If you have a spare fuel pump relay you might try swapping it. I'm not sure if yours has a separate relay or if it is built into the MAS relay. The older cars had a separate relay.

I'm wondering if your relay is actually energizing the pump when you turn the key to on, or only when you crank the engine. Also, the system is built to keep the pressure up when the engine is off. If it's leaking down it will be hard to start.

Surely a search would reveal a lot of info about this.

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2012 E350
2006 Callaway SC560

I believe the relay you are referring to is the black box next to the klima relay? I have an extra one of those, I will look in to that this evening.

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Eugene

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2

Lorainfurniture, I think you are on the right track with the age related therory. I bought this car in early March and it did not have the fault it does now. It started doing it about 2 weeks later. However, after replacing everything anyone could suggest it still does it. I'm not sorry I replaced all those parts. The car is in great shape, but I got it without records, so now I do have records, for this group anyway. I keep searching for dry rotted or corroded stuff and I fix anything I can find, but so far nothing has helped except making the EHA a little richer. It's been suggested that in doing that I'm just covering up the real problem and I think that's probably the case.

I'd like to pursue the fuel pressure leak-down therory next. What's a good procedure?

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2000 Mercedes S500
1990 Mercedes 560SEL
1970 Triumph Spitfire

Well what happen now? did you fix it? just want to bump up this thread...cheer

Have you replaced the Fuel Pump Relay yet? I would also look into testing the injectors, and residual fuel pressure...also check for vacuum leaks. (Don't forget the injector seals too)

Do these cars use a coolant temp. sensor??

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

Still not fixed. And I think I may have flubbed my dub. I picked up a used computer, which worked fine but didn't solve the problem. So I turned the EHA adjustment another 1/4 turn CW. Which seemed to make it little better but did not make the start/stall/chug-chug behavior go away.

After I readjusted the EHA, I started to reset the duty cycle. When I hooked up my meter the KOEO reading was 70%. This is a California car, and the first time I set the duty cycle I got the correct 85% reading, so I must have installed a federal computer. I replaced it with the original but the KOEO reading is still 70% and I'm having a hard time reading the duty cycle. It doesn't seem to read accurately anymore. At the moment I have the mixture set be feel and by ear, and the mileage is down from 20 to 16.

Did I damage something by installing the federal computer in the California car?

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2000 Mercedes S500
1990 Mercedes 560SEL
1970 Triumph Spitfire

I decided, at my local indie's suggestion, to replace the oxygen sensor. It didn't fix my start/stall/chug-chug/start/run problem, but it did allow me to set my duty cycle to 50%, and the engine is smoother and idles better. I filled it up this afternoon, hopefully my mileage will go back up to normal.

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2000 Mercedes S500
1990 Mercedes 560SEL
1970 Triumph Spitfire

My old 1990 300se developed the start stop syndrome,if i left it running for about 5 mins it would just cut out, no drop in revs. After 15 mins or so it would start but then after 5 mins cut out again. Fault was traced to a faulty crankshaft sensor. Replaced that.So far so good.

If you find out any info on fuel pressure testing, be sure to post some info. I'm going to look around too and talk to my Indy as well, see if he has some tools or a procedure to follow.

An often overlooked cuase for stalling.
Hall effect sensor on the back of the speedo. It can cause intemittant havoc.
It seems that once you take your foot off the throttle and you are slowing down, this sensor's signal tells the software in the EFI module to prepare for idle mode, without it the computer thinks you actually want the fuel supply to stop all together and as such, shuts down because that is what it thinks you want it to do. Something so small can cause so much grief .

Its start/stall/start/chug-chug/run behavior is only at startup. It never does it when driving. It runs and drives extremely well. If not for this one little thing, it would be as perfect a runner as you could imagine.

I have a new throttle microswitch on the way. I decided to try it as you can sidestep the "start/stall/start/chug-chug/run" thing by holding the throttle open during cranking, then holding it open a little for a few seconds. Usually you can then take your foot off and the car will be idling perfectly. However, there are times that it will stall as soon as you take your foot off the pedal when you've held it down during cranking. When this happens if you let it go through its "start/stall/start/chug-chug/run" thing it will be fine.

It's seems to need the "start/stall/start/chug-chug/run" thing to happen before it will idle properly.

Replacing the throttle microswitch is probably a crazy idea, but Phil sells them for only $28, so "hope springs eternal."

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2000 Mercedes S500
1990 Mercedes 560SEL
1970 Triumph Spitfire

Well . . . the throttle microswitch did not solve the problem, nor did the new fuel pressure regulator I installed next. I wouldn't have replaced the FPR if I hadn't found a brand new one sitting on a Volvo specialist shelf, it was the only MB part he had, and was cheap enough that I couldn't pass it up.

The injectors all look as though they haven't been touched since the car left Germany, so they are next. I ordered them today, so by the weekend they should be in place.

Is there anything in paticular I should be aware of for the RR?

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2000 Mercedes S500
1990 Mercedes 560SEL
1970 Triumph Spitfire

I have the same car with the same issue. I've done everything on this thread.

Disconnect the fuel return line at the fuel distributor. Take the air gun from your compressor and blow out the line. You should hear nothing but bubbling in the gas tank. If it builds up any pressure at all, even just for a second, you probably have a bad check valve in the tank.

It's what happened to me...

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A.S.E Tech A1,A6,A7,A8 & MVAC 609 + EPA 608

Unless stated otherwise, any question I ask is about my greymarket 1985 380SEL.

MrsSudz/Erika
could you kindly posts the pictures of the Engine and the hose etc.Mine is a 94 E200.I have changed OVP,Fuel Pump Relay fuse,Bosch Spark Plugs,Had the wiring harness relooked to no avail.

Am at my wits end
dongra