Hi all, i have a W reg 2000. FH12, Its a 420 bhp model. Its quite low geared running at 1580 revs at 50 mph. Using a
3 over 3 with splitter. The trouble i am gaving is low down torque and fuel consuption. It is used on local work. It doesnt start pulling till 1300 revs below that it would pull a tissue. It pulls strong then till 1800 -1900 revs. Trouble is this affects duel consumption. Currently at 5.7 mpg. Our other Volvo is an Fm12 380. 9 SPEED higher geared pulls as low as 1000 revs up to 1600. Pulls like a train. Returning 6.7, 7.2 on the same work. WHATS WRONG! ■■?
ATB Red
not the engine, it is the gearing, probably in the diff
Gearing will not affect the rpm that the truck starts pulling, if peak torque is at 1200rpm it’ll be at 1200rpm no matter what gears it has, if the truck is lower geared than the other one, theoretically it should pull better 
I would check the rpm sensor first, it may be telling lies 
Does it have hub-reduction axle(s)? Is it a double drive?
Try the turbo boost sensor, the fuel pump is a wearing part on these and quite common and iro £200, had one on mine about 6 months ago as it wernt quite on song!
any warning lghts or engine codes on the display?
moose
shuttlespanker:
not the engine, it is the gearing, probably in the diff
Totally agree and good idea about the rpm sensor. Where is it?
Saying that if it is the rpm sensor then sheeeeet 5.7mpg.
I was told it could do with having the engine recalibrated
Not twin drive not sure about hub reduction
Gogan:
Does it have hub-reduction axle(s)? Is it a double drive?
Had a fuel pressure sensor on a code reader. Fitters put a new lift pump on. If its the fuel pump it will slowly die. The fm has had 2.
Moose:
Try the turbo boost sensor, the fuel pump is a wearing part on these and quite common and iro £200, had one on mine about 6 months ago as it wernt quite on song!
any warning lghts or engine codes on the display?
moose
a top end engine set up is also a good idea on these to get the best out of them (mpg/power) valves,injectors etc as over time they can drop off on the mpg/power front!
also have you checked the filter on the end of the stack pipe in the fuel tank?.. or even a leak in the intercooler system?
moose
Moose:
a top end engine set up is also a good idea on these to get the best out of them (mpg/power) valves,injectors etc as over time they can drop off on the mpg/power front!
^this^
Low fuel pressure could, as has been said, be a factor, even something as simple as the wrong micron size on fuel filters can have a big impact. Also check any rubber fuel lines, they go bad from the inside and you get swelling which gives you a fuel restriction.
Sounds economical to Me 
Thats got some strange gearing, normally 12-1300 rpm @ 56 on a highway specced tractor…My last one had a reduction drive axle & that did 6-7mpg on a run out…
What Moose said get the top end re-set. The later version ones like that where fairly good on fuel, maybe try having it remapped too, I had a 420 remapped well the Guy I bought it off did & it was 8 plus…well it was chipped but I do know they can change the torque curve nowadays via a re-map, I’ve a version 2 thats been remapped.
How much to do a top end set up and what is involved?
Back on the FM today yippee
Redrooster:
How much to do a top end set up and what is involved?
Back on the FM today yippee
It used to involve a set of feeler guages, now it’s a little more complicated, basically it’s setting up valves, injectors and engine brake, as an engine wears they go out of adjustment
Cost depends on where you go 
it’s geared totally wrong for the work it’s on.
did a blind deaf bloke buy it?
did a woman buy it?
but seriously, change the fuel filter, the pre filter, and do away with the pump gauze.
I have driven two lorries that pulled the same. One was totally worn out. A full engine kit and it sang. The other was an Fl10 and the pump wasn’t opening fully. Drove the FM today and honestly it would have pithed (abv) all over the Fh420 in any gear at any revs. A pleasure to drive apart from the rough ride and p poor brakes.
set the rockers, change the filters, clean or remove the gorse & then see what it does. if its not running rough or taking a long time to turn over & start then its not an “rpm” sensor. mebbies dodgey injector bein w reg ad imagine its high km’s posibly fuel pump on its way out but do first recomendations first & let us know,
to do top end it means removibg rocker cover & setting the rockers which i have seen be a mile out.
Rough guide!!!
newmercman:
Redrooster:
How much to do a top end set up and what is involved?
Back on the FM today yippeeIt used to involve a set of feeler guages, now it’s a little more complicated, basically it’s setting up valves, injectors and engine brake, as an engine wears they go out of adjustment
Cost depends on where you go
truckers boy:
set the rockers, change the filters, clean or remove the gorse & then see what it does. if its not running rough or taking a long time to turn over & start then its not an “rpm” sensor. mebbies dodgey injector bein w reg ad imagine its high km’s posibly fuel pump on its way out but do first recomendations first & let us know,to do top end it means removibg rocker cover & setting the rockers which i have seen be a mile out.
We have had it two years and tbh it has never pulled well. The driver on it just revved the ■■■■ off it!!!
Recently had an occassional starting problem. It turned over like the stop solonoid was out. I know they dont have one. After 5 mins of trying it fired up. It gappened a few times more. Thats when they picked up on the fuel pressure sensor. They were going to change the high pressure pump but sid the lift pump instead. I was told if it happened again to turn the key off then on and wait 29 secs and continue till it fires.
will look into getting it set up at a local specialist. In the meantime will use tge FM. By the way it has done 700k.
if its taking that long to turn over look into a crankshaft or camshaft position sensor fault.
Only an odd time
truckers boy:
if its taking that long to turn over look into a crankshaft or camshaft position sensor fault.