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Vacuum Diagrams

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Vacuum Diagrams
Vacuum Diagrams
dude hell yeah thank you so much, i finally found the correct diagram...SWEEETTT!!!! lol i guess the truck is an 84 Cali. with a manual trans...ha ha nice...
No problemo.
Good to hear......the rats nest shall be put to rest.....lol
praise the lord!!! lol
Vacuum Diagrams

Thanks: I used this diagram to figure out why my truck was not starting.  I had a leak in the vacuum line between the EVV and the distributor. 

I'm hoping this is the reason why my truck won't start when it's cold outside.  Anyway it can't hurt the fix the leaking vaccume line.


It's been warm this last two days and my truck starts up fine when it's 60 deg F outside. But when it drops down into the 30's the truck is harder (much harder) to start.  I put a new battery in the truck to help me get it started.  It take a lot of cranking before it finally fires up when it's cold outside.


This vaccume leads to the distributor and I think it's part of the vaccume advance system on the distributor.  Not really sure how that affects cold starts.


All summer long I had a bad IC unit inside the distributor and the truck would not start at when it got hot. It was not getting a spark after the distributor's IC Unit got hot. So I replace that IC unit inside the distributor and the truck started up fine during the warm weather months.


When these trucks get old there is a lot that can go wrong but I've been lucky so far.  My truck has almost 200,000 miles on it and it's a 1986 truck that I got in Sept of 85. 


It's leaking oil at the value cover and I need to get that fixed somehow.

There is no vacuum advance at idle and thus none at  start-up. Vacuum advance is from a small port in the carb that is above the throttle plate. At idle there is vacuum below he plate and ambient air pressure above where the port is. When the throttle plate is opened slightly the plate moves slightly above the port and exposes it to vacuum... and vacuum advance happens. Well it does if the engine is fully warmed up. If the engine is cold there is no vacuum advance no matter where the throttle position is. .

Thanks for the input Mike. 

I want to check the timing to make sure it's set right but I read that I have to plug up the vaccume line on the distributor.  Do you know how to do this?  I can't reach the distributor easily to take the vaccume hose off it at it's base. It's hard for me to see where the vacume lines go when they dip down into the lower part of my engine.


As I stated there is no vacuum at idle so you do not need to remove the hose when setting the base or static timing. If the idle is too high both vacuum and mechanical advance may be present but at 650-750 it isn't.

OK now I see what you are saying. I must be unlucky as my idle speed shows 850 to 1000 rpm on my tac inside the truck when I am stopped and in neutral. 

I was getting ready to go outside and hook up the timing light to the truck and see what the timing is set to while it's idling.  Perhaps I could slow down the idle speed adjustment screw a little? 


I need to check the compression in all four cylinders again to make sure it's ok.  And I probably need to have the values checked and adjusted to factory specs when I have them take off the value cover and replace its gasket. I have oil leaking out from the value cover where it fits over the engine.  I lose about a half quart of oil a month or two.  It's making my engine messy and I need to get that fixed. One guy at the local repair shop scared me when he told me that if it was leaking because of a warped head that it would cost me a lot more money. But the guys at Pep boys can adjust the values and put on a new value cover gasket for about 200 bucks.  I probably could repair the gasket myself if it were not so cold outside these days. But I can't afford to be without my truck as I have no other form of transporation right now. My 72 Caddy is in the shop getting a new carb job on it right now.


Why does the Hanes manual say to plug the vaccume hose then?  I'm confused by two different people telling me different things.  But I can't ask the manual questions like I can with you online in these forums. :)  Thanks for the help.  I'll check it soon and see what the timing is set to. 


I need to be able to read the timing though.  I suspect that not being able to mark the timing point with some white chalk or paint will make it harder to read the timing.  I'll just have to try it and see what happens. I've not timed a engine since I did it on my old Datson 240 Z.  That was way back in 1973  to 1984.  I had that Z car for ten years and my dad had one of the original 1972 Datson Pickup trucks. I guess it was a 720 back then?  I can't remember what model it was. But we drove it until it front end ball joints almost fell apart before we put that truck to bed for good.


The Ignition Timing

3 DegreesBefore top dead center*Set at warm idle speed (650 - 700 RPM)*Distributor vacuum hose disconnected & plugged*Transmission in drive (parking brake engaged)


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