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'88 560SL - 2nd generation "original owner", 17k miles
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Discussion Starter #1
First, let me admit to the following: due to circumstances outside my control, I haven't started/driven the car in four years. My '88 was inherited from my father who passed several years ago. He was the original owner, it has 19,500 miles. I have the service records, not too much to comment on, other than all required service had been performed when I received it = it had just over 17,000 miles. Until now, it has always started/ran without issue.

About a month ago, I connected the battery terminals and fully charged the battery.

Once the battery was charged, I tried to start the car, but it wouldn't fire, but cranked quickly and seemingly non-stop.

I suspected the fuel was the issue, I removed as much as I could, put a bottle of "fuel drier" along with 5 gallons of fresh 93 octane fuel.

After waiting a few days, I returned to start the car, it fired in less than a second of cranking, went to a steady, but high, cold idle - ran for approximately 5 seconds, then stalled.

Since then, and as of now, it will start immediately after stalling, then run for approximately 5 seconds, then stall again. I can repeat the process several times, but the end result is the same, it stalls.

I have downloaded the Startek Manual, and have started to familiarize myself with the fuel system and related components.

Any thoughts as to where to start the troubleshooting, based on what I've described?

Any input/advice would be appreciated.

Thank you!
 

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1986 560SL with M120 V12 Engine, 1988 560SL Stock
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10,196 Posts
The first thing you need to do is a fuel pressure test in accordance with the manual. Then report back.
 

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I second his opinion. Long term storage is especially hard on Bosch K and KE jetronic fuel injection. You will need to spend some money on a good fuel pressure gauge designed for this system. These systems are complex and not to be tackled unless you want to learn that skill. Might be time for a good Indy shop to diagnose.
 

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2020 C 300 Coupe, 2017 SL 550
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36 Posts
I agree with the two other posts. The fuel pressure is dropping off. I personally would suspect the fuel filter would be restricting flow after the initial pressure is met. If the car was not stored with fuel stabilizer it will varnish and gum up. I personally own 11 cars and keeping good fuel in the lesser driven cars is a challenge. Good luck.
 

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I remember some vacuum actuated fuel part with a little screen inside that was gummed up. I also remember that I changed a relay that was behind the glove box around that time. I think there were two back in there that looked about the same. Black cubicle boxes.
 

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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
Joined
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10,196 Posts
I remember some vacuum actuated fuel part with a little screen inside that was gummed up. I also remember that I changed a relay that was behind the glove box around that time. I think there were two back in there that looked about the same. Black cubicle boxes.
Sound like the fuel pump and ideal control relay. I have no idea what the vacuum actuated fuel part could be on an 89 , I assume 560SL. The update you profile police are going to have a word with you.
 
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