Pc170lc-10 no start no change in rail pressure

[Hew's Mobile]

Hey everyone new to posting so I hope it’s being done correctly to reach you all. Have a komatsu pc170-10 no start. No issue until machine came off the trailer and operator started it with a little sniff (I know I know inlet heater) However when I got on site I got right into the monitor to check for codes and pressure. Low rail pressure code did pop but a few hours before that days operations and wasn’t active. I also gave it a small sniff since It wouldn’t start or smoke after priming. That sniff made it start right up and the fuel pressure ranged fine through the throttle selection. All the way up to 19000 psi without a real load. After that day it would not start again. Fuel was moving through. Injectors suspected as passing through so those were replaced. Monitor rail pressure still showed 309-370psi. Fuel pump replaced Still same pressures. Never any codes. Never started again. I’m leaning with pressure sensor but worried about ecm problem

 

[coalrulz]

If you are sure you have a good fuel supply to the injection pump, then I would check for fuel leakage after injection pump.
Have you checked leakage rate from common rail pressure limiter valve?
Did you replace head mounted fuel connectors (quills) when you replaced injectors?

 

[funwithfuel]

Agreed with safety valve/ limiter valve. 309/370 psi may as well be 0 and could very well be 0. You state you had 19k with no load. That seems pretty high for a full throttle/ no load condition. In service mode, you should have a screen that shows actual and target rail pressure. Are you tracking alongside one another or is one upside-down?

 

[Hew's Mobile]

Quills were replaced with injectors. When the machine ran I did see command vs actual and it was all within each other plus or minus. No start issue I’m having now command calls for 5800 but the actual sensor pressure not moving and not showing zero had me confused. But that would make sense that even if it showed in the 300s that would be equivalent to nothing. I was assuming more accuracy.

 

[funwithfuel]

Gotta look at overall expected pressures to be observed. Could be looking at 25-27k so 2-5% of that in a perfect world is your margin of error. You've verified flow from the fuel pump to the rail?

 

[Hew's Mobile]

I also failed to mention the limiter was replaced. They are cheap enough and in stock at the dealer so figured save the headache for something easy and quick. Filters new
Pressure relief
Return check valve (back of head)
Injectors. Quill tubes. And connector nuts
High pressure Fuel lines
Fuel pump

I’m going to measure the returns during cranking and see if they are normal against the books table. My bigger concern was the zero change on the pressure sensor through the monitor. Even with everything. Knowing I have fuel in there. I figured the pressure should still fluctuate before returning directly to the tank. Unless I had a massive obvious external leak

 

[funwithfuel]

Check and verify your oil level and condition. You may have a damaged fuel tube, or o-ring which could be dumping fuel to crankcase. Just a thought. It can and has happened.

 

[Hew's Mobile]

That was one of my first checks was fuel in oil. Noted fuel just shy of top of hash marks and no smell of fuel in oil. That was before I had gone back to do fuel filters so I’m sure the owner was cranking that thing like a mad man as he waited for me to get back the next night to throw those on. But since I have had no increase to oil level. Or any smell of fuel in oil.

 

[Hew's Mobile]

 

[Hew's Mobile]

couldn’t do a video but that is my monitor before cranking and then while cranking

 

[funwithfuel]

Check return volume off the safety relief. If it's high, meaning any fuel at all, you are going to want to remove the rail and check the surface that the safety mates up with. If the rail has opened for any extended times, it may have etched the face. For testing only, you can unplug the metering valve. The pump fails to open, so you should get max rail pressure in a few revolutions. If you don't see a value change, cracked an injector feed line loose. Does the rail pressure sensor still show~300psi? If so, the sensor could be flat. Now crank the engine with the line loose. Does fuel leak from the nut? We're trying to verify flow. Good luck

 

[Simon C]

How many hours on this unit. Have seen faulty pressure sensor before, talking faulty and new. Rereading all that has been tried. Think about over supper.
Simon C

 

[Simon C]

Wondered if the sniff of either could of broken part of the air inlet heater and maybe bent one cylinders valves. Just a long shot, but also has a clamp on been put on the inlet heater to see if it is drawing enough amps. If the cylinders are not hot enough maybe they won't fire. Have seen a Cat 3306 with lots of hours that was no go without glow plugs. Wonder if it would fire up with a good blast of WD40 while it is cranking.
Simon C

 

[Marcrus]

Pretty common for the plug pins to the rail pressure sensor to spread out and cause this issue as well as intermittent running, has rial pressure sensor and new buggy back harness fix it.
Otherwise is the fuel tap on and have you blown back through the line to make sure nothing is blocking tank pick up?