fuel pump "tuning" debunked.

chapel gate

Well-Known Member
Supporter
Promoted Company
I am in england
May 26, 2014
3,854
2,338
113
near, leek staffs.
after a recent post about fuel pump tuning and a predictable response of "better take it to a pro mate" I thought I might shed some light on what is often clouded in mystery and myths. I'm by no means an expert but here are my findings. feel free to correct or add, particularly the aussi lads as they are pretty much the experts on this.

first off you really need at least an egt gauge and preferably a boost gauge as well. some of the "pros" will claim they can tell off the amount of black smoke coming out the back, I find this hard to believe as ive had mine running pretty clean on the smoke front but reaching high egts on long uphill drags. I suppose if the main fuel screw is just turned a little and the other adjustments tweaked a little 9 times out of ten it will be fine...

anyway.

strictly speaking its not actually the fuel pump that is being tuned, the only adjuster on the fuel pump is the main fuel screw, this just fire more fuel In there, period. were playing with the boost compensator, some cruisers don't even have this on, but we have a turbo so we do. it sits on top of the fuel pump and its purpose is to increase the amount of fuel In relation to boost. it does this via the pipe that comes off the top that allows the manifold pressure created by the turbo to overcome the spring and push the fuel (aneroid) pin down. the profile of the fuel pin is followed by the, yup, follower pin..

pump.png
so if you imagine the follower pin sitting against the fuel pin as the boost pressure increases the fuel pin moves down, allowing the follower pin to extend into the recessed section, as the follower pin is extended more into the recesses more fuel is allowed in, until the flat section is reached and then ultimately fuel is cut back when the full diameter of the pin is reached again.
you will notice a section of the profile is more aggressive than the other, as mentioned on other forums when you turn the diaphragm this turns the fuel pin to allow the more aggressive side to face the follower pin, allowing more fuel in, and earlier in the rev range.

pump1.jpg
the fuel pin inserted back in its housing.

pump2.jpg
this picture shows the spring and star wheel, at the bottom is the fuel pin attached to the diaphragm.
some suggest cranking the star wheel right down, this reduces the tension on the spring allowing the fuel pin to move with less boost, the problem being you will reach the fuel cut off part of the fuel pin too early, so at say 2700rpm the motor will be starved of fuel, power will drop, boost will drop and egts rise.

bottom left is the cam that the other end of the follower pin sits against, this pushes a lever in the fuel pump that allows in more fuel. a little match mark can be seen where the pin sits.

pump4.jpg


close up of spring and star wheel, the wheel can be accessed from the right hand side with a flat head screw driver through the hole left once the nut is removed.

pump8.jpg




the follower pin inserted back into the bush it sits in, there is also a O ring to stop diesel finding its way into the chamber the fuel pin sits in.

pump9.jpg


here is the cam that we saw before installed. the spring and nut in the foreground screw in and keep the cam against the follower pin, and therefore the follower pin against the fuel pin.

pump10.jpg


here is the assembly on its side. in the middle is the cam, to the left you can just make out the coiled spring. as said before as the profile of the fuel pin is followed the cam pushes against a lever in the pump adding and reducing fuel. to the right is the main fuel screw with the anti tamper sleeve still intact. again, screw this in or out and it pushes on a lever in the pump increasing or reducing fuel. at the bottom is a idle up cam for iirc the power steering, again this pushes against a lever in the pump.. the hole on the left is where the throttle pivot pops through.

pump5.jpg


diaphragm and fuel pin back in place, note the marker pen mark so I know the most aggressive profile of the fuel pin is against the follower.

pump3.jpg


here is the top of the whole unit, the bit that can be seen in the engine bay with a nut on top, when the nut on top is turned it rotates the tapered cam which presses the fuel pin further down its profile. this introduces fuel earlier in the rev range so the turbo spools up sooner, increasing low down response. the match mark can be seen. turn the taper so that the thickest section sits on top of the fuel pin.

pump6.jpg

again a marker pen to mark the thickest part of the taper before tightening the nut back up.

