Fuel Injector? Fuel Injection Pump?

[vande17941]

I have a 230sl (1966) that is fouling one of the plugs consistently because that cylinder is running way too rich.

Is it possible or likely it could be a bad injector causing the rich condition in that cylinder? I'm worried that it could be the fuel injection pump....but could that cause only one cylinder to be rich?

I'd like to get some advice from some of the guys on here that have experience and know their stuff.

FYI- All the ignition components are in top shape, compression is 150-160, leakdown is about 17%.
Thanks.

[Jonny B]

What cylinder is experiencing the fouling? Is this a new issue, just occurred, getting worse? Automatic? Original injectors? Inj pump ever rebuilt? A few more details will help the experts assist.

[vande17941]

This is a 230sl with 52k original miles...has never had the head off, never had the injectors or pump off. I'm suspecting that it has disintegrated valve seals and I'm actually oil fouled in the cylinder. I went with a w9dc plug and it improved Once I get it hot and run it hard,...it runs awesome. Compression and leakdown are awesome.
I'm thinking I will test the injector for proper flow, and then consider a valve job that I need to do anyway.

[ja17]

Yes, check the injector.  At 52K You should not need head work.  Maybe remove the valve cover and use a flashlight to see iif the valve seals on that cylinder are still seated on the valve guides.

[garymand]

Just one plug, huh?     Not too bad I think.  1st swap injectors.  If it doesn't follow the injector, take a look at the valve guide seals.  They can be replaced with the head inplace.

[vande17941]

Thanks everybody. I will pull it apart this weekend and check the valve seals and the injector

[vande17941]

Figured it out...wasn't running rich. Pulled the head and saw the #4 cylinder exhaust valve was missing the stem seal. Also, the valve guide was slipping up/down acting as an oil pump into the cylinder. At the machine ahop...can't wait to get her back together.

[ja17]

Yes you will have to order an oversize valve guide. Have the head checked for flatness since a loose valve guide is often caused by overheating. However, only mill the head as needed.

[Shvegel]

I second Joe's advice to not mill the head unless needed.  Also if I remember correctly the new valve guides are stepped at the top tp keep them from dropping into the cylinder head.  I would replace them all.