I ve had a crank no start issue for a few months. 1995 xjs 4.0 lhd
what ive tried so far
1. new cps
2. new plugs
3. new battery as mine would go flat after a few days
4. sent out ecu and got confirmation its communicating
5. yesterday day i pulled coil and plug from cylinder 1 and 6 separately. Positioned plug and coil upside down n top of engine so i could see a spark from the plug as i cranked the engine. I saw nothing . So assume no spark
6. checked fuses and reseated ecu and ecm relays
my observations
1. tach jumps when cranking
2. I can hear fuel pump priming. I have a full tank of gas
3. given the no spark i have not check the fuel pressure at the fuel rail. Wonder if i should anyway
My suspicions
1 my security system has always been suspect. The car only came with one key no fob but locks both doors and trunk from drivers side lock. The red led by cig lighter sometimes illuminates . The key will chirp sometimes.. my convt top has never worked by the switch. I put it down manually . Quarter windows dont work. Ive notice in the wiring diagram it is somehow tied the the security system.
can i remove the security module from the trunk area to take that system and any starting issues it may cause out of the equation
Thanks,Jeff

 

Jeff,

A few thoughts:

You mentioned putting the plug "upside down" on the engine. Are you keeping an earth contact with the plug through the engine to see if it is sparking?

Is the fuel pump definitely running, both for 2 seconds when the ignition is turned on; and then whilst the engine is cranking? It can be quite difficult to hear it. People often get confused with the sound of the ABS pump in the engine bay running.

I would definitely try and pin down if this is a fuel or spark issue that's preventing the starting. Have you tried to see if it will cough on Easystart or similar?

The security system could be an issue in preventing starting. However, it's not linked to the hood lowering problem. I've never been aware of any link between the systems on all the XJSs I've seen.

I'm not sure why your OBDII port can't be read by your mechanic. Even early AJ16 XJSs, such as mine should be able to be read. However, I don't think reading any OBDII codes is going to be teh way you solve the starting issue. I would think that backprobing the plug wires on the ecu is more likely to verify where the issue lies.

Good luck

Paul

 

Have you checked the inertia switch at the passengers door hinge?

 

Thanks Vee yes that has been checked and is engaged

 

I could not get it to fire with starter fluid sprayed into the maf
is there a way to earth the plug ? I am working solo

 

Jeff,
STOP throwing new parts at the car.
Check to see that you are getting fuel/pressure to the engine.
Disconnect the line at the fuel rail.
Use of a Fuel Pressure gauge might give you an accurate diagnosis.
Not a positive result...then work back towards the fuel filter....
Report back.

 

Ok i just completed a fuel pressure test. When i turn the ignition on the pump is priming and i get a little over 30 psi. When i crank the engine the pressure gauge stays the same. I would think it would increase as the fuel has no place to go. But when i hold in the fuel release valve on the gauge and crank the engine i can see gas flowing.or it seems to

 

Where are you putting the pressure gauge?

 

I disconnected the hose from the rail . The gauge is at end of hose

 

Fuel should be at 43psi, or thereabouts.

I wonder if the regulator is bad, or the fuel filter could be blocked. After that, I hate to say it, but it could be a dying, or blocked fuel filter...

 

I will get a more accurate fuel pressure reading today and report back. Should I be getting 43 psi at the priming stage?thank you

 

Have you checked the crank position sensor? Gunk on it can mess up the signal.

 

The regulator should not allow more than 43psi, and the pump either runs or it doesn’t, so yes, I would expect to see 43 psi at the priming stage as well.

 

I’m getting a solid 35 psi at priming and it holds there when cranking over the engine. Others have said this is sufficient but I am going to change the fuel filter anyway as I don’t know when it was last done. Going to move onto spark today as I suspect this to be the issue or my security system

 

It sounds like it would be enough, but pull the little hose off of the fuel pressure regulator. Do you smell any gasoline? Do you see any hint of moisture? That would point to a failing regulator.

 

Ok I hook a multi meter to #4 coil connector plug on the wiring loom and I get 12 + volts at the plug with ignition turned on. Hindsight suggests I should have check for voltage while turning over, cranking, the engine. As I’ve read that is singled from a different circuit from the ignition just being turned on. Is that correct?

 

I’m afraid that’s not a good test. I think you’ve tested the fuel pump relay feed. 12V key on, engine running, should be ground?

Coils receive differing voltages depending on rpm’s. 700RPM=0.30V, 1,000RPM=0.45V, 1,500RPM=0.60V, 2,500RPM=1.08V

Fuel Injectors also receive differing voltages depending on RPMs. Not same as coils though.

 

Dang!
,

 

Pull a coil out, put a plug in it and reconnect the wiring, lay it on the engine so that the shell of the plug touches the bare metal block somewhere and crank the motor, you should see a blue spark if the coil is working.

That should cross coils off the list?

 

Jeff.

As Vee has said and we've discussed, you really need to find a way of seeing the spark flash on an engine-earthed plug whilst the engine is cranking. Can be difficult I know if you're on your own, but it's the only way.

Good luck

Paul