spdgpfast

Hello, I am new to this forum and to Mercedes Benz. I just bought a 89 560 sl that has been sitting for a couple of years without running and when I start it it runs very rich and miss fires, so rick that if I crack open a fuel line allowing it to leak it smooths out a little. I was told that these cars have a fuel enricher in place of like a choke on a carb motor and that it is stuck on. Does anyone know what I am talking about?

abiby

They were probably referring to the cold start injector. However, I doubt that is the issue.

Just for grins and giggles, put in a couple of bottles of techron fuel additive and run the hell out of it... Probably can't hurt and possibly might clear out some of the crud causing your issues.

slik560

Ditto. The CIS injection does not like to sit idle. Run it a lot and do some wide-open acceleration if you can. I'm assuming that you've changed out the oil and checked the coolant. Good luck.

Rule of thumb on Techron is not more than 3 bottles between oil changes.

spdgpfast

Thanks for thr replies, But I've tried all af this, I have pulled the injectors and cleaned them in carb cleaner, I have spray carb cleaned the fuel distributor, I ran compression....130-135 lbs on all eight, new plugs, checked spark on all eight and all is good. Trust me I've had a few hot rod toys at all alltitudes from sea level to 20,000 ft above sea level so I now a little about air to fuel mixture, not to sound like I know it all because I don't but when you crack open one or even two fuel injector lines, therfore the fuel goes all over the intake(and leans out that cyl.) and not in the cylinder and it smooths out and stops smoking rich black smoke out of the exhaust that's telling me it's way too rich, why, I haven't learned this FI system yet but I know it's getting way too much fuel.
Thanks for all your help and comments, keep em coming!

slik560

This is a short description of the system with some diagrams, if it helps. I've got a mechanic that is an expert on these, so I leave any fuel issues to him. Sorry I can't be of more help. Sounds like the cold start valve is stuck open, but that's just a guess.

Good luck!!

spdgpfast

Yea! Now that's what I'm talking about! Thanks slik560 this helps alot! The cold start valve is the part that someone else said it sounds like. So now I just need to locate it and clean or replace we'll see, I'll keep you posted on what happens or what I find.
Thanks a bunch slik560!

spdgpfast

Hey folks, I've been laid up from shoulder surgery so I haven't done anything on this but I would like to test the fuel supply pressure, can anyone tell me where the fuel pump relay is located on a 1989 560 SL? So I can jump pin 30 to pin 87 with a fused switch and test fuel supply pressure?
Thanks Again for your help!

hotshoe

If you remove the glove box liner (4 plastic rivet pins) and look all the way back to the firewall you will see 3 black relay boxes approx. 3" wide. the FPR is the one on the left, in the back position (closest to the firewall. Pretty much the other two must be removed first to get the FPR out. It is MUCH easier to make a wire harness with alligator clips to go from the positive side of the battery to the positive terminals on the two fuel pumps. Trust me, it is very tight quarters under the dash.

spdgpfast

Thanks, that's where I thought it was but wanted to make sure since I'm recovering from shoulder surgery I have the time and I figured I'd ask. And with that being said and me being 6'4" tall and a bad shoulder and big hands I think it's time to get my son involved he's 18 and skinny. I think the control plunger is sticking again so I just want to check the FP before I remove the fuel distributor to free up the plunger. Has anyone taken the intake around the sensor plate off and gotten too the plunger to free it up? or can it only be done by taking off the fuel distributor. I've removed the distributor and done it this way before I was just looking at it wondering if you could maybe spray some PB Blaster or Marvel Mystery oil up in there without removing the dist. and all the lines. But alot of shortcuts end up with shortcut results! wasted time!
Thanks Again for all the help!