Monkey Truck Posted December 31, 2013 Report Posted December 31, 2013 Out of no where, I've developed a small problem. When I decelerate or coast into a stop sign, the truck begins to slighly backfire then the engine begins to hickup and then dies out as I come to a stop. I can usually restart with no problems, runs great going back up through the gears, but then will do the same thing upon deceleration as I slow to a stop. I pulled off the distributor cap and checked the points. Visually they look good, only have about 1000 miles on them. I appreciate any ideas or help. Thanks, Eric. Quote
Jeff Balazs Posted December 31, 2013 Report Posted December 31, 2013 Could it be float level related?....I think I might check that. Jeff Quote
Don Coatney Posted December 31, 2013 Report Posted December 31, 2013 Backfire through the carburetor or exhaust? Quote
Monkey Truck Posted December 31, 2013 Author Report Posted December 31, 2013 Backfire through the carburetor or exhaust? Through the exhaust. Quote
Merle Coggins Posted December 31, 2013 Report Posted December 31, 2013 Backfire through the exhaust, especially with throttle closed, usually indicates an over lean condition. MIght want to check for any vacuum leaks, or check your idle mixture screw adjustment. It could be that your ignition timing is a little off too. Wouldn't hurt to double check it. 1 Quote
Don Coatney Posted December 31, 2013 Report Posted December 31, 2013 Through the exhaust. Check for an air leak in the exhaust system. This will cause a backfire boom and that can lead to a possible exhaust system blockage that will cause a misfire and stumble at idle killing the engine. Quote
Plymouthy Adams Posted December 31, 2013 Report Posted December 31, 2013 when was the last time this engine was brought into proper state of tune? Quote
Monkey Truck Posted January 1, 2014 Author Report Posted January 1, 2014 when was the last time this engine was brought into proper state of tune? Not very long ago, only about 1000 miles on the tune up. Has been running great up until now. Quote
Plymouthy Adams Posted January 1, 2014 Report Posted January 1, 2014 do not rule out possibility of something slipping out of adjustment, getting gummed up or flat out smoked points from leaving the ignition on with the points closed and being burnt in the process...investigate this first..quick and easy to rule out... 1 Quote
Monkey Truck Posted January 1, 2014 Author Report Posted January 1, 2014 do not rule out possibility of something slipping out of adjustment, getting gummed up or flat out smoked points from leaving the ignition on with the points closed and being burnt in the process...investigate this first..quick and easy to rule out... Thank you. I might just replace the points and see if that helps. Quote
48Dodger Posted January 1, 2014 Report Posted January 1, 2014 Always good to double check your work after a tune up. If its backfiring through the exhaust, it might be (in addition to what everyone else is saying) a fouled plug (or busted plug) allowing to much "raw" gas to migrate down the pipe. As it is, most engines have a Volumetric Efficiency (VE) of 0.8, or 80 percent. Meaning 20 percent of the exhaust out the cylinder is unburned fuel (HC) which is what a catalytic converter is designed to burn up. But in the old truck's case, a hot exhaust pipe can put on a show if theres enough fuel. At higher RPMs the extra fuel can get "resorted" and dipersed so as to go unnoticed....and I'm not talking a completely dropped out cylinder, but one with a fouled plug that has a VE of say 40 percent or less. Enough to cause problems. A cylinder that's completely out will shake the motor at certain RPMs. Just thinking out loud and throwing stuff til it sticks...lol. 48D 1 Quote
