Hello all, looking for some input on this situation. Have a cat 972k S/N- LZ4W00267 that am having some fuel system isue with. So bassic rundown on what happens is after starting machine, it is demanding around 7k psi rail pressure. Actual rail pressure is around 4900 psi. After 30 seconds to a min later, it throws an active event of E398 for low fuel rail pressure. But as soon as it does that, the rail pressure jumps up to to match desired rail pressure and holds it no problem. At that point it also derates the engine 20% power. Then 3-4 mins later, it throws the 1-7 code for the cylinder #1 injector not responding properly. So here's what I've done, I have ohmed out and load tested injector harness separate, and engine wiring harness to ecm connector with it disconnected, and no issues were found. I also ran through all the tests on Cat ET. Have also swapped #1 and #3 injector with no change. Has new fuel filters on it and base fuel pressure to HPFP is 102 at idle. Any input is appricated, kind of leaning towards ecm at this point. Not sure why fuel rail pressure would bump back up after is throws the active even code for low pressure.
That does sound a bit ECMish to me. Don't be surprised if there's two issues. Can you verify there's nothing silly going on such as rising engine oil or fuel smell from the radiator? Would like to rule out codes being caused by leaking injector seals or a crack in the injector bore. I know you've swapped injectors which has virtually ruled this out, but stranger things have happened. Any resent samples taken? You don't have a test ECM you can try do you? Then there's your issue of rail pressure. So you've got good pressure to the HPFP and you've basically ruled out injectors. Doesn't leave much in between. SIS has some good troubleshooting steps for low rail pressure. When you key on, does rail pressure read zero? Edit: Then again with a suspect ECM can you really trust what it reads?
following with interest
Did you already run the fuel rail pressure test? Also did you check the screen filter in the tank. Pressure relief valve is also suspect. Just cheaper than the ecm that should be checked off. Also post the product status report for us to view. Does it have an electric lift pump?
So after looking back through some pictures I took last week of the 1-7 code when I was there to diagnose an EGR balance valve code (3409-5), it had thrown that 1-7 code 400+ hours ago and did not affect machine operation. Originally when I was there last week for the EGR balance valve code, the machine was derated and I fixed the issue causing the egr code (bad connector to solenoid valve), thats when I discovered the actual derate cause was this silly low rail pressure issue. I would say there are deffenitly a few different things going on, and after finally getting it to go through a fuel system function test, it failed 3/4 the way though with an $1120 error for "Fuel Pump Not Timed Correctly". Now the pump appears to have been replaced before (machine has 17.8k hrs) but has been running fine for thousands of hours this way untill now, at least 4-5k since this customer has owned it. So at this point my only other thought is the pump is getting weak enough and may be a bit out of time, causing this issue. Will dig into it more this week. Edit- Also to answer your question on reading of rail pressure, it does read zero when key on.
That’s a new one for me. I’ve never seen that happen before. Guessing the pump is worn. Oh well, at least you are on the right track now.
You could be right. As you said once it's been running a while the actual versus desired rail pressure stabilizes. I think if it was rail pressure leakage through the relief valve you would be seeing E499 Rail Pressure Leakage events logged. Again though stranger things have happened. Might also be worth looking at the two outlet check valves on the pump. If they're there, they'll be on the block side of the pump about mid-way up and are usually horrible to get to. They have a needle/seat and possibly a spring inside. If they have the slightest damage or debris stuck inside them it will cause all sorts of issues. For reference engine was shipped with 375-5244 HPFP. This updates to 379-0150 HPFP, then 493-9679 HPFP, then 511-7975 HPFP which looks to be current. Apparently the latest software becomes important when updating the HPFP too, as well as the pump feed line to the rail. If a new HPFP solves the issue I'd be looking into fuel quality issues. If the 1-7 code comes back I'd be playing ECM swapsies I think.
Will update when I get back going on it, maintaince is not very good at this outfit. Will most likely be putting a new HPFP on and seeing what happens at this point.