Pagoda SL Group
W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: twistedtree on March 17, 2012, 20:47:59
-
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?
-
Bad injector.
-
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
-
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.
-
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?
-
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.
-
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.
-
Are you sure it's fuel related and not oil fouled?
-
Post a picture of the failed No 2 spark plug and that should tell us something.
-
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?
-
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.....
-
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.
-
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?
-
Rotate no. 2 piston in the FIP a 'smidgen' leaner.????
-
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.....
-
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.
-
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.....
-
For what it is worth, that looks like oil, not gasoline, is causing your problem.
-
Peter. How about a hotter/colder plug in 2 for additional data?....
-
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.
-
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.
-
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.
-
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.
-
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?
-
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.
-
OK, I'm back and I think I finally got this one figured out. To make a long story short, it turns out the condenser was not making good ground contact with the distributor body. The result was flakey spark, fouling plugs, and fouling points. After a lot of cleaning and buffing of the distributor housing and the condenser mounting band/bracket everything appears to finally be working correctly. Once it finally occurred to me that this might be the problem, a screw driver between the condenser body and distributor body yielded a spark which confirmed the problem.
-
That small bracket that holds the condensor on is available and I'm starting to include it for most of my rebuilds.
Looking carefully at the spark plug electrodes would tell me what I need to know. Weak voltage will present as a dark but dry fouled plug. Closer inspection will reveal that just the very tips of the plug are clean where the current was jumping across.
Unlike oil fouled plugs that are usually coated with hard brown deposits, or fuel soaked glugs that are shiny and wet, these plugs appeared to be dry which started to lead me down the path of fauty ignition.
I was standing in the pits at a race track one day watching a small group of men discussing the particulars of a set of used park plugs. One of them had a flash light and a magnifying glass. After looking at this one plug like an oricle inspecting the entrails of an owl, he pronounced that the spark plug from the problem cylinder had low voltage. Someone brought over a tool to test for such things and that's what it was.
Later, I asked him how he knew about the fouled spark plug. All he said was that the plug told him what was wrong. Being young and not accustomed to those who gaurd their secrets, I pushed on and asked what he meant by what he had just told me. He must have been a patient man because he pulled out a book with coloured pictures of used spark plugs.
'' Find the one that looks like this one. '' He instructed me. He had kept the used plug and pulled it out of his pocket. Placing it in my hand hand he asked, '' Are you always so curious? ''
'' Yes, sir.'' I answered.
I looked through about 20 pictures but nothing looked exactly like the plug in my hand. Not wanting to fail his test, I pointed out two pictures that looked similar but also pointed out that they didn't really match and that they were only close to the one in my hand.
'' Can't find it, eh? ''
'' No sir. ''
'' Well, that's because it's not in that book.'' He asked me for the spark plug and continued with his lecture. '' See, this plug is firing but it's not producing a good kernal.''
I wasn't sure what corn had to do with spark plugs so all I could say was, '' OK? ''
He knew that this was over my head so he detailed the things that would prevent good cumbustion.
'' The kernal is the actual spark the plug makes which starts the fuel burning,'' he explained. '' This plug isn't getting enough voltage so the flame front, or spark kernal, isn't hot enough to burn all of the fuel. The plug looks dark because the unburned fuel is leaving carbon deposits on the electrodes.'' He held the plug up to he light and continued. '' See how only the very ends of the tips are are clean? '' I nodded that I could see what he was pointing out. '' The voltage will jump across and only keep that area clean but the rest of the plug will be sooty. Only weak voltage will do that.''
'' Oh...... thanks.'' Was all I could say.
I was only about 15 or 16 at the time but I never forgot what that kind man taught me. I was just another nosey kid hanging around getting in the way but he took the time to show me one of his many secrects. That man was my brillant uncle, long passed away but never forgotten.
-
And the real kicker to finally getting this car running right was the mixture which it turns out was very lean. I think I originally read about this here somewhere, but it bears repeating....
