Gutless 300TDi Auto

[Countax]

Well i cleaned out the marmite from inlet manifold which Les Henson showed in another thread and also blanked off the EGR and fitted a new pipe from intercooler to manifold in the hope it would give my disco a bit of get up and go, but the vehicle still seems gutless. When Les did the cambelt and found out the amount of marmite in the manifold he also mentioned it sounded a bit 'tappety' so i will have a go at these next.

I don't want to go down the route of tweaking the pump and fitting a bigger intercooler just yet.

I have had the vehicle since new and just want to get it back to its normal performance level. Milage is approx 75k.

I cleaned out the inlet manifold but the head inlets are still covered in marmite as they look too risky to clean out incase the stuff gets pulled into the valves or cylinders.

I have a boost guage in my D90 i could pull out and use to check the turbo boost.

What things should i look at and in what order to try to sort out the performance?

Nigel

[Budgie]

Doing the tappets will help if they haven't been done in a while.

When was the inside of intercooler last cleaned?

If all that Marmite is in the inlet manifold then it stands to reason it'll be clogging the intercooler as well.

Also nice clean air & fuel filters may help.

Are you still running standard size tyres? As any increase to the rolling dia' of the tyres will effect the overall gearing of the vehicle.

[Countax]

Doing the tappets will help if they haven't been done in a while.

When was the inside of intercooler last cleaned?

If all that Marmite is in the inlet manifold then it stands to reason it'll be clogging the intercooler as well.

Also nice clean air & fuel filters may help.

Are you still running standard size tyres? As any increase to the rolling dia' of the tyres will effect the overall gearing of the vehicle.

The intercooler looked very clean, the marmite only started after the point at which the exhaust recirulation pipe joined the air inlet pipe to the manifold. But i will take your advice and clean it out.

Filters were changed at last service so i guess they could be ready for news ones again.

Tyres are normal size.

What about the lift pump? I heard they can start to weaken and cause poor performance. Is there a way to test it?

Nigel

[Disco_Dunk]

I just replaced mine, as I have a similar lack of guts (and so does the motor ) - they're only cheap from Paddocks (~£15). The new fuel lift pump definitely helped, but hasn't solved it completely.

I'll be de-marmiting next........

Dunk

The intercooler looked very clean, the marmite only started after the point at which the exhaust recirulation pipe joined the air inlet pipe to the manifold. But i will take your advice and clean it out.

Filters were changed at last service so i guess they could be ready for news ones again.

Tyres are normal size.

What about the lift pump? I heard they can start to weaken and cause poor performance. Is there a way to test it?

Nigel

[Pete Attryde]

Just to throw a spanner in to the lift pump theory I just changed mine and it made no obvious difference and I know the old one was knackered as the arm that runs on the cam was completely detached from the rod inside the pump so was most definately not pumping.

Pete.

[Cal]

Check the pipes coming off the fuel sender unit under the inspection hatch on the boot floor - the unions often rust and get pin holes in.

I've got a similar problem at the moment and think it's them - I've covered them in Vaseline to try and find where the problem is - no joy so far.

Are you getting any extra smoke on start up in the morning?

[Andy]

does it play in water? i spent nearly a year trying to work out why my disco was getting slower & slower. turns out that the tank breather hangs down the side of the tank & when i was stuck in puddles it was sucking in carp. sandy soil & diesel = a lovely jelly like goo that blocks the pickup rather well in the tank. it was that thick it never got sucked up enough to be seen in the sedimentor either.

[Countax]

does it play in water? i spent nearly a year trying to work out why my disco was getting slower & slower. turns out that the tank breather hangs down the side of the tank & when i was stuck in puddles it was sucking in carp. sandy soil & diesel = a lovely jelly like goo that blocks the pickup rather well in the tank. it was that thick it never got sucked up enough to be seen in the sedimentor either.

Disco is strictly used as a school run vehicle or dog kennel so does next to no milage per year and certainly not used in deep water. Checked the tappets as per Les's suggestion yesterday. A couple were at 0.24 rather than 0.20 so adjusted them back to the right setting.

Nigel

[Budgie]

If it only does short runs each day then try taking it for a good long run, keep at a steady 60 and run it for an hour or so. This should give it a bit of a clear out.

You never know!!

