Disco Fuel System

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Dom-300tdi

Active Member
Posts
181
Sometimes when driving through town at low speeds my disco is a bit 'lumpy' so to speak and with my foot on the accelerator pedal in a fixed position the revs jump up and down a bit. Changing the fuel filter and bunging some injector cleaner through made a big improvement but its still not 100% all the time.

I'm thinking there may still be a restriction in a different part of the fuel system. The sedimentor is an ovbious one but I cant get that appart. Its a pig to get to without having the car up on a ramp and pretty much every connection is ceased, cant even slacken off the drain plug with pliers!

Also wondering if in the fuel tank itself there is another filter, like mesh over the end of the pipe? Can anyone confirm if such a thing exists? Also what is the tank made of on an M reg 300tdi disco; is it metal or plastic? I cant tell cause it's covered in so much waxoyl :D

I friend of mine reacons my disco is undertuned and could benefit a lot from having some tweaks done in the right places. How much should I expect to pay if I took it to a garage that does that sort of thing and is it worth doing , or is it actually easy enough for a novice to attempt without doing too much damage?
 
Sounds like air getting into the system.

Check the following.

Bleed screw on fuel filter
injector spill pipes
Sender unit under the carpet in the boot

If you have concerns over the sedimentor, bypass it as test and if this solves your problem get the angle grinder out and fit a new one.
 
Dom-300tdi said:
I'm thinking there may still be a restriction in a different part of the fuel system. The sedimentor is an ovbious one but I cant get that appart. Its a pig to get to without having the car up on a ramp and pretty much every connection is ceased, cant even slacken off the drain plug with pliers!
Click to expand...

Sounds like some form of diesel starvation, you must work out what is casuing it. Mike is on the correct path but you don't need to bother bleeding your lines as the bosch pump does a good job of this, however a hole in the line may be drawing air, if it's drawing air it's not drawing fuel. On the motorway in 5th gear does she sit at 75 odd without problems? Does she have some go left as well? If so then it probably is NOT a blockage as the fuel is getting to the engine at motorway crusing speeds.

Is your lift pump working properly? If it has failed the injection pump actually has enough suck to pull diesel from the tank in a fully primed diesel line but it does cause fueling issues and could lead to issues like you describe. Although it can do it it struggles beyond about 3000+ rpm and would also struggle obviously to draw enough diesel if there is a pin hole leak - air offers less resistance so more air that diesel - which is different to some air in the systerm at this stage there is simply not enough fuel. Also a little bit of thinking out of the box here but at a low steady speeds it is likely the injection pump may not be turning fast enough to bring the diesel up steadily enough.

Dom-300tdi said:
Also wondering if in the fuel tank itself there is another filter, like mesh over the end of the pipe? Can anyone confirm if such a thing exists? Also what is the tank made of on an M reg 300tdi disco; is it metal or plastic? I cant tell cause it's covered in so much waxoyl :D
Click to expand...

Plastic. There should be a mesh but it is not that fine, more to stop things that might block the lines, also back to the motorway speed thing, if it can get enough fuel then, it's probably not a blockage.

Dom-300tdi said:
I friend of mine reacons my disco is undertuned and could benefit a lot from having some tweaks done in the right places. How much should I expect to pay if I took it to a garage that does that sort of thing and is it worth doing , or is it actually easy enough for a novice to attempt without doing too much damage?
Click to expand...

I don't think it is undertuned, I think it needs something fixed not tweaked.

I would sort the fueling issue first, then think about EGR removal and inlet manifold, intercooler and pipework cleaning. Get it close to the way it left the factory with a good service and see how you feel she responds then.
 
Last edited:
Mike:

I changed the fuel filter yesterday and checked the bleed screw at the same time.

Injector spill pipes were looking tatty so I replaced those too.

My boot is lacking carpet atm as i've been doing some welding so the sender will be easy to get to. What am I looking for exactly and is it easy to remove? From memory,where the pipes come out and the electrical connections go it looks like a oversized bottle top. Does the whole thing just unscrew?

Disco Mania:

In the last couple of days I have removed the EGR, also done and oil + oil filter change and fuel filter change. Intercooler cleaning is on the list for the near future.

You have got me thinking now about the fuel pump. When I changed the fuel filter, I was following instructions in the haynes manual which said to slacken the bleed screw and then to operate the manual lever on the fuel pump until fuel without air bubbles spills from the screw. I must have pumped that lever 100 times and never got any fuel comming out of the bleed screw. I did wonder at the time if maybe the manually operated part of the pump was not functioning correctly but assumed all must be well as the car was still starting and running ok.


Hmmmmmmm
 
Another thing which is probably related now that I think about it. At low revs it has very little power; it always seems like it struggles to pull away but once its got going and you put your foot down it goes ok. This being my first landrover, first 4wd, first diesel and probably the oldest car i've ever owned too I figured this lack of power when pulling away was the norm, now i'm beginning to think otherwise.
 
As you look at the fuel sender unit the white plastic elbows have copper pipes fitted into them.
The copper corrodes and in turn splits the plastic causing an air leak.
I am havin a similar problem on my 300tdi at the moment and i found 2 small pin holes in the fuel line about 12 inches up the line from the sender unit.

With regards to the lift pump it operates off the cam so if the lever on the inside is not in the right position it will not pump anything, try manually cranking the engine over using the bottom crack pulley, or turn the ignition over using the key very quickly and keep trying until its in the right position, you will know when it is as you will feel the pressure.

When you change your fuel filter fill the new one with clean diesel before you fit it and the system will have very little air in it and will self bleed.

keep us posted
 
to check the operation of the lift pump disconnect the fitting after the lift pump into the fuel filter housing and crank the engine. if the is a decent flow then the lift pump will be sound, i had almost a foam of diesel and air at this position which definately told me it was air in the line.
 
Tomorrow I'll take a look at the pipes coming off the fuel sender and see what I can find.

I'll also do as you suggested and take the outlet pipe off the fuel pump and see what comes out.

Is there an easy way to intentionally prevent the engine from starting while I crank it to test the fuel pump ?
 
Alright not to clued up on sorting ya problem out but i had a 200tdi and a mate of mine did something to it i dont know excatly what he did he said he wound the pump up will find out and post 2mrw but it took him no longer than 3-5 mins to do and it made a hell of a difference it pulled well from start was quite nippy for a big motor and i didn't notice a change in fuel use. I now have a 300 and me mate is dunna change the timing belt and wind the pump up next week sometime
 
Dom-300tdi said:
I'm thinking there may still be a restriction in a different part of the fuel system. The sedimentor is an ovbious one but I cant get that appart. Its a pig to get to without having the car up on a ramp and pretty much every connection is ceased, cant even slacken off the drain plug with pliers!
Click to expand...


There is every possibility that your problems are related to the fuel sedimenter and it being full of crâp.

You do not need to remove the whole assembly, just the bowl. It comes off after you have removed the 11mm long bolt that holds it in place. Accessed from the top using a ring spanner it should come undone without trouble. Sometimes the bowl will stick a bit on it's rubber seal, so just tap the bowl lightly with a rubber mallet to loosen it.

Be ready with an ice cream tub or similar to catch the diesel. Clean the bowl of all the jelly-like substance often found there and the rubber seal and replace.

When you restart the engine, keep it on a high tickover for a couple of mins to bleed out the air. Job done !!

Don't ever try to move the white plastic tap on the bottom of the bowl - they just snap off !!
 
I managed to get a new sedimenter off ebay for a fiver so now even if I mess this one up beyond repair I can just swap it out.

Last time I tried to get it appart I was trying to remove the fuel line first as the haynes manual says to remove the inlet pipe and raise it above the tank level (or block it) else when you remove the bowl it will drain the contents of the tank. Is this true ?
 
Biglad is correct, remove the bowl with the ignition turned off and u wil be fine.
Wear some goggles and crappy clothes because u will get covered when u take it off.

The fuel only flows when the car is running.
 
MikeDISCO said:
to check the operation of the lift pump disconnect the fitting after the lift pump into the fuel filter housing and crank the engine. if the is a decent flow then the lift pump will be sound, i had almost a foam of diesel and air at this position which definately told me it was air in the line.
Click to expand...

Mike, how can I turn over the engine to check the fuel pump is working without the engine actually starting (guessing there will be enough left in the pipes between the filter etc for it to start even with the fuel supply not connected) or does it not matter ?
 
Dom-300tdi said:
Mike, how can I turn over the engine to check the fuel pump is working without the engine actually starting (guessing there will be enough left in the pipes between the filter etc for it to start even with the fuel supply not connected) or does it not matter ?
Click to expand...


There is a fuel solenoid on the injection pump, if you pull off the electrical connector no fuel will get through to the engine.

Also, if you just give the ingnition key a quick flick on & off, to turn the motor over, it won't start.
 
Right guys, I have an update for you. Thanks for all the help so far..

Today I removed the section of boot floor which covers the fuel sender unit and inspected the pipes and plastic bit. Got to be honest, I really couldnt see anything which looked like a split or crack so I left it all alone.

Then poked my head under the bonet and removed the output pipe from the fuel lfit pump which leads to the input side of the fuel filter and discovered something interesting.....

Removed the wire going to the injection pump solonoid, turned the key in the ignition ... nothing, tried again - nothing, one more time for maybe 2 seconds and yet not a single drop of fuel came out from the lift pump. I'm not sure how much fuel the lift pump would normally move in the space of a few seconds, whether it would just be a dribble or quite a steady stream, either way the nothingness makes me think the pump is dead.

Is it an easy fix?
 
u shold get a steady squirting of diesel mate. sounds like u need a new lift pump.
£20-£25 take u less than hour to fit it.
 
I've had a browse though ebay and found there seem to be three alternatives:

Unbranded for around £15

Delphi Branded for £25

Landrover branded (though with a delphi sticker on the one in the photo) for £80

Is a lift pump a lift pump ? Will I be ok with the cheapest option or will paying a few quid more actually benefit me in terms of quality/performance ?
 
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