How can this be? Fuel Pressure?

[Wally19]

How can this be. At idle, Crusing, and WOT, my Pre Fuel Pressure is about 1-2 psi LOWER than my post pressures. I am running a Stewart Warner Set up Identical To Steve St. Laurent, and I've checked the switch to make sure that was right. I cant firgure it out. Its consistent all the way thru the scale. Bad Sender? Ideas.

 

[Briar Hopper]

That's the pressure differential ACROSS the filter. You lose about that much due to the restriction. If it's much more than that , say 3-5 psi difference, I'd say it's time to change the filter.

 

[Wally19]

Briar,



I could agree with you if my Post PSI reading was lower than my Pre PSI reading. But its not.



My Pre PSI reading is lower than my Post PSI reading.



I ain't arguing with ya if your right, just want to get this straight.



It seems Backwards to me.



Jason

 

[Big White Beast]

I have the same set up......

Just different results. Mine read normal with a drop from pre to post. Maybe a bad sender? Are they grounded adequately? Some switches look like they are in one postion but are actually the opposite. Did you meter the switch?



Just curious, how quickly do yours react. Mine seem to be slow as molasses. I had a mechanical gauge on prior to these and I could drop to 7# on a WOT run. Now I can't hold the pedal down long enough (Way too fast for a big truck with my weight) to see it drop below 10#. Still nice to have for monitoring the filter and if it ever goes critical.



Garrett

 

[rickhans]

Why not just swap the two sending units and see if it follows the sending unit or stays the same?

 

[redneckdr]

switch

i agree with the thought about the switch. remember that on a switch, you generally make a contact with the contacts opposite of the direction you throw the handle, ie. switch handle up makes the contact for the lower contact(s) and the middle contact(s).

 

[Wally19]

Big White Beast, As far as the switch, i metered that when installed it. And yes if does make the contact opposite the throw of the switch. Ive looked at the Wiring countless times. I know thats right. As far as pressures, my gauges are just as slow. And i also had a Mech. Gauge prior. On the Mech Gauge, i could get it down to about 8#, but it was bouncing so bad it was hard to read. On the Elec. Gauge, I can only get 10# if im lucky.



B'gate, I might try and switch the Senders tonite. If its consistent, then i found my problem.



Thanks for the Responses.



Jason

 

[pwr2tow]

mine done the same thing, I just switched the units around, keep in mind that there is a difference in the units or you will be thinking you need to change filters all the time. \Ron