Ok I got a new battery and new coil. I even switch some relays and still nothing. I have put in a new starter and rebuild the alt. Any advice???

 

Hi EFrazen,

If I understand the title in your post, your '94 has good fuel pressure and the spark plugs are wet with fuel, but the spark plugs are not firing. Is this correct?

Does the VCM display a fault code (Diagnostic Trouble Code or DTC) when you turn the key to position II without starting the car and press and release the VCM button on the trip computer panel to the right of the steering wheel?

Besides the battery and coil, some of the other things that can prevent spark are:

Failed Crankshaft Position Sensor (CPS). The classic symptom is that the tachometer reads 0 rpm while cranking the engine. No DTC is triggered.

A worn distributor cap and rotor (these should be renewed as a matter of course);

A loose or failed king lead between the coil and distributor (how old are your ignition wires?);

Corroded electrical connections such as the grounds/earths used by the ECM (2 on the intake manifold studs and one on the bulkhead/firewall behind the cylinder head0, and the connections in the battery power wiring;

Failed ignition amplifier module or loose or corroded connector or broken harness wires (the amplifier is the flat black plastic component mounted on a flat metal heat sink directly below the coil).

Failed cold solder joints in the fuse boxes;

Water damage to the CPU;

Faulty ignition switch.

Among the relays you swapped, did you change the O2 sensor heater relay?

I'm sure others will offer more possibilities. I would clean the grounds/earths I mentioned above and replace the distributor cap and rotor (available at most auto parts stores these days) and see if things improve.

Let us know how it goes.

Cheers,

Don

 

Nope. Pretty thorough as usual, Don!

My only advice, such that it is, is to check the little stuff first. I one time spent an awful lot of money tuning up my non-starting '91 only to discover it was the $11 fuel pump relay. Oh well, I guess the other stuff needed doing at some point anyway.

Cheers,
Scott

 

Scott,

I may have completely misread the OP. I could only assume from the phrase, "yes on fuel" in the title that EFrazen has concluded fuel delivery is not the issue. But we all know what happens when we assume... :-)

Good advice to check the fuel pump relay (which is in the trunk behind the right side trim panel, near the right tail lamp & BFM). Bryan N at the Jag-Lovers forum has posted an excellent procedure for testing the fuel pump circuit that has worked for me every time I have needed it. It will isolate the O2 sensor heater relay, fuel pump relay, wiring between the fuel pump relay and fuel pump, etc.

Also, in the '94 there are six relays mounted on the firewall and at least a couple of them (ignition relay? O2 sensor heater relay?) are known to cause starting issues when they begin to fail or corrosion develops in the relay bases. It would be a good idea for EFrazen to disconnect the battery negative cable, remove all six of those relays and clean the bases and relay terminals with a small wire brush and electrical contact cleaner spray.

Cheers,

Don

 

Yes my 94 xj6 does get fuel but no spark. I did put in new wires cap and rotor a less then a year ago. But will replace them. And will check out the things you all mentioned. I will let you all know how it turns out.

 

It would be worth checking the inside of the distributor cap for arcing or terminal erosion and check the tip of the rotor, and check that the king lead is secure at the coil and distributor.

Have you checked to see if the tachometer reads at least some rpm (for example 200) while cranking? Sudden CPS failure is a very common cause of no start on the XJ40, and if the tach reads 0 while cranking you've found your problem. Replacements are available at fair prices from auto parts stores like O'Reilly or your favorite Jag Specialist.

Please keep us informed!

Cheers,

Don

 

Don & EFrazen:

I wasn't suggesting the fuel relay, only sharing some personal testimony.

However, speaking of fuel… While you say you have fuel at the rail, are you sure about the correct fuel pressure at the rail? Should be 40 psi as I recall. Just another thought.

Cheers!
Scott

 

I did check it and it read 0. So I ordered a new CPS. Thanks for that info I will let you all know what happens after I install it.

 

Ok here is my update. I got the part today and put it in and my car started right up. Thank you very much for the advice.

 

+1 on the CPS… dirty little culprit. Thanks for reporting back!
Scott

 

Yeah! Love a positive result! Thanks for letting us know it was the CPS.

Happy motoring!

Don

 

Good job EFrazen!!!