Timing and vacuum advance
12-23-2008, 04:17 AM
#17
Three Wheelin'
ok, but mine is 20 x 40 x 6 m high.... i have a diesel "blower "... but doesn't help much at evening unless i ignite it at noon... which means 25 l diesel a day...
We are gonne build a small garage at the house for my lift , si i can heat it in winter more "cheaply"...
We are gonne build a small garage at the house for my lift , si i can heat it in winter more "cheaply"...
12-23-2008, 07:14 AM
#18
Rennlist Member
OK, taking it off center into speculation land just a little bit...a little knowledge is dangerous...What about the time/temp sensor (what I meant to say, above)?
If I could get my car started at all, it would be flat until 3000 rpm, then explode with power. I found a way to move the distributor to make it start, but was then rough at higher revs.
Is it possible this could be contributing for Tom? ( Changed time/temp, now starts when cold instantly, and also what seems to be full power throughout the rev range.)
If I could get my car started at all, it would be flat until 3000 rpm, then explode with power. I found a way to move the distributor to make it start, but was then rough at higher revs.
Is it possible this could be contributing for Tom? ( Changed time/temp, now starts when cold instantly, and also what seems to be full power throughout the rev range.)
12-23-2008, 10:26 AM
#19
Instructor
Thread Starter
Yeah, that would suck! (breaking off a piece of wood in the cyliner, that is). I have some metel dowels, too, I'll use. And go really slow when turning it. I can't really see how this could be the problem either (how the ring could be in the wrong position), but who knows. Maybe the key is missing. Worth checking.
That is a great picture of the vacuum hose routing from another '82. But it points out a couple differences between it and my car:
#2 is as described.
#3 is the ported one that I have now correctly attached to the distributer advance. But it was also connected to the "diverter valve" (for the air pump), so now I have "T" so that port 3 connects to both the distributor advance and the air pump diverter valve. (In some other post I read that the diverter valve is supposed to be ported vacuum.) Does the car from the picture above have an air pump?
The front side of the TB on my cart has two ports, not just the one labelled "1" in the picture above. They are side by side, with one just slightly higher than the other (see picture attached here). Both have vacuum at idle. I'm pretty sure one of them (on the right in the picture) is supposed to go to the distributor retard, and the other (left in the picture) was connected to the purge valve (for the charcoal canister) and I have left it there. So, now I am wondering if the charcoal canister valve is supposed to get ported vacuum (not that I can see that making much of a difference in my timing/stumbling problem).
And I'm still thinking there is something wrong with the vacuum advance/retard on the distributor, because the retard just does nothing at all.
It's still 18 degress in my garage, so I'm going to let it warm up to the balmy 30s before I get back to fiddling.
That is a great picture of the vacuum hose routing from another '82. But it points out a couple differences between it and my car:
#2 is as described.
#3 is the ported one that I have now correctly attached to the distributer advance. But it was also connected to the "diverter valve" (for the air pump), so now I have "T" so that port 3 connects to both the distributor advance and the air pump diverter valve. (In some other post I read that the diverter valve is supposed to be ported vacuum.) Does the car from the picture above have an air pump?
The front side of the TB on my cart has two ports, not just the one labelled "1" in the picture above. They are side by side, with one just slightly higher than the other (see picture attached here). Both have vacuum at idle. I'm pretty sure one of them (on the right in the picture) is supposed to go to the distributor retard, and the other (left in the picture) was connected to the purge valve (for the charcoal canister) and I have left it there. So, now I am wondering if the charcoal canister valve is supposed to get ported vacuum (not that I can see that making much of a difference in my timing/stumbling problem).
And I'm still thinking there is something wrong with the vacuum advance/retard on the distributor, because the retard just does nothing at all.
It's still 18 degress in my garage, so I'm going to let it warm up to the balmy 30s before I get back to fiddling.
Last edited by Tom Rathjen; 11-27-2011 at 10:08 PM.
12-23-2008, 11:05 AM
#20
Rennlist Member
Timing marks can be off if dampner was put on backward when doing timing belt. My '81 had a problem where the advance unit had actually fallen off inside the distributor. A P.O. had rotated distributor timing full forward to get running and other than poor mileage (maybe 11mpg) car ran o.k.. It even passed smog twice with no problems.
