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Well, we still have not heard the results of testing with the spark tester or the noid light. Maybe the testing was done, but did not publish the results?
Easy to check the engine compartment fuse box with a voltmeter on the downstream side of each fuse.
Test was completed checking for pulsing on the primary side of the coil. When pulses are present, the timing pickup and ECM interface are verified. Even though a more precise test tool would be a graphing meter or oscilloscope (I just ordered a basic unit), a noid light can also be used to check the coil primary circuits (attach between center and either edge wire). The advantage of the noid light is it's sensitivity to both current and voltage. If the noid light blinks, but still no spark can only mean bad coil or bad wire. If no blinking, likely bad CPS still (frustrating I know).
Afternoon developments - I just can't shake how CPS-like alllllll these symptoms have been, but two new ones have gone in with no change... So I tested continuity to make sure the wires are OK.
- CPS plug to ECU wire 1 (black/yellow, connector 0636, pin 32 on ECU plug): Continuity
- CPS plug to ECU wire 2 (pink/black, connector 0636, pin 46 on ECU plug): Continuity
- CPS plug to ECU wire 3 (ground, black, connector 0636, pin 45 on ECU plug): Continuity
Pretty proud of my custom leads to reach from the ECU to the engine haha...
Last edited by Brandon318; Jun 1, 2025 at 06:33 PM.
The "ground" is actually shielding (screen in England, SCR) for the signal wires. It should be only grounded on one end. If there are pulses at the coil primaries, then the CKP sensor is doing its job.
Welp welp, I installed another new Bosch CPS and still same result. No biggie, nice to have a spare, but anyway... I think we can officially rule out the CPS.
Another potential clue... When I crank it over, there's a very distinct smell of gas coming from the engine bay. I don't see spraying anywhere obvious.
This may sound silly, but I came across a youtube video where the person had a no start issue on their Disco. Turns out it was a faulty brake switch.
Obviously there are no silly pitches at this point. Gosh everything is exactly as he's experiencing, I feel what he felt haha. I of course went right out and check the brake pedal switch, but it was all good... unfortunately. What a saga.
Maybe focus on getting spark first. CKP sensor feeds ECU, ECU sends low voltage signal to coils, coils create high voltage pulses, transmitted on wires to spark plugs, creating properly timed sparks. The sequence is failing at some point along the line. Find that point then get spark back.
That brake switch no-start problem happened on my 96 D1 by the way. Luckily died in my parking spot at home, it would crank away but not start, guessing it cuts fuel rather than spark. Smelling fuel might be a good sign that injectors are working.
IT RUNS! Holy ****. What a saga. Ended up being the thing I least expected. As a last attempt to throw a part at the car after exhausting so much troubleshooting efforts, I ordered another internal fuse box and I've never experienced such a gratifying feeling turning that key and hearing it start right up. Literally didn't even hesitate. Wow.
Not accepting that as an official fix, I had to dig further. I took apart the fuse box and thing I found the culprit. No idea how there's corrosion here. Never had a windshield leak and it's always been a California car.
I'm so stoked to drive it around tomorrow! Looking back through the thread history I'm actually really thankful for this experience. I learned an absolute ton of electrical troubleshooting. Still have so much to learn, but feels really great leaving this project with some lifetime knowledge accrued.
Also glad this resulted in me replacing the CPS. That was something I always felt haunting me on long road trips... is this gonna be the trip it dies? ...so to have that done feels awesome too.
