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Adjustment on 1HD-T fueling


Super Moderator
Feb 24, 2010
Country Flag
Well, I have to say that I don't generally twiddle with things that I don't understand, but spurred on by the pretty poor performance of mine on the way to Scotland, I thought I'd make a couple of simple adjustments to the fueling. I followed the guide on LCOOL and gave the top screw a half turn clockwise and the toothed rotor two clicks likewise. Now, I am not pretending that it goes like a rocket sled, but I do think that it has made a difference. Only been down the road but it seems to have a greater sense of urgency. I shall give that a go for a bit and see. I have no desire to wind up to 200 bhp and 3 mpg but the ability to over take a tractor would be nice.

As usual words or warning, encouragement or wisdom appreciated. I did not make the third adjustment.

Did you notice any change/increase in the amount of smoke being generated at full pelt, Chris? Difficult to tell in bright sunlight when you're in the driver's seat, I know... :auto-layrubber:
What's full pelt Andrew? I got up to nearly 40 mph and it seemed fine. Don't think I am allowed to drive faster than that on my licence am I? Only just turned the screw, been about a mile so have not had chance t give it the beans yet. I revved it on the drive and it looked perfect. I'll let you know. Like I say, it hasn't ripped my face off with acceleration but it feels just that bit different. Got to nip out later will give it some clog then.

When I first got my 80 series the motor was as flat as a pancake. No pull below about 2200rpm.
Always seemed to struggle to climb hills so I did all the adjustments on the LCOOL site.

I put 3 clicks on the toothed rotor. Six, yes 6, turns on the top screw, still no smoke out the back. Also fiddled about with the diaphram as mentioned on LCOOL to move to point of least resistance.

Made a bit of a difference but still felt a bit sluggish with a bit of a flat spot at around 1800rpm.
Also found that as it's a manual with a fairly slow gearbox I was chasing it down the gears on steeper climbs.

What did make a huge difference was one turn on the main fuel screw. Now it will pull from about 1000rpm all the way up, no hesitation, no flat spots. Makes me believe all the talk on the forums about buckets of torque etc. I'll have to back off the top screw adjustment now as it smokes a bit on hard accelleration.

It's now a different truck, eager to go, pulls well and still gets 26mpg overall.

Richard, where is this magic screw of which you speak? Don't want to twiddle too much too quickly, but I have noticed a difference in the mid range but bottom end's still quite flat. Overall so far, it feels smoother when it pulls like better fuel delivery.

You're will be a bit different than mine as you're is a 12V model.



The screw is a 6cm long threaded rod with a locknut and a crimped ring to limit adjustment. The locknut is a 12mm. You need to screw it in to increase the fuelling.

I found the easiest way to adjust was to remove the whole lot, put it in a vice and move the lockring one turn anti-clockwise then refit.

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I shall take a peek.

Cheers Richard.

Are these things being 'leaned off' to get them through the emission tests at MOT time ???

I used to have to do that with an old Volvo I had. If I forgot to re-set it after the MOT it would die as I pulled out of a road junction :shock:

Just a thought.

AFAIK it takes clouds of smoke for an older diesel to fail not just a bit.
I have turned my pump up quite alot as mine is a auto and you dont get the same power in my opinion. I have only turned the screw in on the rear of the pump,the screw that someone is showing you in the pic cris. Makes a massive difference. I will have to have a play with the one on the top of the pump by the sound of it. Yes mine does smoke more.Not to much of a big deal but you can keep turning it down untill you get it right. Only turn the screw quarter turn at a time. U may have to take the locking and off it first as they are set so you carnt mess with them.
Hiya Karl. Alright mate. Not chatted for a bit. We still need to sort THAT thing out when we can. Whilst we have some Summer left Ha Ha.

Interested to hear about the fuel screw. I will need to look into that. I don't know why people would go to the trouble of doing those three adjustments if all you needed to do was turn that one. Mine is better for the adjustments, Not startling but better. I still have an idle problem where the whole engine rocks and shakes the car sometimes. I have heard that this might be a leaking injector. Dunno if pulling them is easy or worthwhile. You can pull spark plugs and tell a lot about you engine, can you pull injectors and tell if there is problem in a similar manner?

The screw being pointed to is the main Load Volume Screw that regulates the fuelling right across the rev range.

I generally find that most trucks are under fuelling as the pumps get tired so always start by tweaking the main LVS and then move on to the finer adjustments if time and budget allow.

The adjustments on the LVS are very sensitive. Ideally aim for around 1/8th to 1/4 a turn at a time and be very careful to hold the adjustment as you nip up the locking nut - I have an S shaped ring spanner that is ideal for that.

Ideally you are aiming to boost the fuelling to the point that it is just starting to smoke and then back it off a little - black smoke is unburnt fuel from over fuelling. If you over fuel too much the head temps go up as well which leads to all sorts of problems.

When you start to play with the fuelling always make sure that you keep a log of the changes that you make - I have had one or two customers tweaking it too much in different directions and then struggling to get it back to sensible performance.

The other thing to bear in mind is to ensure that your pump, injectors and valves are all in good condition and performing as expected - if the truck isn't running right and then you try to boost the fuelling to compensate it can also lead to problems.
Well like a twit, I ignored my own advice and went fiddling. To save my blushes, I shall miss out how it happened, but safe to say I screwed up and ended up losing the original settings on the main fuel screw. Well the beggar wouldn't start. Not a cough for an hour or more. Despite some help from Julian V it still wouldn't start. I cracked a fuel line, no fuel. I pumped the primer, no fuel. In the end, I took the fuel line off and pumped. Still no fuel. The fuel shut off solenoid was working too. But no derv to be seen. In the end fearing flattening the batteries and burning out my starter, I poured some fuel into the hose and shoved it back onto the filter. Whoosh, it started this time. Bit smoky and rough but it settled down. A few runs around the block and I got it back to where it was. As the idle goes up and down with the screw, I just set the revs back to where the were. But in the meantime, I got a glimpse of how much more power there is in there. That's what I have been missing. So tools away. Glass of wine and wait for the weekend when I will try again for that small increase in get up and go. But interesting that the filter primer pump seemed to do nothing and the fuel pump didn't seem to want to raise any fuel.

Is this a known issue? Is my fuel pump part of the problem of low power?


Got the message. Glad you got there in the end.

I have found some primer pumps to be very weak although I wonder if it is due to air getting into the pipes (worth getting a short length of see through pipe to check this).

The lifter side of the injection pump can get tired which is why we fit the Walbro pumps down near the tank to help things along but I doubt this was your problem.
Thanks Julian. Well the old tricks are the best, eh? That seemed to pull through once the engine was running. I never hear the pump on this thing. Is it electric? Where is it anyway?

I haven't looked for it yet so have no idea.

The lift pump is part of the injection pump assembly, so it has to suck it all the way up from the tank! Not hard to see how it could get tired and need some help :)
Ahh, it's a lift pump. Thanks Jon. Didn't know that. Still feeling my way around the big bits. That has to work pretty hard then. Especially if you have a blocked strainer or cap etc.

I shall be more careful next time. It all started off pretty well. Still, running fine again. I think that where is is (was) set, it was barely running. Another twist anticlockwise and the engine nearly stops. I know more turns = more fuel, but getting up to speed so far must be using far more than it should do. With a little more 'go' I can get through the gears more quickly. Time will tell.