ECM controlled lift pump

[rancherman]

Were these    ON-OFF  only,      (Batt voltage)   or   did they  put in a   variable  concession for   different     loads?     *vp 44's*

[Mopar1973Man]

No. The ECM is a ON or OFF state typically. The only time its a modulated state is during cranking which a rapid ON to OFF state at a 50% duty cycle. This gives the reduced fuel pressure for the start up. So the other reason the ECM controls the the lift pump is crash safety. Say you involved in a accident knock out. If the lift pump is wired to just a key ON then the fuel pump could be fuelling a fire that might kill you. Where with the ECM in control the ECM sees no tach signal and shuts down both VP44 and the lift pump for safety. Kind of like the old 12 valves once the engine died the mechanical lift pump stopped too.

[rancherman]

Thanks!

reason I asked was   fuel lab's  pumps  can be  controlled  for   rpms ..  according to  varying  pressure needs  at   Idle  and  WOT...     

   more for  gasoline  injected  stuff  I imagine...

[TFaoro]

Fuel Lab doesn't play well with our ECM

[CSM]

If fuel lab has a variable speed for pressure regulator system, screw the ecm. it would not be required for the fuel system except as a safety measure.

[TFaoro]

ECM is just an on/off trigger. The fuel lab changes the speed of the motor based on what you want. I think cumminsdog over on CF hooked his up to run at a higher speed when the throttle is greater than 50%

[rancherman]

Thanks  guys.  I  asked  just to see if  that  may have been a variable  in  erratic   pressures.   I'll  cross that off the  list!

Still  doesn't  dismiss possible   poor  current  coming from the ecm...   which a   relay would eliminate.

[Mopar1973Man]

I never did like the idea of the ECM directly powering the lift pump. It should of always been a relay direct part. Can you imagine what the heat stress is like with a semi-locked up pump in the dead of winter on the MOSFET's in the ECM?

[CSM]

I never did like the idea of the ECM directly powering the lift pump. It should of always been a relay direct part. Can you imagine what the heat stress is like with a semi-locked up pump in the dead of winter on the MOSFET's in the ECM?

 

I should add a relay.  Good idea. 

[rancherman]

Mosfet?    wazzat?

[TFaoro]

My ecm triggers a relay, which is hooked straight to the battery. Then the power travels down to the pump. Are you guys saying your ecm powers your pumps?

[CSM]

My ecm triggers a relay, which is hooked straight to the battery. Then the power travels down to the pump. Are you guys saying your ecm powers your pumps?

I've never checked, but from what Mike wrote, I assume so. 

[Mopar1973Man]

Mosfet?    wazzat?

 

Here is what a MOSFET is..

http://en.wikipedia.org/wiki/MOSFET

 

Here is the MOSFET's in the ECM

 

As for lift pump wiring... As you can see there is two lead out of the ECM I can assume there is two MOSFET's controlling the fuel pump in parallel to handle the normal current load.

[TFaoro]

Oh wow... I like the way mine is hooked up better. The ecm only has to provide enough power to keep the relay closed!

[Mopar1973Man]

Oh wow... I like the way mine is hooked up better. The ecm only has to provide enough power to keep the relay closed!

 

Same here... My AirDog is relay driven so the ECM is never loaded with the pump loads.

[CSM]

Mine should be as well then.  Didn't think about that.  Penguins are falling off my iceberg!