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SemiSweet · 02-21-2021, **(Subject: 2350 fuel pressure decay Fault code 4726 )**

Thanks. I will check in with an update once I get this downloaded and tested.

SemiSweet · 02-24-2021, **(Subject: 2350 fuel pressure decay Fault code 4726 )**

Well,
I was able to get a new “proper” program downloaded into the truck with no issue.

Picked up two loads of grain today.
I noticed that the truck has more of a knock sound to it like a fuel or injector knock especially at idle, kinda clickity clackity for lack of a better term. Much More so than the previous tune. Not sure if this is expected or if it’s caused from an underlying injector issue that I have not diagnosed yet.

The 4726 code did not come active today which is weird since the rail pressure is still dropping off. My rail block off caps are not in yet to do the tests.

Boost regulates to 32-33 under a hard pull. Although Under heavy engine braking I noticed it will climb up to 37-38 Briefly.

Temps are good, coolant sits at 190 and oil 210-220

Turbo sits at 58% at low idle if I high idle it goes to 20%

Probe temp on the exhaust manifold Climbed as high as 720deg loaded 140k lbs on a long uphill pull

I haven’t noticed any less power compared to the previous tune .

Rawze · 02-24-2021, **(Subject: 2350 fuel pressure decay Fault code 4726 )**

(02-24-2021 )SemiSweet Wrote: ...kinda clickity clackity for lack of a better term. Much More so than the previous tune.
...

your previous tune was wound up to tight.

without a tiny bit of lash in the head at idle, the top end does not get lubed very well. Just make sure your valves are adjusted properly.

SemiSweet · 02-25-2021, **(Subject: 2350 fuel pressure decay Fault code 4726 )**

4726 code came back today. Did a cylinder cut out test and when I cut out cylinder 5 the fuel knock is completely gone . All other cylinders sound the same. I think I will start the injector return flow test with cylinder 5 and see what happens. I bet the injector is done.

SemiSweet · 03-06-2021, **(Subject: 2350 fuel pressure decay Fault code 4726 )**

(02-24-2021 )Rawze Wrote:
(02-24-2021 )SemiSweet Wrote: ...kinda clickity clackity for lack of a better term. Much More so than the previous tune.
...

your previous tune was wound up to tight.

without a tiny bit of lash in the head at idle, the top end does not get lubed very well. Just make sure your valves are adjusted properly.

Update,
I was able to borrow rail caps from a neighbor mechanic and found three leaky injectors 1,2, and 5. No more knock and clicking noises and now i have beautifully smooth running Cummins. Rail pressure did not drop all night long, it truly is a beautiful thing!

The real bad thing about the original de mandate tune is that the Check engine light did not come up. Out of maintenance sake I connected insite to check things out and the code was there. The truck didn’t seem to run to bad. For someone who didnt have insite or a good ear it could have been much worse as damage would be done before a person realized there was a problem.

I Appreciate your help on this Rawze!

Waterloo · 03-06-2021, **(Subject: 2350 fuel pressure decay Fault code 4726 )**

I would still run the overhead, that cam shaft and rollers are not cheap. Cummins makes bank on them with these new motors and customer neglect.

SemiSweet · 03-06-2021, **(Subject: 2350 fuel pressure decay Fault code 4726 )**

(03-06-2021 )Waterloo Wrote: I would still run the overhead, that cam shaft and rollers are not cheap. Cummins makes bank on them with these new motors and customer neglect.

... I found this out the unfortunate way after finding a bad lobe right after I bought the truck. I replaced the cam and cam followers about 10000km ago. Everything is good up there now. Shimmed the oil pump as well with 80cents CAD. It runs 35psi hot at idle and 42 psi on the road. When I was running the engine with the valve cover off to verify oil flow I pulled up slightly on all the rockers and it just pours out of the tips which verifies the passages are clear. Overhead is set at Cummins specs. There is a lot of oil moving up there especially just behind the cam and under the rollers.

Chamberpains · 03-07-2021, **(Subject: 2350 fuel pressure decay Fault code 4726 )**

How exactly did you pull up on the rockers with the engine running? With your hand? Or a tool of some sort? Where did you grab them at?

SemiSweet · 03-07-2021, **(Subject: 2350 fuel pressure decay Fault code 4726 )**

(03-07-2021 )Chamberpains Wrote: How exactly did you pull up on the rockers with the engine running? With your hand? Or a tool of some sort? Where did you grab them at?

Literally grabbed with my hands at the end of the rocker arms above the cross heads with slight upward force to hold the clearances apart longer. Careful do this at your own risk it was out of my own curiosity that I stuck my hand where I probably shouldn’t hah! But it was an interesting result .