CAT 279D nightmare, cam/crank waveform wanted

Bullitt · 2026-08-16T03:43:35.000Z

I'm trying to sort out a shop nightmare... Rented out a CAT 279D (GTL). Reportedly it "melted" two hydraulic hoses out in the field. Talked to the tech that worked on it, and he told me the hydraulics go so hot that the hoses melted out of the crimped fittings (Kurt compression style). Fast-forward a week later and the machine gets back to the yard. Couple of the guys ask me to take a look because it's making a strange noise. Sounded like a bottom end noise in the engine but wasn't entirely sure. Told them to pull the rocker cover and look for any loose rockers, and if not yank the engine and flip it upside down and pull the sump. Turned out #3 spun a rod bearing. All the other rod and main babbitt looked fine. Not sure what caused the spun rod bearing, but it beat the hell out of the crank and the cylinder bore. Shop sourced a reman Kubota V3307 long block to replace the original ~3300 hour engine instead of rebuilding. Injector's got sent out to get tested, came back as perfect condition. Shop's senior tech and his apprentice did the engine swap, and it wouldn't crank afterward. Another tech got involved, and they determined the starter was faulty. After the starter was replaced, and it still wouldn't crank the three of them started randomly moving wires around. The main ground terminal eye that was supposed to bolt to the engine block was on the starter B+ solenoid terminal. They moved the ground terminal to the field side of the starter solenoid. The engine would crank momentarily, and then stop, repeat. Super asked me to take a look at it, after putting the ground back on the engine block, it wouldn't crank it all. I poked around and determined that even though the ECM was communicating, it had an internal fault. The shop sourced a used ECM out of a CAT 279D from eBay. Turns out it takes a special program to flash these ECM's, and not just ET WinFlash. I replaced the ECM and encoded the injector trim without flashing. Got the engine cranking over like it should, but it still wouldn't start... Started chasing fuel, lift pump -> high pressure fuel pump had a lot of flow and no air. Rail pressure was reading 0 psi. Pulled the fitting from the HPFP -> common rail and there was nothing. Disconnected the SCV connector and cranked over, now there is fuel coming from the HPFP to the rail. I asked what procedure they used to time the fuel pump, and they said that because it was common rail system it didn't need timed. I told them to yank the engine again and time the fuel pump and we will see what happens. Reinstalled the engine, cranks but doesn't start... At this point they are upset with me because I told them to install the HPFP properly, and they had to R&I the engine again to do it. They scratch their heads for a couple of days and suggest replacing the HPFP. I get connected with ET and to my surprise, the common rail is building a ton of pressure now. During cranking ET is saying desired is ~4000psi, and actual is like ~6000psi quickly. I pulled the injector fuel return line from the cylinder head and put it in a graduated cylinder. CAT spec says no more than 30ml in 30 seconds of cranking, I measured 15ml. So fuel is getting to the injectors, the return is well within spec, and the injectors passed the lab testing prior to the ECM getting fried. I put channel 1 of my Picoscope on the camshaft position signal return. Channel 2 on the crankshaft position signal return. Channel 3 amp clamp on injector 1. Channel 4 amp clamp around the negative battery cable. The ECM is commanding injection, I got textbook current signatures from all 4 injectors using the amp channel. There is no evidence of combustion, not a single puff of smoke from the exhaust. I pulled the glow plug from #1 to see if there was any fuel coming out of the cylinder when cranking. It's hard to tell, I put a white piece of paper over the glow plug hole out of desperation, didn't seem like any cherry fuel was coming out. At this point I think the engine timing is still suspect. I can tell from my waveform that injection is happening on a compression stroke. But I haven't confirmed the right cylinder's compression stroke. If anyone has a known good capture I can compare mine against it would help a lot.

BullittJunior MemberSep 6, 2026#22

Nige said: I take it that the guys who worked on it before are now shrugging their shoulders and muttering “witchcraft” under their breath.? Click to expand... It's not my first rodeo dealing with issues like this; in the end, it is just a lot of finger-pointing. I would enjoy it a lot more if people could set aside the ego and just use it as a learning experience, but most of the time it becomes too personal (and nothing changes). I try to keep things objective, explaining what was wrong and how to increase success rates. Despite not being in a lead role at my current employer, I make myself available to the guys to try and keep the work flowing; things like service information, obscure electrical issues, difficult hydraulic problems, diagnostic software, etc. When things go this badly, no one gets to walk away unscathed when no one will take responsibility, not even myself, which was just involved to get it done and closed out. In this situation it was "Well that's how I was told to do it" and "The service manual I was using probably had a mistake in it" and there is a tangible amount of animosity towards me . My manager apologized for throwing me in the middle of it, which I do think he was trying to avoid.

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