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+--- Thread: X15 CM570 intermittent fuel pressure drop (/showthread.php?tid=10792)
X15 CM570 intermittent fuel pressure drop - Specialist - Yesterday
Hey guys,
I’ve got a bit of a headscratcher here with a QSX15 CM570 and thought I’d throw it out there to see if anyone’s come across something similar.
The engine’s fitted to a road milling machine and is down on power under heavy load with no fault codes.
Here’s the weird bit. During milling, the fuel shut-off solenoid seems to close for a split second, fuel pressure drops away, and the revs fall from around 2100 to 1500ish before picking back up a second later.
I’ve been logging it through INSITE data monitor logger and checking the actual voltage supply from the ECM to the fuel shutoff solenoid. Sure enough, the voltage drops straight to zero at random times.
Here’s what I’ve tried so far:
1. Pulled the valve out of the fuel shutoff solenoid and gave it a run. The engine runs sweet as, but the supply voltage still drops out randomly, and INSITE still shows the fuel shutoff command going to “Close”.
2. Had a look at the previous wiring repair. The bloke before me replaced the wiring from the ECM to the fuel shutoff solenoid and also swapped the ECM, but apparently that didn’t sort it out. I haven’t gone through the wiring properly yet, but it looks like he might’ve just joined the new wire onto the back of the ECM connector instead of replacing the female terminal properly.
What doesn’t quite add up is that even if the wiring’s dodgy, why is INSITE still showing a “Close” command?
3. Ruled out a fair few fuel supply issues. New IFSM gear pump, lift pump and fuel filter. Checked the inlet screens and relief valves, and even tried running fuel in and out of an extra jerry can. No joy.
4. It only plays up under load. At rated RPM with no load, it runs fine as. The problem only shows up when the machine’s actually milling.
So, keen to pick your brains on a couple of things:
1. Is there any OEM wiring or external safety device that can send a shutdown request to the ECM and make it command the fuel shutoff solenoid closed? Could something on the machine side be telling the ECM to shut the fuel off?
2. If the keyon or main power supply has an intermittent dropout, could that make the fuel shutoff solenoid close for a split second and cause the revs to drop before recovering, rather than killing the engine completely? I haven’t had f/c1117 come up either.
At this stage, I reckon I might have to get stuck into the wiring harness and go through the lot — fuses, relays, power supplies, earths and connectors — if I can’t find the culprit.
Has anyone run into this sort of issue before, or got any ideas on where else I should be looking?
Any thoughts would be much appreciated.
RE: X15 CM570 intermittent fuel pressure drop - Rawze - Yesterday
NOTE: The engine will run fine ... and shut down just fine with the guts removed from the fuel shut off solenoid.
The solenoid itself is a secondary safety feature only. - Otherwise, if someone does remove its guts... and then the engine stumbles and does not shut off right away with key-off then this is a clear sign of a fuel (metering) solenoid in the IFSM is also getting leaky and/or a leaky injector (or 2) is causing it.
That being said.. the only way to likely find out why the solenoid is randomly being commanded to shut for like you describe would be to monitor the engine data via Calt$erm software.
On a guess however ...
== My first guess would be a flaky ecm. Those ecm are notorious for getting flaky and cutting out randomly as they get age on them, or suffer excessive vibrations. - This is very common as they get old, especially if no one has bothered to replace the crank shaft damper at 500k mile mark.. to prevent higher frequency vibrations.. which is well known for making ECM flaky. These days, you could put 10 used ecm's on and find that all 10 are flaky .. and then swear its something else. - Banging on the ecm itself hard (almost enough to dent its casing) will reveal it, making it cut out.
NOTE: It is also VERY EASY to damage the shutoff solenoid circuit output if some idiot tried to jump the voltage to it from the batteries .. and they do not disconnect the wire for it that goes to the ecm. - Voltage will back-feed thru the wire and short out / damage the circuit that activates it inside the ECM and then it gets flaky as h$ell or it fries all together internally in the ecm. This is NOT a good thing... and its very easy for some idiot to do this.
== My next guess would be .. if it is not the ecm itself... would be the key-switch in the dash signal getting flaky into the ecm. ECM is getting an Intermittent signal to tell it that the keys-witch in the dash of the vehicle is no longer on. - This is common too.
== My third guess .. if there is any normal logical reason for ecm to only temporarily shut it off... would be an over-pressure (spiked pressure) event in the IFSM .. and the ecm shuts off the solenoid for a moment to protect the engine/IFSM ... but that should throw an alarm ... one never knows, but maybe not if it happens, then recovers fast enough.
I.E.> If there is a leaky injector because the overhead rockers are out of adjustment badly, and / or simply a leaky injector getting bad enough ... a bad injector can back-feed combustion pressure backwards into the IFSM and spike the fuel pressure. Doing a proper injector leak test(S) on the engine will reveal this ...
info: https://rawze.com/forums/showthread.php?tid=7747&pid=67948#pid67948
... just some thoughts... the beer is talkin'.
RE: X15 CM570 intermittent fuel pressure drop - Specialist - Today
(Yesterday )Rawze Wrote: ...
... just some thoughts... the beer is talkin'.
Appreciate the genius ideas as always!
I reckon I’ve got a fair idea of what to do next, but something else just popped into my head that I thought I’d share.
* When the dodgy stuff happened, I checked the fuel pressure at the quick connect coupler on the base of the IFSM, and it wouldn’t go above 270 psi. Does that mean I can pretty much rule out faulty injectors or solenoids?
* Before I started diagnosing it, the bloke before me had already done the following work,
- RnR the cylinder head, renewed the cam bushings, checked the cylinders with no obvious issues found, fitted a new head gasket and set overhead.
- Replaced four injectors.
- The customer said there was some unburnt fuel-looking leakage around certain cylinders on the exhaust manifold. I’m guessing that’s what led to the head job and injector replacement in the first place.
Apparently, the engine sounds much better since the head job, but still revs drop randomly as I mentioned. It has been sitting in the workshop for 3 weeks.
* One of the ECM connectors for the OEM harness is now stuck pretty badly in the ECM connector housing. I can’t undo the retaining screw because it looks like someone’s already flogged the thread. Makes me wonder whether the bloke before me even tried swapping the ECM.
* Anyway, I pulled the guts out of the fuel shutoff valve, and it runs fine until a fault code comes up after about five minutes. The code is something along the lines of ‘fuel shutoff valve mechanically not responding’, and then it goes into torque derate.
The engine shuts down nice and smoothly when I turn the key off, without any stumbling. So my gut feeling is that the metering solenoids and injectors are probably OK, although I’m not ruling anything out just yet.
I’m leaning towards a dodgy ECM, like you suggested. I’ll try swapping the ECM myself after the weekend and try direct power to the keyon and main power so I can narrow things down a bit further.
I’ll keep you posted, Rawze! Thanks again for the help!