SAFETY ALERT: C8.3 Fuel Leak
Took our coach out a couple days ago to get our annual TX "Safety Inspection", which is a bad joke, but not the subject of this post.
Arriving back home, I left coach idling in driveway for about 10 minutes while I swept the parking spot. Pulled back into spot, shut engine down. Stepped out of coach to go into house, and noticed a rather large (2' diameter) wet spot on the driveway where coach had been idling. Did the "dip finger in it and smell" test (no raunchy jokes please) on the liquid - determined it was diesel fuel. This was disconcerting, because our engine has always been (for 5 years of our ownership) very tight and leak-free. So, investigation required!
Got out today to see what's the problem. Coach was raised up, safety stands in place. Started the engine and crawled under the rear end. I can immediately see fuel dripping off one of the metal fuel tubes on the passenger side of engine block. Shut down engine, raised up the mattress platform. Closer look with flashlight revealed the fuel was dripping off a metal clamp that secures a fuel tube (Photo 01 & 02). This tube runs from engine mounted fuel filter base over to the injection pump, so is therefore a low pressure (30 psi) supply tube. The area on the block immediately adjacent to the support bracket was wet with fuel (Photo 03).
I removed the fuel tube from the engine and took it to my bench (Photo 04 & 05). Could not see any obvious problem, so I loosened the retaining clamp and slid the bracket to the side. BINGO! As soon as I moved the bracket, I saw the problem: the rubber "padding" on the clamp did not go all the way around the fuel tube, plus the rubber was falling apart. This had allowed direct contact between the metal clamp and the metal fuel tube. A polished area on the tube indicated it had been moving around in the clamp due to engine vibration (Photo 06). On the back side of the tube (hidden in Photo 06) the contact between the clamp and the tube had worn away quite a bit of material, resulting in a obvious "notch" in the metal (Photo 07). Although I could not actually see a "hole" in the tube, I was pretty sure this was the location of the leak.
To be absolutely sure, I reinstalled the fuel tube on the engine without the support bracket. Started the engine, and fuel immediately started dripping off the shiny spot on the tube. Bending way over the top of the engine and looking with a flashlight and a magnifying glass, I could actually see a tiny little spray of fuel coming from the corner of the "notch". The hole must be microscopic, but at 30 psi it allows a substantial quantity of fuel to escape. And, of course, it would have gotten steadily worse with time, so glad I caught it.
Now I have to come up with a replacement fuel delivery tube, which may be a bit tricky. I looked up the part number on our Cummins QuickServe account, and came up with 3926263. Haven't found any immediate online source for this part, but still looking. I may be forced to ask for help from the local Cummins shop, which I hate to do because they are such A-Holes. We'll see.
BUT, the important thing I wanted to do is get out the word about this potential failure point. Any members with the mechanical C8.3 might want to inspect this fuel tube and support bracket area. If you can correct the inappropriate factory support device with a better item, you could avoid having to deal with a fuel leak. Although a fire would not be likely from this leak (all the hot stuff is on the other side of the engine), it will sure make a mess on your towd, and could possibly strand you in a inconvenient location.
The OEM Cummins metal clamp with rubber insert (Photo 08) is a poor choice for this application. It is better suited to securing electrical wiring. I will look around and come up with a better device to secure my replacement/repaired fuel tube, and post what I find in this thread.
Topic: SAFETY ALERT: C8.3 Fuel Leak