fuel mileage drop problem solved!
 

just an update on the recent radical drop in fuel mileage i experienced
after doing a rebuild on my Carter BBD (87 YJ 4.2L) from about 17-18mpg
to something like 5-7mpg! there were no obvious signs of excessive fuel
consumption (black smoke clouds) or leaks in the system, and she seemed
to run and start ok.
turns out to have been rather simple and rather complicated at the same
time. when i took the carb apart i noticed that the stepper motor didnt
move very freely - the shaft appeared to be sticking in the bushing or
something. i pulled the shaft back out so that the pins were in the
forward position and put it back together. the next day i did the
nutter which recommends placing the pins in the full forward position.
now when i got this beast the CTO had been broken off as well as the O2
sensor being disconnected, so i had a pretty good hunch that the
stepper motor had been inactive for a long time (hence the corrosion
and the sticking). thus i hoped that taking the computer out of the
loop would bring the fuel mileage back up (or something like that). i
also bypassed the charcoal canister (bad purge valve), retightened the
carb mount nuts and the manifolds, and rechecked that there were no
vacuum leaks.
well none of it worked - and needless to say with gas going for $3+ at
the pump it is alarming to practically be able to WATCH your gas gauge
drop as you drive down the highway! then a few days ago i remembered
that having the stepper motor pins in the full forward position richens
the mixture. so i figured - what the hell i'll put em in the full lean
position and see what happens.
and VOILA! gas mileage is back to ~17-18 mpg and she runs like a top!
so CTO and O2 no good -> stepper motor doesnt move -> i 'rebuild' carb
and inadvertently put the pins in full forward position -> stepper
motor cant move because corrosion/old/POS -> disconnect computer ->
stepper cant move b/c no signal (obviously) -> restore pins to full
lean position - problem solved!
whew. anyway i just wanted to post about this because while i was
researching on this list it seemed to me that i ran across alot of
folks posting about their problems, then getting some responses and
possible solutions and then nothing else. it would be nice to hear what
exactly the problem turned out to be and how exactly it was solved (or
not) - at least more often.
so here ya go.
cheers all and thanks for all the help.
bennett

Re: fuel mileage drop problem solved!
 

Thanks. We all like to find out what happened after a thread like that,
especially if it is a success story!

Earle

"bobvonbob" <bennettvonbennett@gmail.com> wrote in message
news:1155235681.817873.136000@m79g2000cwm.googlegr oups.com...
> just an update on the recent radical drop in fuel mileage i experienced
> after doing a rebuild on my Carter BBD (87 YJ 4.2L) from about 17-18mpg
> to something like 5-7mpg! there were no obvious signs of excessive fuel
> consumption (black smoke clouds) or leaks in the system, and she seemed
> to run and start ok.
> turns out to have been rather simple and rather complicated at the same
> time. when i took the carb apart i noticed that the stepper motor didnt
> move very freely - the shaft appeared to be sticking in the bushing or
> something. i pulled the shaft back out so that the pins were in the
> forward position and put it back together. the next day i did the
> nutter which recommends placing the pins in the full forward position.
> now when i got this beast the CTO had been broken off as well as the O2
> sensor being disconnected, so i had a pretty good hunch that the
> stepper motor had been inactive for a long time (hence the corrosion
> and the sticking). thus i hoped that taking the computer out of the
> loop would bring the fuel mileage back up (or something like that). i
> also bypassed the charcoal canister (bad purge valve), retightened the
> carb mount nuts and the manifolds, and rechecked that there were no
> vacuum leaks.
> well none of it worked - and needless to say with gas going for $3+ at
> the pump it is alarming to practically be able to WATCH your gas gauge
> drop as you drive down the highway! then a few days ago i remembered
> that having the stepper motor pins in the full forward position richens
> the mixture. so i figured - what the hell i'll put em in the full lean
> position and see what happens.
> and VOILA! gas mileage is back to ~17-18 mpg and she runs like a top!
> so CTO and O2 no good -> stepper motor doesnt move -> i 'rebuild' carb
> and inadvertently put the pins in full forward position -> stepper
> motor cant move because corrosion/old/POS -> disconnect computer ->
> stepper cant move b/c no signal (obviously) -> restore pins to full
> lean position - problem solved!
> whew. anyway i just wanted to post about this because while i was
> researching on this list it seemed to me that i ran across alot of
> folks posting about their problems, then getting some responses and
> possible solutions and then nothing else. it would be nice to hear what
> exactly the problem turned out to be and how exactly it was solved (or
> not) - at least more often.
> so here ya go.
> cheers all and thanks for all the help.
> bennett
>

Re: fuel mileage drop problem solved!
 

