om606 no start, vacuum in fuel lines? - Page 2 - PeachParts Mercedes-Benz Forum

pmari · #16 10-30-2008, 06:31 PM

That's a better way Terry.
There should have been some fuel in that line

Looking at the schematic below...There seems to be no tank screen. But... A2104700306 is the part number for the fuel strainer. There IS a fuel strainer according to the EPC. I don't know how to lift the picture from the EPC

Like most others it's at the bottom of the tank.

http://www.peachparts.com/shopforum/attachments/diesel-discussion/38226d1163965668-om606-fuel-flow-schematic-fuel-lines.png

Shamelessly lifted from another site..... http://bp3.blogger.com/_p71v9ofBM6w/R5ZR4hrNUFI/AAAAAAAAAIQ/XCBQ40qtPDQ/s1600-h/fuelflow.JPG
First the fuel goes from the fuel tank to the fuel heater. (funny looking thing in the top right corner)
(1) From the fuel heater to the prefilter screen
(2) Prefilter to shut-off valve
(3) Shut-off valve to lift pump
(4) Lift pump to fuel filter
(5) Fuel filter to shut-off valve (again)
The shut-off valve feeds the injection pump through a port in behind. The injection pump sends fuel to the injectors, but also has a return line where excess fuel exits
(6) Excess fuel goes out the return line, where it meets the fuel flowing back from the injectors
(7). This connection is made at a port on the fuel filter housing, where a percentage is drawn back into the filter, and the rest is sent back to the tank (8).

Not shown above... fuel first goes through the tank filter/strainer to the feed line, that goes to the fuel heater.

OM606 Fuel Flow Schematic...

TMAllison · #17 10-31-2008, 01:05 AM

That blogs a good numbered description of the fuel path. Cant tell you how many times i've typed that out.

Will add that one to my collection.

NY300SD · #18 10-31-2008, 10:27 PM

I've been out of town for a couple days. I tried the car again when I got back this evening and it started right up. Ran rough for a couple minutes then everything was back to normal. Took it on the highway and it ran great.

I'm very relieved and very confused. I know it will happen again if I don't figure it out.

Thanks for the links and advice. Looks like I need a Mityvac for next time this happens.

NY300SD · #19 11-03-2008, 12:59 PM

OK, big @#$^ing clue here.

Fuel lines are filled with massive bubbles until it's just air and it quits. Good thing the viton o-rings arrived the other day.

I suspect that the thicker, cold fuel exacerbates the problem and creates the no run situation, while warmer temps flow better and don't suck in as much air, hiding the problem. It has always happened after a night in the 30s, but disappeared on warmer, sunny afternoons. I can see that the fuel isn't gelling, it's moving pretty fast in the clear lines.

I have viton injector return lines as well, the one I can see is really weeping. Also clean the crossover pipes, I'm sure they're plugged up. I have some b99 on hand for that.

The car is in a very nose down situation, I hope I don't get a driveway full of B80! Can't exactly move it right now.

I have a few links saved with information regarding the o-ring replacement, but if anyone has any advice for someone doing this for the first time, please speak up!

Thanks

TMAllison · #20 11-03-2008, 02:48 PM

Do the pre-filter oring first; its about th only one that can leak enough to kill a running engine.

NY300SD · #21 11-03-2008, 03:26 PM

Quote:

Originally Posted by TMAllison

Do the pre-filter oring first; its about th only one that can leak enough to kill a running engine.

Interesting. I changed it twice since I've owned it. Maybe I didn't get it on right. Come to think of it, I had a hard time getting it back in there, seemed too big. Anyway, I have the viton replacement and I'll be sure to use it.

Also, last time I had the engine running I noticed some major bubbling on the outside of the braided injector return line near the filter. Seemed to be happening in surges once in a while, maybe that's why I didn't notice it before? I knew it was leaking and making a mess. I wouldn't be sucking a bunch of air in there would I?

I have the crossover and the plastic cover off. Next up, the rest of the intake pipes.

TMAllison · #22 11-03-2008, 03:47 PM

The braided return line shouldn't be the issue, it is the tail end of the fuel path and ught to send fuel back to the tank.

The kill switch/bolt on top of your fuel filter has 2(?) orings on its shaft. Sometimes folks tighten it down too much and pinch one of those.

Check the prefilter, crimp the hold down washer to get more downwrd force on the prefilter and/or use a bit of silicone grease to help seal it.

NY300SD · #23 11-12-2008, 10:19 AM

Update:

Ok, ready for the verdict? Gelled biodiesel. Yep.

Despite the fact I that I had a winter of biodiesel experience without a single mishap. And despite the fact that the tank was so full that I could see the fuel, and it was NOT gelled, and that I had a couple gallons of petro-diesel mixed in.

Last year I was using homemade stuff with an '82 SD. This time I have been getting B99 at the pump. Seems to have a much higher gel point!

My guess is that it locked up in the lines between the tank and engine compartment, and took the better part of a warm day to thaw out. Hence the car eventually starting and running like nothing ever happened.

It has B50 in it right now and I had no problem keeping it running this morning. Temperature got down to 30F last night.

Thanks for all the repys, you guys nailed the problem right away.