What causes plugs like THIS??

jagwit · Post by **jagwit** » Thu Apr 12, 2018 2:24 pm

Today, I took the car for a drive and then pulled a plug afterwards.

It looked perfect, no trace of that white powder. Coolant level had not changed from before the drive.

So I’m rather relieved!.

jagwit · Post by **jagwit** » Thu Jun 07, 2018 1:10 pm

Less than 1000km later and we have this:

: tn_20180607_150153.jpg (79.76 KiB) Viewed 3018 times

Front of engine on the left, back of engine on the right.

I should add that I found the servo diaphragm was torn, every time the brakes were applied, huge amounts of unfueled air rushed into the intake manifold - right where the rearmost two cylinders draw their intake charge from.

Could it be that this is resulting from all that unfueled air entering the intake manifold behind the carbs closest to the bulkhead??

Gfhug · Post by **Gfhug** » Thu Jun 07, 2018 2:13 pm

Philip, where do you class cylinder 1 as being? Front or back of engine?
No 6 is at the front. Just might help us understand where you think this un-fuelled air is reaching.

Geoff

jagwit · Post by **jagwit** » Thu Jun 07, 2018 2:27 pm

Gfhug wrote: ↑
Thu Jun 07, 2018 2:13 pm
Philip, where do you class cylinder 1 as being? Front or back of engine?
No 6 is at the front. Just might help us understand where you think this un-fuelled air is reaching.

Geoff

O heck!! Yes, then I've got my spark plug numbering wrong!! I'll fix it.

Series1 Stu · Post by **Series1 Stu** » Thu Jun 07, 2018 4:00 pm

Are you saying that replacing the servi diaphragm cured this problem?

Regards

jagwit · Post by **jagwit** » Thu Jun 07, 2018 4:54 pm

Nope, I'm saying it's the only and most likely cause for the plug's condition found thus far.

Obviously, I'm fixing the membrane and THEN I'll be keeping an eye on the plugs. IF the plugs THEN remain good, the conclusion will be that the broken membrane caused the plugs to become fouled as per the pics.

jagwit · Post by **jagwit** » Sat Jun 09, 2018 8:51 am

Another observation which might be relevant in this instance. The RH exhaust (which serves the rear three cylinders) appears to be burning more grey than the left one.

: tn_20180609_104454.jpg (69.67 KiB) Viewed 2959 times

jagwit · Post by **jagwit** » Fri Dec 21, 2018 11:38 am

Update:

This car has now been driven quite a bit since doing all this work and the plugs are no longer fouling as per post #1.

I am now convinced that the vacuum leaks were the main cause of the plugs manifesting like this.

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What causes plugs like THIS??

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