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- Monrovia, Ca.
Hey guys. I've been working on commercial HD diesels for a while. Have seen a trend over the last 2 years or so of some municipalities, private individuals and local fleets starting to switch to bio or blend it. Cummins has recently approved the use...on an official stance...before, they neither approved or disapproved the use of bio...of B20. I had a Vons grocery truck with an N14 come in a while back complaining of dying. No faults logged in the ECM, checked rail and restriction, dynoed it, test drove it, could find nothing. Had gerat power, didn't even hiccup. I'd send it back, and 2 days later, it would be back...with the same complaint and we came up with NTF. Last week, it came back, did the usual checks, all the same. Told Vons, maybe it's an ECM, or a fuel pump. That if it was mine, i'd do the least expensive thing first...a fuel pump. Went ahead and put a pump on it, started it ran fine. Arranged a return to them with a drive away service. He came and got it and came right back. Came and got me and said it died on him 2 blocks away. I start looking at it and notice that the filter...a drop in Davco with a clear top bowl...the fuel level was above the top of the filter...indicating a plugged filter, Checked restriction, 2", normal!! Went on a test drive, it dies, no lights, and restarts w/o cycling the key. Limp it back and start checking things again, then I notice the fuel in the filter is , well, not there! look down in the housing and it's all foam. Check restriction, 23" at idle! Shut it off and the fuel was pulled up into the housing with alot of foam.Start bypassing things and when the fuel gets on my hands, it feels funky and stinks and is a deep yellow....bio, no biggie, seen it b-4. Any way, got down to bypassing the ECM cooling plate, restriction went away. Pulled the check valve and found the problem. There is an o-ring on the plunger of the valve. It is non replaceable. After the o-ring is installed, the end is kind of crimped to prevent the o-ring from coming off the plunger. The o-ring was swollen and was out of the groove just far enough that when the fuel demand, ie flow rate increased, it would pull the gooey expanded o-ring into the holes in the plunger cutting off the fuel. That particular valve has been in use on the N14 since '91. I have seen the valve plugged, but never seen the o-ring off of the plunger. Called Cummins Tech services, They said that this is starting to happen when the owners start using biofuel blends. Talk about a nightmare to find!
