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Registered
1989 420SEL
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7 Posts
Discussion Starter #1
Hey guys,

Here's a head scratcher: My 420SEL starts right up without hesitation when cold, but acts like it isn't going to start after driving the short distance to my office. It has never failed to start, but it usually requires 2 tries. I haven't noticed this behavior at any other time. After starting, it runs and drives as normal. There are no hills on the way and the parking lot is level. I have changed the oil, oli filter, air filter, air pump filter, plugs, plug wires, distributor cap and rotor. The fuel filter and fuel pump were changed last year. Incidentally all repairs have been done with proper OEM parts.

I'm not really worried about this, but I don't want it to progress to something worse.

Any ideas?

Thanks
 

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Registered
1991 560SEL
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563 Posts
on my 1991 560, same symptom. Root cause was multiple original fuel injectors no longer holding pressure/were dripping fuel into the cylinder when the engine was off. Would result in slightly flooded engine. Replacing all injectors with new Bosch solved that issue.
 

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Registered
1985 500sel and 500sec 2012 E63 1989 Porsche 911
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5,094 Posts
accumulator?
 

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Registered
1991 560SEL
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563 Posts
WHen I replaced my fuel filter/pumps/accumulator, my issue still persisted. Once the injectors were tested(leakdown), the issue was found. Once they were replaced with new, the issue was resolved.
 

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Moderator
1991 500SEC sub 50K mi. 1987 560SEC Now 150K mi. 2018
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4,035 Posts
Les is right..

It's been my experience that with a bad accumulator the warm/hot engine just won't start at all, until cooled down.
It can be a most inconvenient & aggravating condition.

M
 

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Registered
1989 420SEL
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7 Posts
Discussion Starter #6
Ok thank you SEC, and vdubpower, and Les. I'll buy a kit, and will keep you all updated. This forum is amazing!

--john
 

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Outstanding Contributor
350SDL, '17 GLS450, "Grandpa's Roadster" Project Car
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3,033 Posts
Before you throw parts at it, pressure test the system to see if that's the problem. Anything that allows fuel pressure to bleed off will cause the same symptoms.
 

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Registered
1989 W124 260E
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1,124 Posts
I also go for fuel pressure test .I have this problem on my 124 m103 engine .I changes everything other than fuel pumps .I reckon i have a weak fuel pump .. Last September i changed the injectors .Depressurise the system before working on the first 4 injectors .I replaced the first 4 then it rained so i stoped . But started the car up to check for leaks after i had changed 1-2-3- 4 all ok no leaks . Next day went out and pulled the loast two injectors .Did this without removing fpr to release the pressure . I broke open no 5 hard line and removed no 5 injector refited it along with no 6 , Strange thing was after i finished i realised what i had not done .I never seleased the tank cap or removed the fpr or ran the engine to take the pressure off the injectors .I saw no fuel from the last 2 injectors So i know my pressure was down .
 

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Registered
1985 MB 500sel (Euro)
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154 Posts
Yes, JFlor please let us know how this turns out. My car has always been a slow starter and has had slightly leaking injectors (a puff of gray smoke after sitting all night, for several years now). However, a few months ago it started to hard start about an hour after being driven. I still suspect the accumulator and am about to change it. Will get to the injectors later.
 

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Moderator
1991 500SEC sub 50K mi. 1987 560SEC Now 150K mi. 2018
Joined
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4,035 Posts
a slow starter and has had slightly leaking injectors (a puff of gray smoke after sitting all night, for several years now). However, a few months ago it started to hard start about an hour after being driven. I still suspect the accumulator and am about to change it. Will get to the injectors later.
With respect given to the above advice.

RE: Accumulator failure: When the accumulator fails/leaks, the fuel [under pressure] vents through the compromised diaphragm directly into the fuel return line/or back to the tank. Whether or not this could/might affect a 'cold start' is debateable.
A 'hot start' can be darn near impossible should the Accumulator be compromised.

M.
 

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Registered
1989 420SEL
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7 Posts
Discussion Starter #12
Hey guys,

Sorry for my absence. Stewpot: I will let you know. However it may be a while, as the car is running ok right now, and ugh yet another 500 bucks for injectors! But I will pressure test the system at least and then we'll go from there.

Much Appreciated,

John
 

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Registered
1991 560SEL
Joined
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563 Posts
Hey guys,

Sorry for my absence. Stewpot: I will let you know. However it may be a while, as the car is running ok right now, and ugh yet another 500 bucks for injectors! But I will pressure test the system at least and then we'll go from there.

Much Appreciated,

John
I went with these. Arrived in Bosch boxes, new, and from all indicators..appeared to be..Bosch.

 
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