Truck is at operating temperature, although what I describe below happens while starting at cold temp. I installed the FRRP-100 last weekend and set the pressure to 19.0-19.5psi at idle. Notice the normal initial 2 sec run at ~21.5 psi. After starting, it runs at ~15.5 psi for 15 sec and then jumps to 16 psi - finally it jumps to 19 psi and the engine sound different. Coincidently the ScanGauge 2 comes on at the same time. Is this a function of Open vs. Closed loop of the VP44? Is this a function of the ECM? Thank you.

I wonder if the grid heaters are causing the voltage drop so the pump doesnt get enough power to maintain pressure until they turn back off.

I wonder if the grid heaters are causing the voltage drop so the pump doesnt get enough power to maintain pressure until they turn back off.

Truck is at operating temperature and wait to start was finished.

http-~~-//www.youtube.com/watch?v=FNkZWRsFaRQ&feature=youtu.be

Looks like a voltage drop at first start (grid heaters post heating) then the pressure pops up after grid heater shut off. More of electrical issue than a pump.

Looks like a voltage drop at first start (grid heaters post heating) then the pressure pops up after grid heater shut off. More of electrical issue than a pump.

Hey Michael, Does your Air Dog 150 do this in the winter? It was 60'f this morning and in the afternoon this scenario disappeared

Put a voltmeter on the battery and see if the the drop in pressure corresponds to a drop in voltage. Try to use a digatil meter and run jumper wires to the cab so you can watch fuel and voltage at the same time.

Mine will be low on start up and seems to follow the volt meter in the dash. First start up in the morning it takes a few seconds for the volt meter to come up to 14v and the pressure moves with it. This happens even when warm, just takes a little less time.

Mine is same way. After grid heat shuts down pressure is up. I can watch volt meter and pressure. It does this whenever grid heat on.

Mine is same way. After grid heat shuts down pressure is up. I can watch volt meter and pressure. It does this whenever grid heat on.

I get the same fluctuation with my airdog raptor 100

I also get the same fluctuation.

Hey Michael, Does your Air Dog 150 do this in the winter? It was 60'f this morning and in the afternoon this scenario disappeared

In the dead of winter with minus temps and both grid heaters cycling in for post heating I might see 0.5 to 1 PSI fall each time the grid heaters fire just after starting. Now with cool summer morning temps like 40-60*F out no I don't see any drop at all. My power is hooked up in the PDC for the AirDog not at batteries or at alternator (well technically its the alternator line in the PDC).

In the dead of winter with minus temps and both grid heaters cycling in for post heating I might see 0.5 to 1 PSI fall each time the grid heaters fire just after starting. Now with cool summer morning temps like 40-60*F out no I don't see any drop at all. My power is hooked up in the PDC for the AirDog not at batteries or at alternator (well technically its the alternator line in the PDC).

Thats where mines hooked up too but still get the fluctuation when grid heaters go on and off. Micheal we all get that fluctuation cause we don't all have a pair of 500 lb. 8D batteries in our trucks like you

In the dead of winter with minus temps and both grid heaters cycling in for post heating I might see 0.5 to 1 PSI fall each time the grid heaters fire just after starting. Now with cool summer morning temps like 40-60*F out no I don't see any drop at all. My power is hooked up in the PDC for the AirDog not at batteries or at alternator (well technically its the alternator line in the PDC).

I think there is a post you did 2011 about an alternate wiring on a post in the relay panel, is this what you are referring to? If so, do you have images or schematic? I would like to install it on my truck. Thank you.

Is it possible that when the grid heater comes on, the injection pump is also asking for more fuel, thus the pressure drop. Some computer controlled gas rigs do dump more fuel during warm up as a means of electronic choke control. Just a thought, I don't know.