Fouled spark plug... ????

[ocjason]

What could be causing my plug to have dry soot carbon on it.

Thanks

[ocjason]

This is my 1972 MFI I am having the trouble with.

[emac]

Too rich

Ernie

[422flat6]

Have you been through Check, Measure, Adjust?
Do all the plugs look like that or just the one?
What's your plug gap? 0.6 mm is spec.

In addition to CMA, search this forum for CMA2 by Grady Clay and check the following:

• Check your cap and rotor for burning or carbon tracks on the contacts.

• Verify your plug wire(s) have continuity with a multimeter.

• Use a spark tester to see how strong of a spark you're getting. Should be bright and blue.

• Is your warm up thermostat getting hot air from the heat exchanger, clean, and fully leaning out the MFI pump at operating temp?

• How many spring washer pairs and spacers do you have in the warm up thermostat? Should be 25 pairs and 1-3 spacers.

• Is your microswitch adjusted properly and is the overrun solenoid on the MFI pump functional? Apply +12V and listen for a click.

I've been chasing a similar problem on my '72 T. I had 6 black carbon fouled plugs, found the cap and rotor were badly burned. I replaced the cap and rotor and that revealed that #6 was lean and the other five were varying degrees of black. I'm getting 14 mpg, which is too low, suggesting it's too rich. I had the injectors cleaned and the problem is still there. I've decided to get the MFI pump rebuilt. I gotta get the plugs evened out before I can lean out the pump or else #6 will go too lean.

What plugs are you running? If they're all looking like that and nothing else is wrong it could just be that the plugs are too cold. I wouldn't switch to hotter plugs first though without checking everything else because that could be just treating the symptom.

[dicklague]

Do you know the AFR reading?

[T77911S]

just one or all 6.

if jsut one i would swap injectors and see if the problem moves.

[ocjason]

It is just one plug. Passenger side closest to the front. I will try the CMA recommendations. I will also try to swap the injectors. the cap and rotor look ok.

[ocjason]

If it is the injector. Where do you guys recommend sending it out to be cleaned? Im in Orange County CA.

[bpu699]

Bad injectors usually run lean... if its just the one cylinder, are you sure its firing regularly?

[patz]

EPI Engine Performance Injectors. Cleaning, Testing, Rebuilding, Flowing

[422flat6]

If you need your injectors cleaned, send them to an MFI specialist. Gus at Pacific Fuel Injection or Mark at MFI Werks. These injectors are more like diesel injectors than anything. Opening pressure is over 200 psi. Mark cleaned mine and I was very happy with the results and his service.

[T77911S]

swap injectors and see if the problem moves.

dont speculate or spend money, test things.


its been a long long.......long time since i opened an injection pump but there could maybe be something inside making one cylinder rich.

the other option is the other 5 are running lean and the mixture is set rich to compensate.
again injectors or air leaks.

[tobluforu]

Also, pull out the idle/air screw and check to see if the port might be clogged. I doubt it, but what the heck.