300 Tdi Power Loss

[oneten110]

Picture the scene, doing a steady 60 mph, truck loses power for say half a second then proceeds as normal, but this happens a couple of times a minute. This is when there is less than quarter of a tank of diesel.

When the tank is full, no such problem, but if I try to accelerate from 60 in 4th, the engine does not accelerate at all, revs do not pick up. If I drop down a gear, it accelerates initially then just stops accelerating and starts to slow down. Lift off and it goes back to cruising at 60 with no trouble at all. It will accelerate on downhill slopes, but the slightest uphill and it struggles to maintain speed. The turbo boost gauge says that the turbo is boosting to 16psi initially then it just falls away as the revs die off.

Anybody got any ideas please?

Edited December 18, 2005 by western

[western]

Possibly the lift pump, have a read of this in Tech Archive

Edited December 3, 2005 by western

[BogMonster]

There might be some sort of problem with the fuel pickup in the tank, maybe getting air in to the system? It sounds odd.

Apart from the fact it only happens with a 1/4 tank I would have said blocked fuel filter, as that can cause the same thing. I actually had that happen to me a couple of weeks back in a 300Tdi 110, was driving out to the airport, thought when I left that it was slightly sluggish but put it down to the 40mph headwind on the airport road, by the time I was halfway there it was staggering up a hill in 3rd that should have been possible in 4th or 5th, and by the time I was nearly there it was down to 15mph!!! If you backed off to no throttle then floored it you would get a burst of initial acceleration then it would die away, same if you stopped (which we did several times) it would rev to about 3000rpm then die back to about 2300-2500 and cough and judder. Scrounged a fuel filter from somebody, fitted it in the car park (gravel car parks absorb diesel quite well ) and 100% normal service resumed.

I'm pretty sure it will be fuel starvation of some sort so I suggest you check right the way through; i.e. tank pickup, sedimentor bowl (if fitted), fuel filter, lift pump, and check all the pipes are OK and not crushed/kinked. But most of these things would be the same regardless of whether the tank was empty or full, other than that I give up I'm afraid

It isn't likely to be the cause but while you are at it check the throttle cable adjuster hasn't unwound itself, mine did that the other day and a tweak up restored about 30bhp

[oneten110]

Thanks for the tips chaps, The tank is a recent fitment, all the pipes are new, the pickup is new, the return is new, as is the filter, there isn't a sedimenter fitted. I have only recently installed the engine, as a replacement for a V8. That is how I can vouch for the newness. I have also had the accelerator cable problem, a couple of times. Baffled me first time, but not since, it took a while to prevent further occurences.

I'll try the filter, because you never know what muck has been swilling around in the bottom of a tank after a change from petrol to diesel. Trouble is not really knowing the history of the engine except that it came out of an insurance write off, quoted as having done 67,000 miles and seems quite fit, it is definitely "tighter" that my other 300 Tdi that has done 250,000+ miles.

But before using it, I changed the timing belt and pulleys, checked the valve clearances, flushed out the oil system and dropped the sump to clean out any gunge therein, changed front and rear crank seals, that sort of stuff.

Tis a funny thing (on an entirely different subject) but I was once offered a 3 year posting to your locn to look after the entire fuel installation, but it was unaccompanied and I was just married.

[JST]

my 110 had the same problem going petrol to diesel conversion. full tank no probs. 1.4 tank no power.

the problem was the submerged electric pump that had been in for the petrol engine. ditched this and i ended up using a fuel return pipe as the pickup from the tank, with the return no just going to the top of the tank.

[oneten110]

I have removed the original fuel pump and done as you have with yours, picking up from the pipe that is attached to the sender unit and returning to a new pipe installed in the top of the tank where the original pump used to reside.

[was a nice truck?]

A mate of mine had the same/similar problem turned out to b e the brass gauze on the pick up pipe in the fuel tank. These are only fitted to petrol vehicles it seems .His solution was to ditch the gauze knoeing he had a good fuel(diesel)filter fitted in the line. Hopr this is of some help DW B)

[headhunter]

I have removed the original fuel pump and done as you have with yours, picking up from the pipe that is attached to the sender unit and returning to a new pipe installed in the top of the tank where the original pump used to reside.

Is the tank a sealed system?

I used to have similar problems years ago when the pump caused a vacuum in the tank because the filler cap did not have a vent in it.

It was ok with plenty of fuel in the tank, but as the fuel level lowered the remaining air/void became a vacuum which reduced the flow of the remaining fuel.

John

[JST]

i did it the opposite way around to that. the bit that goes in the top of the tank with the long metal arm going down that is meant to be the spill return i used as the pickup. no guaze on end either.

[oneten110]

Right then, It all came to a conclusion last night on the way home from work. Dawdled through the fiasco that is the A41, onto the North Circular, the truck feeling particularly flat on acceleration. Paused at the traffic lights before the start of the M1, Nailed the accelerator and errr nothing, it struggled up the incline onto the M1 and was flat out at about 45 MPH. By the time I passed Mill Hill station it was down to 35, and by the time I got it into the carpark at Scratchwood services it would barely tick-over.

The only bit of luck was having a spare filter in the truck. Changed it, more in hope than expectation and instant success!!

The filter I removed was less than a month old and had done less than 1,000 miles. SO I wonder what caused such a sudden demise?

Todays problem? The alternator died! Again, less than a month old. Harumph!!!

Edited December 4, 2005 by oneten110

[Porny]

The filter I removed was less than a month old and had done less than 1,000 miles. SO I wonder what caused such a sudden demise?

Was the old filter full to the brim with diesel when you removed it???

If not, then the lift pump is probably on the way out.....

Ian

[BogMonster]

If not then it probably wouldn't have bled the new filter though...

It proves that just because something has been replaced recently doesn't mean to say you should rule it out! Glad it was such an easy fix in the end

Still don't understand why only happening with 1/4 tank of fuel though - maybe a combination of the blocked filter and the lift pump having to work harder to lift fuel from an almost empty tank??? Odd

[oneten110]

It was getting dark as I changed the filter so I couldn't really tell if it was full or not. In truth I don't think it was, but I have got a new lift pump on the way anyway.

I will let you know what happens next time I get below a quarter tank. I hope that it was all part of the same problem, but we shall see.

[JST]

i hope that done the trick.

[oneten110]

All seems well now, I have run a few tankfuls through the old girl and taken it so deep into the red section of the gauge it was near running on fumes when I came to fill up. All of this with no repeat of any of the problems previously experienced

[siggy]

It did the same on mine I stuff in a bottle of the stp diesel injector clean and drained the fuel filter and it hasn't occurred since

throw some injector cleaner in every 3000 miles (when you do the oil change as she like them as well)

[oneten110]

Thanks for the suggestion, I run it with millers diesel aid all the time, IIRC one of the functions of that is to clean the injectors

[Broke1stDay]

16 years later...  this thread really helped!  Thanks all!