96 Disco V8i - Possible Ignition Issue

Me again. :)

Okay, after much 'thinking time' ie. not working on the car, I finally did some fiddling last weekend and the Disco decided it wanted to start again - only thing done was to change spark plugs (old one were quite black) and use some "start ya bastard". Took it for a spin and it seemed happy enough, although the idle was still a little rough.

Today I tried to start the beast again after sitting for a week and it sprang into life. After idling for a couple minutes it stalled and now I'm back to being unable to get the thing to fire. :mad:

I have spark at HT and spark plug and I have fuel.

I decided to check the voltage at the injectors, and it's here that I have questions I'm hoping someone can help with. After disconnecting an injector plug I turned the igniton switch to ON and checked voltage on the plug. I have 12V on BOTH wires. If I then crank the engine I continue to get the same voltage on BOTH wires. I was expecting to get a pulse on one of the wires rather than a constant voltage? Does this indicate a problem with the ECU, or is this normal when cranking?

Looking forward to finally working this out.

Quote:

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Originally Posted by TooQik

Me again. :)

Okay, after much 'thinking time' ie. not working on the car, I finally did some fiddling last weekend and the Disco decided it wanted to start again - only thing done was to change spark plugs (old one were quite black) and use some "start ya bastard". Took it for a spin and it seemed happy enough, although the idle was still a little rough.

Today I tried to start the beast again after sitting for a week and it sprang into life. After idling for a couple minutes it stalled and now I'm back to being unable to get the thing to fire. :mad:

I have spark at HT and spark plug and I have fuel.

I decided to check the voltage at the injectors, and it's here that I have questions I'm hoping someone can help with. After disconnecting an injector plug I turned the igniton switch to ON and checked voltage on the plug. I have 12V on BOTH wires. If I then crank the engine I continue to get the same voltage on BOTH wires. I was expecting to get a pulse on one of the wires rather than a constant voltage? Does this indicate a problem with the ECU, or is this normal when cranking?

Looking forward to finally working this out.

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You will need a LED test light for the injector test. Both sides of the injector plug will be at 12 volts unless you are at the exact moment when the injector is firing. Only a LED test light will show the speed of an injector pulse. Connect the tester across both wires of the injector plug and it should pulse with the remaining 3 injectors on the same bank.

If you get spark consistently from the coil lead but not from the plug lead then either your rotor button or your distributor cap may be faulty. There may be moisture condensed in the cap. As the engine warms up moisture evaporates low in the dissy and condenses in the cap part. Needs a quality moment with a hair drier to fix.:eek::D:p

After almost three entire months of "thinking time", today I decided to attack this problem again, and lo and behold....it's fixed.:)

This morning I decided to try and fire up the beast after having it sitting in the drive way since the last time it stalled and refused to start again. As suspected it sprang to life, albeit idling at just under 2000 rpm (which it has never done before). I let it idle until fully warm and turned it off again. From there it refused to start again, as I suspected it would (wouldn't ;)), as this seemed to be the course of events since the problem arose.

I'd picked up a second hand distributor and complete intake manifold with all sensors and injectors during my "thinking time" - so I decided the first thing to swap in was the idle control valve (seeing at the beast decided to idle high today) and the distributor. What do you know, problem gone. My Disco is once again a happy camper.

Many thanks to everyone who contributed to this thread, it's only taken five months, an ignition module conversion (thanks bee utey), new igniton coil, new fuel pump, new fuel filter, rewiring of the fuel pump (damaged wiring and plug), new fuel regulator, new spark plugs, a check of every relay and fuse, an examination of the alarm ECU, time searching for the immobiliser spider only to discover that I don't have one (or it's darn well hidden and I'm still yet to find it) plus a second hand distibutor and idle control value to fix the problem.

My alarm "spider", is under the bonnet near the brake servo, luckily for me some previous owner removed the wiring.