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I have no choice but to take another stab at this.
And Michael,,, thanks for the help in the past. Invaluable support. Confidence Builder. Guide. Really! Thank you all.
This car went under water. I got the car for next to nothing and today everything works, except this one NAGGING issue that I can't figure out... Granted the time it deserves hasn't exactly been given (maybe) - but it's time.
The way it is now, I have a hand held remote trigger to start the car, engaging the starter solenoid. Starter relay is completely bypassed. I get in, turn the key to the ON position, grab the trigger and press the button. Car starts RIGHT up and has for, well since I decided to "solve" the problem this way. All's good. Turn the key off, car shuts down. No battery drain, no battery or charging problems. Car reads key. All AC and ON (pos ii and iii) key position function and work. Ignition and fueling system fully alive and well. On key turn and function all associated systems that should come on and go off thru all key positions except the one (start/crank) - work like normal. Car jist WON'T crank with key turn. At one point, it would crank,,, SOMETIMES...
I am TERRIBLE with electrical stuff. It's a problem, lol
This is not 100% confirmed BUT (see images) the green wire coming from the trans (P/N) gives 12v key on... The O wire from the starter relay to ECU doesn't seem to go to ground to engage the relay,,, to then send V to starter solenoid at starter. Something to this effect. I've also had a hard time taking readings (bad with electrical stuff!)...
The car knows what gear it's in. No transmission faults and (forgive my memory in nomenclature) the gear selector switch on the RH of the JGate seems to be talking rightly to everything. Doors lock when I put the car into gear. Gear selector (JGATE) is locked until I press the brake pedal.
Does the brake pedal on 2003 and up cars need to be depressed when starting? I have never known.
I started looking at things again last night and today,,, and not to trying or wanting to LEAD this discussion or it's direction (take things wherever YOU think is best) but I've noticed this thing. See images below. The "Not in Park Switch" at the jgate and it's associated wiring. In the legend for figure 3.1 I cannot find a wire connector location or description for the 2 connectors or junctions POST FC87-3. FCS47 and FC3BR are missing in the detail...? Or am I misreading? The diagrams also don't seem to give a CLEAR indication as to what the signal from the switch to the BPM activates or inhibits... Looks like console out? to get to it and,,, is it a micro switch? Like on my 2002 XK?
Also, the inertia switch when I found the car was STILL filled with pond water! and was completely fried... It's been removed from the system and the two wires that tell the rest of the car the inertia switch is NOT tripped are soldered together and heat shrunk. The third wire in the connector to the switch was capped.
Quick q: how have you jury-rigged the start - a switch from B+ somewhere to the starter motor red/white wire?
Ha! Hey Man...
Forget,,, how could I???
I was in Manhattan the other day, paid to park. Explained to the first guy the "start" system,,, who didn't pass it along. Came back to a bunch of angry Bengalis who couldn't move the car around as they needed, lol... Oh, my life!
I have placed the trigger between the NW wire and the WR wire in the diagram... Works like a charm. The green and orange wires are capped for now.
Well we know the starter works
WE know the wiring to and from the relay contacts are good.
Did you try changing the relay as the contacts could be burnt as the starter solenoid is a high load ??
Did you measure the voltage across the G and O wires with the key over in start ? If you have 12v then the relay is faulty.
Now as judge judy would say just answer the questions above. Then we will make a judgement.
Well we know the starter works
WE know the wiring to and from the relay contacts are good.
Did you try changing the relay as the contacts could be burnt as the starter solenoid is a high load ??
Did you measure the voltage across the G and O wires with the key over in start ? If you have 12v then the relay is faulty.
Now as judge judy would say just answer the questions above. Then we will make a judgement.
I tried multiple relays. It wasn't a relay thing...
The last time I jumped into this issue with a DMM I THINK I remember seeing 12v on the green and 12v on the orange. I didn't think the ECU was triggering by creating a path to ground... But why is the question....? And why (in the beginning) sometimes,,, and never now...?
Instead of fixing it you could always just wire that relay coil straight to the ignition switch...
Thanks D,,, I hear you. But I would like to exhaust the possibility of getting it working as designed before taking an alternative route. I haven't just yet...
Is it possible it COULD be that last stage (iii) on the switch that's gone wrong? There was water. Is that ingnition always 12v even with car off? That's (the key switch itself) been burning in the back of my mind as well as a possibility... Have you had the ignition switch on one of these beasts opened up,,, or worked with one?
OK - let's work backwards from the starter relay. You need to replace it for the tests.
If you're bridging contacts 3 and 5 of the starter relay presently to start the car, then fuse #3 (25A) in the engine compartment fusebox is good, and you have B+ at the right place (brown/white wire).
Ignition on (ii) and in park or neutral. Measuring at the relay pins -
What voltage do you see on the Green wire between the ECM, TCM and the relay?
I mean, this looks exactly like the XJS part (which I had apart 3 weeks ago - don't ask, lol) and what's going on inside the thing isn't so complicated... I would like to see inside - I think. There are some springs inside the size of a pencil lead,,, I don't want to be messing with though, less I must
OK - let's work backwards from the starter relay. You need to replace it for the tests.
