Author Topic: HELP!!! MISFIRE/STALL  (Read 978 times)

AceWolff

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HELP!!! MISFIRE/STALL
« on: 26 January 2021, 12:30 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.
~Ace

Alec300SD

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Re: HELP!!! MISFIRE/STALL
« Reply #1 on: 26 January 2021, 12:56 PM »
Air incursion from new fuel line, clamps not tight enough, wrong internal diameter for replacement fuel hose?
Excessive water in fuel/tank?
79 W116 300SD 'Stormcloud' new as of 10/22/2017
78 W116 300SD 'Desert Rose' new as of 01/26/2014
83 W126 300SD 'Rena 2.0' with engine from 82 W126 300SD Rena' (SOLD and crushed 11-20-2017)

daantjie

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Re: HELP!!! MISFIRE/STALL
« Reply #2 on: 26 January 2021, 03:45 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.
Daniel
1977 450 SEL 6.9 - Astralsilber

AceWolff

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Re: HELP!!! MISFIRE/STALL
« Reply #3 on: 27 January 2021, 09:33 AM »
Yeah, the vacuum lines are worn thin.

Guess I have a fun day ahead of me
~Ace

AceWolff

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Re: HELP!!! MISFIRE/STALL
« Reply #4 on: 29 January 2021, 04:48 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
~Ace

AceWolff

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Re: HELP!!! MISFIRE/STALL
« Reply #5 on: 29 January 2021, 05:01 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.
~Ace

AceWolff

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Re: HELP!!! MISFIRE/STALL
« Reply #6 on: 29 January 2021, 05:02 AM »
I'll post some good pictures up today of what I'm dealing with
~Ace

rumb

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Re: HELP!!! MISFIRE/STALL
« Reply #7 on: 29 January 2021, 07:14 AM »
I'll take a stab and say your fuel distributor and WUR need rebuilt.
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

AceWolff

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Re: HELP!!! MISFIRE/STALL
« Reply #8 on: 29 January 2021, 07:29 AM »
What is the wur?

Where even is the fuel distributor.
~Ace

daantjie

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Re: HELP!!! MISFIRE/STALL
« Reply #9 on: 29 January 2021, 09:35 AM »
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.
Daniel
1977 450 SEL 6.9 - Astralsilber

rumb

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Re: HELP!!! MISFIRE/STALL
« Reply #10 on: 29 January 2021, 11:36 AM »
If you have kjet then this will get you started understanding your system

https://www.youtube.com/watch?v=a4fJAfXYxWk
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

AceWolff

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Re: HELP!!! MISFIRE/STALL
« Reply #11 on: 29 January 2021, 01:50 PM »
Alright so I have D-jet.

Just have injectors under the air cleaner
~Ace

AceWolff

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Re: HELP!!! MISFIRE/STALL
« Reply #12 on: 29 January 2021, 01:52 PM »
I have enough stuff to put a pressure gage on the fuel rail. What should my psi be?
~Ace

daantjie

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Re: HELP!!! MISFIRE/STALL
« Reply #13 on: 29 January 2021, 02:10 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/

Daniel
1977 450 SEL 6.9 - Astralsilber

s class

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Re: HELP!!! MISFIRE/STALL
« Reply #14 on: 30 January 2021, 12:10 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.

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL