Next mystery - Plug keeps fouling out

[twistedtree]

On to the next mystery.  My engine has been running like crap and I finally started trying to sort it out and quickly discovered that the #2 cylinder wasn't firing.  The plug is also black, but not wet.  I checked for spark and there was plenty.  I checked compression and it's 170 PSI.  I checked for fuel at the injector and it gets wet.  I also checked my notes from when I first got this engine running and was reminded that I found #2 was not firing back then, but that replacing the plugs (BP5ES) solved the problem.  Or not.

I cleaned up the fouled plug and swapped it with #1.  On restart all cylinders were firing fine, but within 10 minutes #2 had dropped out again.

My mixture seems OK using the split linkage test, and all other cylinders seem to run fine without fouling.

Any ideas?

Oh, and I checked the resistance on the #2 wire and measured 1k end to end which I think is correct?

[Benz Dr.]

Bad injector.

[twistedtree]

You figure it's allowing the cylinder to be over-fueled?  What's the best way to test?  I've got a pile of spares, but they are 200 miles away from where I am now with the car, so I can't just swap and see.  Maybe I should just swap #1 and #2 and see if the problem follows the injector?

Thanks

[twistedtree]

Here's what I've done to further isolate this problem:

- I tried swapping the #2 and #5 injectors to see if the problem followed the injector and it did not, so from that I conclude the injector is not the issue.

- I also tried new plugs and #2 again fouled within a minute.  That rules out a defective plug

- I tried interchanging the wires for #1 and #2 to see if the problem might be the wire even though it appeared I was getting a good spark.  The problem stayed with #2.

At this point I don't think there is anything left except the FIP.  However, I don't know enough about the internals of the plungers and rack to be confident that this is an understandable failure mode.  I think a stuck plunger would cause inadequate fuel, not excessive fuel.  I'm guessing (but don't know) that bad internal seals would also cause less fuel delivery, not more.  But others have said in the past that these injection pumps go rich when they fail.

Does anyone have any other bright ideas about what might be the cause of this rapidly fouling plug and dropped cylinder before I pull the FIP and send it off the to FIP Spa for a facelift and makeover?  I would send the injectors too for good measure.

[Cees Klumper]

Just a SWAG but could it be the distributor cap (crack, or something else, causing bad spark intermittently)?
That or, more ominously, something like a coolant leak to cylinder no 2?

[twistedtree]

Thanks Cees.  After all, SWAGs are what auto repair is all about :-)

I neglected to mention that I replaced the cap, but not the rotor, points, or condenser because my local  part supplier gave me all the wrong stuff. :-(

As for the coolant leak, my thinking is that any compromise of the combustion chamber large enough to cause complete loss of a cylinder would show up in a compression test.  Does that seem like a reasonable assumption?  Also, when runnIng there is no abnormality in the exhaust, and burning coolant is usually very distinct in smell, if not visually as well.

[wwheeler]

If there was excessive fuel in #2, wouldn't it run rich before it fouled out and you would see some black smoke out the tailpipe? Seems like the plug would also be very wet if there was excessive fuel.

[Benz Dr.]

Are you sure it's fuel related and not oil fouled?

[stickandrudderman]

Post a picture of the failed No 2 spark plug and that should tell us something.

[twistedtree]

Are you sure it's fuel related and not oil fouled?

I'm sure that I'm not sure     

I'd need to have a pretty high intrusion rate of oil to keep fouling a plug, wouldn't I?  And if that much oil is making its way into the cylinder, wouldn't I see low compression?

[twistedtree]

I'll get a picture in a little bit.

Because I've got good compression, I've ruled out a number of things, perhaps incorrectly.  With good compressions, I'm assuming I don't have:

- Blown head gasket
- Antifreeze leaking into the cylinder
- Oil leaking into the cylinder
- Stuck valves

Am I jumping the gun by assuming these things are OK?

Speaking of running rich, just smelling the exhaust I'd judge the car is running rich, but playing with the split linkage test says the mixture is OK.  I wouldn't stake my life on it, but an over-fueled and non-firing cylinder seems to be consistent with these symptoms.

And now to find my camera.....

[twistedtree]

Here's a picture of the #1 and #2 plugs side by side, left to right.  These are new plugs and have run for only about 10 minutes.  #2 was wet and smelled of gas when I pulled it out.

Another thing to consider is that the P.O. had built a home-made injection calibration machine and I'm 90% certain that he worked on this injection pump.  The other sample of his FIP work that I have resulted in this thread http://www.sl113.org/forums/index.php?topic=15817.0 on "Massively Rich Mixture" and ended up with a complete rebuild by H&R, and a real chuckle from Hans over what he found.  The bottom line is that I have a lot of circumstantial reasons to suspect the FIP.

[twistedtree]

Another thought.....  I know the fittings on top of the FIP where the lines attach can restrict fuel delivery if they are over-tightened.  Can they also cause over-fueling if they are not tight enough?

