cool

 

a 278 code is loss of power at the ecm on the lift pump circuit, and a 434 code is battery voltage below 9.6v before the 30 second timeout on the ecm. basically if you unhook the batteries within 30 seconds of turning off the key the ecm doesnt have time to shut down and sees the power loss. a common cause for the 434 code is loose battery cables and that may cause the other code also, start there and if you cant find anything let me know and ill see if i can do some more digging, sorry but was really really busy at work today (which is Cummins Atlantic Inc. in Charlotte, NC). hope this helps some.

 

Dear Keith,

Wow, thanks. Does this make sense? The truck loses power at high speed. At 60 mph or so the power just cuts off and then I have to down shift at 45 mph and build up rpm's again. I changed the fuel filter and it was beyond filthy, this seems to have alleviated the problem but it still happens just not as much. What do you think?

Jim and Nancy

P.S. This truck is our dream Food Truck, thanks for the help.

 

the clogged filter could have possibly gotten your lift pump. when the filter is clogged the lift pump cant flow its potential causing premature failure. this could be your problem as the greater the load on the engine the more fuel it demands, but not necessarily more rpm. in a higher gear at the same road speed there is more load on the engine than in a lower gear even though it is higher in rpms. if you have access to a fuel guage, check the pressure output of the lift pump, and if the pressure is ok then the volume maybe not enough. i will see if i can get you some specs. sorry again really busy again today.

 

Dear Keith,

Thanks for the advice. Is the lift pump in the tank?

Jim

 

on a 98 24v i believe its mounted on the drivers side back corner of the block below the filter housing, at least thats where its at on the pickup and light duty truck engines.