I'm noticing air in the little transparent fuel filter that is just before the injector pump. How much. if any, is ok?

Sometimes it seems to get more air then it fills again. Im trying to find the source of the leak as Im not getting very far, but will get little jolts of power here and there, but it seems if Im climbing a hill she starts to stall again.

Im guessing its because of the angle of the little fuel filter where the air is getting into the line direct into the pump.

Any Ideas on where to look?

An air bubble in the in-line filter is entirely normal.

Loss of power from fuel delivery could be bad fuel lines (the two going to and from that filter, specifically), clogged filters, clogged tank strainer, IP problem of some sort, injector problems...

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1992 300D 2.5T 249k - Parked with a bad transmission
1981 300SD 142k - Daily driver

If the filters aren't fairly recent, they could be changed.

In the current weather, you may have some fuel freezing issues if there is moisture in the diesel. Before you change the filters, I suggest you add some diesel fuel supplement.

If you have not added anything like this, prior to winter, head to Cdn Tire and get some some Power Service Diesel Fuel supplement. This will eliminate any water in the fuel.

Also not a bad idea to pick up some Diesel911, same container but red, and keep it in the trunk. This will liquefy frozen diesel in about half an hour, in an emergency (but only use it in emergency, as it contains alcohol).

Check that all the hose clamps on your fuel hoses are tight, and don't forget the very short hose between the clear filter and the lift pump housing. I had a fuel freezup last January and it turned out that was loose enough to let in air.

If you have a serious air leak, the car may 'grunt' or 'puff' at idle.

__________________


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

Hmmm, Is it normal for the in-line filter to almost completely fill with air, then fill up again depending on demand?

BTW this is a 85 300TD.

I also noticed air in the transparent fuel line that leaves out of the spin-on fuel filter. Could this be a result of the air getting in the main incoming line through the in-line filter?


Im trying to track the flow of fuel in this area, but I dont quite understand the way it goes around the fuel filter and injector.

>fuel delivered from the tank through main line, through the in-line fuel filter, then through the lift pump (upgraded to newer BOSCH spring loaded pump) and into the injector somewhere?

Heres where my understanding lacks. Does anyone have a detailed indication as to how the fuel flows from the injector and through the filter(s)?

Thanks

No. It is not normal.

fuel travels: tank-prefilter-lift pump-main filter-IP-injectors....surplus back to tank

from your description it seems that you have air in fuel issues
inspect hoses and if possible tank strainer.
mind the weather...if cold,you might have a wrong fuel also....


.

__________________
w126 500SEC gen II euro, powered by OM617 turbo stolen from 84 300SD 2.88 diff,EGR blinded
next wish/project: w114 coupe OM603 powered

Thanks.

What is the function then of 3 lines coming in/out of the main filter? Obviously on in and one out, but then theres 3 more... which way do they flow and to where?

Thanks

P.S. Also, what is the i.d. size of the fuel line to and from the ip/lift pump and in-line filter?

5/16

the 3-way banjo on fuel filter housing mixes fuel return of sec filter and injectors via cigar hose to the tank.

you can find and fix air bubbles by trial and error replacing parts one at a time, or do it the easier way with a mityvac.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I was just looking online and parts stores are saying 7mm? for the same?

Is the 1mm difference (5/16 being slightly larger) going to be less of a tight fit?

it's 8mm/5/16" 7mm may be for the clear lines... not sure, I've always replaced them with OE dealer hose...

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

the lines on top of the filter are return lines...

the two rear lines are FROM the lift pump into the filter, and out of the filter into the IP, the fitting on top with the T in it, come from both the IP, and the injectors return fuel back to the tank through the banjo hose...

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

great thanks. Ill try and track this down following the hoses and replacing or cutting down suspect parts and replacing some hose clamps. Ill have to go with the 5/16 hose as 8mm is not easy to find at the local shops here.

We're getting the cold snap early this year... (-14F)

How important is the cigar hose? Ive never had one and have never noticed anythign in particular with performance, however, I dont know otherwise...

Some engines are sensitive to missing cigar hose. Most are not.

So you choose the trial and error method?

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked