Air in the fuel system, car sluggish then died. - PeachParts Mercedes-Benz Forum

asnowsquall · #1 12-09-2008, 02:39 PM

So wicked cold the other day. Car started good as I had it plugged in. On the drive to work more and more throttle, slower and slower, find myself trying the make the car go by pushing in my seat which does nothing

. So pull over and let it idel then its OK. After work on the way back it died. Couldn't get it to keep running and then gave up. Went back today and pulled the secondary filter and it had air in it. The diesel was down about atleast a half an inch or more. Filled wit Kero as my primer pump does nothing and I was able to get it running. Changed the primer pump with another used one which pumps atleast but does leak like heck when you pump it. Still not running the way it should. When I pulled in to park it and it was stumbbling I unscrewed the primer and tried to assist the pump and the idle jumped up like something was happen for the better. Wonder if my lift pump is bad? Seems liek air is getting in somehow. I will change the secondary filter just to know that its new. The primary is new and still looks clear. Engine has 307+K on it, was/is old style primer. Getting cold out to Friggin around with this stuff.

rrgrassi · #2 12-09-2008, 02:44 PM

A bad primer pumps can let in enough air so that the car will not run. Lift pumps do eventually go out as well. Also, when was the last time you looked at the rubber lines at the tank, and checked the plastic fuel expansion tank?

Have you tried the fuel supply and return in the coke bottle trick yet? IF the engine runs with no air leaking, then you know the leak is further down the line.

oldsinner111 · #3 12-09-2008, 03:11 PM

Sounds like nasty tank screen.If primary filter is clean switch cigar line with it.Use the cigar or return line for fuel.See if that helps.

asnowsquall · #4 12-09-2008, 03:30 PM

Filter in the tank is clean, checked it last summer. Haven't checked the overflow tank.

Would be nice to have a pressure gauge, and lines you can see through. When the fuel lines were new could you see through them?

I've got another used lift pump on a engine, but I'll do more toubleshooting before that swap. Do you loose a lot of engine oil when pulling the lift pump?

Dave

Biodiesel300TD · #5 12-09-2008, 03:38 PM

Quote:

Originally Posted by asnowsquall

I've got another used lift pump on a engine, but I'll do more toubleshooting before that swap. Do you loose a lot of engine oil when pulling the lift pump?

Dave

YES! I have a big oil stain in my driveway because my catch pan was doing it's job in the wrong spot. Which means I dumps about a cup or two of oil on the driveway, before I noticed my catch pan was in the wrong spot.

Lift pumps are pretty robust on these cars. I would suspect that your primer pumps are letting air in.

You say you cleaned the tank screen, you could rule it out just to be safe by switching the supply and return lines in the engine bay to see if it solves the problem. If not then you know it's not the tank screen.

Chad300tdt · #6 12-09-2008, 03:43 PM

Hey Dave,

When I had a similar problem it was rotted fuel lines above the subframe. I ended up cutting out the section of hard line and replacing it with rubber fuel line from the tank to about under the driver seat and used the old hard lines as a bracket system to zip tie the rubber lines to. The leaks started out small enough that they just let air in and caused a nuisance. Then they got a bit larger over a few days and I saw a few drips on the garage floor. Once replaced, all the problems were gone.

Also, my expansion tank was cracked and all 3 nipples were broken off and it didn't cause any performance problems. It just caused diesel to overflow through my spare tire well when the fuel expanded due to having my space heater on high in the garage while working on the wagon last winter.

A new plastic tank is $120 from the dealer, but I'd look for an early w123 metal tank if you need one and can find one.

barry123400 · #7 12-09-2008, 04:06 PM

Any chance you are loaded up with summer fuel? You did say when you filled the remaining space in the fuel filter with kerosene it started right up. As you well know kero is one of the thinners for diesel fuel.

daw_two · #8 12-09-2008, 04:11 PM

And I know just the person who has one.

Not to hijack this thread, but if anyone needs one, please PM me.

Oh, and I think that air is getting sucked into your fuel system. Was the secondary filter tight? You mentioned how cold it was.....I'm just thinking about how metal (along with most things) shrink when it gets cold.

asnowsquall · #9 12-20-2008, 07:06 AM

OK, so very cold yesterday and snowy, trying to go and get my air compressor tank which is part of my Christmas present. Cars running crappy and I'm having to ditch it into snowbanks as its stopping on me. So I'm thinking to myself this is a heck of a way to get killed. Me on the side of the road, even though I'm in front of the car and kneeling on the bumper incase I get hit maybe I'll have half a chance. I mean I'm off the road but who knows. So a big revelation, got to fix the car. Clean up the garage enough to get it in, let it defrost a little. Go out to check on it at 9:30pm in my jammies and winter coat. Decide, what the heck, change the lift pump, took about 30 minutes. After changing it, the primer pump it full of fuel quickly, unlike before. Stuck the carback outside where its friggin cold out and plugged it in. Started this morning nice, and runs good. Haven't driven it yet but I think I got it. It looks to me like the short piece of fuel hose on the old pump was dry rotted as when you trist it you can see these lines. At some point I'll pull it off and put some air to it and see if I get any air bubbles on the outside indicating leaks. This will proove if it was the lift pump or not.
Now I just need to repair the drivers window so it works in the channel properly, the 2" gape at the top is letting snow in.

Stay warm and happy holidays.
Dave

asnowsquall · #10 12-20-2008, 06:09 PM

Well that didn't do it. So...I took a 3 qt container and stuck clear lines in for a supply and return and ran the car like this. It was about 4 degrees out and it ran fine with no air. Still not going to wave the victory flag. Going to pull the lines at the tank and see how the diesel runs out of the tank. May need to run a new line. Maybe just tye rap some rubber hose on for now. We will see.

asnowsquall · #11 12-20-2008, 08:58 PM

So under the car I go to disconnect the fuel line. Diesel comes out of the tank like I would have expected. I had the line disconnected under the hood and IMO the diesel didn't come out of the line that fast when I disconnected it from the fuel tank. Hooked up the compressor at the tank end, and took the line under the hood and put it in a bottle. I'm not 100% sure that the bottle was totally dry to begin with but the diesel had water in it. Now I could see where water in the fuel lines could freeze and restrict flow. Time will tell. Started it and drove it around fine, but it had warmed up in my garage. Its like 1 degree out right now, so tomorrow morning will be the test. Going to order new filters and the primer pump piece, also going to get new fuel lines as it need them.

el sea · #12 12-20-2008, 09:26 PM

Have you found any water in your fuel? Are you buying bio-diesel? We are seeing more and more issues - oh we clean fuel tanks and this seems to be the leading cause to most fuel issues.

Luther

asnowsquall · #13 12-21-2008, 06:16 PM

No Biodiesel.

So it looks like that was it! I left the car out overnight in the single digits and it runs great. Drove about 6 miles in the single digits and not one hickup. Popped the hood and no air in the lines. Time will tell but this is looking good. The only other variable is that I threw on another used prefilter that I had. The one that was on the car wasn't that old but it didn't flow diesel through it as fast as the other used one I had. So I'll get two new filters.
Finger crossed that this is it, its too cold to be messing around with this outside.

Dave