Fuel pipe and filter replacement Defender 90

Keep getting air into my 2.5 TD fuel feed, and can't isolate the air leak, thinking of replacing all the tubing with new with Fuel line and brass fittings. How about the filter, can you just replace with a 200tdi filter ? , they seem simpler and not so many connections to for air leaks . ? What size are the fittings, looks like 8mm Od piping with a 6mm internal dia.?

Take the banjo off the top of the filter housing, there is a tiny hole in it, make sure it isn't blocked.
The only place air can get in is on the negative side of the lift pump.

Do you mean between the lift pump and the tank ?

Splashman237 said:

Do you mean between the lift pump and the tank ?

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He means the banjo union on top of the fuel filter head, and is right that the tiny hole can block up.

I wouldn't go replacing the piping and so on, just go through the unions, checking olives, and that the nylon tube hasnt swollen up or split. The leak must be in the negative pressure part of the system.

Are you sure the filter element is sealing properly, is it Delphi, or a cheap Fram or suchlike?

No idea whether a Tdi filter would work, but I do know they are a lot more expensive than 296 element.

You may find the spill rail is the best place to start as its a common place for air to get into the system

I don't think Tdi fuel setups will work for you, if I recall properly your current fuel return comes from the top of the filter and Tdi ones come from the pump

i'm also thinking of redoing the fuel lines on the 300tdi with cupro 8mm od. rubber is pricey for the proper stuff, plastic is alright, but a bit meh

The fuel system in negative pressure from the tank to the feed pump, the rest is positive.
A leak on the positive side will show as diesel is forced out.

The banjo in the top of the filter is to bleed air out, you will always get air in the system , but it has to be able to bleed out via this tiny hole.


How do you know you are getting air in there?

nobber said:

The fuel system in negative pressure from the tank to the feed pump, the rest is positive.
A leak on the positive side will show as diesel is forced out.

The banjo in the top of the filter is to bleed air out, you will always get air in the system , but it has to be able to bleed out via this tiny hole.


How do you know you are getting air in there?

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The air is appearing in the injector pump after I've gone only a few miles,I It bubbles and froths when bled, then runs ok for a few miles and once again looses power and need the injector pump bled again. I assume the air is coming in with the fuel from up the line , either the filter , lift pump or most likely from the pipe tank to lift pump or return line from the injectors.

Splashman237 said:

The air is appearing in the injector pump after I've gone only a few miles,I It bubbles and froths when bled, then runs ok for a few miles and once again looses power and need the injector pump bled again. I assume the air is coming in with the fuel from up the line , either the filter , lift pump or most likely from the pipe tank to lift pump or return line from the injectors.

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It's had a new lift pump and most banjo coppers washers, and new filter

Splashman237 said:

It's had a new lift pump and most banjo coppers washers, and new filter

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Put some clear pipe in and observe, I had this issue a while back, I replaced the filter, reseated all the pipes, cleaned out the banjo, thers is only so much you can do , I was baffled, it turned out to be a defective feed pump.

Any fuel leakage anywhere either in the system, or on the injection pump itself?

No other leaks of diesel or signs of air going in. I'll try the clear pipe trick see where it's coming from.

Last time I remember this coming up in a thread, it turned out to be pipe damage at one of the unions. Worth disconnecting on the neg side between the filter and the lift pump and having a close look at the end of the pipes - even the slightest damage can let air in.

Hmmm still not found it, did take out the tank intake filter gauze nd pipe and it was clogged up with gunge so cleaned that but still no good very little air now in injector pump when I bleed it so I'm thinking maybe that's not the problem, what else could be causing it to go gutless at about 50 mph ? Feels like a lack of fuel but maybe I'm looking in the wrong place , could it be turbo , or maybe dump valve ? Struggling to know where to look now .... Any suggestions appreciated .

Usually if there is any air in the pump it wouldn't run at all!

Have you ever had the injectors tested or serviced.

