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International-9.0
Advanced Member
USA
459 Posts |
 Posted - 03/19/2008 : 6:19:54 PM
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We have a 1986 366 that was running horrible. Anything at a fast idle and above would cause a vacuum rushing sound and the engine would bog down until the rpms went down and then it would rev back up and then back down...etc. We found some disconnected hoses at the charcoal filter. Apparently it has some kind of solenoid that was opening somewhere in the fast idle rpm range and it was allowing too much air into the carbeurator. If you all out floored the engine, it would delay and bog down, then pick up and take off as long as you kept it at full throttle.
Does anybody know how this device was supposed to work? Did it suck gasoline vapors out only above a certain rpm? I know those filters are supposed to keep vapors out of the atmosphere but that's about it.
We plugged the hole up for now so that problem is eliminated, but it is also backfiring. When you really step on it and then let off it will powwwwwwwwwww!!! Sometimes out the tail pipe and sometimes up into the air cleaner. The exhaust fumes are something terrible as well so I assume it's running really rich or really lean. I haven't seen any black smoke. One mechanic thinks rich and one thinks lean. The only trick I've yet to try is waiting until the engine is good and warm and pulling out the choke to see if it runs better, but I suspect it is running too rich. Anybody have any insite on this engine? |
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Wolf0r
Top Member
USA
2181 Posts |
Posted - 03/20/2008 : 06:43:02 AM
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| Rebuild your carb and (tempoary disable the canister) check for other vacuum leaks. Carb kits are cheap for those Holly carbs, and easy to install. Buy a couple of new floats too. |
“The good thing about science is that it's true whether or not you believe in it.”
Neil deGrasse Tyson |
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IBTMech
Top Member
USA
973 Posts |
Posted - 03/20/2008 : 5:39:14 PM
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The backfiring might be caused by the air pump dump valve sticking open (if equipped).
I would bet the carb is a Rochester Quadrajet and the power enrichment valve is notorious for sticking and the accelerator pump cup likes to come off if the unit has sat around for any length of time. Have fun! |
If it doesn't fit, FORCE it.
If it breaks, well, it needed replacing anyway.
Pullin' wrenches for 45 years. |
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International-9.0
Advanced Member
USA
459 Posts |
Posted - 03/20/2008 : 7:01:59 PM
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| Eric, thank you for your insight. I assume the dump valve is the valve the directs the pump air either to the air cleaner or to the exhaust manifold? This bus sat for a few years only going our 2 or 3 times in a year at most. If you remove the air cleaner is the enrichment valve or cup visible? One day next week I might try and get some pictures. |
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baptistbusman
Advanced Member
USA
301 Posts |
Posted - 03/20/2008 : 8:20:21 PM
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Definately needs the carb rebuilt, I agree Wolf. I actually removed that whole air cleaner setup on one unit that was having all kinds of trouble. Took off the 2 pumps, and plugged up the holes in the manifold. You wouldn't believe how better it ran.
Get some seafoam, and suck it up through the vacuum lines. It will do a world of good for that engine. |
1 Timothy 1:15 This is a faithful saying, and worthy of all acceptation, that Christ Jesus came into the world to save sinners; of whom I am chief. |
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Wolf0r
Top Member
USA
2181 Posts |
Posted - 03/21/2008 : 06:40:01 AM
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| baptistman you know your 366! I squirt straight carb cleaner into the float bowls through the vents. Sitting is rough on them, agree with the seafoam. |
“The good thing about science is that it's true whether or not you believe in it.”
Neil deGrasse Tyson |
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Aint Skeered Racing
Senior Member
United States
68 Posts |
Posted - 12/27/2008 : 5:22:35 PM
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| I have the same problem untill I rebuilt the carb and changed spark plug wires then there wasn't any issues anymore |
Jimmy Volk #76
Aint Skeered Racing
School bus racing asphalt Figure 8s and oval dirt racing
Owner of 26 racing buses
14 buses destroyed
12 buses running |
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International-9.0
Advanced Member
USA
459 Posts |
Posted - 12/27/2008 : 8:40:43 PM
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| Wow, you brought up an old topic. I meant to say they solved the backfiring by cutting off the air pump belt. They like to red-neck rig things around here, but it did work. I assume that th dump valve was sticking as previously mentioned. The fumes are still something awful, but I keep it from idling too much. |
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cng mech
New Member
United States
2 Posts |
Posted - 01/02/2009 : 10:38:26 AM
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| that vehicle doenst have a holley with a governer on it,, does it?by the way im new to the board this is my first post!!---rich |
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International-9.0
Advanced Member
USA
459 Posts |
Posted - 01/02/2009 : 3:16:52 PM
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| Welcome to the forum Rich. I have no idea if it's a holley, but it does have a governor on there; I've tested it. It will cut out just before the overspeed light comes on. |
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cng mech
New Member
United States
2 Posts |
Posted - 01/02/2009 : 5:34:18 PM
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| im pretty sure holley were the only ones that made a carb with a goverener for that year.we have 2 bobtail pick ups(1986) with that same set up.had same issues.i replaced the carbs with a regular holley 4bbl and put msd rev limiters on them.i also had to replace the egr solenoid and clean out the egr ports and did tune up,,runs great now.i hope this helps. |
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1986 Cheverolet 366
