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Garage => Mechanicals => Topic started by: AceWolff on 26 January 2021, 03:30 PM

Title: HELP!!! MISFIRE/STALL
Post by: AceWolff on 26 January 2021, 03:30 PM
1974 450SE California emissions

Long story short, bought car sight unseen, drove ⁶ hours home (drove like a dream)

Now the car will not stay running unless I'm on the gas, shakes misses and stalls.

Just finished putting on new points/wires/plugs/cap/rotor/cool


P.S. car ran out of fuel prior to this

New fuel line from tank to pump.

I can't figure it out, the throttle response is great but it won't stop misfireing.
Title: Re: HELP!!! MISFIRE/STALL
Post by: Alec300SD on 26 January 2021, 03:56 PM
Air incursion from new fuel line, clamps not tight enough, wrong internal diameter for replacement fuel hose?
Excessive water in fuel/tank?
Title: Re: HELP!!! MISFIRE/STALL
Post by: daantjie on 26 January 2021, 06:45 PM
What I would suggest next is to check all vacuum connections.  There are multiple hard plastic lines that by now will likely be very brittle.  Replace as needed.  Also check the rubber boot connections between the vacuum hard line and the part it is connected to, like a vacuum switching valve for example.
Title: Re: HELP!!! MISFIRE/STALL
Post by: AceWolff on 27 January 2021, 12:33 PM
Yeah, the vacuum lines are worn thin.

Guess I have a fun day ahead of me
Title: Re: HELP!!! MISFIRE/STALL
Post by: AceWolff on 29 January 2021, 07:48 AM
Found a few lines that needed attention,  but it didn't help the situation. I was told it could be a stuck valve, is this possible?

The electric is not looking all that good either. Almost all the wires are cracked to shit. Same with the big plug on the ICM
Title: Re: HELP!!! MISFIRE/STALL
Post by: AceWolff on 29 January 2021, 08:01 AM
So I got the car to run seemingly normal. So I go for a test drive (2 miles each way to the gas station)

It continues to degrade the longer I drive,  it starts where it's misfiring when I'm slowing down,  then it gets to be where it's misfiring holding steady at 40mph. It quickly becomes worthless after,  having no power, I have to keep my foot on the gas at all times,  even when slowing or stopped.

WHYYYYYYYYYY

New coils/plugs/wires/cap/rotor

Oil looks good and it keeps good pressure.

I just don't get it.
Title: Re: HELP!!! MISFIRE/STALL
Post by: AceWolff on 29 January 2021, 08:02 AM
I'll post some good pictures up today of what I'm dealing with
Title: Re: HELP!!! MISFIRE/STALL
Post by: rumb on 29 January 2021, 10:14 AM
I'll take a stab and say your fuel distributor and WUR need rebuilt.
Title: Re: HELP!!! MISFIRE/STALL
Post by: AceWolff on 29 January 2021, 10:29 AM
What is the wur?

Where even is the fuel distributor.
Title: Re: HELP!!! MISFIRE/STALL
Post by: daantjie on 29 January 2021, 12:35 PM
WUR = Warm Up Regulator.  All KJET cars have this, at least in the W116.  So if you have KJET then you have a WUR.
Fuel distributor is the "spider looking" thing you will see when you take off the air cleaner housing.  You will see 8x hard lines coming off it going to the injectors.
Before you look at these 2 components, you HAVE to check fuel pressures first, no other way to diagnose fuel delivery issues on KJET.  You can buy a test kit pretty cheaply online, then plumb it in and take readings.
Title: Re: HELP!!! MISFIRE/STALL
Post by: rumb on 29 January 2021, 02:36 PM
If you have kjet then this will get you started understanding your system

https://www.youtube.com/watch?v=a4fJAfXYxWk
Title: Re: HELP!!! MISFIRE/STALL
Post by: AceWolff on 29 January 2021, 04:50 PM
Alright so I have D-jet.

