On my truck my attitude moniter shows about 2-3 fuel psi for a split second when i start the truck even with the airdog 100 setup. After a split second it jumps up to 16-18. Is this normal/ok?

Thanks
jeff

 

That is normal, when you turn the key, the pump momentarily kicks in, then shuts off when the engine cranks. Once the engine is running, the pump kicks back in. Not sure of the logic as I'm no engineer...

 

ok thanks!

 

I was wondering the same thing.

I get the same thing with my airdog 100. When I turn to ignition I get around 4psi for a split second and then drops to zero. When I start the truck I get 15psi at the vp and 17psi at the airdog unit.

 

yep same here

 

Yea its normal. Mine does the same attitude does the same thing with my FASS 150.
makes sense to me. Ive never heard any problem come from it. I dont worry about it anymore.

 

VP's like to have little to no positive pressure for start up/cranking. Once the engine is running, that is when the VP wants fuel.

 

Dinner, could you please explain why? Will it cause problems if there IS positive fuel pressure at startup?

 

To be honest I can't remember why, I just remember always reading about it. I remember people saying that the truck will crank longer before starting if you have constant pressure. As far as problems go, it may do more harm than good to diaphragm in the long run, IMO.

I'll see if I can find the correct answer or get some guys that know to post up.

 

That would be great if you could find that info. I've been using a Holley pump for a year and a half and it's wired so that it runs as long as the ignition is in the "run" position. The truck starts within 1 second of cranking, but if it's bad for the IP then I'd rather rewire it. I really need to get a wiring harness extension and completely bypass the OEM pump. Does anyone know where's the cheapest place to get one of those?

 

The only issue with having the constant pressure at start-up can be hard starts.

 

Thanks, Halo!

 

The ECM controls the LP with two modes. One is 100% mode when the truck is running the other is 25% mode while the engine is cranking. This second mode reduces injector pump inlet pressure during starting.