[glenn]

Rotate no. 2 piston in the FIP a 'smidgen' leaner.?

[twistedtree]

I tried another experiment.   I got two lengths of clear plastic tubing, and fit them over the pipe nipples on the FIP for #1 and #2, then cranked the engine for about 10 seconds.  The amount of fuel that accumulated in each tube was the same, so I no longer believe I have unequal fueling between cylinders.

Back to the drawing board.....

[stickandrudderman]

Looking at your picture and reading the info I suspect you have an oiling problem on No.2 cylinder.
You will need to do a compression check, a cylinder leak test, a block test and a manifold vacuum test.
However, be warned that none of these will necessarily tell you where the failure (if any) is, although the manifold vacuum test is my favourite as a worn out engine can still pass the other three tests.
You may end up stripping the engine and even then it might take knowledge and experience to identify the cause of the fault.
If you need a straw to clutch at you could try changing the valve seals as this can be done without major surgery.

[glenn]

I tried another experiment.   I got two lengths of clear plastic tubing, and fit them over the pipe nipples on the FIP for #1 and #2, then cranked the engine for about 10 seconds.  The amount of fuel that accumulated in each tube was the same, so I no longer believe I have unequal fueling between cylinders.

Back to the drawing board.....

That means -forget the smidgen.....

[ejboyd5]

For what it is worth, that looks like oil, not gasoline, is causing your problem.

[glenn]

Peter. How about a hotter/colder plug  in 2 for additional data?....

[Benz Dr.]

After thinking about this a bit I thought that maybe a really simple answer might work. Try a new distributor cap - then I saw that you changed that.
I had a distributor once that had a bent shaft and one side of the cap wasn't firing. I can't imagine how this could ever happen because the shafts are very hard metal. In this case, the rotor wasn't coming close enough to the post in side the cap and so it simply wouldn't fire one spark plug. I'm not ruling out ignition on this one.

  OK, so when you drive the car at speed, does it foul out then as well? Or is it only at idle?

  The pictures of your spark plugs don't tell me what I need to see. Shine a light on the plugs so that the electrodes are highlighted. There would be things I'd like to see but can't because those areas are too dark. I'm particularly interested in what the tips of the electrodes look like.

[twistedtree]

Thanks for all the suggestions.  This one may turn out to be another mundane solution to a perplexing problem.  I decided to step back and re-check a few things and found some linkage problems including a throttle valve that wasn't closed all the way.  That's what happens when you work on too many cars at once and don't thoroughly review your notes before resuming work on one.  I also improved my technique for split linkage tests at speeds above idle.  After getting things set up correctly, it runs better.  Still pretty far off from correct, but better.  This may turn out to be nothing more than a pile of little problems compounding each other.

I need to take a pause for a few days for some travel, and in the mean time have the rest of the ignition parts ordered including new wires and coil.  When I return I'll start clean with all new parts and take it from there.

Oh, one other question.  I have the triangular timing pointer, which I think means I should be using the rear timing scale.  Is that correct?  I ask because when I'm set up on the rear scale things sound retarded to me, and the front scale seems too far advanced.  Can anyone confirm which scale I should be on?

As for how it runs, instead of a smooth exhaust note at idle, there is a throbbing.  Driving it stumbles when you give it gas, but when it gets reved up it tends to smooth out.  With my new and improved split linkage skills, I think it's lean running at about 2000 RPM which might explain the stumbling.

More when I return.

[mrfatboy]

The triangle pointer uses the rear scale (closest to engine).  Would you describe the idle "Throbbing" as "searching" or "hunting"?  If so, I would say its running lean.

[twistedtree]

No, no searching or hunting.  Its stable, but pulsating.  My gut reaction listening to it is that it's a cylinder that's not firing.  That's what got me started pulling plug wires to test for dead cylinders.  But keep in mind that I have very little air time with these motors, and even less with ones that are running properly, so my sense of what's wrong based on how things sound could be off.

[wwheeler]

I may have missed this, but has the ignition been ruled out? That #2 plug doesn't look all that bad to foul itself out after 10 minutes with a good ignition path. I wonder if you put a timing light or other ignition pulse device on the plug wire and see if it still has fire after 10 minutes. Maybe with the 10 minute warm up, enough heat is generated creating a high resistance and kills the#2 path?
 

[twistedtree]

It's still possible that the problem is in the ignition.  I attempted to replace everything, but the local parts shop only got two parts right: the cap and the plugs.  That said, I measured the resistance of all the wires and got 1K which I think is correct.  The only wire that was suspect was #1, but it seems to be firing OK regardless.

I'm in london for a few days so the car is currently on hold.  In the mean time, I have all the correct ignition parts on order for when I return.

I thought I had set up all the linkages on this car, but when I went back and checked I found notable problems, so at this point I'm stepping back and going through things again from the start.  I may have just gotten sloppy on this one.