Vacuum advance to what?

So I finally got to spend an afternoon in a heated garage working on my 1991 Sambar (naturally aspirated). Cleaned the carburator and installed a lower radiator hose heater (Zerostart by Temro). Everything went fine, but we did notice something that had me scratching my head.

When replacing the carburator "top" and hooking the lines back up, we discovered a line that lead to nowhere. It just ended open on the driver's side of the carburator. Following it back I found that it lead to the vacuum advance on the distributor. (I'm awfully proud of that because I couldn't point out a distributor a couple of months ago.)

This could explain much of my crappy mileage. So this seems like a good discovery to me. Here's my question: What should the vacuum advance line connect to? Where?

Also, with the two plastic covers on either side of carb off we noticed a little thing by the throttle that responded when the engine was revved. What is that called? It's not the choke, is it? It seemed like it was reacting to vacuum, but I could be wrong on that.

Just got back from a smoke test, and the truck is running exactly as it did before I started messing with the carburetor (and after I messed with the fuel), or at least very similarly. It used to top out at about 100-105 km/h. Now it's more like 90-95 km/h. Maybe it's just the low temperatures (-30C), but I suspect it's the fuel. I'm hoping that the radiator hose heater will allow me to use the truck on a daily basis for the next little while so I can burn through a couple tanks of fuel and hopefully see an improvement.

 

The truck may have been tuned/timed with the vac advance off and now that you have discovered this you should probably re-time it. and reset all of your fuel mixture settings at the carb. I would hazzard a guess on the the thing reacting to vacuum being a deceleration valve to keep the throttle from snapping closed when you release the gas pedal.

 

It was definitely timed with the vacuum advance off. I did it. Of course, I thought that the vacuum advance was properly hooked up at that point. Live and learn.

And I wanted to rephrase my primary question because I know the vacuum advance should hook up to vacuum. It's just that I'm not sure what is a vacuum line and what's not. Where does the vacuum start? Is there something else that hooks up to vacuum that I could use to solve this mystery.

 

engines should be timed with the vacuum disconnected, then reconnnected when done.

there are several different places to pick up vacuum. there is manifold pressure, and there are several on the carburetor. where to connect it depends on what the vacuum is for on the vehicle. some just use the vac for initial off idle and for full advance rely on the centrifugal weights. you really need a vac diagram for your truck to know where to connect it. you can play around with it and plug it into different places and check how the timing advances with a timing light, that's the hit-or-miss method i have used in the past.

one more piece of advice when working on the carb... make all adjustments one quarter turn at a time and write down how much you adjusted each screw. this will give you a base line so that if your truck runs worse you will know where to set it back to.

 

Ya. I disconnected (the already disconnected) vacuum line for the vacuum advance when doing the timing. But I didn't notice any change in timing with it connected or not (even at about 2000 rpm). This makes perfect sense now.

So I can't just hook it up to any vacuum line. Nuts. So I'll have to arrange with another '91 Sambar owner to either do some poking around for me, or we can do a side by side.

Of course, at the moment, I'm more concerned that I can't get my truck started in the cold weather. But that's a subject for another thread.

 

Me too. Then and now. But the line was disconnected, just hanging off in space the whole time. Until I can figure out where and how it connects, it will remain so. The only thing I've done is plugged any lines that weren't connected to anything, just to keep crud from getting sucked in to vulnerable places.

But I should confirm that vacuum is being generated and that the advance works. Good suggestion.

 

I might not get a chance for a few days but I will pop the cover on mine and see where it goes to for reference.
Hopefully somewhere that the NA's and SC's have in common because I know the intake is different.

I am guessing that the vent line from the 4wd drive system might be hooked up in it's place on the correct port
believe it or not there is a vent from the vacuum diaphram that engages the 4wd that basicly goes nowhere
I can see how if the lines were removed that it would be easy to hook it up by mistake.

 

Timetripper, thanks a great deal. There's no great rush. I'll try to get some pictures taken that show what is going on so that you or someone else can easily compare.

I'm focused on cold weather related issues for the time-being. But swapping lines is easy enough to do at the same time. And now that the little beast is running, it's easy to pull it into a heated garage and work on it for a couple of hours. Its amazing how much of a difference a heated garage makes.

 

Yes a heated work space is great to have.
With the temps dipping to below zero in my neck of the woods I found last night that mine now has a stuck throttle cable.
Revs go up but dont come back down.

 

Throttle cable fixed but guess what? S/C's don't have a vacuum advance on the distributor - it's all done thru the ECU I guess.
Sorry I couldn't help on this one.

 

No worries. Trust me, you've already helped me a great deal.

