Fuel Pressure Question
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New User
Joined: Jul 2008
Posts: 24
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From: Beaumont, TX
Fuel Pressure Question
I just recently installed a fuel pressure gauge to diagnose a percieved lack of fuel pressure. So my question is, what should my fuel pressure gauge do with the key on/engine off?
Currently, when I turn the key on (without trying to start) the fuel pressure gauge cycles once and goes to 70psi. As soon as the HFCM stops running, the fuel pressure drops to zero almost immediately. This isn't normal is it?
Currently, when I turn the key on (without trying to start) the fuel pressure gauge cycles once and goes to 70psi. As soon as the HFCM stops running, the fuel pressure drops to zero almost immediately. This isn't normal is it?
Cargo Master
Joined: May 2006
Posts: 2,116
Likes: 6
From: Florida
this is good to know, i temporarly hooked up a mechanical fuel pressure gauge to mine and noticed the same thing, it spiked up around 60psi, then when the pump cutoff it bled back to somwhere around 20psi and seemed to stay around there,but if i waited im sure it would have dropped off, i assumed the fuel pressure would stay kinda high when the pump was off too. as i was looking into my upper fuel bowl issue, meanwhile i have a gauge and fitting on order so when i get it hooked up this would have been my next question
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New User
Joined: Jul 2008
Posts: 24
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From: Beaumont, TX
Thats crazy. You would think that would be terrible for the injectors to starve them of fuel pressure while trying to start the truck. I know the banjo bolts on the fuel rail have check valves, but I wouldnt think that is enough volume to feed the injectors while cranking. 
Token Redneck
Joined: Jun 2007
Posts: 9,335
Likes: 343
From: Breckenridge, TX
Solution: start the truck while the pump is running/cycle the key if the pump quits?
Cargo Master
Joined: May 2006
Posts: 2,116
Likes: 6
From: Florida
There's an air bleed at the top of the fuel pressure regulator, I'd guess that this would let the pressure drop in a hurry once they pump stops, there's nothing to hold the pressure against.
Solution: start the truck while the pump is running/cycle the key if the pump quits?
Solution: start the truck while the pump is running/cycle the key if the pump quits?
FTE Fan
Joined: Jun 2007
Posts: 344
Likes: 1
From: Winder, Georgia
The first time I hooked up the fuel pressure gauge and saw that pressure drop, I thought there were serious issues as well. Glad to see you got it figured out.
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Hotshot
Joined: Dec 2003
Posts: 15,368
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From: Stuttgart, Ar
Thats crazy. You would think that would be terrible for the injectors to starve them of fuel pressure while trying to start the truck. I know the banjo bolts on the fuel rail have check valves, but I wouldnt think that is enough volume to feed the injectors while cranking.
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