pump13.jpg


everything back together.

pump14.jpg


then bolt the lot to the top of the fuel pump.

so, there are the tweaks to liven up the old girl. all of this can be done without taking the unit off. if you've got a boost gauge and egt gauge fitted, do the adjustments and turn the main fuel screw up an eight of a turn, turn the boost up to 15 psi.

go for a drive. max safe egts are 1250f, higher egts are normally seen towing and on long up hills. so its a compromise of more fuel and drivability, you don't want to fly up to the 1250f mark and constantly be backing off the throttle.


fuel pin.jpg

here is the angle I ground on the fuel pin on my truck so that it slots back in, its needs to be as smooth as possible, I finished it off with polishing compound and the dremel. some very fine wet and dry etc would do too. before you attempt to put the pin back in push the follower pin back first as it can over extend once the fuel pin has been removed.

fuel pin 2.jpg



fuel pin2.jpg


if you want to tweak things to perfection, mark the pin with marker pen, after a bit of driving around you will be able to clearly see the position of the follower pin on the fuel pin.

fuel pin 3.jpg


a view of the follower pin with the fuel pin removed.

fuel pin 4.jpg


something worth doing is taking the sharp edge off the threaded hole top of the picture, it is sharp and could damage the diaphragm when removing and reinstalling it.

that's it really, once you get the hang of it all this can be done in about 15 minutes.

the next step is grinding the side of the fuel pin that is in contact with the follower pin, this will allow more fueling where you choose it to be.

So, finally got round to fitting my intercooler.
power was great above about 2400 rpm. Below this it felt a little lean, so I ground the fuel pin on the lower tapered section of the profile, adding more fuel lower down in the rev range.
IMG_20191020_132737.jpg



What a difference.

I'm reaching max boost, 15 psi, at 1800 rpm. Pulls much better now below 2400rpm.

I'll keep playing.. :)
 
Last edited:

hopeless wanderer

Well-Known Member
I am in england
Aug 21, 2014
726
457
63
ooop North
after a recent post about fuel pump tuning and a predictable response of "better take it to a pro mate" I thought I might shed some light on what is often clouded in mystery and myths. I'm by no means an expert but here are my findings. feel free to correct or add, particularly the aussi lads as they are pretty much the experts on this.

first off you really need at least an egt gauge and preferably a boost gauge as well. some of the "pros" will claim they can tell off the amount of black smoke coming out the back, I find this hard to believe as ive had mine running pretty clean on the smoke front but reaching high egts on long uphill drags. I suppose if the main fuel screw is just turned a little and the other adjustments tweaked a little 9 times out of ten it will be fine...

anyway.

strictly speaking its not actually the fuel pump that is being tuned, the only adjuster on the fuel pump is the main fuel screw, this just fire more fuel In there, period. were playing with the boost compensator, some cruisers don't even have this on, but we have a turbo so we do. it sits on top of the fuel pump and its purpose is to increase the amount of fuel In relation to boost. it does this via the pipe that comes off the top that allows the manifold pressure created by the turbo to overcome the spring and push the fuel (aneroid) pin down. the profile of the fuel pin is followed by the, yup, follower pin..

View attachment 126624so if you imagine the follower pin sitting against the fuel pin as the boost pressure increases the fuel pin moves down, allowing the follower pin to extend into the recessed section, as the follower pin is extended more into the recesses more fuel is allowed in, until the flat section is reached and then ultimately fuel is cut back when the full diameter of the pin is reached again.
you will notice a section of the profile is more aggressive than the other, as mentioned on other forums when you turn the diaphragm this turns the fuel pin to allow the more aggressive side to face the follower pin, allowing more fuel in, and earlier in the rev range.

View attachment 126625 the fuel pin inserted back in its housing.

View attachment 126626 this picture shows the spring and star wheel, at the bottom is the fuel pin attached to the diaphragm.
some suggest cranking the star wheel right down, this reduces the tension on the spring allowing the fuel pin to move with less boost, the problem being you will reach the fuel cut off part of the fuel pin too early, so at say 2700rpm the motor will be starved of fuel, power will drop, boost will drop and egts rise.

bottom left is the cam that the other end of the follower pin sits against, this pushes a lever in the fuel pump that allows in more fuel. a little match mark can be seen where the pin sits.

