StrobeWylan Posted March 27, 2008 Share Posted March 27, 2008 My 1987 DL runs great except when we get rain/snow mix when temp is 30-40F. Happened yesterday and I quickly took off the air cleaner top to look for frosting in the carb. It looked really clear inside. I have 2 parts cars and have tried a coil I know is good, also a distrib. I looked at the distrib and it looked dry. I'll watch it though in case I missed something. The way this happens: It will run great. Then after about 10 minutes (only when theres a rain/snow mix) the power starts to fade. No backfiring. Just a fade of power that takes about 10 minutes til the engine quits. I pull over and wait about ten minutes and it will start up and run great for another 10 minutes. Then it starts to fade again. Actually we had been a climate where we did not get rain/snow mix except rarely. Now that seems to have changed. We used to get snow from Canada and it was a dry snow, took a foot of it to make an inch of water. It came with very cold temps. So this is a new experience for my SUBE. :-\ Any ideas?? Quote Link to comment Share on other sites More sharing options...
robm Posted March 27, 2008 Share Posted March 27, 2008 It really does sound like carb icing. Make sure the hot air tube is hooked up to the air intake. Or rig one up, if it doesn't have one. Good luck. Quote Link to comment Share on other sites More sharing options...
StrobeWylan Posted April 9, 2008 Author Share Posted April 9, 2008 Yea the tube is there. I swapped out a different air cleaner housing just in case it was not switching properly. TOday it rained and was about 50 temp. I took it out on the highway and it ran fine. So it does take the 30-40 degree temp plus moisture to get it to fade power. Like I said when the problem did occur I quickly opened the air cleaner but saw absolutely no icing inside. Quote Link to comment Share on other sites More sharing options...
nipper Posted April 9, 2008 Share Posted April 9, 2008 make sure the temp switch and the snorkle door motor are working. nipper Quote Link to comment Share on other sites More sharing options...
StrobeWylan Posted April 9, 2008 Author Share Posted April 9, 2008 I'm not sure what the temp switch and the snorkle door motor are. Are they what switches the air supply to the heat from the exhaust? Quote Link to comment Share on other sites More sharing options...
nipper Posted April 9, 2008 Share Posted April 9, 2008 snorkle motor is a vacume motor in the snorkle that opens and closes the door, its a diaphram. The temps switch is in the air cleaner itself. Follow the vac line back from the door motor and it will take you right to it. nipper Quote Link to comment Share on other sites More sharing options...
opus Posted April 9, 2008 Share Posted April 9, 2008 Thats what it is. I have the same issue here. I cant find a hot air tube though. Need to find something to make one out of. Mine seems to be about 3' long and NAPA doesnt have one. Quote Link to comment Share on other sites More sharing options...
Gloyale Posted April 9, 2008 Share Posted April 9, 2008 make sure the temp switch and the snorkle door motor are working. nipper I drove both my carbed GLs in Wisconsin winters. I don't think either had a snorkus. The coolant lines at the base of the carb should keep it warm enough to prevent icing. I feel like there is a different problem here. But I can't think of one. So I guess getting some warm air to the carb couldn't hurt. Quote Link to comment Share on other sites More sharing options...
nipper Posted April 9, 2008 Share Posted April 9, 2008 I drove both my carbed GLs in Wisconsin winters. I don't think either had a snorkus. The coolant lines at the base of the carb should keep it warm enough to prevent icing. I feel like there is a different problem here. But I can't think of one. So I guess getting some warm air to the carb couldn't hurt. Well the magic thing here is that in bitter cold, the air cant hold moisture, so you dont get icing. When its near freezing, and the air is holding moisture, you do get icing. nipper Quote Link to comment Share on other sites More sharing options...
StrobeWylan Posted January 10, 2009 Author Share Posted January 10, 2009 Ok, winter has returned and I'm back to trying to solve this. I hooked up a vacuum pump to the snorkel motor and it operates the butterfly just fine. I do not detect any vacuum though on the line that goes to it. When should it have vacuum? Is it when engine warm, cold? Is it outside temp related? I'm confused though. The problem doesn't happen until I drive 10 miles at highway speed. It runs really good when the engine is cold. So if the warm air is used from the heat riser tubing only when engine is cold, how does it prevent carb icing when the engine is warmed up [which is when mine happens]? I'm wondering about the "The coolant lines at the base of the carb should keep it warm enough to prevent icing." as Gloyale mentioned. I see one line that comes from the thermostat and disappears under the carb somewhere. It's the size of a gas line hose. I don't see where it reappears on the other side or another return line. What am I looking for? Quote Link to comment Share on other sites More sharing options...
opus Posted January 10, 2009 Share Posted January 10, 2009 Mine has vacuum at all times. When it is cold, the little do-hicky in the snorkel allows the vacuum to close the flap. When it warms, it closes it. Quote Link to comment Share on other sites More sharing options...
StrobeWylan Posted January 10, 2009 Author Share Posted January 10, 2009 So you have vacuum at the snorkel motor at all times? Quote Link to comment Share on other sites More sharing options...
opus Posted January 10, 2009 Share Posted January 10, 2009 I do. Whether that is right or not, doesnt matter. I dont have many vacuum hoses so that is the route I took. Quote Link to comment Share on other sites More sharing options...
