Crazy Fuel Pressure

genie144

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So I am redoing my fuel system and finally have everything back together. I got the system all primed and the truck running and have some crazy fuel pressure. The gauge is pegged at 100psi. Now the only thing I changed is the entire pre-engine fuel routing (components are all the same). I believe the regulator was set at ~67psi before my project.

What would be causing the high pressure? I need to add coolant so I didn't run the truck very long, but could air in the line cause high pressure? Should I burp the system (remove fuel line at regulator) before I start it next? If that doesn't work, just back out the pressure screw (that is just an alan key on top right?) on regulator all of the way and then move back in?

Appreciate any input.

Sam
 

TARM

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If your gauge is good and not broken, maybe your return line is some how routed wrong blocked or closed off which would created a deadhead on the pump and woudl spike it to max psi which would be over 100psi for a fuelab I think.
 

Charles

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Three main options:

1. Gauge is wrong.

2. Regulator is stuck, tap it lightly and see if it frees up.

3. Return line is obstructed.


To test the reg simply run a short length of hose from the return port to a container and watch to see if there is any spillage. If not, then start dialing the pre-load down. If still nothing then tap the housing with a hammer if you believe the valve could be stuck. Otherwise, it's time to take the regulator apart and see for yourself.

If when you run a short length of hose to a container plenty of fuel is spilling out and the gauge pressure is as it should be, then your return line is obstructed.
 
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BlueWaffle

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what kind of gauge is it? the mfg should have troubleshooting guide for you to check voltage across the terminals. my gauge did the same thing a couple of weeks ago and it turned out to be a bad sender/sensor which Isspro replaced for me...
 

genie144

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Thank you guys. I will check the return line first and see if I am getting anything out of it. I have no reason to suspect the gauge is faulty - it worked flawlessly prior to my project and appears to read the correct pressure right before it spikes. I probably am an idiot and forgot to unclamp a line...

Sam
 

TARM

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From the looks of it you have a good bit of plumbing to that system I could see it being very easy to forget to unclamp or not open a ball or cut off valve somewhere. You should have seen some of the brain farts I had working while tired on my last fuel system revamp. Sitting there scratching my head trying to figer out what was wrong only to be feeling real stupid when I figured what I had done, LOL
 

BlueWaffle

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Thank you guys. I will check the return line first and see if I am getting anything out of it. I have no reason to suspect the gauge is faulty - it worked flawlessly prior to my project and appears to read the correct pressure right before it spikes. I probably am an idiot and forgot to unclamp a line...

Sam

what gauge is it? electric? probably not the gauge but could very easily be the sensor....I've been through 3 in the last year.
 

Charles

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Most people have a mech gauge on the reg. I think electric fuel pressure gauges are the exception more so than the norm.

However, on that topic, my sender was completely F'ed for God knows how long. I recently replaced it and had to reduce the reg pre-load an astronomical number of turns. It was reading 20psi when the actual pressure was well north of 100psi.
 

Tom S

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Most people have a mech gauge on the reg. I think electric fuel pressure gauges are the exception more so than the norm.

However, on that topic, my sender was completely F'ed for God knows how long. I recently replaced it and had to reduce the reg pre-load an astronomical number of turns. It was reading 20psi when the actual pressure was well north of 100psi.

Did you see that post by Dennis on those gauges being problematic?
 

TARM

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Speaking of gauges mine that I place on my reg was faulty. It was reading erratic pressure but with taps and slight torque the pressure would seesaw all over the place. It was a rather cheaply built one. I switched it out for one of better quality and no issue
 

genie144

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I wanted to just provide an update - I was an idiot...

0dd59e30.jpg


Think that caused some restriction?

Ohh and then I had the bright idea of testing my valves while putting fuel in the truck:

d9c4b174.jpg

7c688e2a.jpg


That didn't end well. Had a nice conversation with the west metro dire department about running alternative fuels in diesels though ;)

Sam
 

genie144

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Enough of a mess that someone called West Metro Fire thinking I was gonna blow up the gas station... With diesel... The gas station is right outside the Fire Department... Quite funny...

With that one - no taste of diesel. Got a little in the eyes and ruined some work clothes... Otherwise wasn't too bad. I designed the box, wiring, and plumbing to be able to drop as a single unit with quick connects (electrical) and JIC plumbing. If I hadn't had to wait for fuel line, it would have been a 45-60 minute fix.

Sam
 

TARM

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Glad you got it handled. I recall when I was working on my system and had disconnected some of the lines. One hose must have had enough fuel in it to create a prime. It has hanging right over my face and mouth. Got a complete mouth full along with face and eyes. Then stuck there with nothing to clamp it with or compressed air within reach got another mouth full blowing all the fuel back out the line and breaking the prime. This new ULSD tasted like sh!t. Still better than gasoline any day.
 

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