View attachment 126640

close up of spring and star wheel, the wheel can be accessed from the right hand side with a flat head screw driver through the hole left once the nut is removed.

View attachment 126641



the follower pin inserted back into the bush it sits in, there is also a O ring to stop diesel finding its way into the chamber the fuel pin sits in.

View attachment 126643

here is the cam that we saw before installed. the spring and nut in the foreground screw in and keep the cam against the follower pin, and therefore the follower pin against the fuel pin.

View attachment 126644

here is the assembly on its side. in the middle is the cam, to the left you can just make out the coiled spring. as said before as the profile of the fuel pin is followed the cam pushes against a lever in the pump adding and reducing fuel. to the right is the main fuel screw with the anti tamper sleeve still intact. again, screw this in or out and it pushes on a lever in the pump increasing or reducing fuel. at the bottom is a idle up cam for iirc the power steering, again this pushes against a lever in the pump.. the hole on the left is where the throttle pivot pops through.

View attachment 126645

diaphragm and fuel pin back in place, note the marker pen mark so I know the most aggressive profile of the fuel pin is against the follower.

View attachment 126646

here is the top of the whole unit, the bit that can be seen in the engine bay with a nut on top, when the nut on top is turned it rotates the tapered cam which presses the fuel pin further down its profile. this introduces fuel earlier in the rev range so the turbo spools up sooner, increasing low down response. the match mark can be seen. turn the taper so that the thickest section sits on top of the fuel pin.

View attachment 126647
again a marker pen to mark the thickest part of the taper before tightening the nut back up.

View attachment 126648

everything back together.

View attachment 126649

then bolt the lot to the top of the fuel pump.

so, there are the tweaks to liven up the old girl. all of this can be done without taking the unit off. if you've got a boost gauge and egt gauge fitted, do the adjustments and turn the main fuel screw up an eight of a turn, turn the boost up to 15 psi.

go for a drive. max safe egts are 1250f, higher egts are normally seen towing and on long up hills. so its a compromise of more fuel and drivability, you don't want to fly up to the 1250f mark and constantly be backing off the throttle.

pizzas here.. will add more later.

Great write up :) Thanks...I'll be watching this with great interest as ill be doing this early next week.
I watched a you tube vid of a guy doing a fueling adjustment and he suggested grinding the follower pin at an angle to allow you to push it back into place. Now i know that removing the pin cover means i dont have to do that.
*Edit
Do you think the follower pin is short enough to allow replacement of the fuel pin if the cover is removed ?
 
Last edited:

Firewout

Well-Known Member
I am in belgium
Oct 3, 2014
797
418
83
Antwerp
Garage
I watched a you tube vid of a guy doing a fueling adjustment and he suggested grinding the follower pin at an angle to allow you to push it back into place.
Afaik the fuel pin is grinded and not the follower pin. The grinded edge makes it a lot easier to put the fuel pin back in place.
With a straight edge, the follower pin blocks the insertion of the fuel pin and with the grinded edge, it works like the latch in a door lock and the follower pin is pushed inwards, allowing the fuel pin to pass.
This makes life easier when you want to play with the adjustments. ( or when you're as curious as I am and you pulled the fuel pin out just to have a look and couldn't get it back in place.....)
 
Don't like the adverts? Remove them by becoming a supporting member.   Click here

chapel gate

Well-Known Member
Supporter
Promoted Company
I am in england
May 26, 2014
3,854
2,338
113
near, leek staffs.
Great write up :) Thanks...I'll be watching this with great interest as ill be doing this early next week.
I watched a you tube vid of a guy doing a fueling adjustment and he suggested grinding the follower pin at an angle to allow you to push it back into place. Now i know that removing the pin cover means i dont have to do that.
*Edit
Do you think the follower pin is short enough to allow replacement of the fuel pin if the cover is removed ?
Once the cover for the follower pin is removed the tension of the spring is lost so the follower pin can simple be pushed back with a flat head screw driver once the fuel pin has been removed. Whilst its possible to do while on the vehicle i found it a complete pain in the arse, iirc i removed the TPS and some other bits to gain access. In the end and especially if you want to experiment its easier to grind the fuel pin to get it back in.

