Rover V8 no spark so won't start ?????

[dirtyboy]

Right, I've got a 3.5 rv8 on carbs with an electronic dlm8 type dizzy and coil.

It ran fine, then i wired in a rev counter and oil pressure guage and low oil pressure light, now it wont go??
I've used my live wire finder light pen thingy and this is what ive found so far
- the positive side of the coil is live (with ignition on)
- the negative side of the coil is live ( with ignition on) so all good
I tried clipping my live finder light to the king lead connection of the coil and then to earth and cranked over, but the light does not light up??? which i believe it should, also tried pulling a plug out and resting it on the rocker cover to check for spark but still a no go!
Checked all my wiring, tripple checked my engine earth strap!
Only thing i dont know is should the coil earth through its mounting point on the inner wing???
I though a dead coil seemed likely so I borrowed one of another running car and still the same??

I'm well n truly stuck now so any ideas very much appreciated, ta!

[GreenV8S]

Take the king lead off the dizzy cap and shove a screwdriver inside the end to act as an electrode, position it so teh screwdriver metal blade is very close to the rocker cover or other exposed metal part so that it can spark to earth. Switch the ignition on, confirm 12V to coil +ve. Briefly short coil -ve to earth (no more than a fraction of a second). Be aware that there may be a small shock on this lead as you disconnect it - don't touch the conductor directly. As you disconnect it, the coil should spark and you will see the spark at the screwdriver/rocker cover gap.

If that works, the coil is OK. If not, it is faulty or not installed properly.

If the coil is OK then crank the engine over and see if you get a similar spark. If you don't, then either the dizzy pickup or (more likely) ignition amp have failed or got a wiring fault. You can locate wiring faults by simple continuity tests, but testing the pickup and amp is tricky and probably best done by substitution.

If you get a spark at the coil while cranking then refit the king lead and disconnect one of the plug leads (usual screwdriver trick) and see if you have a spark here too. If not, it's a plug lead / dizzy cap / rotor arm problem.

[dirtyboy]

hi greenv8s , right I gave that a whirl and its better but still not wright. There was no spark as I disconneced the neg on the coil but there was a strong spark as i put the positive cable on and off the battery.
I then tried it with a spark plug in a lead and now the spark is inconsistent. If I crank it over for a split second when it happens to be on that particular plug I get a big spark, however, if I crank it continually I would expect to see spark.... spark.... spark etc as it turns over but there is nothng?
I have also replaced the king lead and dizzy cap.
thanks

[GreenV8S]

I assume you left the coil -ve connected (that's what I intended). If the ignition amp has failed it could be holding the coil -ve down in which case the coil will get very hot and you'll get your spark every time you disconnect the coil +ve. Disconnect the coil -ve from the wiring loom and try briefly earthing it again, now you should see a spark each time you disconnect your temporary earth.

[dirtyboy]

Hi again, the good news is its going!!!
Whilst doing your proposed checks my attention was drawn towards the lead from the coil to the ignition amp. A master bodger had been at work here with a combination of twisted togeather bear wires n duck tape, nice!

So i made that good but it still woudnt go. I put some jump leads accross from our diesel and cranked like mad and it went after about 10 minutes.
I think the battery was a bit low so giving a really weak spark, and then it was just flooding before it had a chance to fire.


That said, my new oil pressure guage isnt working and my low oil pressure light wont go out?? I only ran it for about 30 seconds, as I would hate to damage it. It has a remote filter so i primed the pump by pouring oil down the 'in' pipe until it filled to the top and filled the oil filter up before I screwed it on.
How long should it take for the light to go out and the guage to register?
P.S.by the way the oil pressure sender is the type that is on the front of the remote filter head!

[GreenV8S]

If it has to self-prime it could take tens of seconds, depending how worn the pump is it might not prime at all. It also won't prime if the pickup is clogged or loose. Once the pump is pumping, it might take thirty seconds at cranking speed to fill the system up, that would correspond to a couple of seconds at fast idle.

[Pumaracing]

Bear wires and duck tape? Sounds like a pig of a job. What sort of animal had been at it before you? It otter work once you've fixed those although I suppose there cod be more problems lurking to dog you. I'd be pulling my hare out - I'm no good at electrical issues.

[rev-erend]

If you have wired in a Rev counter then it sounds like you might have left off or broken one of the low tension wires to the coil (+) and (-).

A rev counter works by counting the amount of times the coil fires and then divides by the number of cylinders to give RPM.

It's wired to the (+) and (-) of the coil ..

I believe .. then is no need to touch the original wires to do this..

[dirtyboy]

Pumaracing said:

Bear wires and duck tape? Sounds like a pig of a job. What sort of animal had been at it before you? It otter work once you've fixed those although I suppose there cod be more problems lurking to dog you. I'd be pulling my hare out - I'm no good at electrical issues.

A big pikey one lol! last time i checked duct tape was not renowned for its electrical insulating properties