Don Coatney Posted January 1, 2014 Report Posted January 1, 2014 Always good to double check your work after a tune up. If its backfiring through the exhaust, it might be (in addition to what everyone else is saying) a fouled plug (or busted plug) allowing to much "raw" gas to migrate down the pipe. As it is, most engines have a Volumetric Efficiency (VE) of 0.8, or 80 percent. Meaning 20 percent of the exhaust out the cylinder is unburned fuel (HC) which is what a catalytic converter is designed to burn up. But in the old truck's case, a hot exhaust pipe can put on a show if theres enough fuel. At higher RPMs the extra fuel can get "resorted" and dipersed so as to go unnoticed....and I'm not talking a completely dropped out cylinder, but one with a fouled plug that has a VE of say 40 percent or less. Enough to cause problems. A cylinder that's completely out will shake the motor at certain RPMs. Just thinking out loud and throwing stuff til it sticks...lol. 48D That is exactly why I suggested to check for an air leak in the exhaust system. The introduction of air into this unburned fuel hastens the burning/exploding/backfire process. And this backfire can knock the guts out of an old muffler blocking the exhaust flow thus causing an engine to stumble. Quote
olddodgeguy Posted January 1, 2014 Report Posted January 1, 2014 Did you re-adjust the points after a few miles to compensate for point wear block break in? The points might be a little close. Good luck. Mike Quote
Young Ed Posted January 1, 2014 Report Posted January 1, 2014 What type of points did you use? I had some that turned out to be poorly made in my plymouth and one day the block melted into a pile of goo and my car wouldn't start. Quote
Jeff Balazs Posted January 1, 2014 Report Posted January 1, 2014 Sure sounds fuel related to me. If the points were really bad then it seems to me that you would have acceleration issues or rough running. Dirt or blockage seems more likely to me. Might want to take a vacuum reading as well. Hope this helps Jeff Quote
Monkey Truck Posted January 1, 2014 Author Report Posted January 1, 2014 Thank you all for the suggestions, pointers, comments and help. I'm going to do some investegating today and see if I can fix. Quote
P15-D24 Posted January 1, 2014 Report Posted January 1, 2014 Please post the solution when you find it. Quote
Monkey Truck Posted January 2, 2014 Author Report Posted January 2, 2014 Please post the solution when you find it. Ok will do. Quote
Solution Monkey Truck Posted February 8, 2014 Author Solution Report Posted February 8, 2014 Ok, well after exhausting all that I know about trying to fix my problem (replaced the fuel filter, fuel pump, checked the points, checked plugs, wires, checked for vacuum leak, etc), I gave in and took the truck to a mechanic. I had at least isolated the problem to the carburetor, and in fact the problem ended up being in the carburetor. The official problem was a clogged "idle circuit". The mechanic told me the "idle circuit" tube is about the size of a hair. He said it's very easy to clog. He suggested in the future if that happens again, to pull the idle screw all the way out and blow air, or carburetor cleaner into the hole. He ended up rebuilding it with a rebuild kit while he had it apart. I don't know a whole lot about carburetors, so today was a $360 learning experience. Thanks again for everyone's suggestions above. Quote
TodFitch Posted February 8, 2014 Report Posted February 8, 2014 Glad you got it fixed. But $360? Ouch! Quote
Don Coatney Posted February 8, 2014 Report Posted February 8, 2014 Glad you got it fixed. But $360? Ouch! I agree $360 is high. How long did it take the guy to do the work and what are his hourly rates? Quote
Young Ed Posted February 8, 2014 Report Posted February 8, 2014 I agree $360 is high. How long did it take the guy to do the work and what are his hourly rates? Around here that'd be probably 2hours of labor plus the carb kit. Quote
Monkey Truck Posted February 8, 2014 Author Report Posted February 8, 2014 He charged me $297 in labor, the receipt doesn't show the hourly rate. Carburetor Kit was $53.42 Carb cleaner $ 5.95 Description of work: R & R Carb and repair as needed. I'm guessing he spent 3-4 hours total, not sure. Of course here in California, everything is $$$. Quote
48Dodger Posted February 8, 2014 Report Posted February 8, 2014 80 to 90 an hour in California.... 48D Quote
Dajudge Posted February 10, 2014 Report Posted February 10, 2014 Wow, if I did it right, I saved that much today rebuilding my carb. But that is a big if. We shall see. Quote
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