2.5 DI Engine stutters on rev up, revving up problems

[peteMK2C]

Hi guys,

I have some trouble with my DI camper. I have not been driving around all too much the last couple of years which may have caused the problems.

The engine starts quickly and is idling fine but when I'm revving up the engine fully, it stutters somewhat below the max rev it should reach.
Sometimes it gets to the max rev after 4 to 6 seconds and sometimes it even reaches max rev quickly in one step like it should be.

While driving there seems to be less power and also frequent stuttering when trying to drive the gears fully out to max speed.

I can't adjust the correct idle speed of 850 rpm either. If I do, the engine tends to starve and go off. Also after fully revving up, the engine comes down but tends to keep idling with somewhat higer rpm. If I then try adjusting the idle screw to get down to 850 rpm it will suddenly come down and again tend to go off. It's as if there is some bump in between too high idling and engine going off.

So far I have done:

- cleaning of the Tank (had brownish sticky residues on the bottom)
- new diesel filter
- new fuel hose
- tank filled up with fresh diesel
- added 250 ml Liqui-Moly diesel cleaner in tank

Also, I shoud mention that last year I had the filter assembly changed and fitted an universal screw on assembly because the primer pump on the original Lucas assembly was defective. Doing that I screwed in a standard pipe adapter for an 8mm fuel hose on the Lucas CAV pump. Usually there is a fuel hose adapter for a 6 mm hose with some sort of plastic sealing. I don't know if this change may cause problems with the pressure sensor in the Lucas CAV.

I'd appreciate any help or experience on this issue.

Thanks!

ps: please excuse if my english is not perfect, I'm from Germany.

[Mr twin choke]

It sounds to me like fuel starvation of some sort. Can I ask if the fault was happening only after changing the fuel filter with an aftermarket one? If so it's a likely cause if it is not allowing enough fuel to the injector pump.
If it was happening before the change, I would be suspicious of the injector pump having an internal fault. Since diesel fuel is hygroscopic (absorbs moisture to save you googling it), with lack of use it's possible that there may be internal corrosion inside the injector pump. Due to it being mechanical rather than electrical fuel injection, the injectors require a specific amount of fuel pressure to crack them open or they just stay closed giving you misfiring, rough running and lack of power.

For anyone inexperienced with fuel injection, please remember the risk of pressure injection when working with fuel injection systems. It's not worth the risk of a hospital visit if you don't have sufficient experience to work safely.

[peteMK2C]

Thanks for replying Mr twin choke!

I changed the filter assembly because the system has been starting to draw air and. The engine was starting nice but then immediately starving out due to the air in the fuel line and I was suspecting the defective hand pump. Also I wanted an easier filter change with affordable screw on filters.
I don't exactly remember if the issue with idling rpm and max. rpm was before that change. I still have the original delphi filter assembly. So if the problem won't disappear, I shall try it again with the delphi assembly thought.
Other than that it might as well be an internal issue with the Lucas CAV because I really did not drove very much in the last couple of years.