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Rrrockhound 03-31-2017 05:38 PM

Stalling 300E
 
This happened twice today, once on the way to work, once coming home. Slowing down from about 50 mph to make a left turn, the engine stalled. No warning, it just quit. Restarted easily and ran fine for the rest of the drive.

Here's what I've replaced in the last 14 months and 16,000 miles: Head gasket, O2 sensor, all new copper fuses, voltage regulator, plugs, wires, cap and rotor, fuel injectors and seals, fuel filter and accumulator, OVP relay. The car is my daily driver and has always run great with a normal idle speed and it starts better than when I got it. It now has 152,000 miles.

Any ideas what I should check?

Edit: I just pulled codes from the diagnostic plug and the only one I got was for the air injection system. I unplugged the air pump about a year ago because it was noisy when cold but it's never thrown a code before and I thought it was only for emissions anyway.

Hit Man X 03-31-2017 06:59 PM

This happened to me on the '89... dying fuel pump relay. Which for you should be the MAS relay like my '90.

brooktre 04-01-2017 06:59 AM

I once had an 83 380sel that would stall while running - no other symptoms. It would restart easily and I couldn't figure it out. I checked fuel, battery ground and probably some other things I can't remember. It finally died on the interstate and wouldn't restart. Turned out that the coil died.

optimusprime 04-01-2017 02:08 PM

Check the fuel cap, on the tank .If its has a faulty seal, its loosing pressure. And as post above from brooktre .Earth points must make a good contact to the body .

Diseasel300 04-01-2017 04:27 PM

Quote:

Originally Posted by optimusprime (Post 3697003)
Check the fuel cap, on the tank .If its has a faulty seal, its loosing pressure.

The fuel system does not pressurize the fuel tank. Ideally the pressure inside the tank should be the same as the surrounding atmosphere or at a very slight vacuum to keep fumes inside the evap system.

Rrrockhound 04-02-2017 11:19 AM

Quote:

Originally Posted by Hit Man X (Post 3696886)
This happened to me on the '89... dying fuel pump relay. Which for you should be the MAS relay like my '90.

So do you mean instead of a regular fuel pump relay I have to get an MAS relay instead?

Diseasel300 04-02-2017 12:11 PM

Depending on the year model, the MAS relay *IS* the fuel pump relay. You haven't told us what year your car is.

Rrrockhound 04-02-2017 06:32 PM

Sorry, it's a 1991, and to respond to what someone said, the coil has been replaced.

Stretch 04-03-2017 04:28 AM

Quote:

Originally Posted by Rrrockhound (Post 3696874)
This happened twice today, once on the way to work, once coming home. Slowing down from about 50 mph to make a left turn, the engine stalled. No warning, it just quit. Restarted easily and ran fine for the rest of the drive.

...

Did this happen with foot off the accelerator and engine at about idle?

If so - my vote is for the road speed sensor

optimusprime 04-03-2017 05:15 AM

Quote:

Originally Posted by Diseasel300 (Post 3697013)
The fuel system does not pressurize the fuel tank. Ideally the pressure inside the tank should be the same as the surrounding atmosphere or at a very slight vacuum to keep fumes inside the evap system.

No pressure ,or no vacumm , have it your way. But it will run poor ,and even stop , with a bad fuel cap seal.. May be i said it wrong .But if no sound from it as you lift off the filler cap ,the cap will need replcing ..

Rrrockhound 04-03-2017 09:28 AM

Quote:

Originally Posted by Stretch (Post 3697267)
Did this happen with foot off the accelerator and engine at about idle?

If so - my vote is for the road speed sensor

I was on the brakes, setting up for a turn, so yes, foot off the gas. Not sure what the engine speed was but I doubt it was fully back down to idle speed.

Diseasel300 04-03-2017 09:54 AM

Quote:

Originally Posted by optimusprime (Post 3697271)
No pressure ,or no vacumm , have it your way. But it will run poor ,and even stop , with a bad fuel cap seal.. May be i said it wrong .But if no sound from it as you lift off the filler cap ,the cap will need replcing ..

Again, no. The only reason the cap is sealed in the first place is for emissions (preventing vapor from escaping) and to minimize moisture ingress due to temperature fluctuations.

The tank has a vent to prevent building pressure and has a valve to prevent vacuum. You can remove the cap and drive around all day and have no impact on how the car runs or drives. On a newer car, you can set a check engine light if the purge valve checks for vacuum at the cap (most cars run very slight vacuum to prevent fumes escaping), but this has absolutely no effect on how the engine runs.

All fuel pressure is created by the fuel pump. It doesn't push air in the tank to do this. Not sure where you're getting your information, but I'd check the reliability of your source.

Diseasel300 04-03-2017 10:01 AM

Quote:

Originally Posted by Rrrockhound (Post 3697280)
I was on the brakes, setting up for a turn, so yes, foot off the gas. Not sure what the engine speed was but I doubt it was fully back down to idle speed.

I know you posted above that you replaced the distributor cap and rotor, but have you pulled them off to check their condition since this problem has been going on?

Additionally, is the OVP you installed used, or is it brand new? If it's a used one, I'd suggest replacing it with a new one. When they get flaky, they can be maddeningly difficult to troubleshoot.

If you're handy with a soldering iron, it may be well worth your time to take the cover off the MAS relay and look for broken solder joints on the pins of the circuit card and the pins of the relays.

Rrrockhound 04-03-2017 04:57 PM

Quote:

Originally Posted by Diseasel300 (Post 3697286)
I know you posted above that you replaced the distributor cap and rotor, but have you pulled them off to check their condition since this problem has been going on?

Additionally, is the OVP you installed used, or is it brand new? If it's a used one, I'd suggest replacing it with a new one. When they get flaky, they can be maddeningly difficult to troubleshoot.

If you're handy with a soldering iron, it may be well worth your time to take the cover off the MAS relay and look for broken solder joints on the pins of the circuit card and the pins of the relays.

The OVP was new. I haven't checked the cap and rotor but I will. I'll probably also order a MAS relay too.

Denkpat 04-16-2017 02:56 PM

how to remove the MAS CONTROL RELAY mercedes w124 ?? It looks simple but I am unable to get it pulled.


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