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Registered
1986 560 SL
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10 Posts
Discussion Starter #1
Sorry if this question has been answered in another thread. I searched and could not find a close match to my problem.

My 1986 560SL, if driven the day before and garaged, takes about 3 to 5 seconds of cranking before starting. When warm, it starts right up. It has also been running a bit rough at idle.

I had a 87 Toyota once, and it would act simillarly when starting cold, but I cleaned the fifth injector, used Chevron gas, and then the car started right up when cold.

I imagine we have a 'ninth' injector' which might need cleaning. Being somewhat of a political and environmental animal, I no longer will buy Chevron gas, but I also have not put any fuel injector cleaner in the tank since I bought the car (about 3 to 4 months ago). I am somewhat convinced the car sat without much use since the mid 90s. I have driven the car about 2000 miles since I bought it so any old gas should be somewhat gone, and I always use quality, premium gas.

So, basically two questions. Does anyone use fuel injection cleaner, and has anyone had a similar problem with the ninth injector. Thanks to all in advance.
 

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Premium Member
1984 380SL, 1973 450SLC
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2,174 Posts
My first response is the fuel accumulator, but how long have you owned the car, and is this something that just started to act up???
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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32,357 Posts
Still no profile or pictures.
Accumulator is for warm starts. Cold Start Valve is for cold starts.
Could also be the Air Slide Valve sticking closed.
 

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Premium Member
1984 380SL, 1973 450SLC
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2,174 Posts
OOOOPPPPPPPSSSss, just goes to show, your first thought is not always the best...:)
 

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One of the BW Old Guard/R129, W204 Moderator
1997 SL500- 40th Anniversary
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7,166 Posts
My first response is the fuel accumulator...
Usual symptom is hard starting when warm, but I can see if the pressure bleeds down overnight, the first start-up of the day could be slow.

I wouldn't rule out any source of bleed-down, including injectors, etc. However, your symptoms don't sound to be anything alarmed about. Look for puff of black smoke at first start-up to see if you may have a bit of fuel pooled in the chambers from injector bleed-down. Also, monitor oil level and viscosity for fuel contamination if injectors and symptoms get worse.

Here is a test. First start of the day, cycle your switch key on-off three or four times to run pump and therefore pressurize your fuel system, then start as normal and report back.

My 560 has exhibited reluctance to start quickly ever since I have had it. First start of the day, it will fire off almost immediately, then stumble a bit, maybe die even, then even out to sewing machine-smooth. Successive starts are immediate, without stumble or idle drop. I have not given it a worried thought...

dammit, Rowdie... Quick on posting. Sorry to repeat accumulator issue.
 

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Registered
'80 450SLC Afro RHD Ikonengold
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2,900 Posts
I had similar fault as post #1 until I replaced all the injectors and their seals. I asume that it was 50% blame at each.
Before the injector replace, after couple a weeks at parking on a downslope on a cold African day it would surprise me here and there with an instant start but it would be a hard crank most of the times. It scared the starter motor but it dod not kill it.

You could have a leaky injector(s) that flood the engine (like I had) with identical symptoms. Easier start with full throttle will be a good tell tale of flooding.

@ Ears.
That's the way my car behaves too except (after I got new injectors, seals and full vacuum system glue + cabletie sealing) it will start instantly every time.

_____________________________________
 

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Registered
1986 560 SL
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10 Posts
Discussion Starter #7
Thanks to all who responded. I removed the connector on the ninth injector and put a voltmeter across the removed connector contacts. The engine had not been started for four days. I turned the key to the position where the instrument panel lit up, but not to the start position. I could hear the fuel pump pump, and then stop. I turned the key to off, and then once again to the position to hear the fuel pump. Once I could hear the pump stop, I turned the key to start the engine. The ninth injector connector showed a voltage, about 9.5 volts, for a few seconds, (remember the ninth injector is disconnected at this point), and the car started almost immediately.

So,, my assumption is that the fuel pressure bleeds off after a number of hours, and allowing the fuel pump to pressurize the system, all is well. I put a bottle of Chevron Techron fuel injector cleaner into my full tank of gas. I will continue the cold starts by giving the fuel pump time to put pressure in the system before starting and hope the ninth injector gets cleaned by the Techron in the process, since I think that may be part of my problem. I would rather not take the ninth injector out at this time, but may in the future.

There is no gas in the oil, and I never smell gas, so I do not suspect any leaky injectors. If I take the ninth injector out for cleaning, I will post again.

Cheers,
Bruce Tews
 

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Registered
1974 450sl 1994 bmw 530i 1995 f150 2007 FJCruiser trd se
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41 Posts
The lucas upper cylinder lube & injection cleaner is what i use. How is the "ville" these days?
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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32,357 Posts
I may have to eat my words about the accumulator. I know it keeps pressure in the system for warm starts but I do not know how long it is supposed to hold pressure.
 

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Registered
82 380SL 96 SL500 03 SL500
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6,165 Posts
I believe the manual says pressure should hold for 20 minutes. I also seem to recall Roncallo saying he checked for some additional length of time though I can't recall how much.

IMO, in either case it wouldn't be expected to hold overnight.
 

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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
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10,228 Posts
I believe the manual says pressure should hold for 20 minutes. I also seem to recall Roncallo saying he checked for some additional length of time though I can't recall how much.

IMO, in either case it wouldn't be expected to hold overnight.
I thought it was 30. I checked mine a few years ago and it held for over an hour. Sources of leakage for the 560SL are check valves in fuel pump, accumulator, pressure regulator, injectors and cold start injector.
 
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