Rawze.com: Rawze's ISX Technical Discussion and more

One of my drivers reported truck was running a little rough. I looked at the codes remotely and had the following: 1 count of 4726 active and 2 counts of 0559 inactive. He made it back to the yard and this morning the truck will now crank but not start.

I scanned it and while looking at the data, with key on/engine off, the commanded fuel pressure is 5500 (approximately) but actual fp is <200. And the fuel pressure rationality sensor reads -1100ish. To be completely honest I have no idea what a fuel pressure rationality sensor is.

Anyways. I’ve had a similar situation before and I just tossed a pressure relief valve on there and it solved the issue. So I did the same here but it didn’t change anything. I figured my next step would be trying leakdown tests, but I figured I would have an injector code too if that was the issue but I don’t.

If I crank the engine, it doesn’t build any pressure (based on readings on insite). Either that or it does but bleeds back off immediately. When I just turn the key over, the lift pump activates, but I haven’t tested if it’s putting any pressure out yet.

Just looking for some ideas before I dive in to it again on Monday.

I also have a couple after treatment codes but it appears they stem from the fueling issue stopping regens from happening.

start by pulling the pump apart and hope it is not destroyed?.

I’m assuming you mean the mechanical one as opposed to the lift pump yeah?

Yes mechanical fuel pump.. That 559 code is no Bueno.. Hopefully the pump is intact or its gonna be bad news..

(01-22-2022 )ahrenbenjudah Wrote: [ -> ]I’m assuming you mean the mechanical one as opposed to the lift pump yeah?

yes, if the main fuel pump fails, it destroys the entire engine .. literally ... along with it in only a few hours of run time. It is nothing to play around with at all, and that 559 code is the most common code that comes up when this is happening.
ref: http://rawze.com/forums/showthread.php?t...9#pid15389

hope like h$ell that the fuel pump has not failed. Pull the head off it and inspect it.. replace its guts if they have more than 8,000 of run time on them, or 400k miles. the guts ( tappets, rollers, plungers, etc.) of the fuel pump needs replacing every 400k miles on all model ISX engines that have a common rail to prevent this.

Ok. I’ll start on that Monday.

Ok. Removed the fuel pump head. The barrel springs and retainers look great. The tappets and rollers are perfect. The camshaft is great too.

It has the asymmetric steel plungers and those look good too. The only thing I noticed was that the front plunger remained pushed out of the barrel retainers. Like I could push it in and it would push back out. However, the rear one I had to pull out by hand and if I let go it would slowly drop back all the way in to the barrel.

Following the Cummins test of blowing air in to the inlet of the head, the plungers both extend. But as soon as I remove air, the rear one sinks back in to the barrel.

Not sure if any of that is an issue but it seems that maybe it is. I’ve only ever had issues with the ceramic plungers getting chewed up and being the obvious culprit.

What do you think?

There is a check valve in the fuel pump head. If your plunger is not "popping" back up, your check valve has failed and you will need a new head. The kit I believe comes with new springs, and plungers all assembled. This video explains it well: https://www.youtube.com/watch?v=wKLV4gAUl6o

There's also the rebuild video here: https://www.youtube.com/watch?v=-Gu5Eyx2SWw&t=91s

Replace the tappet and rollers too while you are at it. I just replaced them on one of mine, and it looks like they are updated? There's not a brass part in them, it's this free moving black piece. Someone here must know the technical term. And when you remove them, make sure to check the cam for wear beneath it.