M103 woes, FIXED.
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- B Class
- Posts: 21
- Joined: Thu 13 Jul, 2017 12:01 pm
- Model you own: w124
- Region: Victoria
- Location: Grampians NW Victoria
M103 woes, FIXED.
Hello all, I have come to the end of my ability getting my daily driver 1989 300e back running properly. I'm quite methodical by nature and like to do things right and don't believe in ''she'll be right" and that has worked for me for many years (my hobby is wrenching on hydraulic suspension 1960's Citroens, so methodical perseverance is a learned virtue). I hope the collective brains trust of OZBeNZ is able to point me in the right direction. Here's the issue:
Poor idle, frequent stalling when braking, especially when approaching a roundabout. I replaced fuel injection relay, no more stalling. Still a poor idle, especially when warm. I removed the idle control valve, which was the original dated 10/1989 and was hanging up even after cleaning, so I replaced that as well as the hoses to and from the idle control valve. Idles nicely when cold, but stalls when warm, after erratic idle. This points to either a faulty coolant temperature sensor or fuel accumulator (next to fuel pumps). Coolant temperature sensor reads correct and shows the right resistance with varying temperatures. Replaced fuel accumulator, car starts immediately, but still no cigar. Running very rich too, so checked duty cycle, which pointed to a dead oxygen sensor as it probably was the original as most parts were on this car. Unplugged the oxygen sensor, duty cycle goes to 50%, so closed loop. Idles better when cold, but still very rich. I also found an incorrect installation of the air/fuel intake boot (the big rubber one) when I replaced the idle control valve hoses, with one side sitting on top of the intake manifold instead of over the throttle body. Removed all and sundry, reinstalled the boot and had high hopes of having found the culprit. Well, not so fast, terrible over-fuelling when warm, cold idle good, but almost impossible to restart when warm. Black smoke type of over-fuelling.
When I bought the car 3 years ago (120,000 km) I did a full replacement of all consumables and then some: distributor cap, disc, seal, rotor, spark plugs, wires, injectors and seals, brakes, shocks front and rear, replaced all fuses with copper ones, all filters and fluids etc. I’m convinced the fuel system and ignition system are spot on, I have also replaced both fuel pumps and filter lately. So, I have a 1989 300e that is in very good condition and has 135,000km on it, but is undriveable. Being located in Western Victoria, about 3 hours away from any W124 competent work shop in Melbourne is an additional handicap. Before I give up on this car and very reluctantly send it to the great wrecking yard in the sky would anyone have any hints on what to check next? Suggestions gratefully received. Thanks, Erik.
Poor idle, frequent stalling when braking, especially when approaching a roundabout. I replaced fuel injection relay, no more stalling. Still a poor idle, especially when warm. I removed the idle control valve, which was the original dated 10/1989 and was hanging up even after cleaning, so I replaced that as well as the hoses to and from the idle control valve. Idles nicely when cold, but stalls when warm, after erratic idle. This points to either a faulty coolant temperature sensor or fuel accumulator (next to fuel pumps). Coolant temperature sensor reads correct and shows the right resistance with varying temperatures. Replaced fuel accumulator, car starts immediately, but still no cigar. Running very rich too, so checked duty cycle, which pointed to a dead oxygen sensor as it probably was the original as most parts were on this car. Unplugged the oxygen sensor, duty cycle goes to 50%, so closed loop. Idles better when cold, but still very rich. I also found an incorrect installation of the air/fuel intake boot (the big rubber one) when I replaced the idle control valve hoses, with one side sitting on top of the intake manifold instead of over the throttle body. Removed all and sundry, reinstalled the boot and had high hopes of having found the culprit. Well, not so fast, terrible over-fuelling when warm, cold idle good, but almost impossible to restart when warm. Black smoke type of over-fuelling.
When I bought the car 3 years ago (120,000 km) I did a full replacement of all consumables and then some: distributor cap, disc, seal, rotor, spark plugs, wires, injectors and seals, brakes, shocks front and rear, replaced all fuses with copper ones, all filters and fluids etc. I’m convinced the fuel system and ignition system are spot on, I have also replaced both fuel pumps and filter lately. So, I have a 1989 300e that is in very good condition and has 135,000km on it, but is undriveable. Being located in Western Victoria, about 3 hours away from any W124 competent work shop in Melbourne is an additional handicap. Before I give up on this car and very reluctantly send it to the great wrecking yard in the sky would anyone have any hints on what to check next? Suggestions gratefully received. Thanks, Erik.
Last edited by tomatoes4all on Tue 24 Nov, 2020 4:14 pm, edited 1 time in total.
- Bartman4800
- SLS AMG
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Re: M103 woes, do I give up?
