ml 270cdi drinking fuel on idle but good in normal use

[alfieco]

Hi can someone please help. I've just got myself a 2002 270 cdi ml. All is good with it. It runs well and doesn't use to much diesel until I leave it on idle for 10 min or so. Sometimes when on idle it uses almost 1/4 of a tank in 20 min or so. It's clearly got a problem but I don't know what it is. It had black death so injectors were cleaned and new copper seals fitted. It starts first time and only had a puff of smoke on start once. Car has done 135k. Dose anyone know what's wrong?

 

[E55BOF]

Is it actually using the fuel, or is the gauge reading erratically?

 

[alfieco]

Hi yes it's using it. I've filled and checked the amount used and was about £30 worth. It's done it twice now so I don't leave it on when I'm next to car.

 

[ringway]

Hi yes it's using it. I've filled and checked the amount used and was about £30 worth. It's done it twice now so I don't leave it on when I'm next to car.

Look for a leak from the white o-rings on the end of the fuel lines. When this happens it really will drip heavily. If you have an undertray a lot of the fuel will be caught on that, until you drive away... Park the car over a puddle and see if the water is contaminated with fuel.

It could also be the fuel line nearest the spinning belt which has only around 0.5mm clearance and if not fitted correctly can 'scrub away'.

 

[alfieco]

Ok I'll have a look in the morning in the light. I've just had most of the fuel system pipes replaced because of an air leak which solved the problem of it not starting.

 

[boxbrownie]

It cannot be using that much fuel through normal idle, there has to be a leak somewhere........it would be impossible to use 1/4 tank at 70mph down the motorway for 20 minutes!

 

[renault12ts]

As above, that would be impossible...it would be literally pouring out of the back of the exhaust.

 

[alfieco]

That's my point. Something is wrong with it. There has never been any evidence of a leak (you'd notice 10 to 20 litres of diesel on the floor) I'm at a loss as to what could be happening. I'll drive 10 miles to the farm Imy kids have a horse. Spend about 20 min feeding and sorting the horse then jump back in the car. Blowers on etc to keep it warm as its -2 here in Wales. Then from just under half a tank it will have dropped to just over quarter of a tank. The car doesn't smoke but the temp is low. Around 50 to 65 degrees. Had new injector seals last week with new glow plugs. Air filter which was badly blocked. Oil change and filters Inc fuel. Plus new plastic fuel lines as seals had gone.

 

[johnkyte]

I think this should have been posted on April !st

 

[alfieco]

Lol. No it's genuine. I wish it was a joke. Someone from work thinks it's a leaky injector or 5 and it's dumping too much fuel on idle. I'm running a injector cleaner through the system this week to see if it hasany eeffect on it. Also just been told my thermostat is sticking closed which might be adding to the problem. Got a new one ordered. Should be here next week.

 

[johnkyte]

I dont think an injector can dump that much fuel---thats enough to hydraulically lock the engine

I hope you get it sorted soon

 

[alfieco]

Oh ok. Didn't know that. Has to be a leak then. Going to have to put it on my mate's ramp and see if there is anywhere the fuel is coming from.

 

[E55BOF]

The stuck thermostat (it's stuck open, by the way, not closed; if it was stuck closed the engine would overheat) will cause an increase in fuel consumption, as would running an auxiliary heater if you have one, but nearly a quarter of a tank in 20 minutes? I doubt it. Do let us know when you find the cause.

 

[alfieco]

Oh ok. Would that stop heat coming in to use cabin heater? Last week it didn't warm up at all? I've been looking today and the engine and underside is covered in a residue of something. No oil loss though. I let the car idle for about half an hour today and it's used just under 1/8th with the temp holding at 55ish. All the pipes look ok though so not sure where the residue is from. Also noticed the tip of the exhaust is caked in black soot about a cm up the outside of the pipe.

 

[alfieco]

Hey just an update. I think I've found my lost fuel. Well some of it and it's not an April fools joke ether. Last night I had just under half a tank of diesel so I though I'll put a bit more in to get me through to next pay day. So I put in an extra £30 expecting to take it to 3/4 full. Switched on the car and £30 has filled it up according to the gauge. I'm now thinking that the gauge dropped the first time I tested it and now it's no longer showing a correct reading. Anyone got any ideas on how to fix it?

 

[dokalj]

Perhaps the fuel float in the tank is dirty?

Maybe add some Redex when you next fill up.

 

[alfieco]

Oh could be. I've put in a fuel system and injector cleaner. See if that makes a difference.

 

[alfieco]

Ok well here is an update. I've left it running on idle alot over the last few days on a full tank and it's not using hardly anything so it looks like it is something to do with the fuel sender. I've put in a fuel system cleaner so just seeing how it's going. It's still a bit thirsty so need to do some work to improve things but that's manageable.

 

[proser]

I would also look at getting the thermostat replaced as well, as that is not helping things.

 

[alfieco]

Think that's getting done next week. Just waiting on the past to be delivered. Also getting engine and gearbox mounts replaced. She's an old car so just needs taking care of lol. Bit of a rattle on the aux belt tensioner and a new glow plug relay. Keep getting a glow plus error light after starting. Everything but the relay has been replaced lol.