Fuel tweak on 12 valve

[L18 CGL]

After many searches I think I have confused myself in completing this. Just to check the idiots guide is

1. Write down every change I do so I can attempt to reverse if it all goes Pete Tong

2. Take off 4 allen bolts at the top lift lid slightly and turn the toothed wheel approx 6 turns clockwise and tighten lid back up again.

3. Loosen the nut on top off pump in middle of the 4 allen key bolts and turn screw to point where I feel least resistance and tighten nut back up again.

4. Remove sleeve and crack off the 12mm nut on the bottom right of the OUT bolt ( be careful not to turn screw when loosening the nut) and turn the screw 1/8th of a turn and nip nut back up again.

Q. In step 3 does the screw get turned clockwise or anti-clockwise and same goes for step 4 which way do I turn the main pump screw?

 

[IRLGW]

Step 1 is to turn the toothed wheel 3 CLICKS/NOTCHES. To do this efficiently I recommend that you remove the throttle arm from the side of the head so that you can get to eye level with the toothed wheel. To access the wheel it is by removing a bolt on the rear facing part of the pump and you access via that inspection hole.
On My 93 12V manual the toothed wheel was near the very top of its thread and so I ended up about 30clicks down until I found a noticeable improvement. It is quite important to get your head right in and identify the wheel before starting to fumble around with a screw driver.

Step 2 is to release the diaphram needle locking screw while holding the allen head in place. Then initially turn the allen head 180 Degrees and tighten up again. If you are no impressed with performance the return it to its original position and try the least resistance method. Now Drive it and see how it feels. If it isn't too smokey and you need more power then go to step 3

Step 3
s to turn the main fuel screw 1/8 of a turn (45 degrees). I did this with the metal sleeve in place because if you note the direction of the slotted screw head and then release it with a long socket you can actually see how much it has moved. You just want to to release it until the socket moves and no more and then inspect it. You can then either hold the sleeve with your hand while turning the fuel screw 45 degrees past its original position.

On My 93 12V manual the toothed wheel was near the very top of its thread and so I ended up about 30clicks down until I found a noticeakle improvement. It is quite important to get your head right in and identify the wheel before starting to fumble around with a screw driver.

 

[L18 CGL]

And just to confirm which direction am I turning the screws in step 2 +3 when looking at them is it clockwise or anti-clockwise?

 

[stumog]

why do you do this mod? is it just to turn up the diesel rate to the engine. does this not just make the mpg worse. or does it make the car pick up quicker?

 

[AndycruiserguyLomas]

As I understand it, the pump mods alter the relationship between the pump and the speed which it speeds up the turbo at lower revs. I have done this on my manual 24V GS and it pulls like a train from any revs in any gear. The only thing I didn't do was the fuel rack adjustment as I tried the other adjustment first and it went very well without it. Adjustment of the main fuel screw can result in a lot of black smoke if its overdone.
If this is incorrect can anyone put me right.

Andy

 

[AndycruiserguyLomas]

By the was Stu, your pump has been checked on a proper test rig and is set exactly to spec (not modded in any way)

Andy

 

[stumog]

not thinking of doing as somebody did it to my landy and it now uses more diesel than a r32 golf driven like its stolen. so i wouldnt have that done. goes like stink lots of fun from the lights 528 and audi turbo dont know what went past them!!!

 

[adrianr]

When its done right it can be worthwhile

 

[Towpack]

An explanation here:

http://www.lcool.org/technical/80_series/1hdft_pump_adj.html

Rather than faffing about removing the bolt to access the toothed wheel I found it easier to remove the diaphram cover (4 bolts) and CAREFULLY lift the plunger/diaphram assy just enough so you can see and adjust the toothed wheel more easily. DON'T lift the plunger too far or it will not go back in without a pump strip.

 

[AndycruiserguyLomas]

Thats the way I did mine but you will probably have to modify an allen key to get all 4 out IIRC. Drive one thats been done and compare to standard settings I think anyone will think it's a worth while mod.

Andy

 

[IRLGW]

And just to confirm which direction am I turning the screws in step 2 +3 when looking at them is it clockwise or anti-clockwise?

You are turning everything clockwise!

For the toothed wheel assuming that you use a fine tipped screwdriver, you will want to turn the teeth away from the engine towards you body or normal clockwise if viewed from above. I would try and do it by unbolting the throttle cable arm and getting yoiur head right in to see the wheel. If you make a slip then as previously mentioned its a pump strip down. Mods are 100% worth doing. I did the minimum as above and its a different and safer truck. No more getting bogged down at junctions with heavy trailers. Speed wise you will notice bugger all difference.

 

[Chris]

I did mine, with the absolute minimum. 3 clicks on the cog and 1/8 of a turn in on the mass fuel screw. Mine would stall on really steep inclines when off road. As it got steeper and steeper the car slowed and then stopped altogether with the rev counter stuck on 1500 rpm. This it the torque converter stalling not the engine. The wheels weren't spinning - everything just came to a stop. After the tweak - well, nothing stops it now. Wheels might spin, but the TC doesn't stall. Over time I guess they just go a bit flat. Now you can tweak much more as we know, but a very small touch does make a big and beneficial difference to a flat engine.

C

 

[MikesVX80]

An explanation here:

http://www.lcool.org/technical/80_series/1hdft_pump_adj.html

Rather than faffing about removing the bolt to access the toothed wheel I found it easier to remove the diaphram cover (4 bolts) and CAREFULLY lift the plunger/diaphram assy just enough so you can see and adjust the toothed wheel more easily. DON'T lift the plunger too far or it will not go back in without a pump strip.

That guide is for a 24-valve (1HD-FT) model...does the same apply for the 12 valve (1HD-T) engine/fuel pump?