I have a 1997 Expy with 185K on it. Past few years I've been having trouble with the 4wd system .Shift motor replaced. Solenoids replaced. Actuator replaced. I read numerous threads and I remember one regarding vacuum at the actuator but I can't find it. I think i read it wasn't to strong. So ..... what should the vacuum feel like at the actuator. I don't have a gauge to check it or should I just cross the lines and see if the shaft moves in and out and if it does that means its working properly? Thanks

 

You can use one of those cheap vac tools to actuate in and out. Like say a MityVac, -

http://www.ebay.com/itm/like/311692293104?lpid=82&chn=ps&ul_noapp=true
I think harbor freight has a cheaper one that's brass.

Or you can just use the **** on the dash. Some folks lube the pin up every now and again to keep it functioning.

Nothing wrong with the system. Line may dry out with age and become brittle. If so, it'll break between the battery and firewall area usually. I have a 98 and the ONLY problem I've had in the past is a cracked line.

 

Thanks ... but how much suction should I feel on my fingertips when I pull the lines at the actuator and switch fro 2 to 4 wd? a tad or a lot?

 

You going to have to tell me on that one. IF the actuator pin moves when positioned from 2wheel to 4wheel and back again, it works. So I guess you could disconnect everything and have a friend turn the **** while holding your fingers over the lines....iduno. You could be the judge that way.
Hg's of vac,(inches of mercury) I could help you with. Not familiar your touchy feely method, sorry.

Best of luck regardless.

 

Thanks .... I know I google this actuator problem a few months ago and I found a thread where a guy did mention how the suction should feel. I my mound of stuff I should be able to put a gauge together. I know I have one somewhere. What should the Hg's of vac read at the actuator?

 

I understand that this is an old subject thats been discussed many times. My vac lines to the actuator have already been pulled from behind the battery and now easy to get at. Theres a connector a couple feet from the solenoids so i separated that. Pink line had light suction in 2wd mode. Blue line had light suction in 4x mode. Sooo looks like I will have to drive onto my ramps,crawl under. pull the connectors at the actuator and have the wife switch it for me. I recently put a new actuator on there and it did work for awhile. So either I don't have enough suction (felt strong enough to me to move the pin) Actuator gone already or maybe the shift fork. Kinda why I asked this question in the first place. Just don't know how much suction I should feel. I figured at least one or two of you have tapped the end of a line with your fingertips to feel for it.

 

it never feel like much in small diameter tubing.

get down there and push fingers in and work actuator manually. Your fingers should fit into holes on backside of it, like an egr valve. See if it moves. It can get stuck. After that, the plastic shift fork can be broke. After that, vac at the actuator is the same as at the solenoid, if it is less you have cracked line to actuator or such, . you can hook a vac guage up easily with rubber tubing and taper fitting to check

 

Thanks Mbb. That pretty much is my plan of attack. I just remembered I do have a couple OLD school vacuum gauges I used to tune my carbs with but I still don't know what an acceptable vacuum number is.

 

Well at idle a tight system would have what , 20"-25" hg vac? It might not need that much, but it should probably have whatever the vac cannister has if it has no leaks, basically manifold pressure at extended idle

If you have any appreciable vacuum it should work. It has to work at various engine rpms, etc.

 

Perfect ... thats all i need.