D24T.com  

Go Back   D24T.com > Technical Discussion Area > Diesel Engine and Drivetrain

Reply
 
Thread Tools Display Modes
  #1  
Old 02-13-2021, 01:28 AM
jpliddy jpliddy is offline
Senior Member
 
Join Date: Jan 2014
Posts: 340
Default M.P.G. poor

hi all
following on from my diesel leak .which garage fixed but left me with poor M.P.G.
well today i adjusted the smoke /fuel screw 1/8 of a turn and had a friend follow me on open road he could not see any real smoke when i floored the accelerator
only a slight puff once .so do i just the screw another 1/8 turn and see what that does . power was there better i think he said power was good as he was impressed with acceleration . i won't be able to tell for a while of driving if M.P.G.improves . as you said with this its a little bit at a time till i find the right balance .
when i loosed lock nut a little the slotted screw will turn clockwise even with the crimeped sleeve on the threaded screw !
any comments most welcome .
regards jim
Reply With Quote
  #2  
Old 02-13-2021, 12:12 PM
ngoma ngoma is offline
Supporting Member
 
Join Date: Nov 2009
Posts: 1,351
Default

Might have to experiment several times, turning another 1/8 turn in each time. When it starts loading up with too much smoke and no real improvements you can turn it back out 1/8 or a few 1/8's to find the happy spot.

The no-tamper collar is a nuisance but you should be able to get it loose enough to make the adjustments to the fuel screw.

To really know what is going on with the MPG you need to do the math at each fill up. Miles driven since last fill up, divided by gallons. Must fill up to same level each time (when liquid fuel is visible at the same spot in the filler neck) and really only accurate over several fill ups. Keep track of it in the small notepad you keep in the glovebox that you use to track oil changes, tire rotations, air filter changes, brake pads, timing belt, etc. When you start seeing a trend with the MPG you know something needs attention.
__________________
1985 744 gle d24t
1985 745 gle d24t
Reply With Quote
  #3  
Old 02-14-2021, 12:27 AM
jpliddy jpliddy is offline
Senior Member
 
Join Date: Jan 2014
Posts: 340
Default

thanks NGOMA
yes if im going to get another 1/8 turn up to the smoke screw the anti tamper washer will need to be loosed off . if i attempt it i will need to do it on the car holding locknut and grips on the washer very carefully as its tight for space there .
am i on the wrong track as the garage must of wound the screw back to its original setting as the tamper washer has not been disturbed ;
moving on they have adjusted something on the cold start as they have put anti tamper paint on the nut!
can any adjustment in this area make fuel consumption worse . or might it be the throttle shaft set up thats making fuel consumption worse ,sorry ive thrown a few issues at this problem ,
i have been monitoring M.P.G,consumption for many years i zero the clock at every fill up and take it up to about 400 miles over before i fill up again i always get about 30 mpg around town and local runs so i will be monitoring this as always .
regards jim
Reply With Quote
  #4  
Old 02-14-2021, 12:39 PM
ngoma ngoma is offline
Supporting Member
 
Join Date: Nov 2009
Posts: 1,351
Default

This is an expected idiosyncrasy of refitting the IP top cover.

The fuel limiter screw (sometimes called "smoke screw" or "fuel screw") screws into the top cover and acts on a lever going deep into the main IP body.

The top cover screw holes are larger than the attaching screws, so there is some slop on the top cover final positioning on the main IP body. Side to side, front to back, twisted either way, the top cover can easily be reattached in a new position different than it was before it was disassembled.

The natural result is that the fuel limiter screw may need to be re-tuned after refitting the top cover.

Your question "can any adjustment in this area make fuel consumption worse," well yes, the fuel limiter screw has a direct impact on fuel consumption. If it is screwed in too far will cause overfueling, feeding more fuel than the engine can efficiently burn. The visual clue here is excessive soot out the tailpipe.

Some cut the anti-tamper collar off, to make adjustments easier.

As far as increased fuel consumption, would need to see the numbers, compared to similar weather conditions (colder wintertime temps always increase fuel consumption for me ~15%) and usage conditions (a long trip-- more constant speed highway conditions usually consume less fuel than in-city stop-and-go driving).
__________________
1985 744 gle d24t
1985 745 gle d24t
Reply With Quote
  #5  
Old 02-15-2021, 09:27 AM
jpliddy jpliddy is offline
Senior Member
 
Join Date: Jan 2014
Posts: 340
Default

thank you NGOMA
i have a spare old injection pump here which i have removed the top to expose the lever which the smoke screw pushes against when you wind it in im only seeing the theory of this as i never seen inside one before . and yes i can see that the top cover can go back in a slightly different place due to the bolts being loose fit in the sleevs.. i am monitoring this latest tank of fuel i filled up with the fuel needle is not quite at half way mark yet i have generally got 200 t0 220 at half way mark . i know this is not accurate so the zeroed clock and the next fill up will give me a closer reading will keep you all informed . as said earlier i got another 1/8 of a turn out of the smoke screw but thats its limit due to the tamper proof washer on smoke screw .
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -8. The time now is 12:07 PM.


Powered by vBulletin® Version 3.8.10
Copyright ©2000 - 2024, vBulletin Solutions, Inc.