Big Bore
Active member
I spent the day yesterday helping a friend with a motor swap gone bad. He bought a F550 4x4 7.3L box truck with a blown motor with plans to put a roll off bed on it. He bought a used runner 7.3L and installed it. Right away it ran rough and then died while out driving it. After two days of beating his head against the wall trying to get it started, he sent out an SOS and I went over with a few spare parts and we went to work. Now let me interject in the story, my friend is a mechanic and used to have a local shop. He has extensive experience with trouble shooting the 7.3L and has been using forums as a resource since the old days on TDS. during his own trouble shooting he went through the harness and did complete scan/diagnostics with an OTC.
Anyway, we replaced the IPR twice, ICP sensor 3 times, an injector, and basically went through all the trouble shooting either of us could think of. It would start, then go really high on the ICP then die and wouldn't restart unless we disconnected the batteries. After we got it to start and run it was running really rough with a bad miss and knock. Scanner kept showing #2 and 4 cylinders, which is when we swapped injectors with no change. I could see in his face he was about to push the truck off a mountain and at this point I was beginning to think the motor was toast. It was missing and shaking badly with a LOT of blowby. So much blowby that after we got it running it blew two quarts of oil through the PCV into the intakes just driving it around the block a couple times. I did the oil fill cap test and the cap was jumping up in the air 1/2 inch. Finally after 9 straight hours of work and my bugging the shyt out of Pocket (who was having his own nightmare at the time) we were racking our brains trying to figure out wtf was causing 2&4 to be bad and wtf the miss was all about, my buddy had an epiphany.
At this point I'll backtrack. The blown motor has a broken rocker mount, bent pushrod, and blown a headgasket. Motor was bone stock. However just before blowing up it had some repair work done. The repair was done by Napa Car Care in Eagle Colorado. The repair was installing new VC harness connectors. As soon as I saw them I asked him if they were GtoG because the leads to the repair connectors were all black, no colors, and it immediately made me nervous. He said no they were good, he had ohmed out all the pins etc and said the repair connections were done well.
So back to the epiphany. He looks at me and says "what if those dumbazzes reversed the wiring for 2 and 4?" I'm thinking wtf really? So we get out the tester and pin diagram and sure enough, 2 and 4 reversed on the harness repair. Yes the connections had ohmed out previously, but not in the right order which escaped detection. so we clip the wires and reverse them, fire truck up, and now it runs fine except what sounds like a lifter tick. Drove it around and now it's got power and is not blowing any smoke other than a blue haze from the two quarts of oil in the intake and under load a bit of black. The oil filler cap test wont even lift the cap now. The injectors firing at the wrong time were causing a significant amount of blowby.
By this time it was 10pm so we went and got some pizza then called it a night.
The ticking noise is a bent pushrod in my opinion and he's going to check that today. I'll probably go over to see how it goes. But basically, Napa Car Care in Eagle Colorado cost at least one person who owned that truck a motor, and almost cost another one, may still have depending on what the ticking noise is. Just to clarify, the motor he put in ran great in the donor truck it came from and exhibited none of the problems it had after installing it in the F550. My buddy talked to the guy who did the harness splice because the owners had taken it back there after it blew, which we both think happened pretty soon after leaving the shop going up I70 to Vail. There is no way it would have even made it over Vail pass running like that. The mechanic said he didn't know what the problem was and that it was just a blown motor. Well now we know, the mechanic at Napa Car Care in Eagle Colorado who did the VC wiring harness repair on a white F550 box truck for a catering service reversed #2 and #4 wires which caused a catastrophic failure of his customers motor. Good job Dbag.
So, hopefully maybe there is some useful info in here for someone, and maybe later I'll post the pics of the oil all over the side of buddies F350 and camper 10 feet away when we cleared the cylinder through the GP hole after swapping injectors. I wanted to put the VC back on because I had tried laying a rag over the hole before and knew what could happen ( I think Tom S was there actually) but he said "no, just hold this" cranked the engine and BANG! Good thing I had moved to the other side and was reaching over holding the rag, lmao. Trying to force oil and fuel through the GP hole under compression makes a pretty loud bang when it clears.
Anyway, we replaced the IPR twice, ICP sensor 3 times, an injector, and basically went through all the trouble shooting either of us could think of. It would start, then go really high on the ICP then die and wouldn't restart unless we disconnected the batteries. After we got it to start and run it was running really rough with a bad miss and knock. Scanner kept showing #2 and 4 cylinders, which is when we swapped injectors with no change. I could see in his face he was about to push the truck off a mountain and at this point I was beginning to think the motor was toast. It was missing and shaking badly with a LOT of blowby. So much blowby that after we got it running it blew two quarts of oil through the PCV into the intakes just driving it around the block a couple times. I did the oil fill cap test and the cap was jumping up in the air 1/2 inch. Finally after 9 straight hours of work and my bugging the shyt out of Pocket (who was having his own nightmare at the time) we were racking our brains trying to figure out wtf was causing 2&4 to be bad and wtf the miss was all about, my buddy had an epiphany.
At this point I'll backtrack. The blown motor has a broken rocker mount, bent pushrod, and blown a headgasket. Motor was bone stock. However just before blowing up it had some repair work done. The repair was done by Napa Car Care in Eagle Colorado. The repair was installing new VC harness connectors. As soon as I saw them I asked him if they were GtoG because the leads to the repair connectors were all black, no colors, and it immediately made me nervous. He said no they were good, he had ohmed out all the pins etc and said the repair connections were done well.
So back to the epiphany. He looks at me and says "what if those dumbazzes reversed the wiring for 2 and 4?" I'm thinking wtf really? So we get out the tester and pin diagram and sure enough, 2 and 4 reversed on the harness repair. Yes the connections had ohmed out previously, but not in the right order which escaped detection. so we clip the wires and reverse them, fire truck up, and now it runs fine except what sounds like a lifter tick. Drove it around and now it's got power and is not blowing any smoke other than a blue haze from the two quarts of oil in the intake and under load a bit of black. The oil filler cap test wont even lift the cap now. The injectors firing at the wrong time were causing a significant amount of blowby.
By this time it was 10pm so we went and got some pizza then called it a night.
The ticking noise is a bent pushrod in my opinion and he's going to check that today. I'll probably go over to see how it goes. But basically, Napa Car Care in Eagle Colorado cost at least one person who owned that truck a motor, and almost cost another one, may still have depending on what the ticking noise is. Just to clarify, the motor he put in ran great in the donor truck it came from and exhibited none of the problems it had after installing it in the F550. My buddy talked to the guy who did the harness splice because the owners had taken it back there after it blew, which we both think happened pretty soon after leaving the shop going up I70 to Vail. There is no way it would have even made it over Vail pass running like that. The mechanic said he didn't know what the problem was and that it was just a blown motor. Well now we know, the mechanic at Napa Car Care in Eagle Colorado who did the VC wiring harness repair on a white F550 box truck for a catering service reversed #2 and #4 wires which caused a catastrophic failure of his customers motor. Good job Dbag.
So, hopefully maybe there is some useful info in here for someone, and maybe later I'll post the pics of the oil all over the side of buddies F350 and camper 10 feet away when we cleared the cylinder through the GP hole after swapping injectors. I wanted to put the VC back on because I had tried laying a rag over the hole before and knew what could happen ( I think Tom S was there actually) but he said "no, just hold this" cranked the engine and BANG! Good thing I had moved to the other side and was reaching over holding the rag, lmao. Trying to force oil and fuel through the GP hole under compression makes a pretty loud bang when it clears.
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