Something to check although it still doesn't explain why I can restart the truck and it goes back to normal. Where is this connection, near the tank or near the engine?

 

I have a few more observations to add to the discussion. With the truck cold or after sitting for several hours when I turn the ignition to on and wait to start the truck the fuel pressure gauge does not move, it would normally raise up to 15 psi as the pump primed then slowly bleed off unless you started the truck. Without starting the truck, I can bump the starter and the pressure will raise to 15 psi and stay there while the pump runs. When the sudden loss of pressure happens I don't even have to kill the engine and restart to get the pressures back to normal. I can quickly turn the ignition off then back on (the engine keeps running) and the pressure returns to normal. These observations make me think the problem is more electircal/CPU related and not something mechanically wrong with the LP. I'll try the volume test tonight though if I have time just to rule it out. BTW, I checked three different time again today and still no codes. Could I be intermittently be loosing power to the LP through some problem in the electronics of the truck?

 

Possibly, but probably not. You are hoping your problem is different that everyone else's. You can spend hours and hours looking for a needle in the hay stack thinking your problem is different. Its not. These LP's fail in so may different ways, but one thing is for certain; you are playing Russian roulett with your $1,500 IP. If it were my truck I would not start it again unless the LP is replaced. Then you will know for sure. It's your call.

Good luck, keep us posted.

 

Truck will be parked as of tonight pending volume tests of the LP. I plan on doing at least 10 volume tests and will post the results once I know something.

 

Ho hum.... And this where I disagree with the Cummins approved volume test......If you have a hashed internal regulator, the pump will free flow (0 psi) just fine when not in a closed system......it is only when the pump must flow under pressure that you will begin to see the erratic pressures caused by the worn out needle and seat in the internal pressure regulator. Please believe us when we say that if you have a LP running at erratic pressures, it is on it's way out. While it may be hard for you to believe, the symptoms you have described are exactly the same as what MANY other guys here have experienced when their LP's have worn out. You are wise to park the truck until you have an LP that will maintain proper operating pressures.

 

Wise call Wes. Better to be safe than sorry.

When you get done tear the old LP apart. You will be amazed at how lite duty and fragile they are. On a grinder grind off the bowl boss on the outside untill you see rubber all the way around. The first thing you'll notice is that the pumps are totally submursed in fuel (prefiltered) for cooling and lube. (Should pretty much eliminates the idea of adding waste oil to your fuel. The permenant magnets will attract and hold the suspended ferrous metals.) Second look in the bottom of the bowl. You'll see a circuit board kinda thing. I think it is a heater for cold weather, but look at how delicate it is. Vibration will destroy these pumps PDQ.

There is no way this pump can hold up strapped to the CDT. The vibration alone is enough to kill it. (IMHO vibration IS what kills them) Look inside one and see. They might be good for IN TANK pumping, but not sucking fuel 10 feet away and 2 feet up.

 

Myfuel pressure reading became very irratic at times, for peace of mind and £120, put a new LP on, problem solved..( i hope)..

 

I ended up doing the volume test three times and the LP passed all three times. The more I think about it though the less credibility I give to the volume test, it seems kind of bogus. I changed the fuel filter (it only had about 5,000 miles on it) and the intermittent drop in pressure is gone but the pump still won't prime when you turn the ignition on and wait to start. You can hear the pump run, it just doesn't build any pressure until you bump the starter. I'm stumped on that one. I am about to take a long trip so I think I'll swap out the LP just to be safe but at this point I'm still not convinced that is the problem. I guess we'll find out once I swap it out.