Just have injectors under the air cleaner
Title: Re: HELP!!! MISFIRE/STALL
Post by: AceWolff on 29 January 2021, 04:52 PM
I have enough stuff to put a pressure gage on the fuel rail. What should my psi be?
Title: Re: HELP!!! MISFIRE/STALL
Post by: daantjie on 29 January 2021, 05:10 PM
Might be time to ping member "s class" (Ryan), he drops in every now and then here on the board.  To my knowledge he is the go - to guy for DJET issues.  Unfortunately most of us run KJET systems, so I cannot help much on the DJET.

In the meantime, here is a good post on both KJET and DJET troubleshooting on Benzworld:

https://www.benzworld.org/threads/bosch-d-jetronic-and-k-jetronic-troubleshooting.1223523/

Title: Re: HELP!!! MISFIRE/STALL
Post by: s class on 30 January 2021, 03:10 AM
Fuel rail pressure must be 2.1 bar... Not sure what tgat is in your money.
Check the basics.. Pints gap must be 0.3mm, ign timing about 3BTDC at idle, 40BTDC all in at 3000rpm with vacuum.
Title: Re: HELP!!! MISFIRE/STALL
Post by: s class on 30 January 2021, 03:13 AM
I suspect you may have throttle position switch calibration issues, that the idle contact switch is not working correctly
  PM me your email address and I'll send you the procedure to set it up.

Have you played with the idle air/fuel ratio setting potentiometer on the side of the engine ECU in the foot well?
Title: Re: HELP!!! MISFIRE/STALL
Post by: AceWolff on 31 January 2021, 11:17 AM
I didn't know I had to gap the points. I've never had to deal with them before.

How do you change points properly, because I just put them in with no extra steps.


No I have not, I'm fairly new to this car. And before this I've pretty much only run diesels

You can reach me at

Guywithphone@gmail.com
Title: Re: HELP!!! MISFIRE/STALL
Post by: AceWolff on 01 February 2021, 08:20 AM
Does this car have the OVP?

I have a hard time finding info on the SE in particular.

But I am also having some other electrical issues and I've read that this can cause both problems I'm having.
Title: Re: HELP!!! MISFIRE/STALL
Post by: celberg on 02 February 2021, 12:49 PM
First thing first. Your car went well for a 6 hours drive and suddenly not at all?

No ovp in d-jet.

Do you have the rotor with rpm-limiter? Even if it's new it can malfunction. I had to put another rotor in a year ago. This time i took the one without rpm-limiter.

You might have dirty triggerpoints for the injection valves. Lift the ignition distributor, take the triggerpoints out and clean them. Make sure you put the distributor back with the rotor at the same place.

If you haven't played with the throttle position switch, don't do it.

The idle air/fuel ratio setting potentiometer on the side of the engine ECU does not affect the fuel/air ration when you drive, it only affects on idle. Therefore You can leave that.

Title: Re: HELP!!! MISFIRE/STALL
Post by: Alec300SD on 02 February 2021, 01:00 PM
Did you change the fuel filter after you ran out of gas?

Quote from: AceWolff on 26 January 2021, 03:30 PM
1974 450SE California emissions

Long story short, bought car sight unseen, drove ⁶ hours home (drove like a dream)

Now the car will not stay running unless I'm on the gas, shakes misses and stalls.

Just finished putting on new points/wires/plugs/cap/rotor/cool


P.S. car ran out of fuel prior to this

New fuel line from tank to pump.

I can't figure it out, the throttle response is great but it won't stop misfireing.

Title: Re: HELP!!! MISFIRE/STALL
Post by: AceWolff on 04 February 2021, 10:34 AM
Quote from: celberg on 02 February 2021, 12:49 PM
First thing first. Your car went well for a 6 hours drive and suddenly not at all?

No ovp in d-jet.

Do you have the rotor with rpm-limiter? Even if it's new it can malfunction. I had to put another rotor in a year ago. This time i took the one without rpm-limiter.

You might have dirty triggerpoints for the injection valves. Lift the ignition distributor, take the triggerpoints out and clean them. Make sure you put the distributor back with the rotor at the same place.

If you haven't played with the throttle position switch, don't do it.

The idle air/fuel ratio setting potentiometer on the side of the engine ECU does not affect the fuel/air ration when you drive, it only affects on idle. Therefore You can leave that.


I replaced the points on the top half, does this also have the horseshoe shaped trigger points?

I don't know how to tell if it has an rpm limiter.