Thanks. We all like to find out what happened after a thread like that,
especially if it is a success story!

Earle

"bobvonbob" <bennettvonbennett@gmail.com> wrote in message
news:1155235681.817873.136000@m79g2000cwm.googlegr oups.com...
> just an update on the recent radical drop in fuel mileage i experienced
> after doing a rebuild on my Carter BBD (87 YJ 4.2L) from about 17-18mpg
> to something like 5-7mpg! there were no obvious signs of excessive fuel
> consumption (black smoke clouds) or leaks in the system, and she seemed
> to run and start ok.
> turns out to have been rather simple and rather complicated at the same
> time. when i took the carb apart i noticed that the stepper motor didnt
> move very freely - the shaft appeared to be sticking in the bushing or
> something. i pulled the shaft back out so that the pins were in the
> forward position and put it back together. the next day i did the
> nutter which recommends placing the pins in the full forward position.
> now when i got this beast the CTO had been broken off as well as the O2
> sensor being disconnected, so i had a pretty good hunch that the
> stepper motor had been inactive for a long time (hence the corrosion
> and the sticking). thus i hoped that taking the computer out of the
> loop would bring the fuel mileage back up (or something like that). i
> also bypassed the charcoal canister (bad purge valve), retightened the
> carb mount nuts and the manifolds, and rechecked that there were no
> vacuum leaks.
> well none of it worked - and needless to say with gas going for $3+ at
> the pump it is alarming to practically be able to WATCH your gas gauge
> drop as you drive down the highway! then a few days ago i remembered
> that having the stepper motor pins in the full forward position richens
> the mixture. so i figured - what the hell i'll put em in the full lean
> position and see what happens.
> and VOILA! gas mileage is back to ~17-18 mpg and she runs like a top!
> so CTO and O2 no good -> stepper motor doesnt move -> i 'rebuild' carb
> and inadvertently put the pins in full forward position -> stepper
> motor cant move because corrosion/old/POS -> disconnect computer ->
> stepper cant move b/c no signal (obviously) -> restore pins to full
> lean position - problem solved!
> whew. anyway i just wanted to post about this because while i was
> researching on this list it seemed to me that i ran across alot of
> folks posting about their problems, then getting some responses and
> possible solutions and then nothing else. it would be nice to hear what
> exactly the problem turned out to be and how exactly it was solved (or
> not) - at least more often.
> so here ya go.
> cheers all and thanks for all the help.
> bennett
>

Re: fuel mileage drop problem solved!
 

Thanks. We all like to find out what happened after a thread like that,
especially if it is a success story!

Earle

"bobvonbob" <bennettvonbennett@gmail.com> wrote in message
news:1155235681.817873.136000@m79g2000cwm.googlegr oups.com...
> just an update on the recent radical drop in fuel mileage i experienced
> after doing a rebuild on my Carter BBD (87 YJ 4.2L) from about 17-18mpg
> to something like 5-7mpg! there were no obvious signs of excessive fuel
> consumption (black smoke clouds) or leaks in the system, and she seemed
> to run and start ok.
> turns out to have been rather simple and rather complicated at the same
> time. when i took the carb apart i noticed that the stepper motor didnt
> move very freely - the shaft appeared to be sticking in the bushing or
> something. i pulled the shaft back out so that the pins were in the
> forward position and put it back together. the next day i did the
> nutter which recommends placing the pins in the full forward position.
> now when i got this beast the CTO had been broken off as well as the O2
> sensor being disconnected, so i had a pretty good hunch that the
> stepper motor had been inactive for a long time (hence the corrosion
> and the sticking). thus i hoped that taking the computer out of the
> loop would bring the fuel mileage back up (or something like that). i
> also bypassed the charcoal canister (bad purge valve), retightened the
> carb mount nuts and the manifolds, and rechecked that there were no
> vacuum leaks.
> well none of it worked - and needless to say with gas going for $3+ at
> the pump it is alarming to practically be able to WATCH your gas gauge
> drop as you drive down the highway! then a few days ago i remembered
> that having the stepper motor pins in the full forward position richens
> the mixture. so i figured - what the hell i'll put em in the full lean
> position and see what happens.
> and VOILA! gas mileage is back to ~17-18 mpg and she runs like a top!
> so CTO and O2 no good -> stepper motor doesnt move -> i 'rebuild' carb
> and inadvertently put the pins in full forward position -> stepper
> motor cant move because corrosion/old/POS -> disconnect computer ->
> stepper cant move b/c no signal (obviously) -> restore pins to full
> lean position - problem solved!
> whew. anyway i just wanted to post about this because while i was
> researching on this list it seemed to me that i ran across alot of
> folks posting about their problems, then getting some responses and
> possible solutions and then nothing else. it would be nice to hear what
> exactly the problem turned out to be and how exactly it was solved (or
> not) - at least more often.
> so here ya go.
> cheers all and thanks for all the help.
> bennett
>

Re: fuel mileage drop problem solved!
 

