Can't get a spark?

volkssturm45 · Post by **volkssturm45** » Sat Jan 11, 2014 4:56 pm

Evening all and hello to forum members my name is Simon, got a problem with my V8 that's left me and my mate completely stumped so I thought it was time to turn to some experts on the subject for help hence my post here

Anyway to outline the problem:

Bit of History, I bought a 1987 Range Rover V8 EFi as a base vehicle for a project. Whilst stripping it down I dumped the entire wiring harness and the EFi unit as these weren't required as I went down to the bare chassis and instead fitted a set of SU carbs and electric fuel pump etc.
Now since I stripped out the old ignition I needed to fit just a very basic home made loom to fire the V8 back up. However having done this and as the title of the thread describes we can't get any spark when we turn the engine over. Lots of head scratching has gone on checking the loom etc.
We've fitted a new dizzy and coil (matched set) thinking the module was done for as I've done a major amount of welding and thought the massive amount of current may have creamed it. But still no joy.
The first thing that springs to mind is our home made basic ignition loom and whether we've got it right or something missing? It probably something really simple but you know how these things go when you can't see the trees for the wood so I'd be glad for any suggestions of something we might have missed or lead us in a different direction to check out other details. Even a members basic ignition diagram might be worth a look just to make sure we've got it right.

Cheers all Simon.

Post by **Coops** » Sat Jan 11, 2014 5:01 pm

Hi Simon,
And welcome to the nut house.
lets eliminate a few things:

1: have you tested the power wire going to the ignition to see if it has power???
2: if so does it have power when the key is in the cranking position??

volkssturm45 · Post by **volkssturm45** » Sat Jan 11, 2014 5:06 pm

Hi Coops thanks for the quick reply

Yes we've checked the coil for power (gets hot).

I've even dumped the key turn start for a flick switch for power to the ignition and a push button for the starter motor.

mgbv8 · Post by **mgbv8** » Sat Jan 11, 2014 7:25 pm

If you have 12 volts to the dissy and no spark it indicates that the earth trigger isnt doing its job.

Is the rotor arm matched to the dissy cap. ie Is it making contact with the HT bush in the cap?

You can If you want to test the coil in the car then make sure it has 12 volts available to the + terminal. Ideally run a fresh lead straight from the battery for testing. Pull the HT lead off the dissy cap and stick a spark plug in there. Disconnect the neg wire from the coil and make up a test wire which will connect to the coil neg connector.

You can either wrap a wire around the plug thread to earth or just hold the plug to ground. If you now turn on the 12 volt feed and tap the other end of the test wire from the Neg terminal to a good ground you should see a spark at the plug. When I say tap, I mean tap the wire to ground quickly like twice a second or faster. You should see a spark every time you tap the wire. If you are close enough to the battery then tap the wire straight to the Neg terminal.

This just bypasses the dissy and simulates the action of the points or trigger module. If you get a spark then look at the dissy. If you dont then double check for good earth connections and try again. If still no joy then find out what the resistance readings on the coil should be and check that if you have a multi meter.

Perry

ChrisJC · Post by **ChrisJC** » Sat Jan 11, 2014 10:07 pm

So, if you have an EFi Range Rover, then you should have the ignition amplifier on the side of the distributor.
You need to feed this with +12. You also need to feed the positive side of the coil with +12. The other lead from the ignition amplifer goes to coil negative. This should be enough to get a spark.

The white/black is coil -ve and rev counter. The white is the +ve ignition feed and coil +ve.

If the coil gets hot, something is wrong.

Chris.

volkssturm45 · Post by **volkssturm45** » Sun Jan 12, 2014 2:55 pm

Wow thanks for all the input guys I'm really grateful for all the help and advice that's flooding in, with a bit of luck might get this bug sorted Wink

Yes Chris it's running an ignition amplifier on the side of the dizzy. Dizzy, ignition amplifier and coil are brand new, thought that might be the issue so bought a new set.

I'm going to do some of the test mentioned above see what results I get, we did some of those suggested with mixed results but I'm confident the coil works fine. When I mention it 'getting hot' it was because we left it energized (coil) for a few minutes to test ideas out. Even tried disconnecting the alternator just in case that had issues.

Did a quick test as suggested connecting a spark plug directly to the coil king lead and tapping the neg terminal.....got a spark but very weak?

ChrisJC · Post by **ChrisJC** » Sun Jan 12, 2014 4:45 pm

volkssturm45 wrote:tapping the neg terminal.....got a spark but very weak?

How do you mean 'tapping the neg terminal' ?

Chris.

volkssturm45 · Post by **volkssturm45** » Sun Jan 12, 2014 6:28 pm

As described in Perry's post - advice to test the coil on it's own.

ChrisJC · Post by **ChrisJC** » Mon Jan 13, 2014 9:19 pm

I see. Well that should get you a spark. I am not sure how good a spark as it won't be a clean 'break', and you don't have a condenser in the system. You could remove the distributor, earth it's body, then spin the shaft and see if you get a decent spark.

Chris.

volkssturm45 · Post by **volkssturm45** » Sun Jan 26, 2014 11:56 am

Sorted! Thanks guys for the help and input, finally found the problem was an extra earth I didn't need

Knew it would be something so simple just couldn't see the wood for the tree's as they say. Anyway the mighty V8 has roared back into life this morning after a six year coma....well chuffed

unstable load · Post by **unstable load** » Sun Jan 26, 2014 12:02 pm

Result! Good one.