Sheener Posted April 2, 2022 Share Posted April 2, 2022 - deleted - Link to comment Share on other sites More sharing options...
Gary Lewis Posted April 2, 2022 Share Posted April 2, 2022 Sometimes a backfire on deceleration is due to a blown power valve. You didn't say what the CO levels were, but if it is blown they should be high. Link to comment Share on other sites More sharing options...
Sheener Posted April 2, 2022 Author Share Posted April 2, 2022 Sometimes a backfire on deceleration is due to a blown power valve. You didn't say what the CO levels were, but if it is blown they should be high. High CO and HC. I will change the power valve and see. Link to comment Share on other sites More sharing options...
85lebaront2 Posted April 2, 2022 Share Posted April 2, 2022 High CO and HC. I will change the power valve and see. Backfire on deceleration can also be a bad or not connected correctly air bypass or diverter valve. Its function is to shut off the air into the exhaust to prevent backfires. Before I converted Darth to EFI, on a cold engine, pulling our 10K 5th wheel, going up onto the interstate near our house, when I topped the ramp and slight incline on the interstate and started down towards the Monitor-Merrimac memorial tunnel section, letting off the gas got a huge "boom" and my wife, following in the car said there was a large flame out of the tailpipe. Link to comment Share on other sites More sharing options...
Sheener Posted April 2, 2022 Author Share Posted April 2, 2022 Backfire on deceleration can also be a bad or not connected correctly air bypass or diverter valve. Its function is to shut off the air into the exhaust to prevent backfires. Before I converted Darth to EFI, on a cold engine, pulling our 10K 5th wheel, going up onto the interstate near our house, when I topped the ramp and slight incline on the interstate and started down towards the Monitor-Merrimac memorial tunnel section, letting off the gas got a huge "boom" and my wife, following in the car said there was a large flame out of the tailpipe. What fuel injection did you install? 35year old parts that are expensive to replace have me thinking of that. Did not have the backfire before hooking up the diverter valve and the replacement is over $300. Anyone ever rebuild a diverter valve. Link to comment Share on other sites More sharing options...
85lebaront2 Posted April 2, 2022 Share Posted April 2, 2022 What fuel injection did you install? 35year old parts that are expensive to replace have me thinking of that. Did not have the backfire before hooking up the diverter valve and the replacement is over $300. Anyone ever rebuild a diverter valve. Darth's EFI is a factory setup from a 1990 F250, but upgraded to MAF and sequential running a 1996 EEC-V computer. I would start by checking all the vacuum lines, particularly where they go over the exhaust crossover in the center of the right head side of the intake. Is your vacuum diagram on the radiator cover plate still legible? If not I can post my old diagram. There are two vacuum lines to each air control valve, a red and a black one. The red line should have vacuum whenever the engine is running, black I believe has vacuum with a warm engine, but it could be cold and no vacuum warm. Link to comment Share on other sites More sharing options...
Sheener Posted April 2, 2022 Author Share Posted April 2, 2022 Darth's EFI is a factory setup from a 1990 F250, but upgraded to MAF and sequential running a 1996 EEC-V computer. I would start by checking all the vacuum lines, particularly where they go over the exhaust crossover in the center of the right head side of the intake. Is your vacuum diagram on the radiator cover plate still legible? If not I can post my old diagram. There are two vacuum lines to each air control valve, a red and a black one. The red line should have vacuum whenever the engine is running, black I believe has vacuum with a warm engine, but it could be cold and no vacuum warm. My tag is still legible, and I have access to the one on this forum. I need to test the diverter valve as well. It is a pretty cobbled up mess under the hood. Thermactor system was missing when I bought the truck. Trying to use a harness I got out of a junkyard, but it isn’t very good. I may have to fabricate my own to get it operating, but if the valves are bad and I need to replace, that is close to the cost of converting to efi. Link to comment Share on other sites More sharing options...
85lebaront2 Posted April 2, 2022 Share Posted April 2, 2022 My tag is still legible, and I have access to the one on this forum. I need to test the diverter valve as well. It is a pretty cobbled up mess under the hood. Thermactor system was missing when I bought the truck. Trying to use a harness I got out of a junkyard, but it isn’t very good. I may have to fabricate my own to get it operating, but if the valves are bad and I need to replace, that is close to the cost of converting to efi. Here is what the rat's nest is supposed to look like removed from the engine: Link to comment Share on other sites More sharing options...
Sheener Posted April 3, 2022 Author Share Posted April 3, 2022 Here is what the rat's nest is supposed to look like removed from the engine: Yep, got all that with cut off ends, pinched tubes, broken connectors and despair all over it. May have to fab my own that won’t be as compact as that. Link to comment Share on other sites More sharing options...
85lebaront2 Posted April 3, 2022 Share Posted April 3, 2022 Yep, got all that with cut off ends, pinched tubes, broken connectors and despair all over it. May have to fab my own that won’t be as compact as that. Unfortunately for you, mine is long gone along with the air valves and pumps. If you can find one in a junk yard and get most of it you would be in great shape. Link to comment Share on other sites More sharing options...
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