12-23-2008, 01:49 PM
#21
Rennlist Member
Chris, while it is of course possible that Tom has additional issues with his injection system, what he's describing indicates an ignition problem. Separate systems. Besides, he has the opposite problem. You had poor running until 3K when it would come on like gangbusters. Tom has a stumble at 2.5-3K, right at the point where he is seeing the timing suddenly retarded.
Joe, good point, I had forgotten about the potential for the damper to be installed backward. This is easily spotted -- the markings on the damper should read right side up looking at it from the bumper. This of course has nothing to do with the sudden timing retard, but you're correct -- it's something else that can be put together wrong.
Tom, from what I see in the diagrams I think that the line closer to the idle screw is the one you want. If you have the Tech Doc CD, look in "928 Air Flow Controlled Fuel Injection.pdf" on page 3. The second hose nnear that location must have been added later for a different purpose. Vacuum at idle is fine, but you need to be sure that the vacuum drops faster than manifold vacuum just off-idle.
As for the retard not working at the distributor, I'm not sure how exactly that vac pot is constructed. If it has two diaphragms inside, it's possible the one for retard is ruptured. If there is only a single diaphragm in there, then it's a mystery why it works in one direction and not the other.If you don't have a mityvac, now is the time to buy, beg or borrow one. See if that retard port holds vacuum. If not, replace the vac pot. If it does hold vacuum but doesn't move the advance/retard plate inside the distributor it's time to open up the distributor(no need to remove it from the engine, just look inside) and see if you can see any obvious mechanical problem.
The car should work a lot better and not suddenly retard timing anymore now that you have the vac hoses worked out, but you will want to get the retard issue worrked out ASAP.
Joe, good point, I had forgotten about the potential for the damper to be installed backward. This is easily spotted -- the markings on the damper should read right side up looking at it from the bumper. This of course has nothing to do with the sudden timing retard, but you're correct -- it's something else that can be put together wrong.
Tom, from what I see in the diagrams I think that the line closer to the idle screw is the one you want. If you have the Tech Doc CD, look in "928 Air Flow Controlled Fuel Injection.pdf" on page 3. The second hose nnear that location must have been added later for a different purpose. Vacuum at idle is fine, but you need to be sure that the vacuum drops faster than manifold vacuum just off-idle.
As for the retard not working at the distributor, I'm not sure how exactly that vac pot is constructed. If it has two diaphragms inside, it's possible the one for retard is ruptured. If there is only a single diaphragm in there, then it's a mystery why it works in one direction and not the other.If you don't have a mityvac, now is the time to buy, beg or borrow one. See if that retard port holds vacuum. If not, replace the vac pot. If it does hold vacuum but doesn't move the advance/retard plate inside the distributor it's time to open up the distributor(no need to remove it from the engine, just look inside) and see if you can see any obvious mechanical problem.
The car should work a lot better and not suddenly retard timing anymore now that you have the vac hoses worked out, but you will want to get the retard issue worrked out ASAP.
12-23-2008, 02:03 PM
#22
Three Wheelin'
i have such a compressed air driven vacuum bottle for de-aerating brakes...with that i could check the movement at the inside distributor , putting it on both sides once. ( advance-retard)
12-23-2008, 02:28 PM
#23
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Tom
I think you should try switching the Charcoal check valve and the air pump diverter valve hoses. I think you don't want the Charcoal valve getting manifold vacuum constantly at idle. the Diverter valve though you do want vacuum at idle I think. On my car the charcoal valve is also run through a temp control valve. I removed my air pump on my car but I think the diverter valve was "T'd" off of the #2 fitting with the fuel damper and regulators.
My thinking about the Charcoal valve is that it could be a source of a large manifold leak if allowed to be opened at idle(constant vacuum source). The charcoal purge lines are rather large and they attach with the oil breather line to the intake. I could be wrong but I still don't think it should have constant idle vacuum.
JIM
I think you should try switching the Charcoal check valve and the air pump diverter valve hoses. I think you don't want the Charcoal valve getting manifold vacuum constantly at idle. the Diverter valve though you do want vacuum at idle I think. On my car the charcoal valve is also run through a temp control valve. I removed my air pump on my car but I think the diverter valve was "T'd" off of the #2 fitting with the fuel damper and regulators.