 

Rural, the vacuum line for time advance should be hook to the top of the carb on the back side. I am also working on carb problems, 1991 same as yours. finally got it to start but have no power, top speed 45 km. In the cold weather these things just don't warm up it's -25 C in Regina. I talk to a mech who told me some truck come without termostats or have low temp summer ones. If they don't warm up you will also have power problem. If you figure out the carb setting I would like to know where you ended up setting them.

 

Hey Rural I Have A 91 As Well If I Can Thaw The Box Out So I Can Release The Hatch I'll Have A Look And See If I Can Get Pix. Mine Is Starting Good Here In Three Hills But I Messed Up Started And Went Into House Got Delayed And It Was Sitting For An Hour It Had Stalled Grrrrrrr Dead Battery. Had To Use Vise Grips To Remove The Nut On Battery Cover ,someone Must Have Thought It Held The Truck Together The Way They Tightened It .looking At The Cables Tho If You Are Cranking A Lot You Might Want To Change Them, As They Are Very Small Would Not Take Much To Melt Them. Have You Looked In Your Radiator Resivoir Mine Had About A 1/4 Inch Of Fine Sand In The Bottom I Assume It Is Getting In From Road Splashing.i Still Have No Got A Heater For It And It Sits Out On The Street.proudly On The Front Street Mind You Hide The Ford And Chev Trucks In The Lane Wifes Dodge Mini Van Gets The Driveway Lol. Mine Will Not Warm Up Inside Unless Driving Idle Forever And Not Much Heat Once Driving It Warms Up Inside Fast.

 

Thanks Saskmini and Confuzed. I'm fighting a tenacious infection at the moment, but should get some time to do some serious work on the truck over the holidays. I'll be in the big city in a few days and will use the opportunity to track down some parts and fluids (gasket material, battery, some fuel hose, synthetic gear oils and synthetic motor oil).

Confuzed, thanks for the tip on the battery cables. It looks like most replacement batteries I can find would need new connectors anyway. So might as well replace the cables too.

My Sambar just barely puts out heat at idle when the outside temperature is below about -25C. One of the first things I'll be doing is insulating the lines to the radiator (and the cab heater), but I doubt that will make much difference. Can't hurt though and only costs $5.

I'll take lots of pictures when I'm doing any work on the truck. They'd be useful for discussion, but I've got another idea in mind too.

 

"no power, top speed 45 kph"

Check the points and make sure they're not closed all the time or burned. I had the same problem before I set the points. It will help to have three hands and a mechanic's folding mirror. I ordered new points along with a distributor cap and rotor from Japanoid. I also changed to iridium plugs earlier which helped the engine run quite a bit smoother--Denso IK20 set to 1mm gap.

 

Rural. If you start your truck and suck on the vacuum line you should hear a change in the motor sound. If not check in the line for a small brass fitting. I found some line have them some don't, it could be plugged. if the line is clear and the motor sound changes when you suck on the line you may have a vacuum problem in the carb. I now have mine starting like a charm inside the heated garage, but still no power.

 

heat

Rural I insulated both my lines to the rad and to the heater and put a piece of cardboard in front of the air intake(grill) and no I have left mine idle for an hour in real cold you do not get heat but as soon as I drive it I get heat.Also check your antifreeze level I found mine to only be good to -20 was thickening.No pix yet as I have 8" of snow in the box will have to stay after work one night and thaw it out in the shop.

 

Good discussion going here. Valuable points from all.

Back to the original reason for posting: My disconnected vacuum lines. I've been busy dropping the fuel tank, fixing the problem resulting from a broken bolt, cleaning the tank with methanol, replacing the tank, and finally working the bad fuel out of the system. Still isn't running yet, but I think I'll get it today.

In all this fiddling, I noticed that there is a diagram for the vacuum lines on the underside of the engine cover. That diagram made it clear that the line I thought was connected to the vacuum advance (and nothing on the other end) was just a vent line connected to the distributor cap. There is a vacuum line connected to the vacuum advance as there should be, and once I get the truck running, I'll confirm that there is vacuum as well.

So now my question becomes: Distributor cap vent to what?

I doesn't seem like the vent should be connected to vacuum as that might suck crud into the cap. Maybe I'm wrong on that.

 

I think the cap has a vent line on it due to the location of the distributor near the back of the truck.
Over the years Subaru added "splash" panels on the engine cover that folds down for engine access.
I'm guessing that they had problems with water around the engine when driving thru the monsoons of rain.
It is common for imports to have a vent on the distributor cap - usually a upside "U" made of rubber.

The purpose of any dist. cap vent is to let the ozone that is created when the rotor passes by the tower and sparks have a way out of the cap.