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Heavy backfiring at low speeds

From : issy

Q: you said electronically controlled. i dont see any electrical connection at each injector. how is the injector timing controlled. on the outside of the engine drivers side just under the valve cover there are three gray square 4-pin connectors. each of these connectors contains the wiring for two injectors. if you were to remove the valve cover youd see the electrical wires running from these connectors to each of the six injectors - two wires per injector. timing is controlled by the ecm based on inputs from the crank sensor cam sensor map sensor apps sensor as well as others. being a common-rail engine there is fuel pressure at each injector at all times just like an fi system on a gas engine - only about 100 to 500 times the pressure. the ecm supplies voltage to the injector which causes it to open up and lets the fuel spray. again - very similar to a gas fuel injector. if you have a non-contact infrared thermometer you can possibly read a temp. differential on the exhaust manifold at each port after running it for a while - this might help you narrow down the injector that isnt firing if thats in fact the problem. and speaking of sensors - heres another thought. since you said you had to replace lots of front-end stuff what about the iat/p intake air temp./pressure sensor located on the intake tube just after the air filter none of your codes that you listed pointed to that sensor but many people when changing out intakes fail to hook this back up and the truck runs like crap. .

Replies:

From : cbhvac

check for lean mixture as it would cause the backfiring and the burnt valve to begin with. cbhvac wrote not likely a timing chain he said he has a burnt valve and they only get worse. he also said thats gone with the rebuilt heads... ramman@dodgecity.cc wrote it could be anything but given your story and symptoms my guess would be the timing chain has jumped a tooth. newly rebuilt heads bolted onto a worn out bottom end is frequently a recipe for trouble. you didnt mention how many miles were on the engine before the first breakdown but somehow id imagine on a 77 it was a lot. with the heads already off how much extra would it have cost to hone the cylinders re-ring it and put in new bearings seals & timing gear & chain perhaps a new cam while were in there. probably double the original job but if you had done so you would essentially have a brand new motor except for the carbeurator. it is also possible the rebuilt heads werent fully rebuilt. some rebuilders will simply grind the valves & seats and put it back together with all the original hardware valves springs lifters push rodsrocker arms and keepers. i cannot imagine anyone putting newly rebuilt heads on and not replacing the springs and lifters but im sure it happens. -- ----------------- www.thesnoman.com -- ----------------- www.thesnoman.com .

From : thesnoman

trying to spread the word about my site www.strictlyminiz.com for you dakota drivers .

From : thesnoman

if you fully flush the system there will be no issue of types as the only thing being left in the system is water. -- if at first you dont succeed youre not cut out for skydiving i dont understand how you can backflush against the flow of a running water pump! as per web link this page also does not take into account that to get a recommended 50% ratio you must know the capicity of the system. the manual will tell you that. if the system holds 12 quarts you must put in 6 quarts of undiluted antifreeze then top it off with water distilled prefered by me article also does not mention the problems of changing antifreeze types. i did but would not do it again. i general that page is fos. dick if you are using the prestone flush system then yes the hose with the coupling is the one to use. just remove the coupling and insert the t fitting there. i would also suggest cracking the lower radiator hose loose for draining the radiator it is much faster than using the petcock. remember to use pure antifreeze and not that 50/50 crap when you refill the radiator after the flush and put it into the radiator unmixed. it will mix with the water that is still in the engine to give you the proper ratio. if you want to do it with the distilled water method as some in here like to do then after the flush you will need to remove the lower radiator hose as well as the block drains small hex fittings on the lower block on the sides of the engine to remove as much water as possible before filling it with either that pre-mixed stuff or an equal amount of distilled water and antifreeze. -- if at first you dont succeed youre not cut out for skydiving i want to change my engine coolant and found this article http//www.diynetwork.com/diy/enmaintenance/article/02021diy13808227091900.html it talks about installing the t-fitting in the heater-inlet hose that runs from the firewall to the top of the engine. i have one heater hose which runs on the driver side to the firewall and one that runs on the passenger side. i suspect the one on the passenger side to be the inlet hose that i need to install the t-fitting in. am i right with that that one on the passenger side actually already has a coupling in it so it should be very easy to install the fitting. but again is that one the right hose any other tips for changing the engine coolant are appreciated as well. thanks in advance. axel .

From : Annonymous

not likely a timing chain he said he has a burnt valve and they only get worse. ramman@dodgecity.cc wrote it could be anything but given your story and symptoms my guess would be the timing chain has jumped a tooth. newly rebuilt heads bolted onto a worn out bottom end is frequently a recipe for trouble. you didnt mention how many miles were on the engine before the first breakdown but somehow id imagine on a 77 it was a lot. with the heads already off how much extra would it have cost to hone the cylinders re-ring it and put in new bearings seals & timing gear & chain perhaps a new cam while were in there. probably double the original job but if you had done so you would essentially have a brand new motor except for the carbeurator. it is also possible the rebuilt heads werent fully rebuilt. some rebuilders will simply grind the valves & seats and put it back together with all the original hardware valves springs lifters push rodsrocker arms and keepers. i cannot imagine anyone putting newly rebuilt heads on and not replacing the springs and lifters but im sure it happens. -- ----------------- www.thesnoman.com .

From : thesnoman

it could be anything but given your story and symptoms my guess would be the timing chain has jumped a tooth. newly rebuilt heads bolted onto a worn out bottom end is frequently a recipe for trouble. you didnt mention how many miles were on the engine before the first breakdown but somehow id imagine on a 77 it was a lot. with the heads already off how much extra would it have cost to hone the cylinders re-ring it and put in new bearings seals & timing gear & chain perhaps a new cam while were in there. probably double the original job but if you had done so you would essentially have a brand new motor except for the carbeurator. it is also possible the rebuilt heads werent fully rebuilt. some rebuilders will simply grind the valves & seats and put it back together with all the original hardware valves springs lifters push rodsrocker arms and keepers. i cannot imagine anyone putting newly rebuilt heads on and not replacing the springs and lifters but im sure it happens. .