Mercedes W124 very difficult starting. Long hesitation on acceleration.

Tiny
CORIELTAUVUS
  • MEMBER
  • 1989 MERCEDES BENZ 260E
  • 2.6L
  • 6 CYL
  • RWD
  • AUTOMATIC
  • 140,000 MILES
Note: (Right hand drive vehicle)
Problem preceded by an apparent slight misfire when idling.
Then later, a long hesitation in stuttering revs when pulling away at traffic light.
Then soon after, unable to re-start having stopped to refuel.
Towed home
Changed fuel filter. Which was way overdue anyway.
Managed to restart with difficulty. Each time it failed there was a lot of smoke from (I think) the MAF. Then when it did start it seemed only to fire as I stopped turning engine over. Struggled in low revs for say 10 seconds, then picked up OK.
Restarted OK with no accelerator if left a few minutes, but went back to the difficult mode if left for half an hour.
Took for a run locally and it ran fine until I stopped to to turn across traffic, then it hesitated and almost stalled again. Pushed into 1st gear (crawler) as I was approaching a steep rise and just managed to keep it running till it revved up normally again after 5 or so seconds.

Plugs OK, Ignition distributor head quite new. Had previously re-soldered OVP relay contacts at motherboard because ABS light was on. This stopped the light OK. Replaced EHA valve with a second-hand one.
Help, guys!
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Monday, January 26th, 2015 AT 12:22 PM

4 Replies

Tiny
CORIELTAUVUS
  • MEMBER
Additional information:
I am able to solve my starting problem by turning the ignition key to position 2 for a second or two. Twice. The engine then starts perfectly every time with no accelerator depression. Presumably this means I am pre-charging the fuel system with fuel. Does this suggest that either the accumulator diaphragm has failed, or that a fuel pump output is below standard? Unfortunately I have no gauge to check fuel pressure.
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Tuesday, January 27th, 2015 AT 1:58 AM
Tiny
CADIEMAN
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It's hard to answer you question because we are not able to be at the car. No one wants to mislead u, but hear is some advice.
U will need to put the engine on a scope and check the patterns to find the small miss.
U can rent a fuel pressure gauge at the parts store.
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Tuesday, January 27th, 2015 AT 6:17 AM
Tiny
CORIELTAUVUS
  • MEMBER
HI Codieman, thanks for your reply. I am not aware of the process of checking electronic codes on this car. There is no warning light for "check engine" on the dash. How do I find out about code checking?
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Tuesday, January 27th, 2015 AT 11:50 AM
Tiny
CADIEMAN
  • MEMBER
The parts store will check your codes for free if it is on your car.
But the scope i'm talking about hooking up to your engine to gives u a pattern of each cylinders spark. Then they can tell which cylinder your having a problem with the spark.
Check the codes first and if ok u will need to take it to a shop and have them put it on a scope.
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Tuesday, January 27th, 2015 AT 1:00 PM

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