Thanks. We all like to find out what happened after a thread like that,
especially if it is a success story!

Earle

"bobvonbob" <bennettvonbennett@gmail.com> wrote in message
news:1155235681.817873.136000@m79g2000cwm.googlegr oups.com...
> just an update on the recent radical drop in fuel mileage i experienced
> after doing a rebuild on my Carter BBD (87 YJ 4.2L) from about 17-18mpg
> to something like 5-7mpg! there were no obvious signs of excessive fuel
> consumption (black smoke clouds) or leaks in the system, and she seemed
> to run and start ok.
> turns out to have been rather simple and rather complicated at the same
> time. when i took the carb apart i noticed that the stepper motor didnt
> move very freely - the shaft appeared to be sticking in the bushing or
> something. i pulled the shaft back out so that the pins were in the
> forward position and put it back together. the next day i did the
> nutter which recommends placing the pins in the full forward position.
> now when i got this beast the CTO had been broken off as well as the O2
> sensor being disconnected, so i had a pretty good hunch that the
> stepper motor had been inactive for a long time (hence the corrosion
> and the sticking). thus i hoped that taking the computer out of the
> loop would bring the fuel mileage back up (or something like that). i
> also bypassed the charcoal canister (bad purge valve), retightened the
> carb mount nuts and the manifolds, and rechecked that there were no
> vacuum leaks.
> well none of it worked - and needless to say with gas going for $3+ at
> the pump it is alarming to practically be able to WATCH your gas gauge
> drop as you drive down the highway! then a few days ago i remembered
> that having the stepper motor pins in the full forward position richens
> the mixture. so i figured - what the hell i'll put em in the full lean
> position and see what happens.
> and VOILA! gas mileage is back to ~17-18 mpg and she runs like a top!
> so CTO and O2 no good -> stepper motor doesnt move -> i 'rebuild' carb
> and inadvertently put the pins in full forward position -> stepper
> motor cant move because corrosion/old/POS -> disconnect computer ->
> stepper cant move b/c no signal (obviously) -> restore pins to full
> lean position - problem solved!
> whew. anyway i just wanted to post about this because while i was
> researching on this list it seemed to me that i ran across alot of
> folks posting about their problems, then getting some responses and
> possible solutions and then nothing else. it would be nice to hear what
> exactly the problem turned out to be and how exactly it was solved (or
> not) - at least more often.
> so here ya go.
> cheers all and thanks for all the help.
> bennett
>

Re: fuel mileage drop problem solved!
 

If you still have the 'mixture' screws factory blocked so you can't set
the carb up properly, running it too lean like that will burn holes in
your pistons.

You should put them in the center and hope that is the best for where
the factory set the carb's mix at.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

bobvonbob wrote:
>
> just an update on the recent radical drop in fuel mileage i experienced
> after doing a rebuild on my Carter BBD (87 YJ 4.2L) from about 17-18mpg
> to something like 5-7mpg! there were no obvious signs of excessive fuel
> consumption (black smoke clouds) or leaks in the system, and she seemed
> to run and start ok.
> turns out to have been rather simple and rather complicated at the same
> time. when i took the carb apart i noticed that the stepper motor didnt
> move very freely - the shaft appeared to be sticking in the bushing or
> something. i pulled the shaft back out so that the pins were in the
> forward position and put it back together. the next day i did the
> nutter which recommends placing the pins in the full forward position.
> now when i got this beast the CTO had been broken off as well as the O2
> sensor being disconnected, so i had a pretty good hunch that the
> stepper motor had been inactive for a long time (hence the corrosion
> and the sticking). thus i hoped that taking the computer out of the
> loop would bring the fuel mileage back up (or something like that). i
> also bypassed the charcoal canister (bad purge valve), retightened the
> carb mount nuts and the manifolds, and rechecked that there were no
> vacuum leaks.
> well none of it worked - and needless to say with gas going for $3+ at
> the pump it is alarming to practically be able to WATCH your gas gauge
> drop as you drive down the highway! then a few days ago i remembered
> that having the stepper motor pins in the full forward position richens
> the mixture. so i figured - what the hell i'll put em in the full lean
> position and see what happens.
> and VOILA! gas mileage is back to ~17-18 mpg and she runs like a top!
> so CTO and O2 no good -> stepper motor doesnt move -> i 'rebuild' carb
> and inadvertently put the pins in full forward position -> stepper
> motor cant move because corrosion/old/POS -> disconnect computer ->
> stepper cant move b/c no signal (obviously) -> restore pins to full
> lean position - problem solved!
> whew. anyway i just wanted to post about this because while i was
> researching on this list it seemed to me that i ran across alot of
> folks posting about their problems, then getting some responses and
> possible solutions and then nothing else. it would be nice to hear what
> exactly the problem turned out to be and how exactly it was solved (or
> not) - at least more often.
> so here ya go.
> cheers all and thanks for all the help.
> bennett

