liftpump relay??

[James Schaack]

hey guys,

i searched for my answer but couldn't find what i was looking for. after reading everyone's posts about liftpumps, i figured i better check mine because i never hear any type of pump clicking when i turn the key on. well, i check and sure enough it wasn't making any noise, so i held onto the pump while i turned the key back on (god bless being 6'5") and i still didn't feel anything. so, i did like the R&R manual said and touched the lift pump fuse to one of the positive posts on the firewall and to my suprise, the lift pump ran like a champ. are these liftpumps controlled by some type of relay that may have gone bad? is there something i am missing?? any help would be appreciated.

thanks!

James

[Turbine Doc]

James check this link out you could be having oil press switch bad which turns on the relay.

http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=004860

[James Schaack]

tim,

thanks for the link, i will make that modification over christmas break :D along with the mod, is there any good methods of testing the OPS and liftpump relay? today i felt the pump with the truck at idle and it was not functioning, so i'm guessing it may be the OPS. also, where are the two located? i was reading a post that said the OPS was somewhere on the driver's side towards the cab. is it the piece with the plug sticking out underneath the glowplug controller??

thanks

james

[James Schaack]

well, i replaced the OPS today and that seemed to do the trick smile.gif the liftpump will now run after the truck has been started, but it is still not running before i start. i am going to replace the relay tomorrow and see if that takes care of the problem.

james

[Barry Nave]

Before start the pump won't run. When cranking the pump will run,the OPS will build psi and the pump will start working. When I change fuel filter in my 95 I can go to drive and turn key to start and the lift pump will run to blead air from filter.

[ 12-13-2003, 07:21 PM: Message edited by: Bnave95 ]

[BuffaloGuy]

The '93's with manual trans. are different. Near as I can tell (I have a fuel pressure gauge plumbed in full time) the starter circut powers the lift pump and upon start-up (and release of the key) the OPS then powers it. I noticed if the motor starts right away that there is actually about 2 or 3 seconds when there is no fuel pressure. Then the OPS kicks in and all is well.

The only time you can hear the lift pump on a '93 is at shut down. It will run until the oil pressure falls off. The rest of the time the motor is too loud.

Ken

[James Schaack]

thanks for the replies fellas! i guess it sounds like the system is working the way it is supposed to, learn something new every day!!! god bless TDP!!!

thanks again,

james