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My 560SEL (89) is continuing to have warm start issues. It…

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My 560SEL (89) is...

My 560SEL (89) is continuing to have warm start issues. It is a transition issue from start conditions to run conditions. Something seems to be shutting off the fuel. At idle of with some throttle, the car starts normally and then stops after about 2 seconds ... cold or hot, no issues. Just had the relays for fuel pump, environmental, and OVP. Had a major tuneup about a month ago. Recently had exhaust repaired throughout ( it likely sat in a garage for a long time). So, as it seems to be a control problem, it was sent to a German Auto specialist and had all the controls (PID?) reprogrammed. It works very smoothly now when it starts properly. What sensors or other components should I look at to correct this issue?

Mechanic's Assistant: How many miles are on the car? Has the car been starting normally?

188k. In mild weather it was starting normally, but would occasionally have this issue if it was shut down before fully warming up or after sitting for a half hour or so. Before the tuneup, starting fluid easily dealt with it. Not so much after the tuneup

Mechanic's Assistant: Are you fixing your 560SEL yourself? What have you tried so far?

I have a mechanic that I use, but information is sparse... it's a Kok of head scratching and checking function... intermittent problems are hard

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

Not really, just that information on the starting sequence would be useful

Submitted: 1 year ago.Category: Mercedes
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Answered in 11 hours by:
8/7/2017
Mercedes Mechanic: Pete, Mercedes Mechanic replied 1 year ago
Pete
Pete, Mercedes Mechanic
Category: Mercedes
Satisfied Customers: 33,335
Experience: Over 15 years experience as a Mercedes dealer technician
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Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

If you did not have the fuel pump tested when acting up to see if the pump itself is faulty this needs done.If the pump is acting up internally it will cause this issue here with it needing replaced.If this was already checked and found to be o.k. let me know so we can continue.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated ( should be a link to click on here or above).You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

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Customer reply replied 1 year ago
I'm pretty sure it was - I sent a text to the service writer at my mechanic to double check.It started fine this morning, but it was a bit rough for about 3-4 seconds while the idle dropped from about 1200 to 700 RPM. It has no issues getting enough fuel when I put the accelerator all the way down (getting on the freeway).
Customer reply replied 1 year ago
The fuel pump was tested for pressure and volume. It was in-spec.
Customer reply replied 1 year ago
you have no ideas about what to look at in the idle circuit or the components related to the fuel system on the transition from the starter switch disengaging and idle settling to a steady state? I'm here paying money for a little more than just "did you test the fuel pump?"....
Mercedes Mechanic: Pete, Mercedes Mechanic replied 1 year ago

I apologize for the delay.

I will open your question up for others here to see if someone else can assist further on this as there may be others here that may have more info on what to check or do with this issue.I hope you can get this resolved with ease.No need to reply to my last post here unless it is a last resort as it will keep your question locked to me and others will not be able to view it.If you feel you want to continue to work with me on this feel free to reply at any time but keep in mind in some cases it can be difficult to fully diagnose or help repair this without seeing your vehicle.

Thanks Pete

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Customer reply replied 1 year ago
Yeah - I get the issue. I'm fishing for information on how that throttle body injection system is supposed to work as much as anything else. I'm a pretty good troubleshooter if I have information.... Mercedes has kept the operational details pretty secret for this old technology for some reason.
Mercedes Mechanic: Marty, Mercedes Technician replied 1 year ago
Marty
Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 55,280
Experience: Bosch Certified Master Tech. Over 35 years experience.
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Hi, my name is***** can help. Can you describe the problem? Are you saying the car starts then stalls when you release the key?

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Customer reply replied 1 year ago
but only when warm (not cold or hot). I let the car come to idle with the starter engaged to prove this (not a good long term solution...). It wouldn't run more than a few seconds when warm and starting after releasing the starter switch.
Mercedes Mechanic: Marty, Mercedes Technician replied 1 year ago

Will it stay running after you release the key if you hold your foot on the gas?

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Customer reply replied 1 year ago
No, fuel is cut off regardless of the throttle position. (at least it seems like fuel is the issue). More throttle seems to make it run slightly longer, but it's less than 1 second of difference. I can vary RPM until it stops altogether.
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