What causes plugs like THIS??

Talk about the E-Type Series 1
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jagwit
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#21 Re: What causes plugs like THIS??

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!.
Best Regards
Philip
71 E-type V12 Coupe,
80 XJS (EFI by Megasquirt & EDIS-6 + 5sp manual overdrive)
73 Jensen Interceptor
74 Interceptor (EFI by Megasquirt + overdrive 4sp auto)

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#22 Re: What causes plugs like THIS??

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

Less than 1000km later and we have this:
tn_20180607_150153.jpg
tn_20180607_150153.jpg (79.76 KiB) Viewed 377 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??
Last edited by jagwit on Fri Jun 08, 2018 7:35 am, edited 2 times in total.
Best Regards
Philip
71 E-type V12 Coupe,
80 XJS (EFI by Megasquirt & EDIS-6 + 5sp manual overdrive)
73 Jensen Interceptor
74 Interceptor (EFI by Megasquirt + overdrive 4sp auto)

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Gfhug
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#23 Re: What causes plugs like THIS??

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
S2 FHC Light Blue

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#24 Re: What causes plugs like THIS??

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.
Best Regards
Philip
71 E-type V12 Coupe,
80 XJS (EFI by Megasquirt & EDIS-6 + 5sp manual overdrive)
73 Jensen Interceptor
74 Interceptor (EFI by Megasquirt + overdrive 4sp auto)

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Series1 Stu
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#25 Re: What causes plugs like THIS??

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

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

Regards
Stuart

If you can't make it work, make it complicated!

'62 FHC - Work In (slow) Progress
'69 Daimler 420 Sovereign
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#26 Re: What causes plugs like THIS??

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.
Best Regards
Philip
71 E-type V12 Coupe,
80 XJS (EFI by Megasquirt & EDIS-6 + 5sp manual overdrive)
73 Jensen Interceptor
74 Interceptor (EFI by Megasquirt + overdrive 4sp auto)

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#27 Re: What causes plugs like THIS??

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
tn_20180609_104454.jpg (69.67 KiB) Viewed 318 times
Best Regards
Philip
71 E-type V12 Coupe,
80 XJS (EFI by Megasquirt & EDIS-6 + 5sp manual overdrive)
73 Jensen Interceptor
74 Interceptor (EFI by Megasquirt + overdrive 4sp auto)

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