617 stalls at idle - PeachParts Mercedes-Benz Forum

LUVMBDiesels · #1 12-24-2007, 12:01 PM

I had left Bruno the Dieselshlepper up in NY when I took the Suburban down to WV. The wife was driving him to the train station when he stalled out on the Mid-Hudson Bridge! She cranked him over and he started right up so she kept going. On the way home he gave no trouble. That was two weeks ago. Now that I am home, I have been taking a look at him. I changed both fuel filters thinking that could be causing the problem. I did see some debris in the pre-filter but the fuel in the main filter looked clean. I filled the new main filter with Diesel Purge and he started right up. I took him around the block and he stalled out! He started back up but is not running with his usual power. I can rev it up to 4500 in the driveway and the boost gauge comes up to about 3psi. I don't remember it ever moving with no load before. Sometimes with my foot on the accelerator it will just slow down and stop! Oil pressure is good at 3+bar. He will only run for a couple minutes before just stopping. It doesn't seem like he is starving for fuel, he just stops --no surging or coughing.

Could it be a blocked exhaust? bad fuel? (I had just filled him up before turning him over to the wife...) or do you think it is something really bad?
He has never given this kind of trouble before!

Thanks guys!

and Merry Christmas!!

turbobenz · #2 12-24-2007, 02:56 PM

Maybe you have a vacuum problem, and its shutting off the engine. Also make sure your breather hose to the top of the air filter isnt clogged up, beucase if it is your crankcase pressure will increase on load and stall the engine.

LUVMBDiesels · #3 12-24-2007, 03:00 PM

Quote:

Originally Posted by turbobenz

Maybe you have a vacuum problem, and its shutting off the engine. Also make sure your breather hose to the top of the air filter isnt clogged up, beucase if it is your crankcase pressure will increase on load and stall the engine.

The vacuum system is working correctly I believe. The door locks work and the transmission shifts smoothly. I will check it and the breather.

Thanks for the tips!

junqueyardjim · #4 12-24-2007, 04:05 PM

Because of the sex change. You know all those Benz's start life out as females.

superbeast1098 · #5 12-24-2007, 05:40 PM

Could it be the tank strainer picking up some stuff in the tank and getting plugged???

toomany MBZ · #6 12-24-2007, 05:54 PM

Quote:

Originally Posted by superbeast1098

Could it be the tank strainer picking up some stuff in the tank and getting plugged???

This gets my vote. However, after stalling, open the fuel cap, do you hear any air sucking sound? The tank is vented, and I've heard of a similar problem.

MTUpower · #7 12-24-2007, 06:51 PM

The 616/617 need two thing to keep running: air and fuel. Start with that in mind and work backwards. If your turbo has issues then it may cause the engine to stall. Take a in depth glance at all the stuff near and around the turbo. Check for fluid and air leaks. Check the air intake system. Check everything you can think of related to air intake. If the turbo suddenly is oil starved you may have a air intake issue. Next is fuel. If you have a large piece of algae or something else which could plug the fuel pick up, you'll stall. Since the fuel system is mostly one way (from the fuel tank to the engine) you may suck up a item that blocks fuel. When the engine stalls the piece no longer has sucking holding it and it falls back into the fuel. It randomly floats around in the fuel tank then it's sucked up again. Check the fuel delivery system for things out of the ordinary. While it may be something strange, the usual procedure is to rule out all the simple things first to get a baseline. When it stalls out next time, remove the fuel line to the primary filter and blow on it (if you surround it with a rag the fuel will not touch your mouth). If it starts right up and acts fine afterwards you can guess that you a chunk blocking the line in the fuel cell. This is what the previous two posts are suggesting, and I agree it is the most likely cause of your problems.

Robert Squires · #8 12-25-2007, 12:16 AM

* LUVMBDiesels, a 617.95 series turbo diesel will come up on boost just sitting in the driveway, 10psi or better by 3500rpm. So I don't understand your reading of 3psi at 45oorpm.
* If a diesel stops (for lack of fuel), it's already emptied the spin-on fuel filter. It won't "start right up again". It'll probably take more cranking than the battery and/or starter have in them, particularly if it's cold out (cold battery, reduced elec output, etc.). Are you sure you don't have an oil-soaked air filter element or some such thing to block the air inlet?

LUVMBDiesels · #9 12-26-2007, 07:40 AM

Quote:

Originally Posted by Robert Squires

* LUVMBDiesels, a 617.95 series turbo diesel will come up on boost just sitting in the driveway, 10psi or better by 3500rpm. So I don't understand your reading of 3psi at 45oorpm.
* If a diesel stops (for lack of fuel), it's already emptied the spin-on fuel filter. It won't "start right up again". It'll probably take more cranking than the battery and/or starter have in them, particularly if it's cold out (cold battery, reduced elec output, etc.). Are you sure you don't have an oil-soaked air filter element or some such thing to block the air inlet?

Robert,

Your second point is why I don't think the engine is being fuel starved. It will start right up once i turn the key. It does not not crank until the filters are filled with fuel again. (I have tried doing that after changing the filters and it takes forever to fill the main filter.) I will check the air filter and associated hoses.

As to building boost in the driveway under no load, I don't remember it ever doing that, nor do the EGT's come up until the car is under load and moving. Then the boost goes right up to 13 (where I set it) by 3000 RPM, again depending on load. it will cruise at 30-3500 RPM under 5 PSI if we are on a flat piece of highway.

LUVMBDiesels · #10 12-26-2007, 07:42 AM

Quote:

Originally Posted by junqueyardjim

Because of the sex change. You know all those Benz's start life out as females.

Bruno has always been male... What else could a smelly, smoky, slow old car be?

Now the BMW, she's a girl-- high strung, fast, and high maintenance!

Same for the Suburban and Jeep

Robert Squires · #11 12-26-2007, 04:56 PM

* I think someone posted a line about a vacuum-related issue. I've never seen this but I could imagine the case where the vacuum switch on the column/ignition lock occationally decides to allow vacuum to the fuel shut-off valve without the key being in the off position. The next time it spontaneously shuts off, if you hurry (I don't think the lever will stay down indefinitely), maybe you can catch the (manual) fuel shut-off lever in the down position. This will reveal whether the rack was moved (by the shut-off valve) to the off position.
* If the rack isn't moved to the off position, it doesn't seem to me that it's a fuel-related problem. Even some bad fuel wouldn't act like what you're describing. Bad fuel would cause the engine to lumber to a stop, and then restart only with difficulty, probably not firing on all cylinders.

LUVMBDiesels · #12 12-29-2007, 10:57 AM

Steps I took this morning:

1) Flushed the fuel lines with 20psi compressed air. Got nice bubbling sound in the tank.

2) Started the engine with the fuel tank cap off to eliminate the vent as a problem. Engine still ran for 5 minutes and stopped

3) Disconnected the crankcase breather, opened the air filter and finally just took off the '710' cap. NO CHANGE in behavior. the engine starts right up runs for five minutes and stops!

4) Started it up and held my finger under the stop lever. no change in behavior!

5) Started it up and held the linkage all the way open. Engine revs and looks OK for a couple minutes and then just stops!

When it stops there is no coughing or spluttering it just slows down and then shuts off. I could hold the rack all the way open and it will slowly loose RPMs then come to a stop.

This has got me stumped. Before I have the car towed to my indy, can anybody explain what is going on. Could my IP be failing?

Thanks,

Joe

#13 12-29-2007, 11:04 AM

I don't know, the only other thing I can think of is unplugging the vacuum line from the shut-off valve to make sure it's not slowly building up vacuum and shutting down. Just a SWAG, but it's easy to try.

LUVMBDiesels · #14 12-29-2007, 11:09 AM

Quote:

Originally Posted by Craig

I don't know, the only other thing I can think of is unplugging the vacuum line from the shut-off valve to make sure it's not slowly building up vacuum and shutting down. Just a SWAG, but it's easy to try.

I was thinking about doing that, but since I can hold the linkage off the stop position and it still shuts down (from a fully open rack) would unplugging the shut off valve work? Is it independent of the linkage?

Thanks,

Joe

Mike D · #15 12-29-2007, 11:24 AM

First things first.

Disconnect the feed line from the lift/transfer pump (not the injection pump). Run a NEW length of hose into a fuel can holding a couple of gallons of FRESH diesel fuel. Bleed and start the car. If the problem goes away and it runs all the fuel from the can, start looking at the rubber pieces of the supply line.

The debris in the prefilter could be old rubber bits from the line. Changing over to the new ultra-low sulpher fuels can deteriorate the original lines and cause them to break down.

I just went through this on my gasser 280 due to the ethanol changes Arizona institutes every November.