Hello all.. 1st post.. trucks broke!! I have replaced on the advice of a friend my stock pump with a holley blue pump on the frame rail.. The stock pump was operating intermittently and getting worse. This new pump worked briefly off the stock wiring. I currently have it hot wired to the battery, start the truck connect the pump drive like heck, truck runs great, disconnect from battery, shut off truck.. continue this behaviour till you have to fix it. Soooo, can someone tell me where or show me a schematic that I can find the fuel pump power source. Thanks!!

Mark

 

did you use the "stock wiring" direct to the HB??? Hopefully that wouldn't be too much of an amperage difference for it could take out the driver in the ECM. Use the factory wiring to "trigger" a relay to power up your HB, but test the "stock" lift pump plug for B+ and ground first.

No Body

 

Thanks for the quick response.. I know I should have triggered a relay but didnt.. I need to know where the b+ comes from?? I cant believe that the ecm runs the fuel pump directly?? thanks
Mark

 

Tell us what kind of truck and year model so we know what you have.

Mark

 

DOH.. sorry its a 2001 24 valve 5 spd..

 

I knew that. Electric lift pump, name like "noisytruck", pretty much narrowed it down to 98.5-2002.....and if it would have been "hardtodrivenoisytruck" I would have known you had a stick trans too

 

ok.. so is there anywhere to find the info I desire? pretty please with sugar on top.. my trucks not hard to drive..

 

sorry just reread the previous posts.. the drivers in the ecm?? no relay?...


Just had a look at the bullydog kit picture, no relay as far as I can see just a pump, bracket, lines, fittings and some wire.. still looking for the fuse/relay for the fuel pump

 

Yes the driver is in the ECM. Bosch uses a MOSFET (Metal Oxide Field Effect Transistor) to power the lift pump. The ECM was designed to drive the Carter lift pump, which draws no more than 4 amps. Using a relay to drive an aftermarket lift pump makes good sense unless you are sure the aftermarket pump draws no more current than the Carter. The reason Bosch used the MOSFET was to allow an easy way to duty cycle the lift pump using the ECM computer to keep pressure low for starting.

If your MOSFET is smoked, it may fail shorted causing the lift pump to not turn off or it could fail open causing the lift pump to never come on. Generally there is no middle ground.

 

Thanks for the info.. I have installed a 15 psi switch on a piece of braided line to the oil filter head (1/8 pipe plug) and supplying the pump ground there, positive from the distribution box with a fuse. The pump only draws 3 amps so I dont think it damaged the ecm, thinking it was my problem all along. working great now, thanks alot!!