[Andy]

oh well if it doesnt go far or in water try driving the tank right down to empty a few times incase fuel has been in there so long its gone stale? im not sure if diesel can go stale but i know petrol does.

i could be talking carp there, but i guess it wont do any harm & its free to try.

only other thing i can think of that hasnt been mentioned is if the adjusterment on the cambelt has slipped so the injection pump isnt quite timed correctly any more. its quite easy to check/adjust with the right tools. its a pain in the arse but do able with just an 8mm (i think) drill bit plus spanners.

[Countax]

oh well if it doesnt go far or in water try driving the tank right down to empty a few times incase fuel has been in there so long its gone stale? im not sure if diesel can go stale but i know petrol does.

i could be talking carp there, but i guess it wont do any harm & its free to try.

only other thing i can think of that hasnt been mentioned is if the adjusterment on the cambelt has slipped so the injection pump isnt quite timed correctly any more. its quite easy to check/adjust with the right tools. its a pain in the arse but do able with just an 8mm (i think) drill bit plus spanners.

Andy,

Thx for the inputs. I don't think its a timing belt issue as the performance was same as before and after Les did the cam belt change. Les just made a comment that he felt it was gutless, but i dont know how many 300 auto's he driven. Its certainly not as quick on acceleration as my D90 200TDi manual. My wife who is main driver of the disco says she can't tell any difference so i guess we have one of the models with an auto box that just sucks up the torque and keeps it internally rather than delivering it to the wheels. It might also be stale fuel as we have been known to regularly go a whole month or two between refills.

Nigel

[Andy]

ahh well if its not changed after a cambelt change it cant be that then. im not sure if diesel can go stale, just out of ideas about what it could be really.

[Disco_Dunk]

Its certainly not as quick on acceleration as my D90 200TDi manual.

Nigel

Nigel...... Your Disco never will be as 'nippy' as a TDI 90 - the transfer box and axle diffs are different ratios, so the D90 has more low-end grunt (and hence gets out of the gate quicker), but the Disco has more legs at the top end.

My 200TDI 90 would be topping out at 75-80, while our 300TDI Disco is more like 90-95 (plus the Disco is heavier than a basic 90).

I really miss my Defender....... if only the s/h prices would drop to the same level as the Disco ones, then I'd definitely get another!!! - wish I'd never parted with her

Dunk

[Andy]

discos might have different gears but that also have smaller tyres, the overall ratio in high is the same i believe. it will always be slower than a 90 though, i think the 90 has about 500kg less kerbweight.

[BogMonster]

discos might have different gears but that also have smaller tyres, the overall ratio in high is the same i believe. it will always be slower than a 90 though, i think the 90 has about 500kg less kerbweight.

Not quite, Discoverys are still higher.

265/75R16 (or 7.50R16 about the same both just under 32") on a Defender is about 9.5% bigger than 205R16 (or 235/70R16 about the same just under 29") fitted to Discoverys. The transfer box difference from 1.222 to 1.410 is about 15%, so the overall effect is a slightly higher gearing.

The main reason I think is aerodynamics, the Discovery we have at work accelerates a lot better at 50+mph than my Defender which has to be down to aerodynamics, especially with the 90 having a roof rack which adds a humungous amount of drag at higher speeds. So the Discofairy can pull higher gears at higher speed.

[Andy]

ahh i'd never calculated it, just assumed as i always seemed to change gear at the same time as defenders when driving about with them. no wonder my disco can be sluggish running 32s then, still fitting 33s when i can afford it.

[Budgie]

I think the auto will tend to sap a wee bit more power than the manual box anyway, especially with a diesel in front of it. You don't notice much difference with the V8s.

Andy, I ended up putting a TD5 Defender 1.410:1 transfer box in my Disco when I put the 33" tyres on as it was crawling up hills on the standard box and I couldn't get out of 3rd gear doing 30mph. So you may notice a difference when you change.

If you're happy doing the work yorself then another option is to put 4.11:1 ratio ring & pinion in both diffs. This will bring the overall gearing back to about normal and has the advantage of catering for both High & Low range, where as the T-box will only effect the High range gearing.

[Andy]

i am planning a 1.4 tbox in the future Budgie, when i rebuild my LT77 i intend to put a new tbox on the back of it & fit the pair together. i suspect my center diff has seen better days as well, i prefer the idea of changing the tbox so ive still got standard parts, easier to sorce if(when) i break it.

with the tweaks/intercooler etc on my lump it seems to pull 32s fine so i expect it to cope with 33s. was passing stock 300tdis up hill on the M4 a few months ago & from the smoke i'd say they was trying (they did pass me doing 90ish on the flat) i'd then pass them holding 65ish up hill for them to bugger off on the next flat bit.