Ill post some more pics over weekend.
 
  • Like
Reactions: Firewout

chapel gate

Well-Known Member
Supporter
Promoted Company
I am in england
May 26, 2014
3,854
2,338
113
near, leek staffs.
Great write up :) Thanks...I'll be watching this with great interest as ill be doing this early next week.
I watched a you tube vid of a guy doing a fueling adjustment and he suggested grinding the follower pin at an angle to allow you to push it back into place. Now i know that removing the pin cover means i dont have to do that.
*Edit
Do you think the follower pin is short enough to allow replacement of the fuel pin if the cover is removed ?
pics added hw.
 

chapel gate

Well-Known Member
Supporter
Promoted Company
I am in england
May 26, 2014
3,854
2,338
113
near, leek staffs.
Thankyou so much :) I was fishing to find a tuner and i even rang a few rolling road places .... I fear that tuning non computerised engines is become a dying art :-(
Gonna get onto this on Tuesday morning armed with the information from your write up.
Top work Sir !
No problem at all.

Let us know how you get on.
 

SeaJay

Well-Known Member
I am in australia
Aug 23, 2016
203
142
43
Western Australia
Garage
with my FT I have a Gturbo set to a moderate 26psi, I found the factory compensator spring too week for that pressure, I had the star wheel wound up to the top of the thread, so I compleatly removed the star wheel and use a thicker longer spring, and fine tune it with shim washers
 

Lorin

Well-Known Member
Mar 28, 2010
1,266
271
83
Bournemouth
Nice write-up. Certainly makes it a lot easier to follow the process. One thing I'm curious about... having followed this thread on pump tuning (55 pages so not a quick read!), it appears the consensus is to tune to AFR and EGT, but not EGT alone. Did you use an AFR meter when tuning?
 

SeaJay

Well-Known Member
I am in australia
Aug 23, 2016
203
142
43
Western Australia
Garage
I welded a bung in the exhaust and fit the AFR semi permanent to see what's going on, I use a magnetic ph mount to the windscreen for the unit. Its in there now so I can see what goes on with the new intercooler (I'm fitting this weekend) when I tow a big trailer down from the North West
 

chapel gate

Well-Known Member
Supporter
Promoted Company
I am in england
May 26, 2014
3,854
2,338
113
near, leek staffs.
Nice write-up. Certainly makes it a lot easier to follow the process. One thing I'm curious about... having followed this thread on pump tuning (55 pages so not a quick read!), it appears the consensus is to tune to AFR and EGT, but not EGT alone. Did you use an AFR meter when tuning?
no I didn't lorin. this is how I understand it. @SeaJay , feel free to correct me.

a EGT gauge is for monitoring exhaust gas temperatures, its to make sure a engine isn't running dangerously hot. so people use that gauge to turn up fuel and keep those temps safe. a blunt instrument for tuning, bang more fuel and air in, get more power out and keeping the heat side of things happy.
AFR is finer tuning, seajay is at the upper end of the tuning scale and getting the AFR right means he is running all of those mods to there absolute potential and getting every last ounce of power out. its almost race tuning.

when I fit my intercooler ill still just use a egt gauge, if I ever get to the big turbo stage I may have a play with one.
 