If you're bridging contacts 3 and 5 of the starter relay presently to start the car, then fuse #3 (25A) in the engine compartment fusebox is good, and you have B+ at the right place (brown/white wire).
Ignition on (ii) and in park or neutral. Measuring at the relay pins -
What voltage do you see on the Green wire between the ECM, TCM and the relay?
What voltage do you see on the Orange wire
With the ignition at position ii (on)?
With the ignition at position iii (crank)?
Great Michael... I'm not at the car but will be in a couple of hours... I'll be reporting back!
Start in the other end. When you turn your key to start position, there should be a ground signal from the ignition switch to the BPM. A Green/Orange wire onto connector FC14 - pin 41.
Just connect a voltmeter or a 12V test lamp between FC14-80 (+12V with ignition on) and FC14-41 and turn the key to start position.
Thanks D,,, I hear you. But I would like to exhaust the possibility of getting it working as designed before taking an alternative route. I haven't just yet...
Is it possible it COULD be that last stage (iii) on the switch That's fine wrong. There was water. Is that ingnition always 12v even with car off? That's (the key switch itself) been burning in the back of my mind as well as a possibility... Have you had the ignition switch on one of these beasts opened up,,, or worked with one?
I've never had to go near the ignition switch, but from time to time I get a no crank/no start which, so far, has always been fixed by wiggling the gear lever in Park. On my Mercedes transmission there is a separate crank inhibitor switch on the transmission itself, worth checking on your ZF I would have thought.
Start in the other end. When you turn your key to start position, there should be a ground signal from the ignition switch to the BPM. A Green/Orange wire onto connector FC14 - pin 41.
Just connect a voltmeter or a 12V test lamp between FC14-80 (+12V with ignition on) and FC14-41 and turn the key to start position.
Ok... Thanks and good idea... For a little more help,,, which figure in the ED has this info(?),,, if not in the ones I posted in the initial post.
I tried multiple relays. It wasn't a relay thing...
The last time I jumped into this issue with a DMM I THINK I remember seeing 12v on the green and 12v on the orange.
After 40 years as an auto electrician, I can tell you that you check the basics first.
If you tried multiple relays then if any were not the brown jaguar ones you could have buggered the output transistors in the ecu due to an induced spike.
Think is not good enough.
What is the voltage orange to green with ign switch in start and gear in P and foot on brake and a relay in place ?
if its zero then you can test orange to earth and green to earth with a relay in place and let us know. Digital voltmeters give spurious readings in many situations being designed for work on circuit boards in TVs etc not cars.
Addendum.
How this works is when the ign switch and XYZ switch ( P/footbrake etc ) is working 12v is supplied to the computer which tells it you are starting (enrichment ) and 12 v goes to the green on the relay. The orange should be earthed by the computer. It seems this is earthing is not happening possibly caused by use of the wrong relay in the past...the output transistor has been damaged with a transient spike due to use of wrong relay.All brown relays have a resistor across the coil to suppress the transient. The solution is to earth the relay terminal connected to orange . This is subject to satisfactory test results as explained above .
Remember the Suntester logo ..."Test Don't Guess"
Last edited by Pistnbroke; 05-27-2022 at 02:30 AM.
Because I am so unsure (and not ashamed) I am going to give a play by play of what I am trying, and looking at...
At this point the trigger and switch IS connected like it always is and I can start the car independent of these "tests" I am doing.
No relay in this circuit, DMM leads are connected directly to wires G and O...as described below, when connected...
Going from the green wire to RED lead on DMM,,, BLACK lead from DMM directly to car chassis ground I get 11.25v with key in the ON position...
With RED DMM lead to green wire and BLACK DMM lead to orange wire,,, with key ON, I get 11.25v as if the orange wire is providing a ground? Is that thinking correct? When I turn the key in this configuration I get NO change in voltage. Stays 11.25v.
And,,, if I connect the RED DMM lead to the orange,,, black to chassis ground I get ZERO volts with key in, of course.
I'll stop here and see what folks say.
I'll say I have a WORKING relay in hand and a way to connect it to the O and G wires if need be, just to see if the relay is triggered WITHOUT the WR and BW wires (for now) connected to the relay.
My "helper" (actually she's the bosssss) showed up and was able to turn the key for me while I "felt" for engagement of the relay. With relay connected (NOT connected to the heavy starter wires) the relay DID NOT fire/engage...
Going from the green wire to RED lead on DMM,,, BLACK lead from DMM directly to car chassis ground I get 11.25v with key in the ON position...
With RED DMM lead to green wire and BLACK DMM lead to orange wire,,, with key ON, I get 11.25v as if the orange wire is providing a ground? Is that thinking correct? When I turn the key in this configuration I get NO change in voltage. Stays 11.25v.
Jay, you need to do those checks with the starter relay in place.
05-26-2022, 07:05 AM
2004 Jaguar XKR - Key Turn Doesn't Engage Starter
