The V8 Owners Forum -

Hi

I have recently converted my 90 from a 3.5 to a 3.9 Efi.

The 3.9Efi I fitted had been sitting around for a few years not exactly sure how many.

Anyway the plugs keep getting fouled with black oil type goo.

My thoughts would be the valve seals are shot from standing round too long without oil.

Before I take the heads off do you think I'm chasing the right thing or should I be looking else where

Thanks in advance
Adi

if they are getting that fouled up i would be suspect of rings possibly.

They get fouled to the point where the engine doesn't start and I have to clean all the plugs.

The fact it was across all the cylinders I was hoping it might have been the rubber seals.

I was scared incase it's the rings.

Cheers
Adi

do a compression test.

They didn't seem to be too bad. Well at least fairly consistant

7: 143 8: 152
5: 150 6: 154
3: 157 4: 160
1: 153 2: 157

Are the plugs just wet and old, It may just be sticky rings, Have you tried new plugs and check the gaps, if it is stickey rings it could be worth squirting WD40 or Diesel down the plugholes and leaving for a few days, and turning the engine over every now and then with the plugs out.

Ian

No 7 is fairly poor, the diff between the lowest and highest should be no more than 10%. Its easy to find out if the compression is caused by bad rings tho as you add oil to the pistons and if the compression comes up its rings, if it doesn't its valves. Could well be your valves are all gummed up and not seating properly. If your plugs are getting that fouled I would expect the engine to be fairly smokey. When does it smoke the most? Valve guide seals would normally smoke most on the overrun.

ian.stewart wrote:Are the plugs just wet and old, It may just be sticky rings, Have you tried new plugs and check the gaps, if it is stickey rings it could be worth squirting WD40 or Diesel down the plugholes and leaving for a few days, and turning the engine over every now and then with the plugs out.

Ian

I'm on my 3rd set of plugs now. Gapped each time they go in.

Haven't tried WD40 but sounds worth a try before the engine comes back out.

Thanks
Adi

katanaman wrote:No 7 is fairly poor, the diff between the lowest and highest should be no more than 10%. Its easy to find out if the compression is caused by bad rings tho as you add oil to the pistons and if the compression comes up its rings, if it doesn't its valves. Could well be your valves are all gummed up and not seating properly. If your plugs are getting that fouled I would expect the engine to be fairly smokey. When does it smoke the most? Valve guide seals would normally smoke most on the overrun.

It smoke worst running under load/full throttle. Tick over not a hint smoke even on startup it doesn't smoke badly.

Thanks
Adi

Sounds to me like rings.

Time for another compression test

On the bright side here comes the chance to build a more torquey motor

Thanks for everyones help

Adi

Long shot
I agree with the above and those things are well worth doing

Are you able to check your EFI is working corectly?

It could be on limp home mode and seriously overfuelling - this will bore wash and then burn sooty / oily with whatever is in the engine
If you don't have test kit disconnect the battery for 30 secs just prior to starting it - it will reset the hotwire Ecu - this may then allow enough of a run to clear the rest of the crap out and get you to running temp to "blow out the cobwebs"

Ian

Thats a good one to try.

Thanks
Adi