Posted February 16, 201510 yr Were these ON-OFF only, (Batt voltage) or did they put in a variable concession for different loads? *vp 44's*
February 16, 201510 yr Owner 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.
February 18, 201510 yr Author 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...
February 18, 201510 yr 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.
February 18, 201510 yr 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%
February 18, 201510 yr Author 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.
February 19, 201510 yr Owner 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?
February 19, 201510 yr 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.
February 19, 201510 yr 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?
February 19, 201510 yr 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.
February 19, 201510 yr Owner 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.
February 19, 201510 yr Oh wow... I like the way mine is hooked up better. The ecm only has to provide enough power to keep the relay closed!
February 19, 201510 yr Owner 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.
February 19, 201510 yr Mine should be as well then. Didn't think about that. Penguins are falling off my iceberg!
Were these ON-OFF only, (Batt voltage) or did they put in a variable concession for different loads? *vp 44's*