Bad or Good Fuel Distributor ?

[ioang26]

560 SL
I purchased a used Fuel Distributor from EBAY,installed it,pressed the air plate before connecting the injector lines and fuel flows from the ports .
Connected all injector lines and started the car. It started OK with a some shaking and keeping about 750 rpms.And it was responsive when accelerator applied, it would rev nicely.

As soon as it reached the normal working temperature ,I pressed on the gas again and it bogs down and it dies.If I press it very slowly eventually it would rev but with trouble.

What is happening here? Any suggestions?
Is the FD bad ?

[Frank Reiner]

ioang26:

A bit of background info on this matter would help; what caused you to replace the FD?

The current symptoms suggest a fault in: A) the mechanical mixture adjustment, B) the feedback mixture control [EHA], C) the ECU.

[ioang26]

The car has been sitting for 2 years or so.
Most of the obvious parts have been replaced: fuel pumps,fuel filter,distributor,spark plugs,spark plugs wires,O2 sensor,Fuel pump relay,rubber boot under the air plate,cracked vacuum hoses,new injectors(after market).The fuel pressure is in specs measured at the FD ports.
Upon starting it today it will not rev up when cold, it will bog down again but a little better response when gas is pressed.
I tried to drive it today and if I only feather the gas it will take off gradually but if I press it hard it want to stall and bogs down.When I drove into the driveway it just died and would not start again.Then waited 10-15 min tried to start and barely parked in the garage.
When measures Duty cycle shows 38-52% at 2500 rpm.The idle is very unstable all the time.

DO I need to get a real rebuilt FD or what is causing all that.

[Frank Reiner]

Originally Posted by ioang26

When measures Duty cycle shows 38-52% at 2500 rpm.The idle is very unstable all the time.

Since you are getting a varying Duty Cycle, we may assume, for the moment, that the ECU and the EHA are operational. The throttle response symptoms suggest that the mixture is on the lean side. A spark plug check should confirm this; dry, clean plug: lean or OK; wet, sooty plug: rich.

Two things could contribute to lean response; the mechanical mixture adjustment (as mentioned above), and the lack of a motion signal from the air flow sensor potentiometer.

The mechanical mixture adjustment is located in a tower just in front of the FD. If there is still a plug in the top of the tower it will have to be removed to gain access to the adjustment. If no plug, a 3mm hex key is inserted and pressed down gently while turning slightly until the adjuster engages a screw underneath. Clockwise is richer; 1/8 turn increments, no more than 1/2 turn total. Keep a note of the number and direction of the turns.

The potentiometer is mounted on the side of the mixture control assembly next to the FD, and has a three wire plug. Pull the plug and check that the resistance between pins 1 and 3 of the sensor varies when the air sensor plate is pressed down through its range. If there is no change or if there is no continuity at all, there will be no enrichment signal to the ECU.

[ioang26]

I checked the spark plugs and contrary on what we think the plugs are sooty black dry.
This is definitely rich condition.
The sensor plate is working properly,according to the tests.
I tried adjusting the fuel mixture but no change in the rough idle condition neither in acceleration problem.
Can I email you a video of the car running if that would help.

[Frank Reiner]

Originally Posted by ioang26

I checked the spark plugs and contrary on what we think the plugs are sooty black dry.
This is definitely rich condition.
The sensor plate is working properly,according to the tests.
I tried adjusting the fuel mixture but no change in the rough idle condition neither in acceleration problem.
Can I email you a video of the car running if that would help.

Did you try adjusting the mixture in the lean direction? Since the FD is not the original (or former) one, the initial setting point for the relationship of the air flow sensor to the metering plunger may have to be quite different.
If you are getting a consistent feedback signal, i.e., the duty cycle continues to oscillate, adjust the mixture in the lean direction until the cycle swings in the 60-70% range. This will be a bit on the lean side, but should allow you to determine if that mixture change improves things.

[ioang26]

Leaning the mixture would do no difference except stumbling at idle.
Yesterday I went to start it again and it would not start at all.Checked for spark with an extra spark plug while cranking the engine and...NO SPARK.
Then measured the battery and it was showing me 11.3 V
What did happen??

[ioang26]

I just did the Duty Cycle again- when the engine was cold 50% then when reached normal
temp went to 1.4 % and that's it . What does it mean?

[ioang26]

Here is some videos of the car running and Duty Cycle:

'86 Mercedes 560 SL - YouTube Start up

MOV021 - YouTube

MOV022 - YouTube Duty Cycle & Vacuum gauge

MOV023 - YouTube Revving and DC

[ioang26]

Any ideas?

[meltedpanda]

The potentiometer, did you check for proper function. Any vacuum hoses disconnected?

[ioang26]

The sensor plate is working properly,according to the tests of the manual for W107.
I don't see any vacuum hoses disconnected . The economy gauge stays on the very left side when car is idling. Measured the vacuum pulled from the intake is 16 in.Hg jumping to 18 in. Hg
The only vacuum leak suspect I have not checked, is the lower intake but that would be a major job to take it apart. What do you think?

[meltedpanda]

what year, is this a Kjet with or without Lamda ? or a KE jetronic?

[ioang26]

It is KE Jetronic with Lamda, 1986

[meltedpanda]

have you checked your fuel pressure, and rest pressure. Cold start valve not leaking? Aux air valve functioning?

Every part is interconnected on the Kjet, all have to be ruled out