Hi there, Im trying to solve my air issue since a few months. Seems only to be happening on Diesel and not on Veg-oil so Its narrowed down to the components that only handle diesel.

One thing however and this isn't the first time I've noticed, is that when trying to prime teh fuel lines with the hand primer pump, I feel like its not working

I can see theres air in the little primary fuel filter and when I start pumping, if I feel a resistance in the pump and hear a slight squeak, I know its pushing fuel through, and I see it moving in the primary filter.

However the primary fuel filter naturally tilts in such a way that the exit towards the IP/hand pump is higher up and will have whatever air may be in the primary pump.

IM not sure if this is the cause for the primary pump to quit working but it seems once air is in there I can never feel that resistance and pump of fuel again and it feels like nothing happening. I even tilt the primary filter to ensure that the air bubble is not the first thing to get sucked into the pump.

Ive pumped and pumped, literally hundreds of of times, and it never seems be doing anything. Is this normal? Is it that the hand primary pump needs to be primed with fuel before it can really suck anything? or can this be a sign of a leak somewhere in that area.

BTW that hand pump is only about 5 years old and is the newer spring loaded BOSH version...

Does anyone have some expertise or experience that may shed light?
Thanks

The squeak is the pressure release valve. That means the primer pump has done its job and there is nowhere else for air/fuel to go.

I am having a hard time visualizing in my mind how the outlet to the lift pump can be higher than the line-in end of it. Can you snap a photo? EDIT: my bad, I just checked pics and I guess many are... don't think mine is (shrugs).

It is normal to have an air pocket in the primary filter. The only time you should have to pump multiple times, before you hear a squeak, is when you have introduced air into the system, such as with a fuel filter change.

__________________


Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Great, I figured that much, Its more when it doesnt sqeek and I feel no resistance (most or all of the time now)


Yes indeed I failed to mention I did just do a filter change, and replaced the O-rings on the hollow filter hold-down bolt hoping thats the problem.

I cant seem to get the system bled again. Ive been turning over the engine as well trying to get it to pump, but I'm not sure how long is too long and I dont want to wear out the battery or the starter. I'm supplementing the battery with a booster when I crank.

Attached is a very basic diagram (in blue) of where the primary filter is located on my car due to the modified veg-oil system (greasecar - ignore the red circle) with the image showing where the bubble sits. (in white) this picture isnt my engine. I just took it off the web. (I wish my engine was that clean!)

Attached Thumbnails

 

Just so I understand what you are doing:

Did you fill the new spin-on filter with ATF or diesel before you put it on?

Do you (or did you) have the spin-on filter cracked a bit so you can see when it starts to overflow?

Did you have the injector lines off for any reason?

I find the Greasecar diagram/pic bizarre. In any case, have you double-checked the clamps at each end of the main filter AND where the short little length of hose that it runs to at the oulet end clamps to the lift pump assembly?

Maybe you want to check that the primer pump is screwed in completely.

All I can think of right now. My '85 is VERY stubborn about starting after fuel filter changes, I have more trouble getting air out than on any other Mercedes I owned.

__________________


Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

No... I used a little diesel that I had handy... But it wasnt enough to fill the filter... ahhh, ATf. I never thought of that or even knew it would b OK to do.

No. Do you do this while cranking? or while pumping the hand pump?

No. Havent doe that yet. But one of my glow plugs just died, so I may be tackling that job very soon, and I will be taking off the injector lines for that.

I know, Its not a great portrayal of whats happening with the fule line flow and direction. Instead of coming straight off the line from the fuel tank it actually goes to a swithover valve so it can switch between veg and diesel.
Yes... Ill need to pull it into the garage down teh road for that. Im tinkering in a sub-zero driveway now...

My big question is weather the hand pump will still pull fuel if its got air in it. And how long is reasonable in order for it to have reached a point where you hear the 'sqeek'?
Thanks

All I can think of right now. My '85 is VERY stubborn about starting after fuel filter changes, I have more trouble getting air out than on any other Mercedes I owned.[/QUOTE]

Leave it loose a bit while you are pumping with the primer pump. You should leave the filter cracked a bit so you can see when you have fuel pressure there, when it starts to dribble tighten it down.

If you don't fill up the spin-on filter prior to installation, it takes much longer to prime the system.

Do you have anyone who can assist you? I suggest you get a helper and have them pump the primer pump for all they are worth, while you crank the car over. I think you just have a stubborn air lock.

If you don't have a helper, try cracking one or two of the hard lines and see if you can get fuel to come out, while you pump. Once you see fuel, go back and try to start it again.

Do you feel resistance when you use the primer pump, as you would normally, or do you mean there is no feeling you are pumping anything now?

__________________


Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

I forgot to make a follow up. Just to say, I went outside again, with a better battery booster, filled the remaining space in the fuel filter and pumped a bunch then just turned over the engine again and after a few tried, coughing and sputtering finally I got it revving up again.

It worked. Thanks for the pointers!

We took off for a trip to town about 45 min drive and just as we were pulling in the alt. and coolant pump went caput. I was able to slowly drive away back home with a very hot engine and a weakening battery as it got darker outside.

Got hoe safe and sound, today I change the radiator and the belts, and glow plugs... Ill be busy..