How many PSI is the fuel pressure switch?

bevans6 · December 08, 2011, 07:27:14 AM

Anybody know? Just curious, I guess. When I was starting my new 8V71T I used my in-line pump to prime, and left it turned on while I got the engine running. A couple of times when it stalled it wouldn't crank again until I turned the priming pump off. I though it was probably the pump tripping the pressure cut-off switch, since when I turn the pump off it cranked again.

Supplementary question

. Does any one run a fuel pressure gauge on the secondary filter head? Seems like that might be interesting information to know.

Brian

luvrbus · December 08, 2011, 07:54:45 AM

Some of the GM guys run fuel pressure gauges Brian I have one here with a fuel pressure gauge and I have no idea what PSI the MCI uses that switch is a trash can item for me lol

good luck

thomasinnv · December 08, 2011, 09:28:55 AM

Brian, that switch operates at 3#. Your inline prime pump running would definitely kill the starter.

bevans6 · December 08, 2011, 10:17:37 AM

I think I will indeed trash-can the switch and add a gauge.

Thanks, Brian

thomasinnv · December 08, 2011, 12:23:27 PM

Brian, as you may know, the purpose of the switch is for starter over ride in case of engine safety shut down. For example, if an overheat sensor or an oil sensor triggers an engine shut down, you can hold the start button in and the engine will continue to run. The fuel pressure switch disengages the starter once the engine starts, otherwise the starter continues to grind while you hold the start button in and move off the road. That having been said, I think the only time I would use the over ride would be in case of extreme emergency where I absolutely HAD to get off the road RIGHT NOW, or in the case of a safety shut down failure, ie. a failed sensor or grounded wire.

bevans6 · December 08, 2011, 12:39:32 PM

My shutdown systems are actually disabled, so they don't need to be over-ridden since they don't work. I have to think about if I will re-enable them and keep the fuel switch, or keep them disabled. Not a decision I have to make in a hurry, it's winter time up here!

Brian

papatony · December 09, 2011, 04:10:48 PM

Brian::: you really need to get those shutdowns working. if you have an engine run away it will destroy your engine and tranny. And it does happen. Tony

Boomer · December 09, 2011, 04:17:11 PM

We disabled all of ours. Just a failure and leak waiting to happen. If worried about starter sticking, not too common of failure, simply start from the rear. We also unhooked the alarmstats. But...make sure your buzzer and warning lights work.

thomasinnv · December 09, 2011, 10:33:07 PM

the safety shut down systems are not going to do anything to stop a run away. Your thinking of the emergency stop flapper in the air horn. If Brian has the newer style fuel rods he doesn't need the flapper anyway, and would be better off without it.