Lift Pump Question

[Case500D]

Hi Guys,



I have a question for those of you who have had to replace your lift pumps. Did the hand primer quit working on yours? I have been having problems at WOT with the engine winding up to 2500 RPM falling back to 2100 RPM (boost drops from 24 to 20 and then back up) and then revving back to 2500 RPM and holding. This was with 11K of trailer on. It did it in both 3rd and OD. I went to change the fuel filter tonight and I can't get my lift pump to work at all. I have tried turning the engine a bit and nothing. I even put a socket on the alternator pulley and turned the engine trying to get the lift pump to engage. Is it safe to assume it is dead? I know this seems pretty obvious, but just want to make sure I sink the $$$ in the right hole. Thanks.



Jeremy

 

[AMikonis]

Jeremy, to be sure, why don't you disconnect the fuel line between the lift pump and the filter and crank 'er over. You'll know pretty fast if it's working. Maybe disconnect the shut-off solenoid so it doesn't start up and suck air in.



Andy

 

[BushWakr - RIP]

Jeremy, my lift pump has one of the 'smallest areas of operation' I've ever experienced on a liftpump. It seems like just the slightest bit one way or another and it's "on a lobe" type behaviour.

Your problem sounds like surging ..... I wonder if you're right on with the LP being bagged or on it's way out. The internal, low pressure side of the VE, can draw fuel for the pump on it's own depending on the height above the tank. In our application it should work fine, but the surging sounds like the liftpump is "getting in the way" and causing peaks/valley's in the fuel pressure/supply.

You must have a gauge kickin around you can use to check the supply pressure from the LP.

I'm leaning toward the LP bud... . filter is clean right??? Haven't run it down to the bottom of the tank lately?? You know better'n that anyway...

Hey, do these LP's have a weep hole on em??? I thought they do... check for any sign of weepage.



Unless you didn't listen to me and you went ahead and used that 1/8" drill bit on those nozzle tips... . now THAT'll make you weep... .



bob.

 

[Case500D]

Hi Andy,



I think I will try your idea to be sure the LP is dead. RIght now I can't get the fuel filter to bleed out because the hand primer isn't working. At least it is warm out, so working on it is not too bad Thanks for the idea.



Bob,



What can I say, I used a 3/16" drill bit on those nozzles. I have noticed a slight decrease in the idle RPM over the last month or so. Seems to me that it has dropped 50 RPM or so. I am kind of thinking this might be because of no LP pressure keeping the internal pressure of the pump up. Just a guess. I tried the LP again this morning to make sure I wasn't missing something, no go It has also seemed to me that the overall range of boost vs RPM was down a bit, but since the PDR turbo I am still getting acquainted with it. I am really hoping it is the lift pump and not the main pump. If I can get the truck running, I will check the LP pressure. I have a gauge I just bought for my Dad's 24-valve. Sad that I may need a new LP too. I haven't ran the tank below 1/4 for at least a year now. Thanks for the help and I will let you know how it turns out.



BTW, the PDR HX-35 is really cool for towing. I can accelerate going up hill on the interstate with 11K on the back. Man that is cool!Oo.



Jeremy