Author Topic: sooted plugs query  (Read 288 times)

Offline Andy Green

  • Posts: 103
  • Name: Andy Green
sooted plugs query
« on: November 25, 2021, 11:13:53 AM »
My 57 Fleetwood engine is not running correctly, removing plugs some are black and some ok. Looking from the front of the car, the left bank of plugs, the outer ones are black and the inner two are ok, on the left bank the outer ones are ok and the inner ones are black. Plugs and wires are new, Carter carburetor has been completely overhauled. Ignition timing is all ok too. Anyone any ideas what the problem is please? Thanks guys.

Offline wheikkila

  • Posts: 299
  • Name: Wayne Heikkila
Re: sooted plugs query
« Reply #1 on: November 25, 2021, 12:22:24 PM »
It sounds like you have a vacuum leak affecting the one bank. Or your rebuilt carb is leaking on one side. Most likely you have a vacuum leak. The carb was richened to compensate. So now it is flooding the other bank. The first thing I would do is look down the carb while it is running, just to make sure gas is not dripping from one side. If no issues there. Then start lookin for a vacuum leak.
                               Thanks  wayne   

Offline J. Gomez

  • Posts: 2294
  • CLC Number: 23082
  • Name: J. Gomez
Re: sooted plugs query
« Reply #2 on: November 25, 2021, 03:30:45 PM »

When you referring the “plugs are black” is that oil or fuel too rich?  ???

If you look at your Service Manual the 365 intake manifold feeds cylinders 2, 3, 5 and 8 on the top passages and the rest on the bottom.

If the plugs are black do to oil there is a possibility oil is being feed by the main vacuum line.  ??? The main vacuum line which connects up to the intake manifold is place on the top and is feed by the top passages.

If your vacuum manifold (on the firewall) and the control valve (on the side of the block just next to the starter) are defective oil from the vacuum pump “could” be absorbed through these and into the main vacuum line on the intake manifold.

You may or may not see the tell-tale of smoke at the tail pipe but the plugs will show it.

Good luck..! 
J. Gomez
CLC #23082

Offline fishnjim

  • Posts: 2171
  • Name: J. Bozin
Re: sooted plugs query
« Reply #3 on: November 25, 2021, 07:58:36 PM »
Depends what you mean by "not running correctly"?   

Start with a compression test to be sure it's not bypassing.   
Gomez has a good lead.   You can check that one fairly easily by inspection.

All the plugs get the same fuel mix from the manifold, so it's not likely the carb. 
The reverse maybe true, the other ones are too lean?   

Blackness by itself isn't a problem, unless it gets to the point where the plug becomes conductive and won't spark.   Carbon is conductive.
Depending on the mileage it maybe deeper issues.   I'd also check the spark with a inductive timing light on each wire and makes sure they're firing properly.

Offline Andy Green

  • Posts: 103
  • Name: Andy Green
Re: sooted plugs query
« Reply #4 on: November 26, 2021, 03:12:34 AM »
Hi Guys,
Many thanks to you all for helping out. I should have said it was a fuel mixture issue making the plugs black and not oil. So vacuum problems seem to be the place to look at next.
I can always rely on you guys to come up with answers, thanks again.



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