Thread: Please help - poor diesel economy

I've got the same car but in manual.

Is it possible that auto's don't do the same mileage? I don't know 'cause I've not had one, but as you mentioned, it does about 750Km on a tank which is 10L/100Km (and I do drive it like I stole it).

Have you changed you Air filter . If this is dirty it will retrist the amount of air and increase the amout of fuel being used.
And are you sure none has played with the fuel mixture, IE does it smoke alot on hard pull away

Hi Goldey, I don’t if the Chemtech is an injector cleaner, if not, put some injector cleaner through the fuel and make sure you take the Disco for a good highway drive to give the injector cleaner a chance to do it’s job.

Cheers.

Does the 300tdi Disco have a MAF? I thought that if the MAF is stuffed, then the system overfuels...?

Maybe something leaking in the fuel delivery somewhere (pump/injectors/etc)...? or maybe even the tank...?

I seem to remember Inc had said something about driving it under load to de-glaze the cylinders etc. Does that cause poor economy, or just sluggish engines...?

The air filter is brand new and the only smoke I've seen is on initial startup which I've been told all of them do. I did follow my wife home from the shops (her in the Discovery and me in her car) and she does drive it like she stole it, and there didn't seem to be any smoke coming from the back.

I couldn't imagine the auto causing a 4l/100k difference over the manual. Maybe time to bithe bullet and take it in for a service and get the mechanic to check the fuel pump settings. This hurts as I'd rather spend my own time doing any work on the car, but this fuel economy is a concern.

Thanks for the replies.

Cheers
Goldey

That fuel comsumption is high for a 300 TDi. You should be getting around 10l/100km. According to LR official figures auto should actually be marginally better than a manual. Have you checked the accuracy of your speedo/odometer against a GPS or those highway odometer testing places ?
If your speedo is OK, it could be the injector pump or maybe the timing is out. However a gross timing problem would see a lot of smoke/diesel vapour coming out of the exhuast ( usually whitish ). There would also be a noticeable lack of performance.
If you're getting the timing belt done, any timing issues should be corrected then ( if your mech knows what he is doing )

If it was leaking somewhere, you'd surely be able to see it. ( puddles on the ground )

If someone has played with the injector pump to the extent that you're pumping that much extra fuel through, it would pay to get it checked ASAP. Doesn't sound like you have an EGT ( Exhuast Gas Temp ) monitor so your EGTs could be excessive, which will do damage.

Originally Posted by goldey

I couldn't imagine the auto causing a 4l/100k difference over the manual. Maybe time to bithe bullet and take it in for a service and get the mechanic to check the fuel pump settings. This hurts as I'd rather spend my own time doing any work on the car, but this fuel economy is a concern.

Thanks for the replies.

Cheers
Goldey

I have a Disco 300Tdi Auto and on saturday i drove it from Brisbane to byron Bay and back on quarter a tank of diesel. Which i was more than happy with

Go to the auto places and put in some diesle fuel additive. The reason being where you fill up depends on the quality of fuel. And supermarket fuel is chaep fuel and has less sulphur in it which is needed in the 300 Tdi. So get an addivtive to add this to the fuel , it also cleans the injectors too.

I think he said he has replaced both the Air and Fuel Filters, Goldney what Tappet clearance was it when you checked them , according to RAVE should be 0.2 mm. if checked and 0.2 mm then no problems.

it is possible that the Bloke who owned the Disco prior to you has played around with the Fuel Pump settings for a Bit more fueling? this is easily checked and adjusted ...i tell you about this later how to set it back to factory..

check all turbo hoses with your hand to make sure there are no cracks and there is nothing loose.. it is possible air is escaping from your air intake .. check the wastegate actuator and boost signal line is NOT loose to the fuel pump wrong boost signal can cause excesive full delivery by the governor..believe me i had this problem before in my 300tdi..no boost signal getting to Fuel pump at all and fuel pump was sending fuel charge purely by the position of the governor..way too much fuel and black smoke...


just make sure the intercooler side of the hoses is tightended up on the alloy hose with the clamps . and you air intake hose is not showing any signs of degredation .. you may even want to upgrade your Elbow and straight piece with Silicone hoses, i've got part numbers for you if you're interested..not expensive..

Phew ..

now for the Fuel Pump Adjustment, i recommend if you've done all these checks and she is still blowing excessive smoke then we need to look at more fundamental adjustments , but i would not set about doing any checks / adjustments to your pump yet...