1989 Mercedes 560SEL no start

[TylerH]

Hi, im new to the forum and am still learning how to use it, so apologies if anything seems off or is in the wrong spot, but my real reason for making this post is that I have an 89 mercedes 560sel that won't start. I bought the car roughly 2 months ago in perfect working order, I replaced my fuel filter about 2 weeks ago and its been downhill since. After the filter change It practically didn't start so I had it towed to a shop that "specializes" in these and they messed quite a few things up, they adjusted the fuel mixture screw completely out of wack and broke my EHA, they also had no diagnostics done for a week and no progress towards an answer. I decided to not work with them anymore and figured id fix it on my own. So as we sit, the airflow meter was taken out inspected, and cleaned, properly adjusted to 1.9mm of free play with no rubbing on the plate and smooth upward and downward motion, a new, leak free EHA was installed, a fuel pump relay, the injectors have been taken out and soaked in sea foam, along with an inline fuel pressure gauge installed on the supply line right before the distributor which reads 90 psi when pumps are jumped and 40-45psi when resting. I've tweaked the mixture screw 1/8 turn in both directions having the freeplay from practically 1.9mm to 2.5mm and the only start i had was at 1.9-2mm but it soon died. I'm quite lost in the process and would hate to buy unnecessary parts or tow it to another shop. Thanks for the help in advance.

[Sugar Bear]

Spark is good? Compression is good?

[Jorn]

If you didn't do this already and it happened after changing the fuel filter, go back and see if it's all bolted up correctly.

[Sugar Bear]

Can/is the fuel filter in backward?

[Skid Row Joe]

Originally Posted by TylerH

Hi, im new to the forum and am still learning how to use it, so apologies if anything seems off or is in the wrong spot, but my real reason for making this post is that I have an 89 mercedes 560sel that won't start. I bought the car roughly 2 months ago in perfect working order, I replaced my fuel filter about 2 weeks ago and its been downhill since. After the filter change It practically didn't start so I had it towed to a shop that "specializes" in these and they messed quite a few things up, they adjusted the fuel mixture screw completely out of wack and broke my EHA, they also had no diagnostics done for a week and no progress towards an answer. I decided to not work with them anymore and figured id fix it on my own. So as we sit, the airflow meter was taken out inspected, and cleaned, properly adjusted to 1.9mm of free play with no rubbing on the plate and smooth upward and downward motion, a new, leak free EHA was installed, a fuel pump relay, the injectors have been taken out and soaked in sea foam, along with an inline fuel pressure gauge installed on the supply line right before the distributor which reads 90 psi when pumps are jumped and 40-45psi when resting. I've tweaked the mixture screw 1/8 turn in both directions having the freeplay from practically 1.9mm to 2.5mm and the only start i had was at 1.9-2mm but it soon died. I'm quite lost in the process and would hate to buy unnecessary parts or tow it to another shop. Thanks for the help in advance.

+
Check contact points 1st

[nulu]

Check both fuel pumps for correct operation and one may quit running after a while, and while your at it check for volume , with fuel pump relay removed via a jumper pins 7 and 8pu should get 1 liter of fuel in 20 seconds , also is this car , ways this car ever sitting a long time , remove the fuel tank strainer and check for restriction in screen

[TylerH]

Both pumps seem to be working fine, and I have more than enough pressure at the distributor to at least get somewhat of a turnover, just no turnover. Unless some sort of secondary system off of the fuel distributor has gone wrong, or its not fuel at all, possibly spark?

[Frank Reiner]

Originally Posted by TylerH

I've tweaked the mixture screw 1/8 turn in both directions having the freeplay from practically 1.9mm to 2.5mm and the only start i had was at 1.9-2mm but it soon died. I'm quite lost in the process and would hate to buy unnecessary parts or tow it to another shop. Thanks for the help in advance.

1) Do your starting tests with the fuel pump relay removed, and a jumper between sockets 7 & 8. The pumps will run continuously; remember to remove the jumper when finished!

2) Continue to richen the mixture (clockwise) in small increments, and note the results.

[TylerH]

Why with the relay removed and jumped?

[Odin911]

You've already done a lot of the right work. With good fuel pressure and a properly adjusted air plate, it sounds like mixture or ignition timing might still be off. Since the EHA and mixture screw were messed with, I'd suggest setting the mixture back to baseline using a duty cycle meter if you can, or at least try a slight lean adjustment from where it last started.

[TylerH]

Originally Posted by Odin911

You've already done a lot of the right work. With good fuel pressure and a properly adjusted air plate, it sounds like mixture or ignition timing might still be off. Since the EHA and mixture screw were messed with, I'd suggest setting the mixture back to baseline using a duty cycle meter if you can, or at least try a slight lean adjustment from where it last started.

How do you properly get it to baseline and how do you get duty cycle without a proper idle?

[agillot1947@gmail.com]

If the car was running before the filter change , you would think the answer would be there . Now that everything has been disturbed , have you tried a shot of starting fluid , if the plugs are in working order , and you have spark , the engine will fire up and die . That way , you know the engine and ignition system is in working order . Next , make fuel pump to turn on , with 75 or so fuel pressure [ measure this at the connection to the cold start valve ] , push down on the air flap , you should hear the injectors coming on , dont over do it , you could hydro lock the engine .

[agillot1947@gmail.com]

Originally Posted by Odin911

You've already done a lot of the right work. With good fuel pressure and a properly adjusted air plate, it sounds like mixture or ignition timing might still be off. Since the EHA and mixture screw were messed with, I'd suggest setting the mixture back to baseline using a duty cycle meter if you can, or at least try a slight lean adjustment from where it last started.

The engine has to be running to do that .