What is the part shown circled in the pic called? Has anyone ever seen one cause fuel delivery issues. Whenever I start car it looks like air gets sucked into the hose coming off of it very briefly (towards the screen). I replaced the o-ring located on the other side of it and the hose has been replaced. I will pull it off and inspect it again if need be but was wondering has anyone ever seen one of these allow air into the system without an external leak?

What seems to be happening is that over the course of about 5 or 6 days I get a fuel starvation no start condition. I'm thinking that everytime I crank it I'm pulling a little more air into the system until I accumulate enough that it does not start. Disregard the big black return hose. That was my testing rig.

I've been struggling with this one.

Attached Thumbnails

 

__________________
Jim

That is the fuel preheater. It sits in the head and warms the fuel. If you pull it out there are aluminum fins that sit in the water passage in the head.

The black rubber hose on the right (towards the rear) is the supply line from the tank.

The clear plug-in hose goes into the pre-filter chamber on the side of the fuel filter tower.

I am having a weird air incursion issue on my 98. I too see air bubbles in the line sometimes. I am off to the store in a little while to pick up a T30 Torx driver bit to remove the fuel shutoff valve (the black cylinder with 3 hoses and an electrical plug) on the IP and renew the o-ring behind it that delivers fuel into the IP after the main (canister) filter. I've already replaced all 6 clear fuel hoses, and the prefilter and o-ring, but can't seem to find where the air is coming from.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

If you find that the source of your air intrusion is the fuel heater or shutoff valve, I'm selling both items plus a few more pieces from a '99 606 with only 74k (see post #5).

I can't remember a fuel thermo ever failing?

It is normal for the short fuel line to the pre-filter to drain back toward the thermo at shutdown. Usually, when the engine cranks that line refills with fuel instantly.

If you have air present in that line when cranking, the leak MUST be down stream from there.

These cars are getting older, I'd check for rotten rubber/bad clamps from the thermo back to the tank.

__________________
Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

I'm more inclined to think that the plastic junction starts to leak, rather than the fuel heater innards. These flexible junctions aren't exactly an example of a stellar design that stands the test of time. I opted to fabricate a block-off plate in order to bypass this item

This is a cold start this morning at 50dF. It still seems that it is "cranking hard" to me. Car is showing 287k miles and is on original timing chain.

start up of 99 E300

Well, watching another youtube video I did not think about the o-ring at the shut off valve. I'll have to check that one out next.

__________________
Jim

FYI- If the shut off valve o-ring is bad you will most likely have a fuel leaking to the floor. I have had to replace the o-ring twice on my shut off valve and each time there was a huge pool of fuel on the floor as a result of its failure.

__________________
Ed
-1984 Mercedes 190D 2.2 5-speed gray market(bought@30,000 miles) (Sold back to original owner@170,000 miles)
-1999 Mercedes E300DT (245,000 miles)
-1999 Mercedes S500 Grand Edition (80,000 miles)

I finally got around to changing that o-ring on the back side of the fuel shutoff valve. It was a lot easier than I thought it was going to be. Removing the washer fluid tank gave plenty of room to get my hands in there.

I got the lines purged after 2 quick cranks, and took the car out for a run. It still seemed to be chugging at 1200 or so rpm. Parked it on my sloping driveway and got out the flashlight. Sure enough there were still bubbles in the line from the outlet of the prefilter to the shutoff valve. I had a spare prefilter and o-ring so I decided to try to change them.

I discovered that the bore where the pre-filter o-ring sat was dirty. So I got some brake spray on a cloth and carefully cleaned the area. I installed the replacement filter and o-ring and went to try to restart the car.

Since the car was parked nose up the fuel drained way back to the tank. It took what seemed like forever to get the lines purged. I had to end up letting the car roll back out of my driveway, and turn it so that it was pointing nose-down on the hill on the street in front of my house, before finally getting it to start. I really miss the hand purge pump from the 61x motors!

Moral of the story, never open the fuel system on your OM60x if the car is not parked on flat ground.

Anyway, after all that, the chugging at 1200 rpm is almost totally gone and the car seems to be idling smoother than before.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech