Excessive fuel consumption

Good evening all.
The title says it all really, until jan this year I've been running on amazon technics (255/65/R16) and I had been achiveing around 200 miles to a full tank. Coming up to Christmas the tyres were ready for a change and with the snow I opted for a set of insa turbo specail tracks. (235/85/R16) Because the tyres were taller and very aggressive I expected my fuel consumption to be higher and the landys performance to be decrease which it did.
•slower acceleration
•low top end speed (55/60mph as apposed to 70mph)
•generally sluggish
•drinking more than George best (rip)

I had fitted on Monday a set of Bf goodrich ATs (245/75/R16). Which I expected being a smaller and less aggressive tyre to vastly improve fuel consumption, speed and power. Ive got my speed back and resonable power but the fuel consumption has not improved. The tank was nearly empty Monday night so I put £25 in which was just short of half a tank, tonight the needle is at the same place as it was Monday before I topped up with only 60 miles covered. At the rate I'm going it's costing me £50 per 7 days and only getting around 80 miles.

I know the 19j is not the best for anything but it should do at least 20mpg if not more. Can anyone shed some light on the situation because I'm spending more on fuel than bills and at the moment I really can not afford it. Thanks in advance.

is it smoking more than normal?

Thinking about it, it is, not a great plume but more so on load. It's black smoke and at night it produces a James bond smoke screen in the headlights of following cars.

Have you replaced your air and fuel filters? I'd check to make sure that there is no air being drawn into the fuel system too. Slacken the bleed nipple on the fuel filter housing and then manually prime the system with the lift pump lever. There should be no air / bubbles appearing from the hole, just a weep of pure diesel. Also check your boost pipes for delamination on the insides, if they're old and brittle they can suck themselves flat inside before the turbo starts boosting. It is also possible that your boost pipes may have come loose or split if they're old too which will simply vent all of your boost pressure straight out to atmosphere. Another thing that is possible with these engines (and which will cause your symptoms) is the boost diaphragm on the injection pump which gives the engine more fuel as the turbo boosts:- it may well have split or torn. Follow this link for a guide on how to check it:

Replacing a 2.5TD boost diaphragm - LR4x4 - The Land Rover Forum

Other than that it could be anything from sludge in the fuel line to faulty injectors, worn bores, a failing turbo or a split intercooler. Check the easiest and the cheapest things first!

-Pos

The air filter is fine, I will change the fuel filter tomorrow and try and bleed the system also. I took the silicone hose from the turbo to the inlet manifold to check it was boosting and it blew my hand away, there also was a good covering of oil inside the pipe. The turbo used to whistle nicely on load but now I can't hear it at all unless the intake pipe is removed. I will check the pipes aswell, I did replace the boost diaphragm a couple of months ago because I thought it was goosed (but wasn't). The injectors were reconned last year. There is a visible oily mist from the rocker cover cap but it's not a fog.

D.G.F.S. said:

The air filter is fine, I will change the fuel filter tomorrow and try and bleed the system also. I took the silicone hose from the turbo to the inlet manifold to check it was boosting and it blew my hand away, there also was a good covering of oil inside the pipe. The turbo used to whistle nicely on load but now I can't hear it at all unless the intake pipe is removed. I will check the pipes aswell, I did replace the boost diaphragm a couple of months ago because I thought it was goosed (but wasn't). The injectors were reconned last year. There is a visible oily mist from the rocker cover cap but it's not a fog.

Click to expand...

You say that the turbo made a more audible whistle previous to what it is now. This suggests (to me) that when the engine is under load and prior to the turbo spooling to full boost, the air flow into the manifold is being restricted. Having the top pipe removed from the intercooler whilst the engine is stationary is a completely different kettle of fish to the conditions when driving, because the turbo is free to spool up without the engine drawing air in at the other end. In order for your turbo to spool up, it needs a flow of exhaust gasses flowing through the exhaust manifold. Your engine will draw air in before the turbo begins to boost and it maybe sucking a pipe shut before the turbo has spooled up enough to create enough pressure to keep the pipes open (or fattened up). In this case the engine will be starving its self of air, the turbo will continue boosting (all be it limited) and the waste gate might open to compensate for a pressure build up on the turbo side of the manifold. Any boost pressure will also be sent down the boost diaphragm actuator pipe to give the engine more fuel (black smoke) and you end up with no power, wasted fuel and a very angry face!

It's worth swapping them all over for fresh pipes for the sake of a fifteen quid or so. What condition is your CAF (Cold Air Feed) pipe in? It's the length of pipe from the air filter housing to the turbo inlet. It must be a wire re-inforced length of pipe and it could also have collapsed internally.

-Pos

The caf is ok, I had it off today to check for that reason. Just to clarify (btw I don't have a intercooler on mine) your basically saying that when the engine first draws air in through the short silicone pipe from the turbo to the manifold, when the turbo isn't putting preassure through the pipe its making the engine suck for it's own air thus possibly collapsing that pipe?

D.G.F.S. said:

The caf is ok, I had it off today to check for that reason. Just to clarify (btw I don't have a intercooler on mine) your basically saying that when the engine first draws air in through the short silicone pipe from the turbo to the manifold, when the turbo isn't putting preassure through the pipe its making the engine suck for it's own air thus possibly collapsing that pipe?

Click to expand...

Precisely that yes. You'll usually have a little bit of turbo lag which is the time between you putting your foot down and the turbo spooling up along with the coinciding increase in fuel. During this time your engine will still draw in a hell of a lot of air with a very strong vacuum, certainly enough to suck a pipe flat or at least suck the internal laminate inwards (if it's an old pipe) - restricting the air flow either partly or completely. Then ofcourse because the engine isn't getting as much air in, it's not pushing as much air out (exhaust gasses), the turbo doesn't spool and it just doesn't take off as so to speak. Do you have any steel / aluminium pipework between the turbo outlet and the inlet manifold (with rubber / silicone joints) or is it all rubber / silicone pipe?

-Pos

The pipe that takes the compressed air from the compressor to the inlet manifold is roughly 6" Long (elbo) which is just a blue silicone pipe and on the joint it is easily collapsable. It has no reinforcement whatsoever.

D.G.F.S. said:

The pipe that takes the compressed air from the compressor to the inlet manifold is roughly 6" Long (elbo) which is just a blue silicone pipe and on the joint it is easily collapsable. It has no reinforcement whatsoever.

Click to expand...

This could well be the problem in your case. If the pipe comprises of two silicone ply's, the internal laminate could have come away from the outer laminate which would then be sucked flat inside the pipe, blocking the air flow. If the pipe is single ply, it may well just suck flat anyway what with the vacuum created by the air intake. You could try a length of this stuff Auto Performance Silicone Hoses or maybe a whole new elbow like one of these Auto Performance Silicone Hoses the more ply's the stiffer it'll be.

I'm not saying this is definitely the cause of your problem, but it's a likely bet. Other than that, check fuel lines, fuel filter and lift pump. Have you checked the lift pump at all? It's an easy check. Pipe between the lift pump and the fuel filter housing off. Turn the engine over and if diesel is launched at your bonnet, it's strong. If it just splutters fuel out, swap it because it wont be able to supply an adequate amount of fuel when the engine is under load / working at a higher rpm.

Do you have a picture of your engine setup at all?
-Pos

Sorry I haven't got any pics of it. I will get a new pipe regardless because it's probberbly been in situ for 20 years anyway. With regards to the lift pump, I will check that when I bleed/check the system and replace the filter. How you have explained that the turbo pipe might be at fault does sound right with the problems I'm having, even down to the angry face! Come on, £25 for 50 miles is a **** take.

D.G.F.S. said:

Sorry I haven't got any pics of it. I will get a new pipe regardless because it's probberbly been in situ for 20 years anyway. With regards to the lift pump, I will check that when I bleed/check the system and replace the filter. How you have explained that the turbo pipe might be at fault does sound right with the problems I'm having, even down to the angry face! Come on, £25 for 50 miles is a **** take.

Click to expand...

I know the piece of pipe that you're talking about, it's a kind of washed out, powdery blue colour isn't it? Swap it, it won't do any harm. Whilst you're running through the check list, also ensure that your waste gate is not stuck open. If you look at the exhaust side of the turbo, you'll see a wastegate actuator with a threaded steel arm that is attached to a metal hinge on the exhaust down pipe. Clamp a set of mole grips onto the little hinged bit and then push it towards the cab to open the waste gate. It should move relatively freely, although there is a spring inside the actuator housing which will fight you and then bring it back to its home position. If it's jammed open even slightly, you wont be achieving optimum boost. You can also remove the actuator arm (usually secured with a 'c' clip) from the hinge and then see if it will pull any further forwards towards the front of the engine. If it does move further this way, adjust the actuator arm so that when it is re-fitted, it holds the wastegate fully closed.

-Pos

That's the pipe I'm trying to describe (do you still think that pipe may be at fault, now you know which one I'm on about?). I will add the actuator to the checklist for the morning! Anything else while I'm at It Thank you very much for your help aswell, I have been really wound up with the ammount it's costing me recently, I wouldn't mind is I was going at F1 speed to warrent the fuel use.

D.G.F.S. said:

That's the pipe I'm trying to describe (do you still think that pipe may be at fault, now you know which one I'm on about?). I will add the actuator to the checklist for the morning! Anything else while I'm at It Thank you very much for your help aswell, I have been really wound up with the ammount it's costing me recently, I wouldn't mind is I was going at F1 speed to warrent the fuel use.

Click to expand...

No problem. It's only a short piece of pipe but if you can squeeze it together with your finger and thumb and feel your fingers on both sides (if you know what I mean) then it's possible that it is being sucked flat or knackered inside. It's definitely worth trying a new one for about £5 or whatever they cost. The things I would check are:

1) Blockage in steel mesh gauze on end of fuel pickup pipe in fuel tank or pin holes in fuel pickup pipe
2) Fuel line blocked / kinked / gunked up
3) Lift pump could be weak
4) Fuel filter blocked or paper filter inside discintegrated
5) Return line from fuel pump to filter housing / banjo bolt hole blocked
5) Plastic mesh filter inside injection pump fuel supply hole blocked
6) Injectors leaking / bad spray
7) Boost pipe from turbo to injection pump split / blocked
8) Turbo pipe collapsing
9) Waste gate stuck open

There's plenty to check! If none of the above fixes it, drop in a 200TDi!
-Pos

That'll keep me occupied for a while then! Thanks again mate. Ial keep in touch if I rectify the problem (or not!)

D.G.F.S. said:

That'll keep me occupied for a while then! Thanks again mate. Ial keep in touch if I rectify the problem (or not!)

Click to expand...

Good luck with it. I'm sure you'll sort it. Silicone boost pipe or fuel filter will probably sort the problem. Don't underestimate the other things though, the smallest of things can really hold these engines back.

Bed time!
-Pos