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 12-09-2008, 04:56 PM

Quote:

Originally Posted by daw_two

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.

Its tight, but I don't knwo if its sealing well. This is where clear lines would help as I could see where the bubbles are.
One thing I noticed this past summer is that when I pulled the fuel line before the primary filter the fuel ddidn't just keep flowing out like it does on my 240D. This car is from Tenn which doesn't rule out rusty lines but it really clean under the car. I'd imagine if the lift pump is having a hard time sucking on the tank that air may come in. I'll figure it out. One other thing I was thinking I could do besides swapping lines is using a clear container with both supply and return lines in it and just drive around liek that to see if it changes it.

TchTchr · #10 12-09-2008, 05:09 PM

Fuel expansion tank???????

Chad300tdt · #11 12-09-2008, 05:27 PM

Quote:

Originally Posted by TchTchr

Fuel expansion tank???????

If your question marks indicate you don't know where it is, look in your spare tire well, toward the front of the well behind the panel that covers the c pillar.

I guess someone bypassed it if you don't have one.

pizzachef · #12 12-09-2008, 05:44 PM

Quote:

Originally Posted by TchTchr

Fuel expansion tank???????

The earlier wagons had metal tanks. If yours in an '81, it is probably metal and you shouldn't have anything to worry about...unless someone sold it in the past to make a quick buck.

In the later wagons they were plastic and mine also had three broken nipples. JB welds did not work. I read that Chad unsuccessfully tried JB weld but I had to try myself. I've since learned that if Chad can't get JB weld to work for an application, no one can