Re: fuel mileage drop problem solved!
 

If you still have the 'mixture' screws factory blocked so you can't set
the carb up properly, running it too lean like that will burn holes in
your pistons.

You should put them in the center and hope that is the best for where
the factory set the carb's mix at.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

bobvonbob wrote:
>
> just an update on the recent radical drop in fuel mileage i experienced
> after doing a rebuild on my Carter BBD (87 YJ 4.2L) from about 17-18mpg
> to something like 5-7mpg! there were no obvious signs of excessive fuel
> consumption (black smoke clouds) or leaks in the system, and she seemed
> to run and start ok.
> turns out to have been rather simple and rather complicated at the same
> time. when i took the carb apart i noticed that the stepper motor didnt
> move very freely - the shaft appeared to be sticking in the bushing or
> something. i pulled the shaft back out so that the pins were in the
> forward position and put it back together. the next day i did the
> nutter which recommends placing the pins in the full forward position.
> now when i got this beast the CTO had been broken off as well as the O2
> sensor being disconnected, so i had a pretty good hunch that the
> stepper motor had been inactive for a long time (hence the corrosion
> and the sticking). thus i hoped that taking the computer out of the
> loop would bring the fuel mileage back up (or something like that). i
> also bypassed the charcoal canister (bad purge valve), retightened the
> carb mount nuts and the manifolds, and rechecked that there were no
> vacuum leaks.
> well none of it worked - and needless to say with gas going for $3+ at
> the pump it is alarming to practically be able to WATCH your gas gauge
> drop as you drive down the highway! then a few days ago i remembered
> that having the stepper motor pins in the full forward position richens
> the mixture. so i figured - what the hell i'll put em in the full lean
> position and see what happens.
> and VOILA! gas mileage is back to ~17-18 mpg and she runs like a top!
> so CTO and O2 no good -> stepper motor doesnt move -> i 'rebuild' carb
> and inadvertently put the pins in full forward position -> stepper
> motor cant move because corrosion/old/POS -> disconnect computer ->
> stepper cant move b/c no signal (obviously) -> restore pins to full
> lean position - problem solved!
> whew. anyway i just wanted to post about this because while i was
> researching on this list it seemed to me that i ran across alot of
> folks posting about their problems, then getting some responses and
> possible solutions and then nothing else. it would be nice to hear what
> exactly the problem turned out to be and how exactly it was solved (or
> not) - at least more often.
> so here ya go.
> cheers all and thanks for all the help.
> bennett

Re: fuel mileage drop problem solved!
 

If you still have the 'mixture' screws factory blocked so you can't set
the carb up properly, running it too lean like that will burn holes in
your pistons.

You should put them in the center and hope that is the best for where
the factory set the carb's mix at.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

