Carburetor cleaner and backfiring?
Thread Starter
Instructor
Joined: Jun 2008
Posts: 166
Likes: 0
From: San Antonio Texas
Carburetor cleaner and backfiring?
I sprayed the outside and inside of my carb very liberally with carburetor cleaner. Is it normal for it to backfire after doing this? I figured it may be clearing out the contaminants that were washed off by the cleaner or something or maybe the excess cleaner that is in the bowl.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
If you have enough fumes around (and in) the carb, it could ignite and backfire through the carb. Carb cleaner is highly flammable and shouldn't be used liberally on a running engine. When checking for manifold leaks, just a light spray at the manifold gaskets in various areas should be enough to detect any air leak path (engine will increase rpm).
Thread Starter
Instructor
Joined: Jun 2008
Posts: 166
Likes: 0
From: San Antonio Texas
This was about a week and a half ago that I did this. It was not running when I did it. At first it was backfiring like crazy. Then it slowed down a bit. I figured that by now it would have all evaporated but it is still doing it a bit although not near as much. I hadn't ran it since I first sprayed it so it sat for over a week. Will it hurt anything if I take it for a spin and try to blow whatever it is out of there? The backfire sounds like it's coming from the carb area but also out the tailpipe sometimes. It just sounds so nasty that I don't want to damage anything.
I'm definitely a novice and just wanted to "clean" the carb. I figured what better way than to spray the crap out of it with some carb cleaner.
Does the expression "He knows just enough to get into trouble" have any bearing here?
I'm definitely a novice and just wanted to "clean" the carb. I figured what better way than to spray the crap out of it with some carb cleaner.
Does the expression "He knows just enough to get into trouble" have any bearing here?
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
If it's backfiring a week later, it has nothing to do with the carb cleaner. You have a timing problem. Get/borrow a timing light to check it out. You don't want to run the engine with it significantly out-of-time.
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,391
From: At my Bar drinking and wrenching in Lafayette Colorado
Spraying carb cleaner on and in a carb does little, if anything at all, to the carb other than rinse irrelevant dirt off exterior surfaces. A backfire up through the carb is an indication of a lean condition. Most likely, you pulled a vacuum hose loose during your cleanup and did not get it hooked back up, causing a lean condition and the backfire. Check for disconnected hoses and vacuum leaks. Carb cleaner sprayed on a carb doesn't do any more or less for the carb that washing the car does to the carb...
Lars
Lars
Drifting
Joined: Apr 2008
Posts: 1,540
Likes: 51
From: Lexington Park Maryland
Spraying carb cleaner on and in a carb does little, if anything at all, to the carb other than rinse irrelevant dirt off exterior surfaces. A backfire up through the carb is an indication of a lean condition. Most likely, you pulled a vacuum hose loose during your cleanup and did not get it hooked back up, causing a lean condition and the backfire. Check for disconnected hoses and vacuum leaks. Carb cleaner sprayed on a carb doesn't do any more or less for the carb that washing the car does to the carb...
Lars
Lars
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Thread Starter
Instructor
Joined: Jun 2008
Posts: 166
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From: San Antonio Texas
Okay, that gives me some good leads. When I was all done I thought that there was a vacuum line that I needed to put back but when I couldn't find it I figured that I must've put it back already. I'll double check that because I was SURE that I had removed one and tucked it out of the way. I did set the timing and replace the plugs just before I did this and am SURE (that word is gonna get me one day if it hasn't already) that I put all of the wires back on the right plugs as I went.
Safety Car
Joined: Jun 2004
Posts: 4,652
Likes: 80
From: Lakeland Florida
Hello
You said you set the timing before you did the cleaning. Was it backfiring before you did the timing adjustment? If not, then your timing is off , and that is causing the backfiring. Also, to do the timing you should remove the vac. advance hose to do it correctly, if you forgot to put this back on, it may also cause a backfire condition.
It appears that the cleaning of the carb with the cleaner, is not the problem as Lars has said, but the other areas you adjusted prior to spraying the cleaner.
kdf
You said you set the timing before you did the cleaning. Was it backfiring before you did the timing adjustment? If not, then your timing is off , and that is causing the backfiring. Also, to do the timing you should remove the vac. advance hose to do it correctly, if you forgot to put this back on, it may also cause a backfire condition.
It appears that the cleaning of the carb with the cleaner, is not the problem as Lars has said, but the other areas you adjusted prior to spraying the cleaner.
kdf
Melting Slicks
Joined: Jul 2006
Posts: 2,291
Likes: 493
From: Salmon Arm, BC
"I did set the timing and replace the plugs just before I did this "
Sounds to me that you may have crossed up some plug wires. Check your plug wires with the firing order..........18436572.
Don't really know how to do the small quote thing.........
Sounds to me that you may have crossed up some plug wires. Check your plug wires with the firing order..........18436572.
Don't really know how to do the small quote thing.........
Last edited by OMF; Nov 21, 2008 at 06:04 PM.
Melting Slicks
Joined: Dec 2000
Posts: 3,407
Likes: 2
From: Carmichael CA
All a Carb Cleaner spray is going to do is evaporate on your vacuum hoses and dry them out making them brittle...causing holes and cracks. You should never use carb cleaner on the outside of a carburator while it's still on the engine with hoses & stuff. I wouldn't even recommend sparying into the carb. If it needs cleaning then pull it and do it right. Now not only do you have to pull the carb and clean it, but also replace all your vacuum lines...way to go bubba.
