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1967 Unimog 404
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19 Posts
Discussion Starter #1
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560sl won't run, help!
I've had a terrible time with my 86 560sl, first chasing a rough idle, mucking around with it, throwing parts at it, and now the bloody thing barely runs at all. Would appreciate any comments.

Started out addressing rough idle, so replaced plugs, wires, rotor-no help. O.K. then replaced injectors, sleeves, o rings, air distribution hoses, no help. Then replaced intake manifold gaskets, throttle body housing, thottle position switch, fuel distributor o ring, fuel filter, vacuum lines and vacuum connectors. Replaced over voltage protection relay. NOW IT IS WORSE. Swapped idle control unit with spare, no differnce. Swapped fuel distributor with spare, no difference. Pulled fuel pumps, seemed to run fine. Fuel pressure test was fine. Drained tank, had clean gas.

Test revealed that it was only running on 5 cylinders. Compression test OK. Now the vehicle will start up instantly, run not bad for the first few seconds, then start running really rough, on perhaps 4 or 5 cylinders. What's wierd is that if I connect the electrical connector to the side of the fuel distributor, I think a fuel flap sensor, the car won't run at all. With this part disconnected, the car will at least fire, but go through the above sequence.

Before I started mucking with it, the car would idle a bit rough but ran very clean and strong otherwise. Smog report showed excellent emmissions. Looks like past owner did the heads on the car.

When I did the intake manifolds, I was a little too carful with torquing the intake manifold studs down and it burned white and made lots of smoke. Then idled at 2000 rpm, but smoothly. Re torqued everything, still burned white for a while, but smoke went away except for a little bit still. I had a bit of a problem getting the throttle body housing-the rubber air duct- with the throttle body causing a big vacuum leak, but now that is on properly.

Where I'm at now is the car will fire instantly, with the connector removed from the fuel distributor, run on all cylinders for a few seconds, then run like crap.

Where do I go now? Please anybody, I want to drive the car into the lake...
Regards, Lawrence.
BTW, this was a "cheap" ebay car, CA with 117,000 mi.
 

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1986 560-SL
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57 Posts
Lake Bound

Hey, Lawrence;

Sounds like you almost have it!!!

1. It's not mechanical - it runs.

2. Most of the electrical can be eliminated - from switch in the "ON" position to "START" - it starts and runs for a bit.

There is a manual available:

"Mercedes - Benz 107 Chassis SL - Class

Electrical Trouble Shooting 1986 - 1989"


From the book, there is an electro-hydraulic actuator (trims the amount of injection fuel & also controls maximum engine speed), Air injection relay, Idle speed control unit, throttle valve switch and an electronic ignition control unit. All could be suspect.

The auto has a diagnostic socket/terminal block that could probably identify the culprit IF you could get the vehicle to a dealer's computer (if it's on the way to the bloody lake).

Don't give up on it - you're probably almost there.

Stan
 

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1967 Unimog 404
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19 Posts
Discussion Starter #3
560sl wont run...

Well, spent some more time on the red POS. Swapped out ignition control module, coil, dist cap no change. Put the timing light on all the spark plug leads; and there is spark. Now I'm pretty sure it isn't fuel and it isn't electrical, and it isn't mechanical.

What's left? Well, I still haven't got rid of the white smoke, which I thought was just some residual coolant left over from replacing the intake manifold gaskets and spilling some coolant. I think I'm wrong about that. I managed to look at the tail pipe while keeping the car running and there was more white smoke than I thought.

So now it looks like coolant in the combustion chambers, presumably leaking from the intake.

When I replaced the intake manifold gaskets I noticed that somebody before me used a lot of sealant around the gaskets. I know the heads have been done. New theory is that the heads were milled upsetting the fit between the intake manifold and the heads, causing the water passages not to line up and leak. F**K.

Now I guess I strip it all apart and use some sealant around the gaskets. I'm so not very happy. Anybody have any experience with this?

Regards, Lawrence.
 

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1986 560-SL
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57 Posts
560 SL

Hello Lawrence,

Sometimes you've just gotta say "S**t" and keep on goin'.

There is a chemical out (can't remember the name right now....... Magnaflux??) for checking for cracks.
The block/head has to be cleaned - you made friends at an auto supply store yet????

There is a site that you can send in questions - they weren't able to help on my speedometer.

www.thebenzbin.com

email them at [email protected]

also www.starqualityparts.com

they used to have a little blues/jazz place downtown - kinda rundown but good music. Also remember the museum downtown - excellent.
 

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00 S500,99 4wgn,87TD
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579 Posts
Are you loosing coolant?? If you have an intake gasket leak, it will be in one of these cy...

Are you loosing coolant?? If you have an intake gasket leak, it will be in one of these cyls.1,4,5,8. You should be able to remove the plugs, pump up the cooling system with 10 psi. It should retain the pressure. look in the cylinders for anti freeze. If you see nothing, rotate the engine with a 27mm socket, because the intake valves could be closed on the suspected cyls.If you get coolant in the cylinders, well you know what to do. PS. I did not here anything about setting the basic co adjustment. Is it set??
 

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1967 Unimog 404
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19 Posts
Discussion Starter #6
560sl

Well, finallly, the red POS, runs-and runs nicely. Thanks to everybody for your help. I put a bunch of goo around the intake manifold gaskets, and now they seal properly. There was also some sort of hangup in the mixture control that I can't really explain, but a bit of adjustment to that made the car fire right up. What a relief, I've been at that job for 3 months. I'm happy I didn't buy the new fuel distributor as the dealer diagnosed...

Now all I have to do is replace the cracked dashboard and the car is done. I'm sure this will be a nightmare too.

Cheers, Lawrence.
 

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1967 Unimog 404
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19 Posts
Discussion Starter #8
Well, the car fires up and runs o.k. now. Still not perfect, but close. In addition to the above I had trouble with my idle control valve, which was swapped for another. I think I am still a bit too lean on the idle circuit, but need to take it to the dealer to set properly I think. Also, may try the car on a dyno and fool around. This weekend I'll have a go at the dashboard, have a former mb Tech to help, thankfully.
Regards, Lawrence.
 
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