bobvonbob wrote:
>
> just an update on the recent radical drop in fuel mileage i experienced
> after doing a rebuild on my Carter BBD (87 YJ 4.2L) from about 17-18mpg
> to something like 5-7mpg! there were no obvious signs of excessive fuel
> consumption (black smoke clouds) or leaks in the system, and she seemed
> to run and start ok.
> turns out to have been rather simple and rather complicated at the same
> time. when i took the carb apart i noticed that the stepper motor didnt
> move very freely - the shaft appeared to be sticking in the bushing or
> something. i pulled the shaft back out so that the pins were in the
> forward position and put it back together. the next day i did the
> nutter which recommends placing the pins in the full forward position.
> now when i got this beast the CTO had been broken off as well as the O2
> sensor being disconnected, so i had a pretty good hunch that the
> stepper motor had been inactive for a long time (hence the corrosion
> and the sticking). thus i hoped that taking the computer out of the
> loop would bring the fuel mileage back up (or something like that). i
> also bypassed the charcoal canister (bad purge valve), retightened the
> carb mount nuts and the manifolds, and rechecked that there were no
> vacuum leaks.
> well none of it worked - and needless to say with gas going for $3+ at
> the pump it is alarming to practically be able to WATCH your gas gauge
> drop as you drive down the highway! then a few days ago i remembered
> that having the stepper motor pins in the full forward position richens
> the mixture. so i figured - what the hell i'll put em in the full lean
> position and see what happens.
> and VOILA! gas mileage is back to ~17-18 mpg and she runs like a top!
> so CTO and O2 no good -> stepper motor doesnt move -> i 'rebuild' carb
> and inadvertently put the pins in full forward position -> stepper
> motor cant move because corrosion/old/POS -> disconnect computer ->
> stepper cant move b/c no signal (obviously) -> restore pins to full
> lean position - problem solved!
> whew. anyway i just wanted to post about this because while i was
> researching on this list it seemed to me that i ran across alot of
> folks posting about their problems, then getting some responses and
> possible solutions and then nothing else. it would be nice to hear what
> exactly the problem turned out to be and how exactly it was solved (or
> not) - at least more often.
> so here ya go.
> cheers all and thanks for all the help.
> bennett

Re: fuel mileage drop problem solved!
 

If you still have the 'mixture' screws factory blocked so you can't set
the carb up properly, running it too lean like that will burn holes in
your pistons.

You should put them in the center and hope that is the best for where
the factory set the carb's mix at.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

bobvonbob wrote:
>
> just an update on the recent radical drop in fuel mileage i experienced
> after doing a rebuild on my Carter BBD (87 YJ 4.2L) from about 17-18mpg
> to something like 5-7mpg! there were no obvious signs of excessive fuel
> consumption (black smoke clouds) or leaks in the system, and she seemed
> to run and start ok.
> turns out to have been rather simple and rather complicated at the same
> time. when i took the carb apart i noticed that the stepper motor didnt
> move very freely - the shaft appeared to be sticking in the bushing or
> something. i pulled the shaft back out so that the pins were in the
> forward position and put it back together. the next day i did the
> nutter which recommends placing the pins in the full forward position.
> now when i got this beast the CTO had been broken off as well as the O2
> sensor being disconnected, so i had a pretty good hunch that the
> stepper motor had been inactive for a long time (hence the corrosion
> and the sticking). thus i hoped that taking the computer out of the
> loop would bring the fuel mileage back up (or something like that). i
> also bypassed the charcoal canister (bad purge valve), retightened the
> carb mount nuts and the manifolds, and rechecked that there were no
> vacuum leaks.
> well none of it worked - and needless to say with gas going for $3+ at
> the pump it is alarming to practically be able to WATCH your gas gauge
> drop as you drive down the highway! then a few days ago i remembered
> that having the stepper motor pins in the full forward position richens
> the mixture. so i figured - what the hell i'll put em in the full lean
> position and see what happens.
> and VOILA! gas mileage is back to ~17-18 mpg and she runs like a top!
> so CTO and O2 no good -> stepper motor doesnt move -> i 'rebuild' carb
> and inadvertently put the pins in full forward position -> stepper
> motor cant move because corrosion/old/POS -> disconnect computer ->
> stepper cant move b/c no signal (obviously) -> restore pins to full
> lean position - problem solved!
> whew. anyway i just wanted to post about this because while i was
> researching on this list it seemed to me that i ran across alot of
> folks posting about their problems, then getting some responses and
> possible solutions and then nothing else. it would be nice to hear what
> exactly the problem turned out to be and how exactly it was solved (or
> not) - at least more often.
> so here ya go.
> cheers all and thanks for all the help.
> bennett

Re: fuel mileage drop problem solved!
 

Mike Romain wrote:
> If you still have the 'mixture' screws factory blocked so you can't set
> the carb up properly, running it too lean like that will burn holes in
> your pistons.
>
> You should put them in the center and hope that is the best for where
> the factory set the carb's mix at.

BRILLIANT! Instead of using an Air Fuel mixture guage to AT LEAST get in
the ballpark for good power and MPG's, you want him to put it "in the
middle and hope".

--
Simon
"I may be wrong, but I'm not uncertain." -- Robert A. Heinlein