How do you test a Vacuum diaphragm?

[FSJ Gambler]

I have a '79 Quadratrac Wagoneer, no front drive shaft.
After taking off the front drive, it went 2 blocks, then no go.

I need to get it in e-drive. Switch in glove box seems not to work.

How do you test a Diaphragm? I've blown into both of the tubes going in until i'm blue in the face.
Nothing happens, the tubes clogged or the diaphragm is bad. I can't afford a $40 Mityvac vacuum pump, so i'm stuck blowing.

Is there anything else I can try?

[fsj1978]

Engine vac... Or better yet SUCK real hard on the vac lines. Just take a piece of vac line, attach it to the tube and try it... The bad thing is that it's got to be lined up right inside the T-case or it won't go no matter how hard you suck. Another thing you can do is put engine vac straight to one of the two solid lines, then get it moving really, really slow (walking speed or less), put it in neutral and rev it to around 2500 and let it drop, that creates more vac. If this doesn't do it in a few tries, swap the vac line under the hood to the other solid line and try again... The other possability is that the two little pieces of vac line that attach the solid lines to the T-case are bad. You may have to change them to get it into E-drive.

[jode]

Not sure why we are doing this on a different thread or why we are talking about blowing again, but here goes....

....YOU HAVE TO SUCK....NOT BLOW!

It is vacuum man!

As was mentioned, all the vacuum you can muster wont switch it if the gears are not meshing...under normal circumstances, (with the truck in motion) mine sometimes takes a few moments of vacuum before engaging...your problem may be that you are attmepting to suck it while you are under it and the vehicle is stationary. Can you unhook the vacuum line at the vacuum source and re-route it into the cab or something so that you can SUCK on it while you are letting the vehicle roll forward a little bit? If not, put the rearend on jackstands (the front driveline is off right?) and then lay under there and rotate a wheel with your foot while applying vacuum (sucking) (tranny in neutral). That should turn the gears and get them to mesh so that the E-drive can engage.
Ont he other hand, I forgot why you can't jsut flip the switch, let the thing roll forward with the engine on in neutral and have it done with? :confused:

as to your question of how to test vacuum, as was mentioned previously, suck on the line and then stick your tongue over it so that the vacuum "holds" your tongue on the end of the line....if the vacuum keeps on holding your tongue to the line, then the diapragm is good...if it loses vacuum, then it aint.....

[Stuka]

to test if it hold vacuum just suck on it then stick your tongue over the line to see if it holds vacuum...if it doesnt then its not gona work right.

EDIT: ok i shoudl have read both post before posting lol. Jode already said how to test..oh well smile.gif

[ November 02, 2002, 11:26 PM: Message edited by: Stuka ]