You can always just pull a plug wire and insert a plug into it and hold it in your clenched fist while someone cranks the motor over. You will know instantly if you have spark. Your arm will only hurt for a few minutes.

Some memories stick with you, that particular one from HS auto shop class c. Oct 1974, i remember well. Some bad words were said.

Doug

 

Tried it no,spark

 

Do you a volt ohm meter?

Check for voltage at the + side of the coil (I assume you car is built like that) when engine is cranking and just with key ON, no crank.

Doug

 

I really wish you took a picture, or better yet, a video of your attempt. The engine cover is magnesium, and is insulated from the rest of the engine with a gasket. I'd love to have seen where the plugs got their ground from. I just want to be absolutely sure it's no spark before we go any further.

I guess I should offer up some help in the case that you are correct, and there is no spark.

1. As you mentioned in Post #1...the security module can cause this problem.
2. EMS Power Relay. I think I read one person having a failed relay causing this issue. It's in the passenger seat knee bolster, under the passenger air bag. It's a light blue relay with a white base.
3. Double test all fuses with a multimeter. Some look good, but it's worth the effort.

 

Thank you Vee , i will take a picture with the set up i used to check for spark so you can comment. I agree as i experienced condensation on the inside of glass over the winter i think moisture has corroded something. I have cleaned and switched the two emc and ecu relays plus checked fuses but i may have missed something as its an awkward position to get to those fuses in the knee bolster. I will report back

 

wardhill68,


My 1996 xjs


I don’t want to create any confusion but I had a similar situation 5 or so years past.

my car would crank but not start or it would take a long series of cranks and finally start.

it ended up being the cam position sensor.

I went through the exact same scenario that you are currently realizing.

Thanks to input from Grant Francis…..One of our leaders I was finally about to diagnose the problem as the cam sensor.

You might want to solicit Grant’s help to see if he has any ideas or considers what I am saying as not necessarily the same issue.

Thanks

Softball60/Paul

 

[QUOTE=Softball60;2860792]wardhill68,


My 1996 xjs


I don’t want to create any confusion but I had a similar situation 5 or so years past.

my car would crank but not start or it would take a long series of cranks and finally start.

it ended up being the cam position sensor.

I went through the exact same scenario that you are currently realizing.

Thanks to input from Grant Francis…..One of our leaders I was finally about to diagnose the problem as the cam sensor.

You might want to solicit Grant’s help to see if he has any ideas or considers what I am saying as not necessarily the same issue.

Thanks

Softball60/Paul[/QUOTE do you remember how you diagnosed it?]

 

wardhill68,

what is the year your xjs

I went through the same process that you did.

1 I knew I was getting fuel
2 ecu checked out okay
3 sprayed engine starting fluid directly into fuel port and it would not fire
4 was getting spark
5 it ran before
6 you installed new crank position sensor

the cam position sensor tells the ecu what is required to start the engine and what order. Other than that it does not do anything else.

hopefully if I remember correctly that is what Grant mentioned in his responses to help me.

I’m not saying that I am absolutely positive that this is your problem. Cam position sensor does not come up much in threads as a common issue.

I purchased a used part that looks like a distributor ($75) with the sensor mounted on top with a sight glass on top. Took the parts needed and replaced same parts in my existing unit. As mentioned earlier, Grant sent me some instructions. You can locate in my posts. If you are having difficulty locating the thread and response from Grant let me know and I will locate the specific thread and let you know.

Softball60/Paul

 

Paul,

At the risk of contradicting you, the engine (camshaft) position sensor does very little. It merely signifies whether No. 1 cylinder is on the firing or exhaust stroke. That helps the ecu to work out quicker how to fire the engine on the correct stroke rather than just throw sparks at every stroke until it ctaches.. A failed sensor will just mean that the engine turns over longer before the ecu works out how to initiate the spark for the firing stroke. The sensor does nothing once the engine has caught and I think you might not even need it connected for the engine to fire up, it would just turn over a few more times before it caught.

That's not to say that it isn't the problem, but Jeff really needs to establish definitively if he's got a spark problem or a fuel problem when the engine is cranking. I share his pain as I've got the same issue with a 6 litre that I'm recommissioning!

Cheers

Paul

 

ptjs1,

You are correct about the #1 cylinder. I did state it does nothing else.

The only other clue was the tach jump a couple hundred rpm’s….mine was e aptly the same.



Softball60/Paul

 

It is not a common failure part. I believe that if you crank the engine long enough, the car will figure it out and start the car without the use of a cam position sensor! Could take minutes of cranking though....

From manual:

"​​​​​​Camshaft position sensor (CMPS)
The camshaft position sensor is a Hall-effect sensor which provides the ECM with a sequencing input so that correct ignition and fuel injection will begin with two-thirds of an engine revolution at engine start. The CMPS rotor has six "windows" of different width of positively identify each cylinder. As a window passes the sensor, the ECM is able to identify the cylinder (1 through 6).

The CMPS is necessary because the crankshaft position sensor (CKPS) gap identifies TDC position for both cylinders 1 and 6. Without the CMPS sequencing input, the ECM would attempt engine start by trial and error, firing each cylinder in sequence; several engine revolutions might be required for successful engine start. CMPS input is not required by the CM once the engine is started."

 

wardhill68,

Any update?




softball60/Paul

 

Nothing yet going back into the fuses and relays maybe pull the security module and disconnect it

 

I don't think anyone has ever mentioned whether it could be a bad TPS. It is a required sensor for starting....

Do you have an OBD2 reader capable of seeing what the position of the TPS is?

 

I have a car soft for xj jaguars I’ve been using. So yes I’ll see if I can get a read on the tps. Do these fail suddenly?prior to this no start I had no problems

 

Yes. Any blip in a TPS sensor reading results in an immediate shut down...even if cruising at highway speeds. Failures used to be reported here much more often, although we don't hear about them as often, this sensor has been known to create some wild effects. Not a cheap part to replace, and not one to waste significant money on used, since the used sensor is likely as old as the one it's replacing.

 

Yes i see its not a cheap part

 

wardhill68,

any update?





thanks

softball60/Paul

 

I was waiting on a mobile mechanic to come yp from rhode island. He claimed to be knowledgable on there 4.0 xjs’s . So far hes a no show so im giving up on him. Jerk award! His name id Josh DiCarlo so im at a loss right now

 

NEVER USE a mobile mechanic, NEVER USE a mobile mechanic, NEVER USE a mobile mechanic, NEVER USE a mobile mechanic!
You are guaranteed to pay for their travel even if they make your car worse than it was.
Always use a mechanic that comes with references from someone you know.
My neighbor called a mobile mechanic, to work on her VW and he made her pay for parts up front.
The parts didn't even fit her car and he left her with the car taken apart and he disappeared.
NEVER USE a mobile mechanic, NEVER USE a mobile mechanic, NEVER USE a mobile mechanic, NEVER USE a mobile mechanic,