1980 BJ40; Replaced diaphragm and now way more black smoke?

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Mar 16, 2010
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Rossland BC
1980 bj40 24v canadian spec

as part of random maintenance, i replaced the diaphragm.

start the truck up and now way more black smoke,
hmmm, removed everything to ensure that the housing/spring/diaphragm,spacers were correct and seated well.

start the truck up again and way more black smoke again??:bang::bang:

The old diaphragm was not torn.

Possible it was stretched and the PO turned up the fuel?, and now that a new one is in place i need to turn down the fuel?
Any thoughts on this subject are appreciated.
 

IanB

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Jan 23, 2010
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Maybe the old one wasn't sealing even though it wasn't torn? Who knows.

Are you getting black smoke on initial startup then it clears, or under acceleration, or what? What there any smoke under any conditions prior to this? Do you have an EGT gauge?
 
Joined
Mar 16, 2010
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233
Location
Rossland BC
getting black smoke when i rev the engine, and plumes of black smoke upon acceleration.

there was bit of smoke and lack of high end power with old diaphragm
 
Joined
Mar 16, 2010
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233
Location
Rossland BC
lead seal not sealed
fuel screw is via DHAC

no noticeable change in idle before or after, ... maybe a little lower
if i blip the throttle, black smoke, and drops back to idle at a reasonable speed
 
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Mar 16, 2010
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Rossland BC
as asked by duncanrm, the lead seal and wire were not present and the DHAC(fuel screw) was screwed all the way back towards the firewall with no threads in front of the locknut


adjusted the DHAC with 27mm, 1.5 turns towards the direction of the rad (read turned fuel down 1/4 turn at a time, six times)

seemed to be progressively better, but dusk became night during the adjustments so we'll see in the am
 
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Mar 4, 2012
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Adelaide, South Australia
Sounds like you're on the right track.. I tend to keep on turning the fuel down until I have just a bit of smoke under very heavy load.. given the lead seal is gone.. all bets are off as to where the fuel was at and it does appear the new diaphragm has changed the behaviour of the throttle..
 

Squash

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Dec 8, 2006
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Sudbury, Ont. CA
Having recently completed a diaphragm swap I feel your anxiety!
My first ride had me thinking that I had fxxxed something up!
Bit the bullet drove for a while and wow better than before, mind you my seal was intact.
 

roalco

 
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Nov 11, 2007
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Vancouver, BC
I agree with duncanrm, you are on the right track, just keep adjusting as you were doing, in 1/4 turn increments, slowly, and you should get near where it was supposed to be.
Good luck!
 
Joined
Mar 16, 2010
Messages
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Rossland BC
thanks to all for the positive responses;

backed off the fuel till its about one full turn from no more adjustment on the DHAC/ fuel screw
and its good now, as per no rolling coal/unburnt diesel/excess black smoke , do need to now bump up the idle

double checking, i checked vacuum on the line that goes from butterfly to top of diaprahm housing and it was present.
interesting maybe - the other line held no vacuum, is this normal and acceptable?

interesting to note;
with the original diaphragm the DHAC/fuelscrew was turned to almost full fuel settings (most of the way towards the firewall)

new diaphragm, and now the DHAC/fuel screw is now almost to full lean setting( most of the way towards the rad)


as part of replacing the diaphragm i also
sealed (hose clamped) the two lines that are involved with the butterfly/diaphragm housing/IP pump
as they were exhibiting signs of age and not , may explain the PO chasing more air by adding more fuel at the DHAC.
 

hj 60

JT1W0HJ6000960839
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Netherlands Hengevelde
I used to let the oil drip out form the diagram and use neatsfoot oil drops for the leather, that would imporve reaction a bit.
Replaced diapgram after a few years (80k kilometers driven),noticable improved reaction to throttle, for the rest everything was the same, old one was not torn.
 

roalco

 
Joined
Nov 11, 2007
Messages
726
Location
Vancouver, BC
Yes, drain the chamber, replace that plug, then add just a couple of drops of neatsfoot oil (as per toyotas maintenance requirement) once a year, will keep the diaphragm supple and ensure a long life.
 

roalco

 
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Messages
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Vancouver, BC
In the interests of honesty, I checked my records and it's been way too long 😱 since I followed my own advice and drained the chamber and added 4 drops of neatsfoot oil. Done now, embarrassing amount of dirty oil drained out....
 
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