Attention: TDR Forum Junkies 
Steve St.Laurent
Staff Alumni
As many of you have probably read I added a pusher lift pump to my truck this weekend ( https://www.turbodieselregister.com/forums/showthread.php?s=&threadid=19767 ). The only problem with the install was that my fuel pressures were a little too high for my Stewart Warner fuel pressure gauge setup ( https://www.turbodieselregister.com/forums/showthread.php?s=&threadid=6113&highlight=fuel ). I have to verify the numbers with a mechanical gauge but based on input from Enterprise Engine performance and from SW it looks like I'm hitting around 20 psi with the lift pumps operating and the engine off, 19 psi with the engine running, and 18 psi at sustained WOT.
The SW fuel pressure senders have a resistance of 240 ohms at 0 psi and 33. 9 ohms at 16 psi. Checking the resistance of the senders with the engine running it was 15 ohms which pegged the gauge to around where a 19 psi mark would be. So what I did was put 3 - 10 ohm resistors in series (or you could use just one 30 ohm resistor - I had the 10 ohm ones lying around) between the gauge and the switch (soldered them together and put a crimp connector on either end and then covered them all with heat shrink tubing to avoid shorts). That brought my gauge back into the range that's displayable. By my calculations (I'll verify this later with a mechanical gauge) 15 psi on the gauge is around 19 psi and 1 psi on the gauge is around 3 psi. Right now this looks to be the best solution if you are over the 16 psi range by just a bit. I searched around and the next gauge that I could find is a 0-100 and at 20 psi it would be very inaccurate.
I'll just adjust the numbers in my head, I know that 15 psi on the gauge is normal now (19 psi actual) and that if it falls below 7 or 8 psi that I should start looking into it. Main use for the gauge most of the time (at this point hopefully) will be to tell differential pressures across the filter and that will work fine.
The SW fuel pressure senders have a resistance of 240 ohms at 0 psi and 33. 9 ohms at 16 psi. Checking the resistance of the senders with the engine running it was 15 ohms which pegged the gauge to around where a 19 psi mark would be. So what I did was put 3 - 10 ohm resistors in series (or you could use just one 30 ohm resistor - I had the 10 ohm ones lying around) between the gauge and the switch (soldered them together and put a crimp connector on either end and then covered them all with heat shrink tubing to avoid shorts). That brought my gauge back into the range that's displayable. By my calculations (I'll verify this later with a mechanical gauge) 15 psi on the gauge is around 19 psi and 1 psi on the gauge is around 3 psi. Right now this looks to be the best solution if you are over the 16 psi range by just a bit. I searched around and the next gauge that I could find is a 0-100 and at 20 psi it would be very inaccurate.
I'll just adjust the numbers in my head, I know that 15 psi on the gauge is normal now (19 psi actual) and that if it falls below 7 or 8 psi that I should start looking into it. Main use for the gauge most of the time (at this point hopefully) will be to tell differential pressures across the filter and that will work fine.
