Fuel pressure bleed off...

[CumminsPower98]

I have some questions for you guys with fuel pressure gauges (or anyone who knows). I finally got my gauge working with a new sender. I used a needle valve and 3 feet of 1/4" hose and mounted the sender remotely this time so I will now see how long it lasts.



My question is: is it normal for the fuel pressure to bleed off just a few minutes after shut down or should it stay pressured all the time? Seems like I remember Illflem saying his did not bleed off. Mine bleeds off pretty quick. Could this mean I have a bad overflow valve? My fuel pressure was 16 PSI at idle and 20 PSI no load 2,000 RPMs. I then changed my fuel filter at just under 6,000 miles and the fuel pressure went up to 22 at idle and about 26 no load 2,000 RPMs. I also get more lift pump "tick" than my buddies. Maybe I need a pump? Any thougths? Thanks!! Truck has 73,900...

 

[illflem]

What I noticed was when I first installed a fuel pressure gauge when my truck was newer was that it would hold pressure for at least a half hour after shut down, at first I thought something was wrong. Now my pressure drops instantly after shut down, something must be leaking back somewhere, truck still starts and runs fine so I'm not going to worry about it.

 

[Extreme1]

Pressures look good!

What is it under load at high boost?

 

[HEMI®Dart]

CumminsPower98,



My gauge takes about a minute to bleed down. I have a 2 month old Piers overflow valve. Your pressures seem a little on the low side. Idle is ok, no load is a litte low. Is the overflow valve still the original? Piers says no less than 15 psi on a hard run. Try pinching the rubber fuel return line a little bit, behind the brake booster to see if you get more pressure.

 

[Joe G.]

Those pressures may be ok. It depends on the outside temperature for some reason. If it's cool I show pressures from the mid 20s to the mid 30s. If the temp is in the 90s or 100s my fuel pressures will be about 10PSI less sometimes even less. Doesn't seem to hurt anything.

 

[illflem]

My pressures are: 22 @ idle, 18 @ high boost and 28 downhill no throttle. Usually cruises on the flat at 22-24. This is with a brand new overflow valve.

 

[CumminsPower98]

Thanks everyone for your input! I noticed that my new filter pressures didn't last more than about half a day. Pressures are back to the same as before. Idle 17, high boost about the same as idle and no load high speed 19. I suppose my gauge may not be reading fully right so I'm not sure. I hooked up a mechanical gauge once and it said the same thing except for high speed it went higher for some unknown reason (about 4 PSI or so). Anyway it runs fine so I guess I won't worry too much at this point. I have yet to check my gravel screen.

 

[illflem]

It could be that your new sender is pooping out right off the bat and reading wrong. I don't think the first one I installed lasted more than two hours before it started reading wrong due to the strong pulsations our 12 valve lift pumps put out frying it. When it went out completely it only read 20 psi all the time but zeroed with the engine off, tricky little devil made me think that it worked for a couple months. Since then I've gone with a mechanical gauge, cheaper and I can trust it.

 

[CumminsPower98]

illflem,



I think its still working but maybe not fully right I don't know. I put in a needle valve in from day one on this sender and cranked it down so i could hardly get any air through it at all. After installing it, I could see the needle of the gauge slightly wavering so I closed it until the gauge was fully steady. It's so close to being shut that the gauge reacts pretty slowly so I doubt I have hurt the sender. It does still go up and down. Well I will just keep and eye on it and see what happens. I will have to try the other gauge again one of these days and see how it compares.