My thinking about the Charcoal valve is that it could be a source of a large manifold leak if allowed to be opened at idle(constant vacuum source). The charcoal purge lines are rather large and they attach with the oil breather line to the intake. I could be wrong but I still don't think it should have constant idle vacuum.
JIM
12-23-2008, 06:47 PM
#24
Instructor
Thread Starter
Today's progress (didn't get to work on it much....cold all day, and having a party at our house tonight):
Verified that TDC on the crankshaft pulley marking is indeed TDC of piston number 1. No big surprise there, but nice to know for sure.
I removed the distributor to examine it and look for something obvious. Also removed the vacuum assembly from the distributor. Didn't see any obvious problem. But I still think that the retard part isn't functioning. Putting manual suction on the advance side produced movement of the armature, but suction on the retard port did nothing. Didn't seem to be leaking, but more like it was already bottomed out or something. Can't take it apart further without destroying it. I went ahead and ordered a new vacuum assembly for the distributor (pretty cheap from (928 intl), so not a big risk.
I didn't have time yet to play with the vacuum hosed per some of the other suggestions above.
Verified that TDC on the crankshaft pulley marking is indeed TDC of piston number 1. No big surprise there, but nice to know for sure.
I removed the distributor to examine it and look for something obvious. Also removed the vacuum assembly from the distributor. Didn't see any obvious problem. But I still think that the retard part isn't functioning. Putting manual suction on the advance side produced movement of the armature, but suction on the retard port did nothing. Didn't seem to be leaking, but more like it was already bottomed out or something. Can't take it apart further without destroying it. I went ahead and ordered a new vacuum assembly for the distributor (pretty cheap from (928 intl), so not a big risk.
I didn't have time yet to play with the vacuum hosed per some of the other suggestions above.
12-23-2008, 09:27 PM
#25
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Tom
I verified tonight, My car has the extra fitting like yours. The fitting is for the divrter valve which I removed on my car. So numers 1-3 are connected just like the WSM photo. I think perhaps the extra fitting next to #1 is for U.S. cars fitted with catalytic converters. Hope all this helps.
JIM
I verified tonight, My car has the extra fitting like yours. The fitting is for the divrter valve which I removed on my car. So numers 1-3 are connected just like the WSM photo. I think perhaps the extra fitting next to #1 is for U.S. cars fitted with catalytic converters. Hope all this helps.
JIM
12-24-2008, 02:34 AM
#26
Rennlist Member
Good Progress, Tom. Did you make sure the engine was at TDC firing stroke when you pulled the distributor? If not, you can pull the PS belt cover and check for the TDC mark on the cam sprocket. Then you can line up the rotor with the mark on the distributor housing when you put it back together.
Good move on the vac pot, it's pretty much a go/no go check and not worth fiddling with.
Good move on the vac pot, it's pretty much a go/no go check and not worth fiddling with.
12-24-2008, 11:32 AM
#27
Instructor
Thread Starter
Oh, yes, forgot to mention that. Yes I did re-verify the cam sprockets were also still in the correct TDC places. No problem there. And when I put the distributor back on, I made sure the rotor was alligned with the proper mark (and I think it was there before I removed it). Of course, I will have to take the distributor off again as soon as the new vacuum part gets here.
12-25-2008, 10:55 PM
#28
Instructor
Thread Starter
Well, I am off to Nebraska for a few days for a funeral. So will report back on this when I am back and can get back to work on it, and when hopefully the new distributor vacuum has arrived.
I hope everyone had a very Merry Christmas.
I hope everyone had a very Merry Christmas.
01-05-2009, 05:09 PM
#30
Instructor
Thread Starter
Happy New Year, everyone.
Just wanted to check in, and confirm that I am still waiting on the new vacuum advance to arrive. So not much I can do till it gets here. Hopefully it will arrive while I am in Alabama Tues-Thurs, so I can get back to it Friday and Sat.
Just wanted to check in, and confirm that I am still waiting on the new vacuum advance to arrive. So not much I can do till it gets here. Hopefully it will arrive while I am in Alabama Tues-Thurs, so I can get back to it Friday and Sat.