No spark at plugs

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paulsv8manta
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No spark at plugs

Post by paulsv8manta » Mon Apr 16, 2018 7:58 pm

Hi guys,
After sorting out the blocked injectors and and put it all back together, the dam engine won't fire!
I've got a spark from the king lead so I believe it's either the cap which is new (as is the lucas rotor arm,) or the distributor which is the 35DM8 version. Now I must admit I did take of the dust cover and spray wd40 into the distributor under the plate to aid lubrication of hidden parts. Have I shot myself in the foot by doing this?



DaveEFI
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Re: No spark at plugs

Post by DaveEFI » Tue Apr 17, 2018 8:40 am

if you have a good spark at the king lead, it means the LT side of the dizzy, below the cover, is working. Which really just leaves the rotor arm and cap, as possible faults. Is the contact from cap to rotor present and OK?
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Re: No spark at plugs

Post by paulsv8manta » Tue Apr 17, 2018 10:15 am

Hi dave, the center part including the spring did fall out of the cap pushed it back in so looks ok.

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Re: No spark at plugs

Post by paulsv8manta » Thu Apr 26, 2018 11:36 am

Hi Dave, so I've purchased a new distributor cap and it's about 1mm smaller in dia. it's a very snug fit again there is still no spark at the leads.

My Distributor has these numbers stamped on the side

41944B <--<<[
35DM8 5082

My engine is a 3.5 EFI and I've been told I have the wrong distributor attached!
The earlier pre-85 cars (35DM8) were tagged as 'carb type'. The later 85-on cars (35DLM8) were tagged 'EFi type'.
And that the weights inside are different for carbs and efi, these distributors have different mechanical and vacuum advance which would generate a different distributor number

Each will have a variety of numbers according to what distributor advance characteristic it has, dependant on capacity and compression ratio of the engine it is intended for.

Do you have any idea how I interpret these numbers to see if I have the correct version?
I have a feeling I'm walking into a whole world of trouble. :roll:

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Re: No spark at plugs

Post by DaveEFI » Thu Apr 26, 2018 12:14 pm

Both carb and EFI SD1 had the same type of dizzy, which changed to the DLM after about '84. The DLM has the power amp mounted on it, so is self contained. The advance curve may well be different, but won't make the engine not start.

If you do have a good healthy spark at the king lead, don't see how it can be anything else than the cap or rotor arm at fault. Given there are 8 plug leads and plugs and unlikely they are all broken.

So is the spark at the king lead very healthy? I'd expect it to easily jump a 1/4" gap.
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Re: No spark at plugs

Post by stevieturbo » Sat Apr 28, 2018 12:13 am

If there is a spark available at the king when testing to ground...clearly that side is ok.

If no spark thereafter, it has to be lead/rotor arm related. Whether faulty...or simply never aligned with the posts to allow current to flow to the outlet.
9.85 @ 144.75mph
202mph standing mile
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Re: No spark at plugs

Post by DaveEFI » Sat Apr 28, 2018 8:32 am

The only other possibility I can see is the spark at the king lead is very weak, and not enough to fire a plug under compression.
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Re: No spark at plugs

Post by sidecar » Sat Apr 28, 2018 10:03 am

What sort of rotor arm are you using? I have had big issues with cheap ones in the past, the insulation breaks down and the HT just ends up leaking to earth. The poor rotor arm misalignment that the standard dizzies suffer from does not help either. (What I mean by this is that the rotor arm does not line up all that well with each HT post when the plug is supposed to fire).

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Re: No spark at plugs

Post by paulsv8manta » Wed May 09, 2018 10:46 am

Sorry for the long response. Waiting for payday!
So now I’ve bought new cap, rotor arm and leads and still no luck.
The spark from the king lead is not a great one I must admit. I’ve checked the connections on the coil and they are fine. The coil is new so now I’m at a loss.

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Re: No spark at plugs

Post by DaveEFI » Wed May 09, 2018 1:31 pm

Ah - remember there is rather a lot after the king lead. The spark has to jump the gap between rotor arm and cap, before getting to the plugs. So if it starts off weak might not make it that far.

Sure you have the right coil for the job? What voltage do you see when cranking the engine at the coil plus terminal?
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Re: No spark at plugs

Post by paulsv8manta » Wed May 09, 2018 3:06 pm

Hi Dave, just measured it and it’s only measuring 2 - 3 volts!

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Re: No spark at plugs

Post by DaveEFI » Wed May 09, 2018 4:05 pm

Is that coil positive (normally a plain white wire if no cold start system) to chassis?

I'm not actually sure what vehicle you have? But even with a ballast resistor cold start system, you should see full battery volts when cranking at the positive feed to the coil. So say something over 9v, and perhaps 9v or so running too.
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Re: No spark at plugs

Post by paulsv8manta » Tue May 22, 2018 9:40 pm

Hi Dave,
I have the Bosch 12v Coil (blau) Blue: 0221119027 with the Ignition unit: QHL-XEI8 all new. I definitely have a weak spark at the king lead when earthing the spark plug.
I have 12v coming to the coil and then on to the ignition unit.
I've checked the integrity of the earth wire from the coil to the ignition unit and that's fine.
The second earth wire from the coil which i understand goes back to the ECU, I'm not getting any reading that this is being grounded, unless it's only grounded when the engine is being turned over/running I've yet to test this route.

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Re: No spark at plugs

Post by DaveEFI » Wed May 23, 2018 9:58 am

Can I just check which dizzy you have? Is it the type with the amp mounted on it - or a separate unit beside the coil?
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Re: No spark at plugs

Post by paulsv8manta » Wed May 23, 2018 10:15 am

Hi Dave it’s the 35DM8 with no amp attached.

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