Maybe I missed it in the quite elaborate list of parts you replaced, but have you replaced the seals around the injectors?
They are easy to replace and cheap but when they go hard the engine idles poorly.
Kent Bergsma has some videos on this, explaining it in detail
Good luck, Bart
They are easy to replace and cheap but when they go hard the engine idles poorly.
Kent Bergsma has some videos on this, explaining it in detail
Good luck, Bart
1963 220 Sb Sedan "Kermit" (Australian Assembly)
1960 220 Sb Sedan "Zum Schlachten" (Early German Assembly, with a torsion bar spring for the bonnet) - Stored in Country WA
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1960 220 Sb Sedan "Zum Schlachten" (Early German Assembly, with a torsion bar spring for the bonnet) - Stored in Country WA
2012 W212 E250CDI
1981 Subaru Brumby 1.8 with Weber and 5-speed box "little utie" - Sold to another enthusiast!
2006 Ford Focus "daily driver"
2002 VW Passat V6 30V Station Wagon (SOLD - This car into a money pit)
2011 Kia Sportage "Missus commuter Bus"
2002 Mitsubishi Rosa Bus (converting it to a motor home)
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- B Class
- Posts: 21
- Joined: Thu 13 Jul, 2017 12:01 pm
- Model you own: w124
- Region: Victoria
- Location: Grampians NW Victoria
Re: M103 woes, do I give up?
Hi Bart,
Thanks for your reply. Yes, I replaced the injector seals too, they were more like bakelite than rubber when I pulled them out. Cheers, Erik.
Thanks for your reply. Yes, I replaced the injector seals too, they were more like bakelite than rubber when I pulled them out. Cheers, Erik.
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- Mercedes Demigod
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Re: M103 woes, do I give up?
Get underneath and give your cat a whack with a piece of 2x2. See if there's any noise.
KE Jet
Have you checked your EHA for leakages? Any fuel smell?
There's a throttle position sensor on the side of the throttle body - they wear out and can cause poor idling and poor economy.
Have you had the fuel pressure checked?
I'm assuming you have non resistor plugs and good ignition leads.
There's a round plate under the distributor. If it hasn't ever been replaced - they break down and ignition voltage gets leaked to ground
135,000 is a good mileage. It's worth getting right
KE Jet
Have you checked your EHA for leakages? Any fuel smell?
There's a throttle position sensor on the side of the throttle body - they wear out and can cause poor idling and poor economy.
Have you had the fuel pressure checked?
I'm assuming you have non resistor plugs and good ignition leads.
There's a round plate under the distributor. If it hasn't ever been replaced - they break down and ignition voltage gets leaked to ground
135,000 is a good mileage. It's worth getting right
Current
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W202 - C200, C180, C180
W126 - 380SE , 380SE (Ex SA Import), 560SEL
W124 - 300e, 260e (ex Japan)
W111 220s (Indonesia) 4 speed manual column shift
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- John Green
- Mercedes Demigod
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Re: M103 woes, do I give up?
Two things:
1) disconnect the ke-jetronic module and go for a drive. See what happens. The ke-jetronic system is just a fancy k-jetronic system where the electrical side of things just fine tunes it. You may have to artificially increase the idle speed as the idle motor will no longer be working. This will help you separate issues with the electronics of the ke-jetronic system with the more mechanical aspects of the system.
2) check the air flow meter potentiometer. You should be able to google the procedure, if it goes open circuit anywhere near idle that could be the issue.
1) disconnect the ke-jetronic module and go for a drive. See what happens. The ke-jetronic system is just a fancy k-jetronic system where the electrical side of things just fine tunes it. You may have to artificially increase the idle speed as the idle motor will no longer be working. This will help you separate issues with the electronics of the ke-jetronic system with the more mechanical aspects of the system.
2) check the air flow meter potentiometer. You should be able to google the procedure, if it goes open circuit anywhere near idle that could be the issue.
Kind regards, / Mit freundlichen Grüßen,
John Green, Member Institute Automotive Mechanical Engineers
http://mbspares.com.au - Supporting Australia's Mercedes-Benz Enthusiasts.
John Green, Member Institute Automotive Mechanical Engineers
http://mbspares.com.au - Supporting Australia's Mercedes-Benz Enthusiasts.
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- B Class
- Posts: 21
- Joined: Thu 13 Jul, 2017 12:01 pm
- Model you own: w124
- Region: Victoria
- Location: Grampians NW Victoria
Re: M103 woes, do I give up?
Thanks for your responses. The EHA is not leaking, the cat is still solid, I had replaced the distributor inner plate and seal as part of my stage zero approach, as well as the correct spark plugs and wires.
