I just installed a glow shift 3 in 1 gauge to monitor egt and fuel pressure. Fuel pressure reads 37-39 psi on average. Hooked in via test port. I am guessing a new HFCM is in my future. No driving issues. I replaced blue spring a little over a year ago, but did not test pressure at that time. From what I've read pressure should be anywhere from 55 to 62 PSI. How long can I drive with this low of pressure or should the Pump be replaced ASAP?

Installing gauges seem to cost me money. In 2011 I installed a scan gauge and noticed 35 degree spread between coolant and oil. Replaced oil and egr coolers then. 2004 Excursion with 130,700 miles.

Thanks in advance for suggestions/tips.

 

Be sure your gauge reads 0 befote your turn on the key...and the fuel pump starts. Or wait for pump to stop and pressure drops back to zero.
I re-zerod mine after installation.

 

Fuel pressure display is digital, haven't seen a way for zero'ing. It will display zero when just turned off.

 

You need to replace asap! You are killing your injectors and they are EXPENSIVE!!!

 

That's what I want to avoid. Trip to my dealer first thing in the morning!

 

I just replaced my HFCM this morning. Cycled key, fired up and pressure slowly climbed to 55-58, while revving it hovered around 60. Turned it off, put up tools, cleaned up the mess, etc. Triple checked pressure and all seemed consistent. Went to move truck a little bit later and pressure is now back to 37-39, no higher!!!!

No leaks. Nothing changed from good reading to bad except when I started it to back it up and reading was low at that point. Could there be anything else I am missing? Blue spring was done over a year ago. Filters look good.

Could something be bad inside the tank that would cause a drop in pressure? Bad part about that is I have a full 44 gallon tank if that is the case.

I plan on putting a mechanical test gauge on it tomorrow ( gotta go to work right now) and seeing what the reading are from that (maybe it is just my electrical sensor). Any help would be appreciated!

 

Since its a Glow Shift, first thing to do is check its accuracy.

 

Are you using oem filters and caps? Had to ask.

 

OEM filters and caps. I will be checking pressure with a pressure tester guage tomorrow to see if it is the sender or glowshift itself.

 

Good call. Nothing beats a mechanical gauge.

 

OK, I think I may know my problem but am a little perplexed. I hooked up a mechanical guage and the pressure looks great, reading around 55. When driving it hovers around 60-62 dips to 58 or so, this was done when the motor was cold and just around the block a few times. Tested the electronic switch by hooking up an air hose to it at various pressures. All seemed well and relfected fairly accurately according to the regulator valve on my compressor. Hooked back up switch and pressure on gauge read about 54. Thought it was fixed. Wife drove truck and pressure range was from 54-63, held steady around 60 or so. She stopped truck to go to store. Gets back in and the gauge only reads as high as 39 again (motor is at operating temperature).

So I speak to a friend who is a mechanic and he states that air could still be in the system and advised to run it for a while and see if it clears up. I am thinking the switch is bad because before I hooked up the mechanical gauge this morning the pressure read 38-39 psi. Reinstall and it reads good, then back to bad. Is it possible that air is still in the system or could a dip in pressure occur due to the truck running at operating temperature?

 

It's not air causing the problem. The pressure would be the same, just with bubbles in it.

 

Try testing the switch with air again after you heat it up with a hair dryer. Maybe the sending unit does not read correct when hot!