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Random stalls

7K views 22 replies 11 participants last post by  93SoCal400E 
#1 · (Edited)
I'd say the last 4 out of 6 times I have been out with the R129 it will sometimes simply shut down when I get to a red light or stop but then it starts right back up. Also on occasion, it seems to want to stall and then revs kick up and it saves itself. Again this only happens while coming to a stop or actually stopped, I haven't felt any blips or stalls while driving.


  • I have no CELs
  • All coils are good and spark plugs are basically brand new as I replaced them a few months ago.
  • I don't think it's the Crank Position Sensor because temp isn't a factor and it will immediately start right back up no matter how hot or cold.
  • I didn't start happening after I changed something, it just started happening.

My thinking is that the fuel pump may be on its way out, but any suggestions you may have I will look into if within my realm of possibilities. The problem is I can't replicate the problem as it is random, it can be hot or cold out and same with the driving time, it can happen within the first few minutes or after a few hours. Also it has been a one time occurance per trip, but I think it has happened twice on one occasion iirc.

If you guys agree with my line of thinking, I would most likely go for the Bosch Pump ($155) or the Hella pump ($158) from Rockauto or one from Autohausaz for $165.51 but it only lists it as OEM and mentions Pierburg which I'm not sure if that is a brand.

Any help much appreciated.
 
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#4 ·
If you guys agree with my line of thinking, I would most likely go for the Bosch Pump ($155) or the Hella pump ($158) from Rockauto or one from Autohausaz for $165.51 but it only lists it as OEM and mentions Pierburg which I'm not sure if that is a brand.

Any help much appreciated.
Has the OVP relay been replaced? I think this could be a cause of the symptoms you describe.

RayH
 
#5 · (Edited)
Pete, I had this problem awhile back. Thing would actually stall on the freeway. My friend Ernie who has a shop said it is usually one of 3 things:

1. CPS

2. Fuel Pump Relay

3. Fuel Pump.

I replaced 1 and 2 and that didn't help - but didn't mind as I really didn't want the engine dependent on a 20 year old crankshaft positioning sensor. And a new relay was just piece of mind.

It was the fuel pump.

You don't need a 20 year old fuel pump, either.

Now here's the thing for our cars, we of the HTT club ... I like OE and even the dealer for some reason doesn't sell the OE Pierburg fuel pump. But I did find a vendor on ebay who sells them - new.
 

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#6 ·
#7 · (Edited)
Gotta run some errands Pete but I will look into my ebay history. What i liked about this brand (besides the first one lastinkg 20 years) is that no fitting changes were required.

I also changed the small gas hoses - I can send you a section of you want - should still have some

Bill (will update later)

Can't find the record of my purchase but just do a search on ebay for Pierburg fuel pump - 2 vendors came up
 
#9 ·
El Gordo

The M112 is notorious for using up crankshaft positioning sensor's

if it hasn't been replaced on your car and it has 100,000 miles or more that's certainly the first thing I would look at. I would replace it on general principles. They're fairly inexpensive and they will ground you if they don't work
 
#22 ·
C.P.S.



I replaced the CPS about seven weeks ago with a Duralast sensor. I have since been educated in the perils of non-OEM parts.

I did't have the the stalling issue until the CPS replacement. It started with RPM drop and recovery at lights/stop signs. Now it stalls at idle while in gear periodically. It also is difficult to start after sitting longer than 24 hrs. That is when it throws a CPS code. CEL clears itself following morning.

I bought a fuel pressure gauge and was surprised by the pressure. 30 psi stored pressure an hour after shutting off the engine, 56-58 psi at idle.

I have a Launch CREADER Touch Pro that shows no other codes stored or current in regards to engine or transmission. HVAC system has achieved nightmare status though. That however, is a different thread.

Mike
 
#13 ·
Boy do I hate that stalling Benz thing! I had a 90 300SE that did that, I replaced almost everything in fuel system and ignition system, ran way better but still stalled intermittently , especially when coming up to a stop sign, turned out to be a non leaking EHA valve, I read somewhere it controls part of idle circuit , good luck man.
 
#17 · (Edited)
:devil:devil:devil:devil:devil:devil

Too late for April Fools but you can always have wishful thinking. :grin

Getting back on topic, I just finished ordering a Pierburg pump from an ebay seller in Canada. With the exchange rate came out to a hair under $116 US Dollars. Expected delivery is July 13th. Will update with results, hopefully this solves the issue.
 
#18 ·
I agree with wlp50.

100K Replace, relay, pump, crank sensor.

But I don't like replacing good old parts with new.

My advice would have been, to test the whole system.

The fastest way is, with a dc amp clamp meter, test voltage drop, to old fuel pump, fuel relay amp, less then 8amp I think is OK.

Now that you got a new pump....

Good price. :)

If stranded,
Here are some Albert's unorthodox ways. ;)

Tapping with a broom stick or anything...

To wake up pump, fuel filter, sometimes it worked... hand tapping the relay is also a good idea.

It was 2am. got us home..

I was her hero.

Till,

The next argument. Haha.

Regards,
aam.
 
#19 ·
Sorry for the off topic brother Pete.....

I miss you brother Albert.......

Glad to see you back in action with all the great advises & jokes....

Best Regards,
Tony:)
 
#20 ·
No problem Tony, my threads all seem to get a little off topic along the way. :wink

I also enjoy Aam's very unique posts. Aam the car never fully died as it always starts back up. I haven't had any luck with tapping dead fuel pump but I have had luck tapping starters. Hopefully this fixes the issue. We will see.
 
#21 ·
Brother Pete.

I would put my money on the fuel pump relay.

See, the points are worn/voltage drop/ less than 11 volts.

Pump shuts down, metal Viagra from the heated pitted relay points transfers to the worn sides. More than 11 volt.

Pump, she is alive. You happy.

To many of these will destroy the relay and pump.

Does this makes sense?

I asked Albert. it made sense.

But,

He never heart of metal Viagra.

Oh,
Well.


Brother Tony.

We go back a long way, many years. :)

I thank you for your kind words,

My best to you and family.

I will try to come more often.

Regards,
aam.
 
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