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Need Some Help From The Smart Guys With An S500

3K views 23 replies 10 participants last post by  MAVA 
#1 ·
Trying to help a neighbor with his S500. Quit on him last spring and he took it to a clueless local cobber. Nine months later still DOA. Will run for a short time then appears to starve for fuel. If it was my 560SL I'd go straight for the fuel tank and strainer, but would appreciate being pointed in the right direction by folks who know what the heck they're talking about.
 
#2 ·
Can you give us some more information about your friends car..year, miles, when the problem started. Was it a "dead bang" stop running? How long does it run before dying? Does it shut down or stumble and slowly die? What operating temperature does it reach?
 
#4 ·
Tell you what I know so far. It's a 1999 with 125K (+-) on the odometer. It appears to have started as a hot stall problem that became one that would run for a minute or two and then appear to starve for fuel.

They're trailering the car to my place tomorrow (seems now it's my problem) and I'll know more then.

Thanks for taking the time to help out.
 
#6 ·
Got the car to the house and have the story.

Quit while running at normal temp. Local cobber changed out fuel pump. Ran normally for a few days. Symptoms (fuel starvation) returned. Cobber replaced injectors. No good. Now car sat since last spring while cobber scratched various parts of his anatomy looking for inspiration.

Now it's my challenge. If it was my 560SL I would go straight for the fuel tank strainer since I can hear the pump run normally it's not the relay (pump cuts out after a few seconds) and it will run briefly (less than a minute) if I let it sit for half an hour or so. Owner did not keep tank full so crap in the tank and bad strainer is where I'd start, but I have no experience with the S500 and need a little guidance. Owner did not keep old pump or filter so can't check for sediment.

A point in the right direction would help.
 
#10 ·
Full throttle or no throttle same result. Cranks on the starter with only an occasional cylinder trying to fire.

Should have mentioned the filter has been changed twice. I just take it for granted that would be done, but you're right with someone doing a cobberoscopy take nothing for granted.

Changing the fuel pressure regulator would be more pleasant than pulling the tank but no way to check the pressure without jumpering relay pins (that I know of) and that scares the hell out of me. My 300E taught me not to wade in blindly without checking with the guys that have been there done that.

Owner is on the wrong end of 70, 4 heart attacks and on oxygen. This car is his last hurrah and the cobber took his money and kept the car almost a year with no results. Loves his car and I just want him to be able to tool around town feeling good about something. Payin' it forward, ya know.
 
#12 ·
billsfan,
You are a good guy to try and help out. That is what makes these forums so great, guys like you, MAVA, all of the Aussies and the guys out of Florida. Let me print this out and go over to my mechanic and see what he says. He has never missed in the 6 years I have been with him. Unfortunately, I've come down with a "gout" attack and can't walk but I won't forget you.
Anziani
 
#13 ·
billsfan,
You are a good guy to try and help out. That is what makes these forums so great, guys like you, MAVA, all of the Aussies and the guys out of Florida. Let me print this out and go over to my mechanic and see what he says. He has never missed in the 6 years I have been with him. Unfortunately, I've come down with a "gout" attack and can't walk but I won't forget you.
Anziani
All you guys in other places...you all just straight up terrible people
 
#14 ·
At the front of the fuel rail is a hex cap. Un screw it and press on the Shrader valve... fuel should squirt out not dribble-out. If the fuel squirts with air-You are out of fuel...

I went through this a few weeks ago..The W140 was showing 1/3 of a tank of fuel, but the tank was empty....

Pressing on the shrader valve will tell the story...

Hey Arlind,

Are you still driving on 3rd gear. Did the the used torque converter fix your problem?

Martin
 
#19 ·
Hello, how about some simple steps.

Remove the air intake cover. Thus exposing the throttle body.

Ask someone to turn the ignition ( not start ). You should be able to see the
throttle plate initialize.

Start the car, you must be able to see the plate move
The movement is proportional to the pedal pressure.

If that is all fine, and the fuel pressure as @MAVA has mentioned exists,

Then you should be looking at the accelerator pedal pedal sensor.

Which should throw a code if faulty.

I have seen the same behavior before which was fixed after the mechanic initialized and calibrated the accelerator pedal sensor.

Best of luck.
 
#21 · (Edited)
Arlind,
No offense taken. I finally got to Ruben yesterday and told him of the starting problem. He said without seeing the car he could onlt speculate but he said go back to the basics. Is it getting fuel? Is it getting a spark? Are the computers doing the right thing at the right time? And something I hadn't considered. He said there is a possibility that the alarm system nay have shut the car down. He advocated getting the codes before much longer.
That is all I can offer.
Anziani
 
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