Relay woes(?) for pusher pump.

[Steve Campbell]

I recently installed (why did I wait so long?) a pusher pump. (I moved the pump from the factory location). Everything is better. My only question; is it normal for the relay to turn on-off-on-off-on-off-on very fast during starter engagement?The rest of the time, it is just as I expected. I made sure I had a good ground. With only the pusher pump, I could have just spliced extensions onto the factory lift pump harness (post connector). I installed the relay because of the recommendations of others here.

 

[Neal Cassady]

Relay Trigger

Steve,



If you are using the factory lift pump lead to trigger the relay, it might cause clicking at startup. I believe the ECM limits the voltage to the lift pump during startup to something like 6 or 7 volts to prevent the lift pump from developing its max pressure during cranking. The voltage reduction may cause the relay to chatter.



Haven't finished my pusher install yet so I can't comment on the relay on my truck. I got the kit from Enterprise, the relay looks like a good quality Hella unit. It opens and closes with one snap when I apply/remove 12 volts. Hope to have the pusher pushing tomorrow afternoon.



Dave

 

[juicedcummins]

Mine does it too and I don't now why. It does it with or without the relay. The factory pigtail from cummins is what I used to get the plugs. Have even gone as far as bending the pins a little and greasing it up.

Any ideas?

 

[RADdodge]

When starting, the ECM limits the duty cycle to the lift pump to 25% to enhance starting. If you are using the output of the ECM to trigger the relay (which you normally would), there is no guarantee that the relay will stay energized at the 25% duty cycle.



Because of this and other reasons, I used the starter relay (terminal 87A - normally on) to energize the pusher pump. I also used a check valve to bypass the pusher pump when the pusher pump is inactive. This way, when you engage the starter, the pusher pump is off and the lift pump, running at 25% will feed the injection pump at it was designed. The fuel goes around the pusher pump through the check valve. After the engine has started, the starter relay is de-energized and the pusher pump engages. You also end up using the fuse for the starter (20A) which will run the pusher pump with no problem. I also use a switch so I can turn the pusher pump on (to prime the aft fuel filter), disable or enable it.