the
ignition switch, or the switch itself.

2) Measure voltage at the coil "-" terminal. Result should be the same as at
the "+" terminal. If Ok, go to step 3. If not....
Disconnect the wire from the amplifier from the "-" post of the coil and
measure voltage again. Less than 2 volts means the coil is faulty. More than
2 volts means the amplifier is faulty.

3) Disconnect distributor pickup coil from the amplifier (this is the
harness from the distributor that plugs into the amp). Measure resistance
across the terminals. It should be 2.2k to 4.8k ohms. If Ok, go to step 4.
If not, replace the pickup.

4) Reconnect the pickup to the amplifier. Measure voltage at coil "-" post
while cranking engine. The voltage should drop. If OK, go to step 5. If
not, the amplifier is faulty.

5) Check distributor cap and wires, distributor rotor arm, spark plugs, coil
wire.


Cheers
DD

 

Doug:

Thank you! I will run all of those tests. The pick up module reads 1.4 on continuity hopefully that is my problem.

I am not getting any spark directly out of the coil. The voltage on the + and - terminals of the coil reads good with the key turned on. Would this also cause no spark directly out of the coil?

Thanks
Scott

 

Yes.

The pick-up coil is the electronic equivalent to old fashioned breaker points.

Cheers
DD

 

Did this get sorted out?

 

Agree, final result, good or bad is good for us in referring to the archives.


A test lamp on the distributor to coil wire should blink when cranked.
Signifies the "make and brake" to load the coil and produce HT for
firing the cylinders.


I suggest a strobe timing light as an important tool. As much as your budget can handle.


Carl

 

Doug:

Followed your test on the Jag

1) voltage at coil tests okay
2) "-" terminal voltage is the same
3) measured resistance on pickup coil it read 1.46 I bought a new one and replaced it the new on reads 1.29
4) I reconnected and tried step 4 "-" post on the coil drops (decided amplifier must be okay
5) Replaced cap and checked all wired to see if they were snug. Still no spark.....

Any further suggestions?

 

Scott:

This may have no relevance, but this exact thing happened to me, except it happened when going up a hill in our town. Suddenly, the vehicle went completely dark.

Turned out to be a bad connection in the circuit that supplies power to the PCM (ECU). The car is lumped with an LT-1. Tracing the failure using the Factory Service Manual revealed the problem.

Bill, Original Owner, 1987 XJ-6 VDP