Need some advise about 450 SL - PeachParts Mercedes-Benz Forum

highpowerd2003 · #1 11-08-2009, 05:23 PM

450 SL won't run, replaced fuel pump, injectors, new wires, coil, will start immediatly gas files out the plugs car stalls will only restart after several hours of setting restart does same things. The car is a 79 Mercedes 450 SL, has 980000. miles been setting for four years. Can anyone help me to figure what I am not doing right. highpowerd2003@yahoo.com

whunter · #2 12-01-2009, 09:58 PM

to SL forum

RadioTek · #3 12-01-2009, 10:30 PM

Sounds like fuel distributor stuck open, and flooding out. Some have had luck taking them apart and cleaning them, but they really knew what they were doing. May have to be replaced, have checked out by mechanic familiar with K-Jet Benzes.

Good Luck

panzerwagen80 · #4 12-02-2009, 06:49 AM

I just went through the entire system on my 450 and have managed to get it running after a 7 year slumber.

First of all did you monkey around with the idle screw or the air fuel mixture set screw?

Hint... The idle screw will be on top of the intake near the back of the distributor cap. It's about the size of a dime and plastic with a wide screw slot. This only adjusts the amount of air getting into the intake.

The air fuel mixture screw is a 3mm hex(Allen head) inside the intake.
it may or may not have a tall aluminum stand off extension that allows you to adjust it through the air filter housing.

If it doesn't have the stand off you will need a long (about 8 inches) allen wrench to adjust it.

Before you take anything else apart or take it to a mechanic I would try to adjust your air fuel mixture as moving the lever up and down may help to dislodge the stuck piston.

Turning the 3mm Allen counter clockwise will restrict the fuel (lean out)
turning clockwise will increase the fuel flow (rich)

If it were mine I would try to turn the air fuel mix as lean as I can get it before attempting to start it again and then turn the screw clockwise in 1/16th increments turning the key with each adjustment until it starts.

Then back it off just enough to smooth out the idle and keep it from dying.
About a 1/32 of a turn should be it.

If the k-jet distributor head has a stuck piston it "might" help to give the center of the distributor head a light but firm smack with a rubber mallet being carefull not to hit the lines.(You might want to do this while you have the screw backed out to the stop point.)

Do not use a steel hammer of any kind.

Good luck with the fuel head issues.

BTW Did you drain the fuel tank?
Clear the lines?
Replace the fuel filter and accumulator?

PanzerSD · #5 12-07-2009, 11:54 PM

Quote:

Originally Posted by panzerwagen80

I just went through the entire system on my 450 and have managed to get it running after a 7 year slumber.

First of all did you monkey around with the idle screw or the air fuel mixture set screw?

Hint... The idle screw will be on top of the intake near the back of the distributor cap. It's about the size of a dime and plastic with a wide screw slot. This only adjusts the amount of air getting into the intake.

The air fuel mixture screw is a 3mm hex(Allen head) inside the intake.
it may or may not have a tall aluminum stand off extension that allows you to adjust it through the air filter housing.

If it doesn't have the stand off you will need a long (about 8 inches) allen wrench to adjust it.

Before you take anything else apart or take it to a mechanic I would try to adjust your air fuel mixture as moving the lever up and down may help to dislodge the stuck piston.

Turning the 3mm Allen counter clockwise will restrict the fuel (lean out)
turning clockwise will increase the fuel flow (rich)

If it were mine I would try to turn the air fuel mix as lean as I can get it before attempting to start it again and then turn the screw clockwise in 1/16th increments turning the key with each adjustment until it starts.

Then back it off just enough to smooth out the idle and keep it from dying.
About a 1/32 of a turn should be it.

If the k-jet distributor head has a stuck piston it "might" help to give the center of the distributor head a light but firm smack with a rubber mallet being carefull not to hit the lines.(You might want to do this while you have the screw backed out to the stop point.)

Do not use a steel hammer of any kind.

Good luck with the fuel head issues.

BTW Did you drain the fuel tank?
Clear the lines?
Replace the fuel filter and accumulator?

Would a Stuck Piston cause my hot engine floods?

panzerwagen80 · #6 12-09-2009, 04:47 AM

Not sure...
Theoretically yes it could, however that housing would be warm at the time and would have expanded with the heat some what and thus not as tight a fit as when it's cool from sitting.

I would be more inclined to think the warm up regulator is not functioning properly, or the auxiliary air is not opening correctly.

It would be really hard to tell why it's doing that without being in the garage with it when the problem occurs.

Can you give me a little more to go on?

What conditions were present when this happened last?

Are you sure you are using the Bosch K-jet?

Steve