1986 bj74 turbo diesel wont turn of with key , well sorta

[krawczuk]

hi, i have a 1986 bj74 3.4 turbo diesel , which has developed a weird problem.....

when i have my foot fully pressed down on the clutch and in neutral , then after i turned the key in the off position , the engine still keeps running on, BUT as soon as i let the clutch pedal come up say even 10 mm or so the engine will cut out , and also when i have my foot resting on the pedal , just enough to get the free play out then a LITTLE more the engine still wont turn off, as soon as i take me foot of- cuts out.

i`ve noticed there is a power booster type device on the clutch pedal , so i presume this is connected to the vacuum pump , and since the engine cut off is connected to a diapragm which in turn is connected to the inlet manifold , that there is POSSIBLY some sorta vacuum leak ???
any clues ?

 

[boogie74]

Yep,

Definitely clutch booster issues. Do an advanced search of clutch in the 70's series section. Make sure you search titles only to narrow your search. I have been through these problems just recently and there is heaps of info in said threads.

Heres a couple of threads to get you started:
https://forum.ih8mud.com/70-series-tech/295406-clutch-noise.html
https://forum.ih8mud.com/70-series-tech/288478-bj74-clutch-booster-repair.html
https://forum.ih8mud.com/70-series-tech/292125-clutch-booster-final-word.html

 

[roscoFJ73]

is there POSSIBLY some sort a vacuum leak ???

Almost definately,or an outside chance the vac pump is dying and cant make enough vacuum.

 

[boogie74]

That was a close one Rosco!!!!!

 

[Radd Cruisers]

Yep,

Definitely clutch booster issues.

What he said...

Make sure your pedal height is set correctly, too.


~John

 

[boogie74]

Hi John,
Would you mind explaining the clutch pedal height thing. I messed around with mine when I did my booster. Thing is I couldn't get
it as high as what it said in the manual so I ended up setting it at about the same height as the brake pedal with an inch or two of
play. Does that sound right? If its not set properly will it allow the booster to leak?

 

[Radd Cruisers]

Hi John,
Would you mind explaining the clutch pedal height thing. I messed around with mine when I did my booster. Thing is I couldn't get
it as high as what it said in the manual so I ended up setting it at about the same height as the brake pedal with an inch or two of
play. Does that sound right? If its not set properly will it allow the booster to leak?

The clutch slave is self-adjusting, so you can leave it alone.

Pedal height is set by two adjustments: one is the pedal stop or limiting screw/bolt, and the second one is the adjustment of the pushrod that actuates the master cylinder. These two adjustments must be made together so that you're actually getting movement of the master when you're pressing the pedal, and also that you do not have the master's piston partially depressed when the pedal is out (dis-engaged).

We commonly see mis-adjusted clutch pedals/master cylinders - and usually it's after we have installed a new clutch... and it's still not working properly.

Adjusting the push-rod: the push rod itself should have a small amount of play when the pedal is fully out and resting against the stop. The end of the push rod as it goes into the master is rounded to fit into the dish-shaped end of the piston. A small amount of play ensures that the piston is not depressed when the pedal is fully up.

If the piston is partially depressed, the valving in the clutch master may not allow the slave to become fully released when the pedal is out. This will cause rapid wear of the clutch (and note that I see LOTS of people who rest their foot on the clutch pedal between shifts and when driving - this is a BIG no-no) as it is sitting very slightly disengaged while driving.

Raising the pedal height more than just a small amount over stock can cause accelerated wear of the clutch booster diaphragm. I have seen a few examples of this when investigating vacuum leaks at clutch boosters. The other thing that I have encountered a few times is excessive pedal travel causing clutch noise and drag on the clutch as the release fork is extended too far.

I think it is best to stick to the factory settings...

hth,

~John

 

[krawczuk]

fixed it !!!!

hi, what i done was :

found the vacuum line from clutch booster to a vacuum canister that was mounted on the inner guard . another vac line went from there to the vac pump.
got a 3/4 inch length of solid rod that pushed up in the line ( about 2 inches ) , that went from clutch booster to vac canister , then i put a hose clamp around the hose where the rod was ....

started it up , foot fully depressed on clutch and turned engine of , it cut out straight away!!!! but there was a funny sorta clicky/clucky noise coming from the booster , i figured that it was making the noise cause i put that rod in , and therefore the resulting pressure from the booster couldnt go any where , so i cut a small hole in the line between the clutch booster and that rod .
no more noise !!!! yay !!!! clutch is just a little firmer , snd still feels perfectly fine...

 

[boogie74]

Nice work,

I did the same sort of thing with mine so the cruiser would turn off and engage 4wd. There was talk in some other
post about the extra pressure on the clutch system causing the pedal bracket to weaken and possibly snap. Maybe
some thing to watch out for.

 

[krawczuk]

Nice work,

I did the same sort of thing with mine so the cruiser would turn off and engage 4wd. There was talk in some other
post about the extra pressure on the clutch system causing the pedal bracket to weaken and possibly snap. Maybe
some thing to watch out for.

mmm never thought about that !!

mark k