MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - horrible gunge on spark plug

Can anyone tell me why a plug should look like this after 800 miles?
I suspect that the water temperature is low but even then this is horrible!
j c rathbone

Still having difficulty with the uploading of picture, will win!
This thread goes with the first attempt re spark plug fouling


j c rathbone

Do you have a 3/4" plug in a 1/2" head?
Jim Merz

The plugs are the ones supplied by Moss, length is 1/2 in.
Thanks
John
j c rathbone

When I got my TD, it had 1/2" plugs in a 3/4" head, and there was no such build up. They looked fine, and I am sure they had been there for a while. The only issue I had was chasing the unused threads in the head to remove some moderate carbon buildup that occured over time, and the plug chaser took it out easaly.

Larry
L Karpman

No clue what that is, but it is scarry looking to me. It almost looks like tiny melted, fused particles on it. George
George Butz

Tell me about the fuel and any additives your using J. C.

LaVerne
LaVerne

Just a guess, but it could be both oil and water (and possibly anti-freeze) getting into the chamber.

Have you done a compression test?

Is your coolant level stable?

Gord Clark
Rockburn, Qué.
Gordon A. Clark

I think Gordon's got it. A head gasket problem or a cracked head.
Don Harmer

jc,

A little more data may help to suggest diagnosis;
All plugs fouled or one?
Any smoke outa exhaust on tickover or accelerating - black, blue or white?

Looks like oil deposit but at only 800 miles there would be a shed loada of blue smoke?

Regards
Graham (honorary Dave)
TD/C 7822
G.D. Smith

Thanks for the interest from y'all.(?)
More info. The engine was rebuilt (rebore, bearings, camshaft) about 4000 miles ago. Converted to unleaded petrol, head and block skimmed. No additives. The gunge build up is on the front two plugs but the back two are blacker than they should be. The engine runs okay and at a quick estimate is returning about 30 to a gallon (English gallon) The water level is constant and doesn't need topping up although I do have concerns about the running temperature which varies between 55 and 70 (55 when it is 9 outside and 70 when it is 25 outside) I will do a compression test this morning and report back.
John
j c rathbone

Re the last message.
The compression test on each cylinder gave between 140 and 135 psi on all cylinders. The test was done when the engine was cold (the test instructionswere when the engine was hot) Can't do that just yet because I ahve got the thermostat out for replacement.
John
j c rathbone

John

Tesco petrol? ;-)

David
David Wardell

John - it's that Continental petrol ! only joking!

See Archives re. plug types but check plug hole depth with piece of bent wire and I can thoroughly recommend NGK plugs say one of their BP range (projecting nose) available everywhere. Why Moss for plugs ?

Nice to talk at Speyer and glad you got back OK.

Cheers John M.
J.C Mitchell

Have you checked the condition of the air filters? Something being sucked through the front carb?
Steve Gee

john, what color is the smoke from your tail pipe and when do you see it? you are burning something besides gasoline in this combustion chamber. it is just a matter of finding out what and to help determine what needs fixing note WHEN you see the smoke. (start up, coming off throttle, applying throttle, idle, etc.) it looks to me like this is something beyond hot plug/cold plug, wrong reach plug. my guess in order of likelyhood: valve guides, head gasket, and less likely if compression test is good, rings. carb, lead fouling with cold plug...scratch the lead fouling...after looking at the pic again it looks like burned oil to me but my computer image may be misleading. best of luck. let us know what you find. regards, tom
tm peterson

jc,

Hmm, Maybe you got the breather hose from the tappet cover hooked up to the front carb air cleaner?

Graham (honorary Dave)
TD/C 7822
G.D. Smith

If two front plugs fouled it definitely suggests a mixture (too rich) problem with the front carb. Try leaning it up a bit. I had this exact problem with my TF and 1/2 turn on lean fixed it.
SEAMUS
F. HEALY

I'm doubting it runs well with that plug in it. How long does it take to end up like that? Did it happen after winter storage? Anyway, I'm wondering if it still fouls new plugs after a nice hard run.

It doesn't look like just a rich mixture to me, it looks like something leaked in during winter storage and the plugs should have been at least cleaned before the first start of the season.
Tom

Deposits
The accumulation of deposits on the firing end is influenced by oil leakage, fuel quality and the engine's operating duration. This quote is on line at http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp?mode=nml. At 800 miles, operating duration can be ruled out, fuel can also be ruled out as not all plugs look that way. Also fuel would not do this at 800 miles.Water/coolant is not on the NGK list as it would clean all of the carbon from the chamber, including the deposits on the plug.
Len Fanelli

Hi Graham(honorary Dave)

Perhaps I'm missing something here but assuming standard rocker cover set up,breather does go to front air filter on a TF !

Cheers (puzzled) John.
J.C Mitchell

jc Do yuo havea breather from the sump and if is it open, if not you will have
pressuriced sump the fume will be pressed to the rocker cower and to the air filter more fumes than normal.
a shot in the dark
thoralf td 4490
t g sorensen

ok, i am going to ask again..WHEN do you see smoke and what color is it? ..throw us a bone here.... we need more info to help troubleshoot. regards, tom
tm peterson

John,

To answer your 'puzzled' comment, nothing in the posts to define TD or TF, but you have inside info from your meet with jc @ Speyer. Sure the standard TF set up doesnt have the rocker cover breather to the front carb, I was guessing a non standard set up which may feed oil droplets to the front carb. The deposit looks very much like it's caused by oil, hence the guess that the breather may be feeding oil to the front carb.

Regards Graham (honorary Dave)
TD/C 7822
G.D. Smith

Hi Graham,

I don't want to prolong this rocker breather issue,but you're right 'jcr' omitted to say on this thread what car he is referring to. His car at Speyer was a TD but I can't remember if he had non-standard twin air filters.

As you say excessive oil could be an issue here - no doubt 'jcr' will give further info. if he feels it necessary.

Out of interest could you confirm that the 'doesn't' in your second sentence should read 'does' ! All standard TFs had the rocker breather to the front air filter as I'm sure you know !

Cheers John.
J.C Mitchell

Have you had bronze guides fitted into the unleaded head? Thee need an extra clearance and allow oil to leak into the combustion chamber. I had endless problems with my TD (now sold)until I found it had bronze guides and "O" ring seals. These are completely usless and after changing to ones from a Mini - which fit over the guide itself and have small garter springs the engine ran sweetly.


Jan t
J Targosz

Jan t - good point reminding me of something I'd forgotten. Now you've got all this advice 'jcr' let us know what you're going to do !

Chers John.
J.C Mitchell

Thanks for the comments, I have been away for a couple of days.
The answer to non member Tom. The problem is not after winter lay up but after 800 miles in 3 days. It was misfiring at low revs but that was closed up points rather than fouled plugs. I was amazed at the tolerance of the XPAG.
To Tim Peterson
No smoke to be definite about but it does seem like oil fouling.
The car is a TD (sorry not to mention it before) with the pipe from the rocker box going to the pan oil filter fitted with a restrictor.
I will find out if the machine shop that did the head conversion used bronze guides it is an interesting thought.
JC
j c rathbone

This thread was discussed between 14/06/2007 and 19/06/2007

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.