Fuel Filter Question

Hello,

Just a quick question regarding fuel filters, particularly those for 200 / 300 tdi engines. I have always been led to believe that the central channel in the fuel filter (i.e. the internal reservoir where fuel is stored after being passed through the filter media / paper) is supposed to be full to the brim with diesel, is this right? I have used various different brands of fuel filter and the last two times that I've changed them (today included) I have found a lot of air at the top of the canister which I imagine is only going to be drawn into the system before firing. My lift pump seems to be in good working order - splashing diesel at the bonnet and my fuel lines are clear too. Surely having a large area of air is only going to cause performance problems. The engine is obviously drawing fuel up to the top of the canister, but air is finding its way back into there somewhere.

Any ideas or thoughts?
-Pos

ive got a clear pipe from the lift pump to the filter ,when the engines not running,there's an air pocket about 1 1/2 inchs long in the pipe,so there must be an air pocket in the top of the filter ,soon as the engine starts the bubble dissapears, I hope this helps ?.oh its a 200tdi by the way

defenderwayne said:

ive got a clear pipe from the lift pump to the filter ,when the engines not running,there's an air pocket about 1 1/2 inchs long in the pipe,so there must be an air pocket in the top of the filter ,soon as the engine starts the bubble dissapears, I hope this helps ?.oh its a 200tdi by the way

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Thanks for that, it seems odd that air can find its way into the system, surely this isn't right.

dunno pos ,but mines been like that for at least 2 years,that's when i fitted the clear pipe,i can only assume the air space fills with dino when the engine starts,but as you correctly say,where does the air come from ?,mines runs great so i'm not really bothered about it,

defenderwayne said:

dunno pos ,but mines been like that for at least 2 years,that's when i fitted the clear pipe,i can only assume the air space fills with dino when the engine starts,but as you correctly say,where does the air come from ?,mines runs great so i'm not really bothered about it,

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I'm trying to rule out possible causes of my bizarre fluctuating idle and I thought that perhaps if the fuel filter was drawing air in, the governor in the injection pump was having the engine rev harder in order to keep the fuel flow the same. Hmm.

put a jerry can of fuel on the roof and gravity feed the injection pump, that way youv'e by-passed the lift pump and fuel filter,at least then you can eliminate these from your problem.

Jerry

Pos my filter is always full to the brim when it gets taken off to be changed , to the extent it starts coming out as soon as the filter is loosned. Its a 200 tdi. So I wod believe you have a very slight air leak somewhere in the system. Are all your hoses all really tight on the connections .

Are you sure its air? Maybe its fumes from the warm fuel collecting at the top of the filter once it stands? There are some volatile elements in diesel that evaporate over time. Nowhere near as much as petrol but they are there.

Loosen and then retighten the banjos on the return lines from the injectors. Should sort it for you pos - some 200s shake them loose on a semi regular basis. If you don't loosen them before tightening and they're already tight you can snap the banjo.

I always thought that it should have been full to the brim - it always did used to leak diesel as soon as I loosened the canister from the housing - something that is now NOT happening what with the fuel level only reaching half way. I had the spill rail banjos off two days ago to fit new rubber pipework between them, so they are all in good shape (and with new copper washers ofcourse!).

As for diesel vapours, I don't think that they should be accounted for in the fuel filter housing considering it should be filled to the brim. If anything, the entire system should be primed right up to the injectors, with no air in there what so ever. I will try and locate an air leak - it's obviously getting in somewhere. I have started to notice that the engine judders under load - fuel starvation or air in the pipework no doubt.

I expect the lift pump me be playing foul again, I've had two faulty units, but I will give it a good once over first.

-Pos

Have you checked the piping between tank and lift pump?

I've found the problem, what a joke It's the lift pump that has packed in AGAIN! I'm on my third one within a year. AllMakes4x4 are officially the new ****part. I'll swap it for a Delphi next week. Basically, with the pipe between the lift pump and the fuel filter removed and the engine turned over, there is not a drop of fuel being pumped up from the tank. If I connect the pipework back together however, the engine will run but it's only relying on the injection pump to draw the fuel up from the tank, hence the reason why my fuel filter is only half full - not meeting demand.

I'll swap that tomorrow or Tuesday
-Pos

I changed mine a week ago and it was only about a 3rd full. I only filled the new one up a third (that's how much diesel I had) then turned the engine over and left it at tick over for a while the bleed itself.

What a PITA!

I thought you had a Delphi on it already?

Ian

instantsquid said:

What a PITA!

I thought you had a Delphi on it already?

Ian

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I know for a fact that it came in an allmakes4x4 box but the unit had a dephi sticker on it - which would make me assume it was a delphi. Then again, looking at the unit I have in comparison to he Delphi units, they do look quite different - mine looks more like a Britpart pump. I don't know why they give up so easily.

-Pos

pos said:

I don't know why they give up so easily.

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'cos they're ****????

instantsquid said:

'cos they're ****????

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They obviously are yes. I've been having quite a few problems with parts recently, all supplied by AllMakes4x4. I tested four 88 degree thermostats, none of which opened at 88 degrees and only one of which partially opened at 110 degrees. The rest failed to open even with a gas axe heating a paint tin of water well above 130 degrees. I'm on my third lift pump within a year too, what the he'll is going wrong! They're not that complex. The lift pump I originally replaced looked like it had been on the engine since day one, that has to have been about 18 years old.

I've got a Delphi in order anyways, who else makes them?

-Pos

I whipped the old lift pump off today (it was a delphi) and found that the cam arm had become detached from the plunger which works the diaphragm. There was a nice collection of metal parts resting in the pump arm recess too. I've now put another Delphi on in it's place and to be honest, I can't really tell the difference. I still have my very annoying random over-idling problem and there still feels to be a flat spot. I think air is getting in somewhere now mind, because when I got home, I fired the engine up, slackened off the bleed bolt on the filter housing and there were plenty of bubbles. Dunno where it's getting in though, I've gone through the entire system (including a new pickup pipe) and there isn't really anywhere that it can get in.

-Pos

Yours is a Disco conversion isn't it? How did you join the TD and Tdi fuel pipes?

Ian

instantsquid said:

Yours is a Disco conversion isn't it? How did you join the TD and Tdi fuel pipes?

Ian

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It is indeed. The fuel line from the tank is completely new. It consists of a new steel lift pipe with a length of rubber (dual ply) fuel line sleeved over and held in place with two jubilee clips. It is also joined to the lift pump in the same way. The fuel lines from the lift pump to the injection pump (including Jose to and from the fuel filter) are the correct 200tdi fuel lines. The return line is the only "botched" length of pipework, where I have simply sleeved the old pipes together with a short length of rubber fuel line. I suppose it could he leaking back up to the fuel filter here, I'll double clip the join.

-Pos