stalling at idle - PeachParts Mercedes-Benz Forum

adamkat22 · #1 01-09-2016, 08:01 PM

i have an 82 300 TD that recently has been almost stalling when i come to a stop. once it starts coughing a little bit i can put it in park and rev it till the light turns green and keep it from stalling. happened for the first time about a month ago. then has been fine until the last few days...and it seems to be happening fairly often now.

this evening i checked my fuel hoses and the hose that comes out of the prefilter had a little slit in it...although it may have been on the far side of the hose clamp (i.e. i'm not sure air was getting in from it). i replaced it, but when i idle the car i can see that even when i fill the pre-filter with the priming pump the filter goes almost empty once the car is idling. i guess i have never looked at the pre-filter when the car is running before, but i assume it normally stays full right?

i did a visual inspection of all other rubber fuel lines and none seem wet anywhere. i also cracked the gas cap to rule out a clogged vent. the in-tank filter is clean and clear.

is there anything else i can do to troubleshoot this evening without having new fuel lines to put on (autoparts stores are closed for the evening)? i am supposed to leave for a long trip tomorrow (in this car) so anything i could do this evening to help troubleshoot would be helpful.

could this be a sign of an IP that is about to die?!

mannys9130 · #2 01-09-2016, 08:10 PM

I doubt the IP is dying.

Sounds like you have air leaks.

Diesel911 · #3 01-09-2016, 10:06 PM

Air leaks to include the hand primer if it is the original one with the shiny aluminum body.

Overflow/Fuel Pressure Relief Valve spring needs to be stretched to a 27mm free length if you have a valve that can be taken apart and or the Fuel Supply/Lift Pump needs rebuilding.

mannys9130 · #4 01-09-2016, 11:36 PM

You need to go from the tank to the IP and check/replace any hoses that are old. You need to check the "clear" (now brown with age) lines that go from the injection pump to the filter mount and make sure they are not cracked at the barb. You need to make sure you have the new style primer, and you need to make sure your filter going empty doesn't change between full and 1/4 tank of fuel. If you can't find any air leaks or other issues, try swapping your supply and return lines with a full tank of fuel and see if the filter stays full. If it does, your tank strainer is clogged.

The prefilter should be mostly full with only a bubble of air at the top. No matter how you try you won't be able to get it 100% full, so don't worry. Nearly empty is bad, but nearly full is normal.

whunter · #5 01-10-2016, 12:17 AM

Quote:

Originally Posted by adamkat22

i have an 82 300 TD that recently has been almost stalling when i come to a stop. once it starts coughing a little bit i can put it in park and rev it till the light turns green and keep it from stalling. happened for the first time about a month ago. then has been fine until the last few days...and it seems to be happening fairly often now.

this evening i checked my fuel hoses and the hose that comes out of the prefilter had a little slit in it...although it may have been on the far side of the hose clamp (i.e. i'm not sure air was getting in from it). i replaced it, but when i idle the car i can see that even when i fill the pre-filter with the priming pump the filter goes almost empty once the car is idling. i guess i have never looked at the pre-filter when the car is running before, but i assume it normally stays full right?

i did a visual inspection of all other rubber fuel lines and none seem wet anywhere. i also cracked the gas cap to rule out a clogged vent. the in-tank filter is clean and clear.

is there anything else i can do to troubleshoot this evening without having new fuel lines to put on (autoparts stores are closed for the evening)? i am supposed to leave for a long trip tomorrow (in this car) so anything i could do this evening to help troubleshoot would be helpful.

could this be a sign of an IP that is about to die?!

#1. This diagnostic needs to start with the fuel tank vent = are you building vacuum in the fuel tank??

What is this valve and why is it dripping diesel?
What is this valve and why is it dripping diesel?

Fuel tank vent pictures + location
93 300D 2.5L Turbodiesel Power Loss

What happens when a tank vent gets clogged.
What happens when a tank vent gets clogged. - PeachParts Mercedes ShopForum

Imploded fuel tank - so sad!
Imploded fuel tank - so sad!

Why do I have vacuum in my diesel tank.....................?
Why do I have vacuum in my diesel tank.....................? - PeachParts Mercedes ShopForum

#2. Then you inspect or verify fuel filter / strainer flow.
http://www.peachparts.com/shopforum/diy-links-parts-category/142399-fuel-delivery.html

#3. Then you need to check the lift pump supply volume / pressure.
I often find the lift pump valves are shot = an easy + cheap repair.
0000900210 OM615, 616, 617 Lift pump valve kit

Then you can consider other issues.

.

adamkat22 · #6 01-10-2016, 08:03 AM

I have a new style hand pump. The first
Time I stalked it was the culprit...I could see fuel dripping from it but I got a wrench on it and a quarter turn later that stopped.

Have tried driving with gas cap off to rule out the vent and have checked the strainer.

Last night I found what I assume are fuel lines I wasn't aware of...in the spare tire well (it's a 300td). Those were braided lines and seemed damp. I assume those are fuel lines (even though there are 3 of them ). I'll replace those and see what happens

vstech · #7 01-10-2016, 09:24 AM

Yes, those are fuel lines, you need to get all of them leak free. It's also possible the tank has failed causing the wetness! Take it out, and inspect it well for cracks.

funola · #8 01-10-2016, 10:17 AM

No one has mentioned pin holes due to rust on the under the car fuel lines. They usually develop under the fuel line clamps. If you undo the clamps and it's moist with fuel, it is letting in air. You can cut a short piece of fuel hose, split it and hose clamp it tight to stop the leak and go on your trip till you are ready to do a more permanent repair.

adamkat22 · #9 01-10-2016, 10:36 AM

I won't rule out leaks in the metal lines by this car is fairly rust free so I'll attack the rubber and braided lines first. I just discovered more moist braided line in the trunk area (where the lines to the tank transition to hard lines I assume). There is no way to swap these without dropping the tank huh?

Diesel911 · #10 01-10-2016, 11:00 AM

I have never seen the arangement Fuel Lines on a Wagon but there could be one Vent Line, Tank Oulet line and one Return Fuel Line.

adamkat22 · #11 01-10-2016, 12:09 PM

Well I bought some 5/16 hose and decided to do the easy lines first (the ones in the spare wheel well). When I took that expansion tank out it had a big crack in it, and the nipple for the middle of the three hoses also had a crack. I don't fully understand how the expansion tank works...and if a crack in it would lead to my air leak problems, but I put some epoxy on it and am going to put it back in while I order another one and see if that hopefully fixed it

adamkat22 · #12 01-10-2016, 04:58 PM

Funola you win. There was a leak in one of the metal supply lines. I couldn't even see it because it's where the line is hidden by some other stuff, but at some point we were blowing a compressor through the lines to rule out a restriction (which there also seems to be due to years of alternative fuel use in its past) and I could see diesel dripping off the line. Cut it and bypassed with rubber hose....now gonna drive it 2000 miles south an escape this winter. Thanks everyone

funola · #13 01-10-2016, 07:18 PM

Nice! Have a safe trip don't get stranded!