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4.3gl frustrating ignition problem! Driving me mad!!!!!!

S

Sicobra

New member
I am really hoping someone can help me as I am pulling my hair out over this problem. I have a 4.3GL Volvo Penta engine with the EST style distributor in my sports cruiser and despite replacing the plugs, leads, distributor cap and rotor all the usual service items I have an issue with intermittent missfires on plug leads number 1 and 3. I have found this while using my timing light, it fires the light consistently and evenly on all plug leads apart from these two, the timing light flash is sometimes regular but often irregular on these leads only!!!).
I found a surprising amount of build up on all the plug contacts inside the new distributor after about 20 hours running and I am also surprised at how big the gap is from the rotor arm tip to the internal cap contacts(what should the be? They are about 3mm on mine!)
Can anyone tell me what I am missing or doing wrong? Could it be a problem with the ignition module inside the distributor? I am getting very frustrated with this problem as the engine starts great, runs OK except for this annoying slight missfire which is stopping it run as smoothly as it should.
Please, please, please put me out of my misery!!!!!!!! Cheers, Simon
 
Sicobra said:
I am really hoping someone can help me as I am pulling my hair out over this problem. I have a 4.3GL Volvo Penta engine with the EST style distributor in my sports cruiser and despite replacing the plugs, leads, distributor cap and rotor all the usual service items I have an issue with intermittent missfires on plug leads number 1 and 3. I have found this while using my timing light, it fires the light consistently and evenly on all plug leads apart from these two, the timing light flash is sometimes regular but often irregular on these leads only!!!).
I found a surprising amount of build up on all the plug contacts inside the new distributor after about 20 hours running and I am also surprised at how big the gap is from the rotor arm tip to the internal cap contacts(what should the be? They are about 3mm on mine!)
Can anyone tell me what I am missing or doing wrong? Could it be a problem with the ignition module inside the distributor? I am getting very frustrated with this problem as the engine starts great, runs OK except for this annoying slight missfire which is stopping it run as smoothly as it should.
Please, please, please put me out of my misery!!!!!!!! Cheers, Simon
Click to expand...

Ayuh,... So,... Why are ya postin' in the Mercruiser forum,..??
 
This 4.3L GL EST system is photo eye, correct? Is so, the rotor wheel breaks the light beam that creates the spark triggering event.
I doubt that you'd have the wrong rotor.
The rotor wheels are cut with fairly decent accuracy, so again, I doubt that this is the issue. .... but never say never.
Double check this and make sure that it is correct.

76338.jpg


BTW, there is a method for cleaning the infra-red photo eye.
Perhaps give that a try.

We are not bound to any certain indexing of the distributor housing, so long as the spark plug leads are indexed correctly as per the firing order.
If you want to eliminate the distributor and/or rotor wheel, re-index the distributor in the engine block.... perhaps by 180*.
Lable and remove all spark plug leads from the cap, and rotate the distributor housing by 180*..... or whatever you choose.
Re-arrange the spark plug leads to accommodate the correct firing order.
Set your BASE advance again.

Fire up the engine and see if the missfire on plug leads #1 and #3 follow the distributor, or follow the #1 and #3 cylinders.
If the misfire follows the ignition distributor, then you have narrowed this down to a distributor problem.
If the misfire follows #1 and #3 cylinders, then this may narrow it down to plugs and/or plug wires, or an actual cylinder issue.


This is using the ole P of E.... process of elimination.


.
 
Last edited:
It may be.

I was thinking that the rotor on this system was integral with the wheel..... but it may not be.
Here's a similar V-8 cap/rotor.

images


So you may be correct.... he may have the wrong rotor.
 
Pull the optic sensor out and look at the bottom for corroded fine wires. If it is the old style they corroded alot.
 
Guys, thanks for all the advice, it has been a great help and we have now through trial and error managed to sort the problem and it was all down to faulty spark plugs! I can't believe it after all the messing about, we had tried more new plugs in the first place and it made no difference, a friend mentioned he had access to a professional plug tester and took all twelve newly purchased plugs away for testing, result, 8 were bad!!!!!! Took them to our supplier who made a call and once the batch cross reference had been made to his supplier it seems that he had been missed out from a recall from the manufacturer for a batch of faulty plugs and I got them, he had over 100 sitting in his stores which have now all been returned. I may have been the victim of this situation but at least I know that no one else will be put in the same situation.
So thanks again for all the advice and suggestions, my engine is purring like a kitten, cheers, Si:)
 
Good to hear you found it.

Could you share the information about the spark plugs? Brand, part numbers, date on box, etc?

Also, thanks for the update.:)
 
Hi, they were NGK and I was told supplied only to the UK market and a very small batch, I will try and get more details just incase anyone else has an issue, cheers, Si
 
Sicobra said:
I am really hoping someone can help me as I am pulling my hair out over this problem. I have a 4.3GL Volvo Penta engine with the EST style distributor in my sports cruiser and despite replacing the plugs, leads, distributor cap and rotor all the usual service items I have an issue with intermittent missfires on plug leads number 1 and 3. I have found this while using my timing light, it fires the light consistently and evenly on all plug leads apart from these two, the timing light flash is sometimes regular but often irregular on these leads only!!!).
I found a surprising amount of build up on all the plug contacts inside the new distributor after about 20 hours running and I am also surprised at how big the gap is from the rotor arm tip to the internal cap contacts(what should the be? They are about 3mm on mine!)
Can anyone tell me what I am missing or doing wrong? Could it be a problem with the ignition module inside the distributor? I am getting very frustrated with this problem as the engine starts great, runs OK except for this annoying slight missfire which is stopping it run as smoothly as it should.
Please, please, please put me out of my misery!!!!!!!! Cheers, Simon
Click to expand...

Maybe try pulling the distributor and checking the gear i have seen where the teeth get sheared away. Anyway just a thought
 
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