Fass Questions

[chazj]

I just had the Fass II pump installed a couple of months ago. I have read the posts regarding "hard starts" with Fass under certain conditions which maybe related to initial excessive fuel pump pressure (if I understand correctly).



Two questions: 1) When I start my truck the FP gauge is initially pegged at 15 lbs. As soon as I turn the key, it immediately drops to zero & then starts.

Is this Normal and, if so, would that mean I will probably not experience the issues I described above? 2) Is the Fass pump running when the ignition is in the "aux" position... like when just running the radio?? Wouldn't want to burn it out or cause other unforeseen damage.



Thanks for any input.

 

[Highfinance97]

Is the Fass pump running when the ignition is in the "aux" position... like when just running the radio?? Wouldn't want to burn it out or cause other unforeseen damage.



Thanks for any input.

no it should not run in ACC but will run when its in the "ON" pos.



Cant you hear it running??? :-laf





Michael

 

[chazj]

I guess it does pay to have "ringing ears" at times as the Fass doesn't compete with the "surround sound" I often experience...



But seriously I just put my ear to the Fass and only heard it "whine" while the engine was running. Just as posted No noise when in the "aux mode" but also doesn't operate when the key is just in the run positon (without starting the engine)... just a quick "whine" while I think it pressurizes the system...



Guess all is normal...

 

[Highfinance97]

Yep thats the noise it wont change when its in run, it should be running the same either way

 

[steved]

As noted, it shouldn't run in the ACC position.



And normally, depending on the ECM, they will come on until the wait to start light goes out (or for at least a few seconds), then stop... as soon as the truck starts, the pump runs continuously. If it is really hot out and the truck was just running, sometimes they won't come on at all until the truck is running.



steved

 

[LowFly]

For your year truck the cycle goes as follows:



Turn the key to Run. ECM will send power to the pump for about 0. 5-1 second. Then it will shut off. Then when you crank on the truck, the ECM will pulse the pump to reduce the duty cycle. This is done to lower pressure while cranking. Then if the engine catches, you got back to run, pump runs at 100% duty cycle.



You can also bump the engine before you start it and this will pulse the pump for about half a second and then run it for about 20-25 seconds. You bump again, it will run it for another 20-25.



If you let the engine run and then shut if off, then try to bump the engine to get the FASS to run, it may not run. I dont know how this works, but you have to let the truck sit for a bit until you can get the 20-25 second run time back.





The newer trucks 05-06 have a direct fues tap. These systems will run in the Run position only. If it runs in ACC, might change the fuse you are tapping to. Make sure its 15-20 Amp fuse that is only hot in run.

 

[chazj]

Thank You Dan! You describe the "run cycle" perfectly in my 02 Ram.



While literate I am by no means a mechanic & thus have all my work done at Imler Diesel in Sacramento. I just find it easier, at times, to ask the questions "here" as opposed to a long distance call to Ken.



Thanks again for your help!!!