Visual inspect turbo, look for oil in hoses, slight but not excessive movement on rotor, no oil or diesel leaks. Check visually that the waste gate actuator moves when you rev it up, at a standstill or drive with bonnet off. If you want to spend money, you could get it boost checked at a fuel injection specialist or similar.

I would think it is equally likely the problem is with the fuel injection pump itself. Could be the boost setup isn't working, or another problem.

Inspect boost setup for damage or leakage first, if the diaphragm is gone you could change it.

If not, two ways to go, injection specialist for testing, or try and source a second hand pump, one that is known to work would be best, for substitution testing.

Injection pump was a replacement supplied through this forum and checked before shipping so should be ok. I'll check boost setup on injector , is there a way I can do that while stationary ? Is there an adjustment on the injector pump for fuel boost ?

Splashman237 said:

Keep getting air into my 2.5 TD fuel feed, and can't isolate the air leak, thinking of replacing all the tubing with new with Fuel line and brass fittings. How about the filter, can you just replace with a 200tdi filter ? , they seem simpler and not so many connections to for air leaks . ? What size are the fittings, looks like 8mm Od piping with a 6mm internal dia.?

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No - the Lucas pump needs to have the lucas head, or a head which preforms the same way. The Bosch heads don't have a air purge system.

As you have found air will stop your Lucas run engine dead, not so a Bosch injection pump as it self bleeds, so basically the Bosch head just simply has an in and an out, diesel air the lot. If you fitted this to your pump you would have no end of trouble.

I had this problem with a 2.5NA (for all intents and purposes the same set up). It ended up being a full fuel system pipe work refit after diagnostics. I am actually currently working on another diesel car which has an air issue just now and I am doing exactly the same for it as I did the 2.5NA years ago. Thing is a pig to start in the morning but then runs fine all day, did the leak off pipes checked for leaks, checked filter heads and all sorts and set up an experiment 2 nights ago. I took a clean 5 litre can, filled with with diesel from the return line of the vehicle with the engine running (to get good clean filtered fuel).

I extended the return line away from the rubber hose as it leaves fuel pump on engine with a piece of clear pipe and put it into the can. I then extended the rubber feed into the pump with another piece of clear pipe, so I now have NO filter (take care) and 2 pieces of clear pipe going into a can with clean diesel. I started the engine and let it run, I saw air bubbles flying down the clear pipe then the engine sat nicely with no air. Switched it off and left it over night, following morning, some 15 hours later, vroom thing starts instantly, better than it has in years. Leave it another 24hrs, again vroom it starts up. So I have now confirmed where the air leak is NOT.

I then added the filer back into the equation but connected the input side into my clear pipe back to my can - so now the filter is the only addition, left it again for a day and again twice after 12 hrs or more it starts perfectly. I now know that the filter and engine bay fuel piping is OK.

Plan now is to replace all the piping back to the tank. It might only be the feed or might only be the return, but this thing has steel pipes and to be honest it's just asking to fail again if I leave it... so have a think about this experiment, set it up carefully and in a way you can drive the car using your new make shift tank for testing.

See how that goes.

Also, another simple thing would be to get a bit of air hose into the system AFTER the filter head to see if it's sending air filled fuel to the pump. Also, have you checked your air bleed off on top of your filter pump? 100% absolutely are you sure, air can pass through the banjo via the tiny hole?

Check the injection pump unions, bleed screw etc. too. Leave nothing t chance.

Splashman237 said:

Injection pump was a replacement supplied through this forum and checked before shipping so should be ok. I'll check boost setup on injector , is there a way I can do that while stationary ? Is there an adjustment on the injector pump for fuel boost ?

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Just look at the boost diaphragm housing check the little cap is in place, and no fuel leaking out of the housing, or being pushed up the pipe to turbo snail.

If the set up is working properly the fuel boost should be automatic, as the turbo spools up the diaphragm moves the little linkage behind it to allow the pump to inject a little more fuel.

The boost diaphragm housing is on the injector pump? Yes ?. If I unhook the pipe from pump to turbo, will I see fuel at idle or do I need to rev or hav it under load ?