2001 2500 ctd..
lift pump runs for aprox one second when key turned on (no start)..
during this time the pump voltage is at 12 volts.
after one second pumps shuts down voltage drops to 6-8 volts...


also 2-6 pound pressure switch turns off fuel pressure light for one second ( add on light ). then light comes back on after voltage drops ..
when engine started the light goes out ..I have not monitered the voltage with engine runnig

pump runs fine on test bench ..replaced with a new one any way ...same sympton ..
??? Is it the powersupply , and where does it come from ?? ECU ??
Help please ...just bought the truck ...And I am learning ...truck has 67k ..and seems to run ok ..But I am reading about the infamous lift pump ...and want to check mine before disaster..

 

update ....ignition on still one second of 12 volts pressure light out ..
after one second voltage drops, pump stops, light come on.

start engine pump goes to 12 volts .. light stays out ..and stays out under load (full throttle to 2500 rpm @ 50 mph)

Am I ok ???

 

thanks to the moderator for moving this post to where it belongs

 

can anyone tell me where does the voltage for the lift pump come from ??
and is a one second run time on ignition on correct??.

 

the power for the lift pump comes from the ECM, and it should stay running longer than one second. Mine will run on initial turn on for approx 10 seconds to purge the system. bumping the starter will force it to run for another 20 seconds and so on after that. This is the way HPCR's run, however VP's like yours should be similar with run times.

 

thanks for the reply ....
now I guess I have to have the ECU checked somewhere