1988 560SL Fuel Delivery Issue?

[orbit398]

New to the forum and the 560SL

Just bought this car to semi-restore for daughter. PO just put new fuel pumps and filter on it. Car started and ran but had old gas in it, one could smell it. Could only drive it a few miles before it die. Sit a bit and started right back up and could continue. Easy fix I thought. Clogged screen in gas tank.

So, I removed the tank and pump/filter cluster. Screen in tank had disintegrated, thus no filter. Tank was dirty too so I cleaned it out well with muriatic acid mixture, rinsed a few time and coated tank with two stroke gas to prevent rust. First fuel pump inlet was full of trash so that was obviously an issue. Took the cluster apart and back flushed both pumps by reversing pump polarity. Both pumps work like crazy so they seem fine. Check valves a free to move as well.

Reinstalled everything, got another fuel filter and replaced the Fuel Delivery Hose and the Leak Off Line. This Leak Off Line attaches to the backside of the Fuel Accumulator if I remember right. I made sure the small tip on the brass fuel suction hose part was clear too that this Leak Off Line attaches to.

Now the car is hard to start and I have to press the accelerator to make it start. It won't stay running if I let off the accelerator. It runs very rough and the exhaust really smells of gas - like the choke on a carburetor car engine is stuck on.

Being the Leak Off Line attaches to the Fuel Accumulator, and with the tank Screen gone, it allowed unfiltered gas to it, I wonder if that may be an issue or clogged.

Next thought was to hook the Fuel Suction Hose directly to an external gas tank to see if that has any affect as that screen in the gas tank is so 'fine', I am wondering if that may be an issue.

thanks for any helpful suggestions.

[Frank Reiner]

Originally Posted by orbit398

New to the forum and the 560SL
Now the car is hard to start and I have to press the accelerator to make it start. It won't stay running if I let off the accelerator. It runs very rough and the exhaust really smells of gas - like the choke on a carburetor car engine is stuck on.

Being the Leak Off Line attaches to the Fuel Accumulator, and with the tank Screen gone, it allowed unfiltered gas to it, I wonder if that may be an issue or clogged.

1) Re: Apparent rich mixture.
Check that the cold start injector (CSI) is not remaining open, due either to mechanical sticking from dirty fuel, or from being energized continuously.
If there is no fault with the CSI, the metering plunger in the fuel distributor may be sticking.

2) Unless the diaphragm in the accumulator has failed, there is no flow through the leak line.

[orbit398]

thanks for the suggestions

[orbit398]

Follow up. I done quite a bit of work since my last post. The complete gas system has been gone through. The engine has new plugs and injectors. New exhaust and O2 sensor. The Fuel Distributor was rebuilt and the idle control valve works properly.

Problem - the engine starts up fine and runs great until it gets to operational temperature. Then is starts to misfire and run poorly.

Looking for suggestions. Perhaps a sensor is causing the issue but an not familiar with them all.

[Benz Dr.]

Did you try adjusting the fuel mixture at the fuel distributor? Sounds like it's going lean as it warms up.