SeaJay

Well-Known Member
I am in australia
Aug 23, 2016
203
142
43
Western Australia
Garage
I am lucky in that Gturbo and PDI are located in the city I live in, if you get your diesel dyno tuned they will use an AFR (or should do) but its about the cost of an AFR to do it, so I bought one. Graeme told me he first tuned his 80 series towing a 4 ton caravan around Australia that way, and that having the weight behind you works well so you can load it up, roll on the power, and watch what's happening
 

Attachments

Grimbo

Well-Known Member
I am in great_britain
Dec 3, 2016
222
118
43
Had a play the other day and did the boost compensator tweaks and then thought I'd wind the max fuel screw in a bit to see if it made a difference.....
The 1HD FT pump has a spot welded anti tamper ring on the adjuster and access is a little tight so I undid the lock nut and wound the max fuel screw right out and broke the anti tamper ring , wound it up and then just wound the adjuster back into the pump.....

First thing I tried was to wind it in a turn more than factory too see how much black smoke it would produce under load....... I figured this would be way too much but wanted to see ......

On starting the engine it now ticked over at 1800 rpm so the screw also must increase volume at all engine speeds.....backed the tickover adjuster right off but it was still idling at 1000 rpm .... quick blast up the road and even under load it wasn't that much more smokey ......

Returned to base and wound tickover adjuster back to just under stock setting and then wound max fuel screw in until I got a 750 rpm idle and went for a drive ....
It now picks up and accelerates hard right round to max revs and still no black smoke..... it really pushes you into the seat in the lower gears ....manual trans and 285/75/16 BFGs .....slight puff of smoke if you blip the throttle hard at idle but less than the wife's E320 Diesel Merc car if you do the same ....

So clearly it's burning all the fuel cleanly .....don't have an EGT gauge fitted and I think the only way to quantify results would be a rolling road .....plan on an intercooler and 3 inch exhaust and if the local 4WD capable rolling road is available I may have to try and get some step by step at the wheel HP figures

Anyone else had the same phenomenon of winding in the max fuel screw a bit affecting idle ?

Slightly puzzled because I've "optimised" more than a few tractors and winding the max fuel screw in never made the tickover rise ( both inline and rotary FIP's ) just ultimately made it into a "rolling coal " type machine if you over fuelled it....

When working for a "field test " dept of a machinery maker we had a couple of tractors and one that claimed to be 115hp on the bonnet was pushing 200 hp at the PTO after we tweaked it ...... backfired on us though because the farmer we were working with kept telling his dealer that his 135hp tractor must be under powered as we would go up hills with 2 round balers on the back in top gear with the rev counter not moving off the stop while he had to go down 2 gears with one
 

Firewout

Well-Known Member
I am in belgium
Oct 3, 2014
797
418
83
Antwerp
Garage
Hey Grimbo,
I could be totally wrong, and I have no hands on experience, but I remember this from my car mechanic course some 25 years ago :
There are 2 kinds of diesel pumps, throttle regulated and rpm regulated.
Baseline was that if you have a pto drive, like a tractor, chances are big that it is rpm regulated, because otherwise rpms would fluctuate under load.
Could be an explanation that the idle rises when you adjust the fuel on a throttle regulated fip vs a rpm regulated one.
 
  • Like
Reactions: Grimbo

Dervis Garip

Well-Known Member
Supporter
I am in cyprus
Feb 17, 2012
1,864
901
113
Famagusta, Cyprus
Garage
Guys interesting topic. Recently noticed carbon build up on the rear exhaust tip something that wasn't there or as much now being obvious to the eye. The fuel pump had a full rebuild in 2018 and in doing so had factory settings applied.

When speaking to my cousin the mechanic he implied that even though the pump rebuilt and factory internal settings are set it's never perfect and in some cases like mine now needs to be rolling roaded and adjusted accordingly. Something the fuel pump specialist cannot do!

At around 80 plus KMPH he seems to say the build-up is occurring. This is something that cannot be done on the exterior adjustments as these are general settings like fuel, idle, etc moreover the pump has to be taken off is a big job having done this myself.

This on modern cars is easy with a laptop being the pumps are electronic and not belt-driven.

So anyhow bottom line is that to get the best and most power/fuel and air mix across the gearing and rev range will need to the rolling roaded and take the pump off to put this right.

P.s this is also to get the most out of the mods on the cruiser i.e 3in the exhaust, top mount intercooler & larger turbo
 
Last edited:
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock    No Thanks