I have recently bought a 2004 Volvo FH12 460 Manual and a B train and put it into work here in New Zealand.
What i find unusual is the truck seems like it wont rev, so i’m after information from those of you that have or have had these trucks.
The truck starts and seems to run fine, it has no fault codes but it is reluctant to rev past the green band on the tacho in low range and will not run above it in high range… it does i think seem to be lacking power compared to other trucks.
So driving on the road, approaching a large hill running in the green band… I split down to increase the rpm so when the truck starts pulling up the hill it should be under power and drop down into its green band as we climb the hill…
But no… This truck SLOWS DOWN BEFORE THE HILL.
Its boost and fuel usage just drop off if you are above the green…
In neutral or with the clutch in, putting your foot to the floor brings the rev’s up to 2150rpm…
It makes for slow trips trying to fight the truck up into its green to keep moving all the time…
Truck is ex large fleet of lease units, and has an awesome service history… Some units i looked at had fortunes spent on multiple clutches, diffs, gearbox repairs and damages…
Truck has now done 760km.
The boost pressure sensor is a common fault, they can also go a bit flat if the fuel pump is worn
you really need the thing plugging in to check fuel and boost pressure are where they should be, also check the fuel filter in the bottom of the tank stack pipe, also the intercooler is holding pressure, check for play in the turbo, if all is ok a top end set up might improve things, I’ve done all the above with mine and then had a re map for good measure the old girl pulls well and I think it goes better than it did 8 years ago when I bought it
moose
It has been on the test computer at one shop who said nothing is wrong with it at all, They said no FH12 will pull above the green as its called torque limiting and is set in the computer, Moose does yours actually rev above the green or stop at the end of the green? This one literally stops accelerating at the end of the green, boost etc just falls off to nothing as if i had lifted my foot off the gas…
This shop also said that the jakes are fine, this model has three stage switch on the column, there is no difference between settings one and two, Setting one works, setting two is perhaps on holiday still… but there is a difference when you switch to three.
I can hear and feel a difference some times when in three, just like half the jakes are joining in and then dropping off… The spud, EGP? is working fine and i think i have a faulty Jake block…
Perhaps i never visit that dealer again…
Another shop said they suspect the boost sensor, they cleaned out the tank pickup and seem to understand what i mean about the jakes… I have not managed to get back to that part of the country for further diagnostics yet…
Its a nice truck, but this really worry’s me as i dont have unlimited funds being a new O/O… Well really who does anyway!
But a truck that wont rev, that the shop says is factory standard… No shops in New Zealand do remapping… But there is a add on block available… but if the computer wont allow it to rev above the green… the block wont help…
Get them to remove the torque limiting by re programming the computer? Maybe only a Volvo dealer can re programme this. I had this on my Scania but only rev limited for the first 30 seconds after starting the engine.
I presume it’s not a dirty turbo as it boosts ok up to the rev limit?
Posted by an interested amateur owner, I have no spanner experience.
It has been on the test computer at one shop who said nothing is wrong with it at all, They said no FH12 will pull above the green as its called torque limiting and is set in the computer, Moose does yours actually rev above the green or stop at the end of the green? This one literally stops accelerating at the end of the green, boost etc just falls off to nothing as if i had lifted my foot off the gas…
This shop also said that the jakes are fine, this model has three stage switch on the column, there is no difference between settings one and two, Setting one works, setting two is perhaps on holiday still… but there is a difference when you switch to three.
I can hear and feel a difference some times when in three, just like half the jakes are joining in and then dropping off… The spud, EGP? is working fine and i think i have a faulty Jake block…
Perhaps i never visit that dealer again…
Another shop said they suspect the boost sensor, they cleaned out the tank pickup and seem to understand what i mean about the jakes… I have not managed to get back to that part of the country for further diagnostics yet…
Its a nice truck, but this really worry’s me as i dont have unlimited funds being a new O/O… Well really who does anyway!
But a truck that wont rev, that the shop says is factory standard… No shops in New Zealand do remapping… But there is a add on block available… but if the computer wont allow it to rev above the green… the block wont help…
Thought’s?
When I first had mine the engine brake was poor, after checking all possible parts a crack was discovered in the valve block under the rocker cover, this was changed and the jake/engine brake worked much better, the air/electric control valve on the side of the engine block can also give problems, including the engine brake sticking on! (these are quite expensive and can be located at either side of the engine block depending on age) mine has only off or 2 other settings as the switch is a 2 position one located on the dash (mine is an early version 2 on a 2002 plate)
I don’t just remember what the truck will rev to, but I do know as a rule the d12 engine as standard does not rev fast from say 700 rpm to 2000 rpm when under load, a re map will alter this and the engine does feel much more responsive which also means you can change up through the gears much faster, you don’t need to rev it as hard before it will take the next gear and keep pulling, and on the plus side the fuel economy has improved as long as you don’t thrash the thing!
just another thing where is your boost pressure gauge reading? as mine is pulling the gauge is right off the end of the clock, it will stay there right down to 1000 rpm
moose
I am going to get the valve block for the jakes replaced, hills with not much jakes is not great… Intermittent operation tells me there is something not right… the shop can change wiring if required while they are doing it.
Im not so worried that the truck is slow to rev, but it wont rev past the green, so that’s 1650rpm i think, just stops flat…
Boost gauge when pulling is right off the end, hit the end of the green on the rev counter, boost drops off even with foot to the floor…
To me, it feels like its in some kind of protection mode… Perhaps the boost sensor is out of wack so the computer drops fuel off at the end of the green to protect the engine■■?
The shop pc showed no fault with the sensor, but again… that computer or perhaps the mechanic may be the problem with that…
Grrrrr
I may have to pull the ECU and fly to the uk to get it remapped…
there is a well known chap in the uk who does re maps,(incl mine) and now also a plug an play tuning box, they are not cheap but do work! scan-tune.co.uk
Moose:
there is a well known chap in the uk who does re maps,(incl mine) and now also a plug an play tuning box, they are not cheap but do work! scan-tune.co.uk
I have just found a couple of places that say they do truck re-maps… but experience wont be like the uk here…
fh12’s in the uk have also an exhaust brake which is located on the end of the turbo, it is used when the engine is cold to warm the thing up faster and also for emissions, you can hear it working as you start up from cold whilst the park brake is on, switch it off and the exhaust note will change
Ok, the exhaust spud thingie has been checked and is said to be in good operation.
Jakes, not coming on fully. Better than sticking on i guess!
Retarder, Sadly not fitted on my unit…
Daft thought could there be a problem with the tach sender on the gearbox VOLVO have had a bad batch of senders in europe the sender does control the revs as well as the tacho
ianto:
Daft thought could there be a problem with the tach sender on the gearbox VOLVO have had a bad batch of senders in europe the sender does control the revs as well as the tacho
Its got to be something silly like that… a sensor working but not correctly.
Interestingly the rev counter is slow to respond also, rev the truck up and down, then the rev counter goes up and down…
Its hard as i have not driven/owned a Volvo before, and i dont have one i can compare it to…