I have not changed the fuel filter. For some reason it still hasn't arrived at my house yet.
Title: Re: HELP!!! MISFIRE/STALL
Post by: AceWolff on 04 February 2021, 10:35 AM
I will also note, someone cut all the wires for the condenser out
Title: Re: HELP!!! MISFIRE/STALL
Post by: celberg on 04 February 2021, 01:47 PM
Quote from: AceWolff on 04 February 2021, 10:34 AM
Quote from: celberg on 02 February 2021, 12:49 PM
First thing first. Your car went well for a 6 hours drive and suddenly not at all?

No ovp in d-jet.

Do you have the rotor with rpm-limiter? Even if it's new it can malfunction. I had to put another rotor in a year ago. This time i took the one without rpm-limiter.

You might have dirty triggerpoints for the injection valves. Lift the ignition distributor, take the triggerpoints out and clean them. Make sure you put the distributor back with the rotor at the same place.

If you haven't played with the throttle position switch, don't do it.

The idle air/fuel ratio setting potentiometer on the side of the engine ECU does not affect the fuel/air ration when you drive, it only affects on idle. Therefore You can leave that.


I replaced the points on the top half, does this also have the horseshoe shaped trigger points?

I don't know how to tell if it has an rpm limiter.

I have not changed the fuel filter. For some reason it still hasn't arrived at my house yet.

A0001582331 is the OEM nr for the one without limiter and A0001582931 the one with. Google with picture and compare with your own.

The trigger points are below the single point for the timing. You see a cable attached to it. You have to take the distributor of the motor.

I don't have the condenser in my 1975 350SE and I'm not alone. You don't have to have it.

You have to set the points and timing correct. Use Youtube if You don't know how to do it.
Title: Re: HELP!!! MISFIRE/STALL
Post by: AceWolff on 05 February 2021, 03:39 PM
Okay cool,  I'll look into this,  if it doesn't help then it's too the shop.

It's too cold outside to troubleshoot.

Thankfully I have an inn with the shop I'm going to.
Title: Re: HELP!!! MISFIRE/STALL
Post by: AceWolff on 08 February 2021, 09:06 PM
Well,  it's going to the shop.

It was 4 degrees earlier and I just can't deal with it.
Title: Re: HELP!!! MISFIRE/STALL
Post by: beytan on 18 February 2021, 10:09 AM
I had a similar problem with my 280se D-jet and it was the control unit ECU ( the big box of electronics that controls everything) I struggled with so many ideas but I now have 2 spares as the replacement sorted the problem immediately. The ECU is a mass of resistors,capacitors attenuators etc. My problem was that the car started and ran for about 10-15mins before it start playing up and misfiring. I only discovered this after replacing the entire ignition system from coil to sparks, aux air valve, all vaccum hoses, sensors and the MAP pressure unit. I found a used ECU for £80 and it worked fine immediately. The problem with the D-JEt is that it is wonderful when its running right but there's a reason why Mercedes opted to go for the mechanical K-Jet after running the D-jet for just  a few years.  I have an 83 280ce coupe on J-jet and never had a problem in 11 years of weekly use. But the D-jet is quicker and doesn't suffer from flat spots  in power.  Hope this helps
Title: Re: HELP!!! MISFIRE/STALL
Post by: AceWolff on 21 February 2021, 01:21 AM
So it's been at the shop for like 3 weeks and all they tell me is it needs to be retimed. They quoted me $900

Fuck that,  it's home now,  I'm going to be putting a canopy over the front with a little heater and get to work.
Title: Re: HELP!!! MISFIRE/STALL
Post by: AceWolff on 21 February 2021, 01:22 AM
Probably tomorrow though. It's 1:30am right now here in Western NewYork
Title: Re: HELP!!! MISFIRE/STALL
Post by: Alec300SD on 21 February 2021, 02:03 AM
I used to have a K-Jet 79 Volvo 245DL wagon years ago, and  the site linked below was an invaluable reference guide.
Hopefully, it will help you to troubleshoot your D-Jet system

https://jetronic.org/en/
Title: Re: HELP!!! MISFIRE/STALL
Post by: AceWolff on 22 February 2021, 07:20 PM
So, try this on for size.