I think it's pretty commonly known that adjusting the shims under the barometric compensator alters mixture across all speed ranges. Rather than removing the BC and changing shims each time you want to adjust the mixture, you can loosen the BC, then wedge a short piece of hose between it and the WRD. All the hose does is create a little friction so the BC stays in whatever position you rotate it to. Then, to play with mixture all you need to do is pull over, rotate the BC a bit, then continue your test drive. It's way easier and faster that shutting down and swapping shims.
I marked a point on the BC at 6 o'clock so I could keep track of exactly how much I rotated it and in which direction. The threads on the BC are 1.5mm pitch, so a full turn is equal to 1.5mm worth of shims, with partial turns being proportionally less. If you rotate 2/3 of a turn to get proper mixture, then you know you need to add (or remove) 1mm worth of shims. Then you just shim it up when you are done and be sure the BC tightens up at the proper position and you are all ready to go. It's also WAY easier than adjusting the main rack screw which typically requires removal of the solenoid to access the screw.
-
Thats a pretty smart hose trick. I like it. Many thanks.
-
Nice story Dan.
When I was a kid my sister married an aircraft engineer and he was very instrumental in my learning about engines. He wasn't at your uncle's level though!
-
This has been one of the more maddening problems I've encountered. With an adjustment to the BC the car suddenly came to life and was running great. Problem solved, right? Wrong. I started it the next day and it was right back to crap. #2 wasn't firing again, and perhaps #4 too. So, off came the FIP and injectors and in the mail they went to the FIP spa.
Hans called yesterday to report 2 sticking pump pistons, 2 injectors that were dribbling rather than spraying, and shot bearings. I shoulda just pulled it earlier. Oh well. I'm now going to round up every injector off every car, plus my spares, and send them for testing so I know what's good and what's not.
-
If you purchase new injectors, be sure to test those too. I bought a set last year, and one of them had to be returned as it was not spraying properly.
-
Happily I have 14 injectors in my spares collection, so I'm sending them off to H&R for testing to sort out which ones are good. Hopefully I'll end up with the replacements I need plus plenty of additional spares.
-
This has been one of the more maddening problems I've encountered. With an adjustment to the BC the car suddenly came to life and was running great. Problem solved, right? Wrong. I started it the next day and it was right back to crap. #2 wasn't firing again, and perhaps #4 too. So, off came the FIP and injectors and in the mail they went to the FIP spa.
Hans called yesterday to report 2 sticking pump pistons, 2 injectors that were dribbling rather than spraying, and shot bearings. I shoulda just pulled it earlier. Oh well. I'm now going to round up every injector off every car, plus my spares, and send them for testing so I know what's good and what's not.
I've been where you are a lot of times. At some point you start to question your questions. This was a case of having several things wrong rather than just one, but fixing each problem still didn't result in a real fix. Been there too......
I have a series of tests that I make. Once I've gone through all of those things then I start to question the pump because everything else affects how the engine runs. If it's not plugs, points, wires, rotor, coil, fuel pressure, fuel volume, fuel return, leaking CSV and a number of other things; then it's likely the pump. Since I like to be sure, I make sure.
During any engine rebuild I do, the pump goes out for a calibration test or rebuild. A full engine rebuild is a waste of money if your pump is not working right. You can destroy a good engine with a leaking pump or CSV. Get your injectors cleaned as well.
I know it's some money to spend but it's one of those investments that is worth a lot more than new bumpers or some other cosmetic item that really doesn't make your car run any better - looks nice though.
-
Dan, that about sums it up. Yes, there were layers of problems here, and you just need to find and fix them one at a time. One of the complicating factors here is working on a car that was recently put back together (mostly) after an unknown amount of rebuild, so there is no baseline of probably-good parts. I think in general people jump to indite FIPs and injectors too quickly. It's the influence of the Random-Part-Replacement method of car repair used by way too many shops. But unlike typical cases where I'd consider a FIP innocent until proven guilty, the previous owner's "calibration" work on the FIP on another car should have been more of a hint. I now consider any pump he's touched to be guilty until proven innocent.