Originally Posted by B Dubya
Good info, but (there's always a but!), how do you prime a closed system if neither the lifting pump nor injector pump can't operate dry?
It's a long story but, I'll give you the Readers Digest version. I did a stupid thing, I READ THE CAT MANUAL prior to changing the one and only fuel filter I have. I'd changed it before but, I didn't read the manual and, had no issues. This time, for some odd reason, I read the manual and, it stated to NOT FILL THE FILTER!!! So, I didn't.
Well, I installed it dry and, fired up the big beast. It ran for about 10-15 seconds and, that was it for about 24 hours. I cranked and cranked and cranked that starter but, no start. So, I called Freightliner, I called CAT, I called a well respected member of this and many other forums. All three suggested for me to PRESSURIZE THE TANK!! Whaaaaattttt?
Well, that made some sense to me. So. I filled the filter and, had the wife push my air compressor hose into the filler neck and, had a rag around it to to the best she could to seal it off. Well, after about 10 seconds or so of pressure in that tank, I started to see fuel, entering the filter base. (I had the filter off for the time being). I quickly installed the full filter.
I then went in and, cranked and cranked and cranked, NO START, HHHMMMMM. So, I figured let's take this one step farther. I went into the coach, removed 48 tons of stuff that SHE keeps under the bed and, exposed my engine. I found the line to the lift pump, from the filter output.
I loosened it and, had her pressurize the tank again. Well, guess what, it started seeping fuel from that line. I quickly re-connected it to the lift pump. I then went forward and cranked the big beast. Guess what, it started to lite off. I kept cranking for about 3-4 more seconds which, seemed like an eternity and, it fired up and, purred like a kitten, er, a, big CAT that is.
What happened was this:
1. The coach sitting at angle such that, it was lower in the front than the rear.
2. I only had about 1/2 or less fuel in the tank.
3. The fuel level, in the tank, was lower than the height of the filter base, at the the time of the filter change.
4. Upon removing the old filter, that's where things went south, AND I DIDN'T KNOW IT AT THE TIME.
5. All the fuel in the line between the tank and filter base, had drained back, into the tank.
6. I now had, approximately 20-25' of EMPTY FUEL LINE from the tank to the filter base.
7. Some how, again I didn't know it, all the fuel had drained from the lift pump, out of the out put side of the filter base.
8. I was now sitting with no fuel in the fuel line from the tank to the filter base, no fuel in the filter, (remember me saying something about "Reading the manual") and no fuel in the line between the filter base and lift pump.
And, like stated in many of my threads, THERE IS NO PUMP IN THE TANK of many of these coaches. So, obviously, there cranking was useless. So, the suggestion of pressurizing the tank, was the only way out of this situation.
So, two things.
1. NEVER, repeat NEVER, install a new fuel filter without priming it.
2. I installed anti-drain valves in both sides of the lines to the filter base, to prevent this from ever happening again. Problem solved.