I retime the points, I bumped the starter until it was on cyl 1 then gapped points at .014.


So I go to start the car, and hear a pop noise, come to find out, the fuel hose from tank to pump (which I just changed because it was leaking like a siv) explodes.

Excuse me?

So I guess I'll be ordering a fuel pump maybe? I don't even know.
Title: Re: HELP!!! MISFIRE/STALL
Post by: raueda1 on 22 February 2021, 08:06 PM
Quote from: AceWolff on 22 February 2021, 07:20 PM
So, try this on for size.

I retime the points, I bumped the starter until it was on cyl 1 then gapped points at .014.


So I go to start the car, and hear a pop noise, come to find out, the fuel hose from tank to pump (which I just changed because it was leaking like a siv) explodes.

Excuse me?

So I guess I'll be ordering a fuel pump maybe? I don't even know.
I wish I could help.  Unfortunately I know nothing of D-jetronic or your car.  But I truly do feel your anguish.  I've also had inexplicable problems of my own.  So, I offer my moral support.  Good luck!
Title: Re: HELP!!! MISFIRE/STALL
Post by: celberg on 24 February 2021, 09:36 AM
It should not explode... that side of the pump is not pressurized. Did you change all hoses back at the pump and attached the exploded hose at the wrong end of the pump by mistake?
Title: Re: HELP!!! MISFIRE/STALL
Post by: AceWolff on 24 February 2021, 11:03 PM
No I only changed the down tube from the tank to pump.

That's why I'm so confused,  where is that pressure coming from?

I have some air hiss out the gas cap sometimes but I'd think the cap would blow off first before that hose.

It sprayed the rest of my fuel out to, like it was still pressurized.


I appreciate the moral support. I have 3k into this car after owning it for 2 months, and have drove it home and no further.
Title: Re: HELP!!! MISFIRE/STALL
Post by: celberg on 25 February 2021, 01:08 AM
No, I think the hoses goes first. You have another one going in to the tank, the return line, check that to. Do a test. Put a rubber glove or something instead of the gas cap. See if it building pressure in the tank. You might have to change the gas cap.
Title: Re: HELP!!! MISFIRE/STALL
Post by: AceWolff on 01 March 2021, 05:10 PM
That's a good idea about the glove.

So i was trying to order a new fuel pump, I suspect this one may be leaking out of the seal,  but I can't find them for under $600

Can anyone throw me the part number for the filter? All I can find is k jet filters.

This is such a headache, on top of it my insurance just jumped me to 400 a month
Title: Re: HELP!!! MISFIRE/STALL
Post by: ADV_rider on 01 March 2021, 09:30 PM
Quote from: AceWolff on 01 March 2021, 05:10 PM
That's a good idea about the glove.

So i was trying to order a new fuel pump, I suspect this one may be leaking out of the seal,  but I can't find them for under $600

Can anyone throw me the part number for the filter? All I can find is k jet filters.

This is such a headache, on top of it my insurance just jumped me to 400 a month

I recommend you change the points and get a pertronix. It's even easier than installing points.
About fuel pump and filter. try autohauasaz . com
https://www.autohausaz.com/pn/69458

https://mercedessource.com/store/1972-1975-r107-350sl-450sl-complete-fuel-pump-conversion-kit
this may help you undertand also how its connected


Title: Re: HELP!!! MISFIRE/STALL
Post by: AceWolff on 06 March 2021, 02:18 AM
Quote from: ADV_rider on 01 March 2021, 09:30 PM
Quote from: AceWolff on 01 March 2021, 05:10 PM
That's a good idea about the glove.

So i was trying to order a new fuel pump, I suspect this one may be leaking out of the seal,  but I can't find them for under $600

Can anyone throw me the part number for the filter? All I can find is k jet filters.

This is such a headache, on top of it my insurance just jumped me to 400 a month

I recommend you change the points and get a pertronix. It's even easier than installing points.
About fuel pump and filter. try autohauasaz . com
https://www.autohausaz.com/pn/69458

https://mercedessource.com/store/1972-1975-r107-350sl-450sl-complete-fuel-pump-conversion-kit
this may help you undertand also how its connected


This is exactly what I needed,  thank you