However, a quick test of the air flow sensor output (running engine and plug partially plugged in to be able to get a reading) last night shows 1.1 V between pins 1 and 2, a 60% deviation on the required 0.7 V. Moving the sensor up and down just a fraction (those Torx 15 screws are a pest to get to!) shows a wildly fluctuating voltage and a change in idle speed. I'll remove the sensor today and clean the carbon tracks as well as the "fingers" behind it and see if this helps; I might need to buy a new sensor as I'm sure it's still the original one that Helmut or Heinrich used on the assembly line in 1989. Also, I'll need to buy a new oxygen sensor, it seems there are genuine Bosch ones for about $140. But first things first.
I'll report back on progress, thanks for pointing me in the right direction, Cheers, Erik.
However, a quick test of the air flow sensor output (running engine and plug partially plugged in to be able to get a reading) last night shows 1.1 V between pins 1 and 2, a 60% deviation on the required 0.7 V. Moving the sensor up and down just a fraction (those Torx 15 screws are a pest to get to!) shows a wildly fluctuating voltage and a change in idle speed. I'll remove the sensor today and clean the carbon tracks as well as the "fingers" behind it and see if this helps; I might need to buy a new sensor as I'm sure it's still the original one that Helmut or Heinrich used on the assembly line in 1989. Also, I'll need to buy a new oxygen sensor, it seems there are genuine Bosch ones for about $140. But first things first.
I'll report back on progress, thanks for pointing me in the right direction, Cheers, Erik.
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- 300 SLR
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Re: M103 woes, do I give up?
Erik, the M103 is a great motor as others will agree.
Unfortunately, I cannot comment on what may or may not be wrong and I'll leave that for others to do as they already have.
Be patient, you are on the the right track and the issues will soon be sorted and your W124 will be purring like a newborn kitten!
Cheers,
Kim
Unfortunately, I cannot comment on what may or may not be wrong and I'll leave that for others to do as they already have.
Be patient, you are on the the right track and the issues will soon be sorted and your W124 will be purring like a newborn kitten!
Cheers,
Kim
W126 86 300SE Champagne
W126 84 380SEC Signal Red
W126 84 380SEC Signal Red
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- B Class
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- Model you own: w124
- Region: Victoria
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Re: M103 woes, do I give up?
Well, I am happy to report that adjusting the air flow potentiometer to 0.7 V has done the trick! It was 1.1 V when cold and increased to 1.4 V when the car would warm up. After removal and cleaning of the carbon tracks on the sensor it looked still very new, new as in recently replaced. After reinstallation and adjusting the car runs like never before. Thanks for the technical expertise John, Bart and Ivanerrol and encouragement Kim, it's much appreciated. To go from wanting to park the car somewhere public late at night with the keys in the ignition to having a well running car, without spending a single dollar, is an excellent result. Thanks again all, Erik.
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Re: M103 woes, do I give up?
Great news! Thanks for all your reporting and follow up and all learnt something.
Craig Baulderstone
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280s's
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280SL Ruby
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350SL Gloria
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450SEL Boris
500SEC's...including Syd
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- 300 SLR
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Re: M103 woes, FIXED.
Yahoo! The M103 PURRRRRRRRRSSSS on!
W126 86 300SE Champagne
W126 84 380SEC Signal Red
W126 84 380SEC Signal Red
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- Mercedes Demigod
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Re: M103 woes, FIXED.
I tried to buy an original one of those potentiometers.
Couldn't find one. Ended up buying a cheap PRC one on steal bay. - Couldn't get it adjusted it all.
Found another one at a wrecker of a relatively low K car - Japanese import.
It would have been nice to see a M103 with a modern injection and ignition system.
Couldn't find one. Ended up buying a cheap PRC one on steal bay. - Couldn't get it adjusted it all.
Found another one at a wrecker of a relatively low K car - Japanese import.
It would have been nice to see a M103 with a modern injection and ignition system.
Current
S212 - E350 Wagon
W213 - E220d
Departed
W211 - E240
W204 - C280
W202 - C200, C180, C180
W126 - 380SE , 380SE (Ex SA Import), 560SEL
W124 - 300e, 260e (ex Japan)
W111 220s (Indonesia) 4 speed manual column shift
W123 230
W116 450SEL
W140 420SEL
W210 E240, E240
W209 CLK 240
W201 190e 2.6 (ex U.K.)
S212 - E350 Wagon
W213 - E220d
Departed
W211 - E240
W204 - C280
W202 - C200, C180, C180
W126 - 380SE , 380SE (Ex SA Import), 560SEL
W124 - 300e, 260e (ex Japan)
W111 220s (Indonesia) 4 speed manual column shift
W123 230
W116 450SEL
W140 420SEL
W210 E240, E240
W209 CLK 240
W201 190e 2.6 (ex U.K.)