00Dog

The #6 cylinder won't fire for the first minute or so on my '86 Mercedes. Should I start by changing the plugs? I don't have anything in the way of diagnostic equipment.

dodgeguy71

I'd pull the plug and you can get a "fake" plug tool at zone or advance to put on there and then it clips to ground, or you can just swap it with a known good plug like, #5. You can disconnect your coil so it won't start and have someone crank it over and see if it fires. You can also use the old plug removed and have someone crank it over and see if it sparks. If not remove spark plug from #5 and put it on #6 wire and crank engine and see if it sparks. If so you probably have a fouled plug, if it still don't spark, but will spark on #5 I'd be looking at my spark plug wire. You could actually swap #5 wire for #6 from distributor...assuming that's how a mercedes is and again use #5 plug, crank and check. Spark, probably wire, no spark maybe something under cap. Also a thing to watch for is carbon tracking on the white part of the plug. Just clean it off well with a cloth and inspect the ceramic. If you see black looking streaks that kinda look like cracks that is carbon tracking and it is suggested that you replace the wires on plugs with carbon tracking. Well, I can't find a picture of carbon tracking on the web as quick as I need to. If it has it you'll notice it cause it won't rub off.

Or, if you know you have not done a tune up in a bazillion years you can just run out and buy some plugs for it and swap them out.

Kenny D

All very good advise except if you disconect the coil so that it wont fire you wont get any spark iether you can iether shut off the fuel or just let it fire for a sec then shut it off as soon as you see a spark.

By the way
DODGEGUY71 love your welding rid, mines all set up in a encolsed trailer

dodgeguy71

yeah, good catch on the coil part Kenny.....have not turned a wrench for someone else in 6 months and it seems my brain is discharging all useless info.....like how to be a mechanic!!

The rig does good.....little fat though. I could'nt do a trailer. Usually have to go get my steel for jobs. I have to get rid of the black toolbox on the left side though, just don't like it. Probably gonna go with another aluminum box but shorter and rig up a spool under the truck for cables.

like your truck, looks sweet!

rockcrawler304

Let's start at the beginning. How do you know it is not firing? And that it is cylinder 6? What symptoms are you seeing?

00Dog

The car shakes. When I feel the exhaust manifold, the rear most one is cold. My mechanic thinks the injector is leaking and the cylinder won't fire until the drip goes away. He said if it were electrical it wouldn't only happen when the engine was first started.

rockcrawler304

Ok that does sound possible. I would pull the plug out and check for spark at the plug when the engine is cold. If you have spark right away you may have an injector problem. I would actually lean to the injector NOT working at first rather than dripping. If it were dripping it would run rich and the manifold would be hot. They do sell injector test lights to at least see if you are getting an electrical pulse to the injector. Keep us posted as to what you find.