Ok i disconnected the cps plug and connected the multi meter to the cps terminals. Before cranking i was getting a reading of -0.00. This stayed the same while cranking over the engine . So would this suggestthe problem lies at the magnetic sensor? Could a dirty tooth ring be the issue? I could spray it down with brake cleaner

 

There comes a point where a multimeter won't cut it, sometimes depends on the quality of the meter, sometimes depends on the settings. I'm not 100% sure how the CPS that Jaguar fitted functions but the best way to see the pulses is with an oscilloscope - some multimeters have this ability - if yours does not the pulses may not be long enough to trigger a reaction in the meter or great enough in magnitude - depends if the meter is autoranging because that feature would definitely impede response. I also don't know if the ECU provides a signal voltage reference that it expects to see change.

Bottom line though you can't measure time based pulses aka digital signals with a standard multimeter.

 

Well i dont have one of those

 

Is the sensor two wire or more ?

If it is 2 wire and it has a resistance in the 2k ohm range I'd say it is fine, but you need to measure on a low AC scale.

If it is three wire then it will be taking 12V or maybe 5 from the ECU and converting that to a voltage - but I don't think Jag V12 sensors are this type.

 

Ben,

It's a 2-wire sensor on a 4 litre. I think the continuity resistance should be c1.37k ohms. Can't remember where I saw that figure. The lack of AC voltage as measured at the sensor when cranking would concern me, but you've made a good point about the nuances of multimeters.


Jeff,

Do you have the ability to borrow a different multimeter to measure that cranking AC voltage? Or else get someone else to accurately measure that continuity at rest?

Paul

 

I have two multi meters i will try them both

 

Same result different meter. But the continuity is there. What i dont understand is how my set up worked in the first place. The red and blue wire coming off the ecu plug is spliced with a white and black wire. I assume the white is power and the black is ground but it seems like this set up would void the cps altogether

 

Got your email Jeff.

My work was with the X300, same car mechanically with 4 doors.
I have read this thread, headache, no gone, whoopee.

I have attached the Cam Angle Sensor setting PDF, and I am NOT getting into discussion about what it does or does not do, its a Jag, move on. Mine cranked looooong time, and I went looking and asking, 20 years ago now. Once I retiimed it, the bloody thing started on the 1st rotation, every time.

My grasp of yours is that it worked fine, then decided not to. You have covered a shiit load of things I would not deem as needed, since it ran FINE before.

Spraying Ether in the MAF, NOPE, too far from the throttle body. Remove that 5/8 vent hose from the camcover, AT the bellows, spray a load in there as see what happens, maybe a fart or 2. That means spark.

TPS, HELL YES. Brilliant design under the throttle body, oily goo, a Jag feature, runs down the throttle shaft, and straight into that TPS, bugga. Hence I pester people to CLEAN the throttle body at every oil change, simple, and FREE. I have had fairly good results cleaning them with Carby Cleaner, sprayed thru the gap at the top, TPS removed, and let dry, repeat, and so on, until the drippings are clean. Some needed a new one.

Crank Angle Sensor, of course,. Mine died in the driveway after a run home from work. Replaced it, found that stupid loom connector full of road trash. Cleaned it out, and sealed with RTV, no more crud..

Now, this is memory. On the Radiator support panel, RH side, just above the headlamp, I KNOW, the XJS is not like this, is a Blue relay. This supplies the 12V Ign TO the Crank Sensor, they fail, often.

You seem to have fuel, sort of, but the In Tank pumps are known for the supply hose not sealing well to the pump spigot. Fuel sprays into the tank instead up the hose. I doubt you have this. A coapsed filter is more likely.

I will keep thinking. but these are simple systems.

OH, does the beast have an aftermarket imobiliser or such. That wiring nonsense screams something aftermarket in the system.

 

Jeff,

I don't know what those spliced wires are doing there, but don't assume white is power and black is earth. Any home-made bodge of wires could have used any colour. Work out where they go to, even if that means carefully undoing the insulation tape on the loom to trace them.

I'll sound like a stuck record, but you have to ascertain if this replacement crank sensor is working. Find a way of working out using a known good multimeter if it is sending a signal by measuring at the crank sensor itself when cranking. DON'T test it at the ecu until you've confirmed it generates an AC voltage signal at the sensor itself. If you test at the sensor, then immobilisers, spliced wires at the ecu etc will have no influence.

Good luck

Paul

 

Thank you Paul, no you don’t sound like a stuck record. I’ll try again for 12 v at the sensor I just figured Id see if I got that at the unplugged female side of the ecu but since I couldn’t get a reading with either meter I’ll go back to the source

 

Jeff,

Remember you're not checking for 12v DC. You're checking for a fluctuating AC volts reading at the sensor itself when the engine is cranking. So, the meter needs to be set to Volts AC, not Volts DC. The figure is on Section 25 of the electrical diagram.

Cheers

Paul

 

Yes i understand. thanks

 

Question; looking at the wiring diagram figure 25 for this car. Could I supply 12 volts direct from the battery to #87 on the elms power relay? Looks like this would power up my ignition coils and o2 sensors. I would remove the relay and stick a 12 v connection into the 87 port. Would this damage anything? I have tried Grant suggestions with the starting fluid in the location he suggested. But nothing. I have not looked at the tps as I don’t know how to get to it but understands it’s under the throttle body. I will see if my cps can read 12 v ac at the plug harness but my first attempt only showed continuity

 

Jeff,

Really, don't worry about anything else if you don't know if that crank sensor is working. Remember it's not 12v ac that you're looking for. And it's directly from the sensor itself. It's a varying ac voltage based on whatever revs it's doing when the engine is cranking. The figures are on the wiring diagram.

Cheers

Paul

 

Ok, ive connected leads to my cps at the plug set my multi meter to ac as shown in the picture with a start reading of 0.00. Went and cranked over the engine and the reading didnt flinch. Tried this several times. So can i now assume this is the third cps that ive bought that is crap?hard to imagine

 

Jeff,

You've set the meter on DC volts.

Paul

 

Well I tried it on both setting to either side of the off position. Forgive my stupidity but I thought the dashes represented alternating now I know .regardless it didn’t change from 0.00 on what I’m assuming it the ac side right of the off position

 

Have you disconnected that mystery spliced-in white wire?

Also, maybe downgrade the sensitivity? I think you're looking for 2.0V when starting? Can your multimeter show you 2.0VAC? I know it should be able to... as 0.02? But maybe time for a more sensitive device?

 

I have not dissconnected that splice as the car was working well with it so I don’t think it is the problem. Both my meters have the same rating on the vac side

 

I would at least disconnect it and see what happens. You can always put it back. Splice in some butt connectors and you're good to go. Something about splicing onto a shielded wire that would concern me. That white wire is undoubtedly introducing some kind of interference that Jaguar specifically wanted to avoid on that circuit.