Skip Posted January 10, 2009 Share Posted January 10, 2009 why not by pass the thermo vacuum valve and feed it constant vacuum for now? Strange that two air cleaners both have bad thermo valves. Have you checked for vacuum at the valve? Done any work on the fuel lines? I've never seen fuel line freeze up on a Subaru though. Some dry gas many not be a bad idea. Quote Link to comment Share on other sites More sharing options...
zyewdall Posted January 10, 2009 Share Posted January 10, 2009 Yeah... maybe run some dri gas, and also perhaps change the fuel filters... could they have water in them somehow? The first thing I'd suggest was carbureator icing... except that I've never had that happen on a subaru. What it sounds like is awfully alot like my diesel truck does if I'm running B100 in temps around freezing -- wax buildup in the filter. But... gasoline doesn't do that normally. Bizarre.... The not starting for 10 minutes is odd... if it was ice buildup that bad, you should definitely be able to see it, I'd think. When it won't start, is it a spark or fuel issue? Or air, I guess. Will it fire up on ether? Have you popped the distributor cap and looked to see if there's moisture in there... I can't really figure out why it would get more moisture as it runs, but I suppose it's possible (I did powerwash an engine once, on a mitsi pickup, and it ran for about a mile after the carwash, then died - -the distributor was completely wet inside when I popped the cap, but it had fired right back up after washing it. Z Quote Link to comment Share on other sites More sharing options...
nipper Posted January 10, 2009 Share Posted January 10, 2009 Did anyone test the thermo valves instead of just assuming they are bad? You should have vacum at the snoprkle motor when the car has warmed up. You can do a simple test. Just disconnect the door and plug the line and see if the issue goes away. nipper Quote Link to comment Share on other sites More sharing options...
tempStrobeWylan Posted January 10, 2009 Share Posted January 10, 2009 Sorry folks, I tried to change my e-mail and must have fouled something up. I haven't been able to post. I e-mailed admin twice but got no answer. So I re-registered so I could let you know today I will try all of your suggestions. Thanks for all this help. I'll try to post the results. Quote Link to comment Share on other sites More sharing options...
tempStrobeWylan Posted January 10, 2009 Share Posted January 10, 2009 While hooking up a hose to bypass the switch I noticed the hose that supplies vacuum to the switch was badly cracked at the end. I'm bettin' that's the problem. I'm gonna change out all the hoses in that circuit. I'm thinking that the switch has to be activated by humidity rather than temp. Otherwise when you're on a dusty county road you'de suck dirt into the air cleaner and that seems contrary to Sube smarts. Quote Link to comment Share on other sites More sharing options...
nipper Posted January 10, 2009 Share Posted January 10, 2009 While hooking up a hose to bypass the switch I noticed the hose that supplies vacuum to the switch was badly cracked at the end. I'm bettin' that's the problem. I'm gonna change out all the hoses in that circuit. I'm thinking that the switch has to be activated by humidity rather than temp. Otherwise when you're on a dusty county road you'de suck dirt into the air cleaner and that seems contrary to Sube smarts. 1- its a thermo switch, period. 2- ALl it is isdoing is getting air from the hot exhaust pipe. It is not bypassing the air cleaner. If it is you have bigger problems or wierdness going on. Quote Link to comment Share on other sites More sharing options...
Skip Posted January 10, 2009 Share Posted January 10, 2009 It was once stated ?on the internet? that carbs are set up mixture wise to ingest air at 100 deg F The thermo switch is placed inside the air cleaner in the air flow going into the carb to maintain this temp. Quote Link to comment Share on other sites More sharing options...
tempStrobeWylan Posted January 11, 2009 Share Posted January 11, 2009 That makes sense Skip. I just bypassed the switch. There is not enough vacuum to operate the snorkel door. I measured it at 4. I then measured vacuum at the line that goes to the switch that operates the air conditioner idle speed thing. It measured 17. The thermo switch gets its vacuum from a fitting on the manifold that has a device there that I don't know the purpose of. The air cond idle switch gets its vacuum from the manifold right near the carb. Any ideas???? Tried the dry gas idea a long time ago, first before anything else (bout a year ago) tried carb cleaner too. But thanks anyway on that. I'm convinced that the fuel lines are fine. It does run like a champ in all conditions except around 35 deg F. Yesterday it was about that temp outside so I road tested it. The humidity felt dry however. Sube ran fine on the highway for a 15 mile round trip. It needs some humidity to fail. Must have to do with the snorkel motor, even though I cannot see frosting, it must be there. The cracked hose I found yesterday was not the one that goes to the switch. My mistake. I goes to the feed through fitting that supplies vacuum to the other switch inside the air cleaner, whatever that one does I do not know. Quote Link to comment Share on other sites More sharing options...
tempStrobeWylan Posted January 11, 2009 Share Posted January 11, 2009 So like you guys have stated, the temp switch is probably fine. Explains why changing the air cleaner housing did not fix it. Quote Link to comment Share on other sites More sharing options...
tempStrobeWylan Posted January 17, 2009 Share Posted January 17, 2009 I 'T'ed into the vacuum line that has 17 of vacuum and ran the thermo switch off it for a few days now. The snorkel door never changes to draw cold air. It's always drawing from the heat source. Does that mean the switch is not working? Haven't had cold weather or damp air since then so do not know if this fixed the problem. Car runs great. This motor only has just under 200k on it. Just getting started. Quote Link to comment Share on other sites More sharing options...
Skip Posted January 17, 2009 Share Posted January 17, 2009 It was once stated ?on the internet?that carbs are set up mixture wise to ingest air at 100 deg F The thermo switch is placed inside the air cleaner in the air flow going into the carb to maintain this temp. So what have your ambient temps been? Quote Link to comment Share on other sites More sharing options...
tempStrobeWylan Posted January 17, 2009 Share Posted January 17, 2009 45 to 55 F So do you mean if it's less than 100 the door draws heat from below? Quote Link to comment Share on other sites More sharing options...
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