We have an older mechanical 466 in a 1992 IHC 4900 that is losing its prime and running rough and stalling. Is the transfer pump part of the priming pump assembly? Thanks in advance.
Your lift pump is bad, the pump portion in the injection pump is bad, you have an air leak somewhere, or the lift tube in the tank is cracked, my 466 got so bad, after I'd fixed all of the above, I ended up putting every line on new along with all the gaskets and seals in the entire fuel system to get the truck to run and keep itself primed, best of luck on your search for the cause of the problem.
Thanks for the encouragement. Do you know if the lift pump is part of the hand primer pump on the injection pump?
I think so but I'll have to look tomorrow to be sure, its been about four years ago I worked on that, since its been starting and stays running I haven't had to look under the hood very much. Thinking out loud, if your concerned its the lift pump, try hooking up a small tank above the level of the injection pump, so its gravity feed into the injection pump, if it still doesn't stay running you have other problems, if it stays running, something leading up the injection pump is causing the problem, not necessarily the lift pump. Then put the tank lower than the injection pump, that should isolate the lift pump or if its in the lines somewhere between the injection pump and the trucks tank, if its stays running its not the pump, if it quits, you have a lift pump problem or something in the injection pump. Had I done this first I could have saved myself a lot of money, for me it turned out being in the gaskets in the lines from the tank to the injection pump and also in the fill tube, which had a crack in it part way up, so if the tank was full it ran pretty good, once it got under half and the fuel sloshed in the tank it would lose prime and quit and was almost impossible to get primed again. If its not a lift pump, you have a serious air problem somewhere to stall out the truck while its running. Also there is a check valve on the fuel filter housing that causes problems, usually it'll lose its prime after sitting a while if its in the check valve though, I'd have to look again but make sure there isn't a screen somewhere in the line, I was thinking without looking there is a screen on both of my mechanical engines before the fuel filters, clean it up to make sure there isn't junk sticking in the line causing it to lose fuel flow to the filters and injection pump, had that problem too on one of the engines I have, and double check the spring and ball on the check valve to make sure its opening like it should. Not sure if I helped or made it worse, but those are just a few things I've had to do over the years on my 466's to keep them going. By chance is there any fuel leaking anywhere even some wet area's?
There was some dampness on the plastic bowl on the water separator and the guys said they had trouble getting it to thread on straight. Replaced it with a filter with no bowl and so far so good. Time will tell though as it stalled before we changed filters initially. Thanks for all your ideas and if it is still acting up I will try a tank mounted above. That is a really good idea.