Randall_428,
Yes, you CAN loose prime actually quite easily if you're not careful. I know, I did it and it was a bit of a nightmare to get that engine running again. It's a bit of a long story but here's the short version. I had a 1/2 tank of fuel when I was going to do a fuel filter change. I had the coach jacked up somewhat with the front end slightly DOWN HILL!!!! When I removed that one and only fuel filter (some CAT/Freightliner chassis's are equipped with ONE fuel filter and some have two) what I didn't realize at that time was, all the fuel in the line between the tank and the fuel filter housing by the radiator, due to the coach facing downhill in the front, DRAINED back into the tank. And, not only that but, apparently it also sucked some or most out of the line from the fuel filter housing to the transfer/lift pump that's attached to the HEUI pump, NOT GOOD!!!
To compound matters, for the first and one and only time I ever followed a CAT service manual, it stated to NOT PREFILL THE FUEL FILTER!
For the next 24 hours, that engine WOULD NOT START! I'd tried everything in my limited power/knowledge to start it, nope, ain't happening. Upon contacting Freightliner and a gent on here that participates in multiple RV forums with the user name of Wolf10, I was advised that the one and only way to prime that engine was to PRESSUREIZE THE FUEL TANK!! Soooo many on the forum stated all I had to do was to cycle the ignition key on and off multiple times to get the fuel pump in the tank to pump up the system and that would be it.
WRONG!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! There is NO FUEL PUMP in the tank on those CAT equipped chassis's. There is only a "lift pump" that's attached to the backside of the HEUI pump on the engine, period. And it has very little priming power. Some CAT engines are equipped with the small priming hand pump which is located very close to where the secondary fuel filter would be, on the passenger side of the engine about half way down the length of the engine. If one is fortunate to have one of those, and looses prime, THEN you have the means to prime the engine. Otherwise the only way is to break the line from the tank at the fuel filter loose, and have someone actually use air pressure (from your basic home air compressor right in the fuel filler port sealed with some rags etc. Once you have fuel oozing from that line, you tighten it and, you should already have a fully primed/filled fuel filter in place.
If you're lucky, you won't loose prime. if not, good luck.
Scott
