2350 fuel pressure decay Fault code 4726
02-21-2021, (Subject: 2350 fuel pressure decay Fault code 4726 ) 
Post: #1
2350 fuel pressure decay Fault code 4726
Hi guys, My truck is showing code 4726 Fuel leakage above normal. No other codes present .Looking for any tips or guidance before I go buy block off fittings for the injector connectors as well as the test banjo fitting. Truck is demandated. Program is with Rawze for review.

What I have done so far:

Performed the fuel system leak test on insite. Pressure measured vs pressure commanded is tight all the way up to 29000psi. Shut truck off and by the time insite re connects...(rarely can I get it to stay connected so 10 -15 seconds) it is down to around 100 psi.

No external leaks.

Re seated and torqued all the connectors on the rail, pump head, and drain header.

Removed pressure relief drain line and capped. Performed the leak test again with zero drops from relief valve all the way to 29000psi.

Fuel pump roller/tappets and barrel/plunger assemblies as well as gaskets were replaced 7000km ago.

The engine shows no sign of a problem. Its starts beautifully every time with no smoke or hesitation. I have no power loss or surging of any kind.
You would think a leaky injector would make it hard starting or want to smoke a little bit or maybe hesitation on the throttle. There is no fuel dilution in the oil which is a nice honey gold color by the way.
Is it possible one of the barrel/plunger assemblies is bad. With pressure dropping this fast it should be something that shows a symptom of some sort.

I realize that I will need to run through the testing procedures that quickserve outlines to drill this down but any extra guidance is helpful.

Thanks,


User's Signature: 2015 389 Peterbilt. ISX 550 18speed 3.70 gears
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2350 fuel pressure decay Fault code 4726 - SemiSweet - 02-21-2021



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