Diesel over fueling

[MuckyPup]

Hi folks, sorry i've been a tad busy of late but i need to pick some brains.

Typical 4.2 Diesel, bloody gutless below 1200rpm pull like a train at 2000rpm with 0.8bar boost but it then over fuels at 3000rpm to the extent it doesn't want to pull through to 4000rpm if it's pulling a load or in a high gear.
When i say over fuels i mean James Bond style black smoke screen.
It doesn't "look" like the pumps been tampered with so i'd of thought it's a fault of some sort or is this typical of over adjusting the main delivery screw?
I need to replace the internal springs anyway, so while i'm in there i might as well be looking for any other faults.
(It's got the nose up low rpm problem but a pusher pump doesn't help)
Any thoughts anyone?

Starts fine, small puff of smoke when blipped, typical puffs of smoke climbing rocks, pulls great between 2000 and 3000
Smells a bit, makes your eyes sting a bit, typical bruiser really.
Obviously it's rare this is any kind of problem, but I want to fiddle and improve the low down flat spot but don't want to fiddle until I get rid of this fault first.

 

[Shayne]

Sounds to me like its struggling to breathe , a K&N air filter should make difference .

 

[MuckyPup]

Taking the filter out, or leaving the lid off makes no difference. Boost is fine, 0.8 all the way from 1200 to 4000.....

 

[Shayne]

What i'm thinking is fuel can't burn without air , wouldn't matter at a parked test but on the move far more fuel will be pumped in .

 

[Lorin]

This might help with the idling issue http://forum.ih8mud.com/index.php?threads/1HD-T-idle-drop-when-facing-upwards-FIXED.597607/

 

[MuckyPup]

The pump springs are next on my shopping list, I tried the push pump ages ago and it made no difference to the Rev drop.

 

[Towpack]

If the main fuel delivery screw has been over 'tweaked' you will get similar symptoms. It affects fuelling across the range but is biased towards the top end/redline. If it's just started behaving this way then it obviously must be a fault. On the 24v versions there are adjustments that can be made for low down and mid range fuelling and grunt http://www.lcool.org/technical/80_series/1hdft_pump_adj.html but not certain if these relate to the 12v models. Unless the air filter is really dirty it's unlikely to be the problem. JMO

 

[MuckyPup]

It's not a new fault, it's always done it so I'm going along that line too, I'm sort of assuming some numpty has fiddled with the main screw. Boost was only about 0.5 bar when I got it so there's every chance it's been fiddled with.
hopefully get the BEB'S done this weekend and have a fiddle myself.

 

[Shayne]

Turn the fuel down to get a better burn or turn the air up to get a better burn - same difference but one gives more power .

 

[fridayman]

How many miles have the injectors done? And how many miles has the fuel filter done?

 

[MuckyPup]

Lol, since I'm now at maximum boost Shayne are you sponsoring the intercooler to crank it up some more?
Besides, it is actually possible to over fuel a diesel and lose power, especially if you ruin the burn like this is. All its currently doing is putting egt through the roof.
injectors have done 150k so could do with a service, forte flush certainly made no difference.
fuel filters done about 6k, didn't improve the nose up dying either but then neither did a pusher pump...

 

[Shayne]

That's what made me say K&N i drive a 1kzte 90 but i've upped the boost on the turbo , upped the fuel added an intercooler and a 3" exhaust , trying to get the mix right proved impossible until i changed the air filter .

 

[Towpack]

Increasing the boost (getting more air in) will help burn the extra fuel being injected and give more power but increasing the boost to any degree will markedly increase the intake air temp, hence the need for an IC. Just adding an IC without adjustments will actually lose some boost as there'll be a slight pressure drop across it. Unless you're sure your turbo is in absolutely tip top condition, personally, I'd be wary of increasing the boost pressure on a unit that's done 150k. JMO

 

[MuckyPup]

First diagnostic step is remove the air filter, ive seen so many "clean" filters ruined by water, just sitting in a damp garage can knacker one.
hence why I already tried it, and left the lid off the air box incase the snorkel was restricting it...
as good as k&n's are and as much as I like them you have to be the first person I've met who could out breathe a new standard filter on any vehicle.
I've known some restrictive air boxes in my time but never a new standard filter, that's why k&n rarely show the figures for zero milage filters, they're only marginally better until the paper filter clocks a few thousand miles...

 

[Towpack]

Had a poor experience with a K&N on a Fireblade years ago so I wouldn't touch one with a bargepole personally.

 

[Shayne]

Mine replaced a fairly new paper filter and the difference was instantly noticeable , i still had to mess around with the fuel a bit to get a balance i was happy with but it was a case of better or not rather than bad or worse with the paper . I need to clean my filter because i can feel a slight reluctance at the top end of the rev range .

 

[MuckyPup]

The only k&n I ever had a problem with was on a bike too. A VTR 1000.
I ended up cleaning it and re - oiling it properly, fine after that.
I think the problem is that some bikes can't pull excess oil out of the filter and it throws the mixture.

 

[MuckyPup]

For people as sad as me who find this type of inches of water interesting; Www.bobistheoilguy.com/airfilter/airtest1.htm

 

[MuckyPup]

For people as sad as me who find this type of inches of water interesting; Www.bobistheoilguy.com/airfilter/airtest1.htm

 

[Dave2000]

I reported the idle issue on my car about 4 years ago here: http://forum.ih8mud.com/threads/odd-idle.371858/

I did all the usual test and confirmed pusher pumps do nothing to alter it at all in fact, they can actually disguise faults like a minor perforation in the diaphragm on the filter head. The conclusion was that the springs in the pump were the problem but I never actually got around to fixing it. Looking at the low cost involved and that it appears to be a '1 banana' job it has to be worth trying.

Never had any joy with the K & N, could be just the fine sand here but they clog waaaaaay too quickly, messy to maintain, and when you look at the OE offerings they are so easy, take it out and run it under the tap, leave it on the side to drain and refit...done! I keep a spare so just swap, then once dry gets put in a bag, and I take it with me when off-roading, never needed it though TBH, I can remove and tap out the sand and put it back, no oily mess blah blah..I assume you still have to oil them...it has been about five years when I used one in a TDi Discovery, so speaking from direct experience.

Hopefully sometime next week should see LC back on the road....do you know how hard it is to type with your fingers crossed?

regards

Dave