New Regulator on Gen 3 with Return... Now running 67 PSI at idle... Is that too high?
February 16th, 2023, 7:44 PM
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New Regulator on Gen 3 with Return... Now running 67 PSI at idle... Is that too high?
EDITED:
Not at 67 PSI anymore... After going on a hunch and attempting to seat the regulator in a little better, I see now that a few points have shaved off to where it now holds the needle between 64 and 65 PSI at idle and only runs up to about around 73 or 74 PSI at initial rev, then will limit to about 70 PSI if I continue to rev the engine.
One other thing though... I had only allowed it to sit for maybe 15 to 20 minutes before checking for pressure loss, after replacing the regulator. It did seem to hold a pressure at around 45 to 50 PSI after shutdown... And had done so after the pressure came down to that level after maybe 5 minutes from shut down.
However, I have now just checked it after a couple hours of shutting down, and there was very little pressure in the system when I went to release it before hooking my pressure gauge. Yet, it did run right up to 70 PSI when turning the key only once, and still starts up much more easily than before, after being allowed too sit for a while.
ORIGINAL POST CONTINUED BELOW:
I was having issues with fuel pressure on a 2001 Tahoe with a 5.3 vortec. The vehicle sat for 2 years with fuel in the system. When I got my hands on it, I had to replace everything from the fuel pump to the injectors. I kept and cleaned out the rails and kept the original pressure regulator. After all items mentioned and everything in-between was replaced, I had great pressure at idle. Running about 54 PSI. However, I kept having random misfire codes and after shutdown, the fuel pressure would seep slowly out of the system to maybe 15 to 20 PSI... And I'd have to turn the starter for several seconds before it would turnover.
At one point, I shut it down and squeezed the return line to keep it from allowing fuel to run back to the tank. The pressure loss slowed down, and when letting go of the return line, I could see a big jump in the PSI needle... So that was the biggest indicator to me that there was fuel pressure being allowed to go back to the tank.
I bought a regulator vie eBay... The unfortunate fact is, I am on a seriously tight budget... And I was hesitant to buy the cheapest one I could find, but the fact remained that, it was either that, or do nothing. So, I got it. installed it. Then, VOILA... It starts right up. At shut down, it will slowly let pressure out, but it will settle in-between around 45 to 50 PSI. I did get a random misfire code for the first ride around the block... But haven't so far since then. I can only imagine that it may have needed to seat itself in and maybe finally did so after getting hot enough for everything to expand.
However, it now hold a steady 67 PSI at idle and races right up to almost 80 PSI or thereabouts when hitting the gas. The run to to high PSI isn't so shocking to me, although I tend to think that it shouldn't get quite that high.
The thing that has me concerned is how it hold such high pressure, just at idle. I have no idea what that can potentially do. I still have yet to smog this vehicle. So, I need the pressure to hold, if only to avoid the random idle misfires.
Any legit commentary and/or ideas about whether or not this is really anything to be concerned about are appreciated.
Not at 67 PSI anymore... After going on a hunch and attempting to seat the regulator in a little better, I see now that a few points have shaved off to where it now holds the needle between 64 and 65 PSI at idle and only runs up to about around 73 or 74 PSI at initial rev, then will limit to about 70 PSI if I continue to rev the engine.
One other thing though... I had only allowed it to sit for maybe 15 to 20 minutes before checking for pressure loss, after replacing the regulator. It did seem to hold a pressure at around 45 to 50 PSI after shutdown... And had done so after the pressure came down to that level after maybe 5 minutes from shut down.
However, I have now just checked it after a couple hours of shutting down, and there was very little pressure in the system when I went to release it before hooking my pressure gauge. Yet, it did run right up to 70 PSI when turning the key only once, and still starts up much more easily than before, after being allowed too sit for a while.
ORIGINAL POST CONTINUED BELOW:
I was having issues with fuel pressure on a 2001 Tahoe with a 5.3 vortec. The vehicle sat for 2 years with fuel in the system. When I got my hands on it, I had to replace everything from the fuel pump to the injectors. I kept and cleaned out the rails and kept the original pressure regulator. After all items mentioned and everything in-between was replaced, I had great pressure at idle. Running about 54 PSI. However, I kept having random misfire codes and after shutdown, the fuel pressure would seep slowly out of the system to maybe 15 to 20 PSI... And I'd have to turn the starter for several seconds before it would turnover.
At one point, I shut it down and squeezed the return line to keep it from allowing fuel to run back to the tank. The pressure loss slowed down, and when letting go of the return line, I could see a big jump in the PSI needle... So that was the biggest indicator to me that there was fuel pressure being allowed to go back to the tank.
I bought a regulator vie eBay... The unfortunate fact is, I am on a seriously tight budget... And I was hesitant to buy the cheapest one I could find, but the fact remained that, it was either that, or do nothing. So, I got it. installed it. Then, VOILA... It starts right up. At shut down, it will slowly let pressure out, but it will settle in-between around 45 to 50 PSI. I did get a random misfire code for the first ride around the block... But haven't so far since then. I can only imagine that it may have needed to seat itself in and maybe finally did so after getting hot enough for everything to expand.
However, it now hold a steady 67 PSI at idle and races right up to almost 80 PSI or thereabouts when hitting the gas. The run to to high PSI isn't so shocking to me, although I tend to think that it shouldn't get quite that high.
The thing that has me concerned is how it hold such high pressure, just at idle. I have no idea what that can potentially do. I still have yet to smog this vehicle. So, I need the pressure to hold, if only to avoid the random idle misfires.
Any legit commentary and/or ideas about whether or not this is really anything to be concerned about are appreciated.
Last edited by pitchman; February 16th, 2023 at 8:05 PM. Reason: Re-tested after trying a fix
February 19th, 2023, 10:56 AM
#3
the fuel tank filler cap...makes no sense. how does a fuel cap stop pressure leakdown in a fuel rail?
pressure spec is 55-62psi no vac to the regulator. pressure should drop 3-10 with vac at the regulator. check if your regulator holds vacuum.
if you have fuel pressure that high and are not setting fuel trim rich codes....try a different fuel pressure guage...yours may be inaccurate.
pressure spec is 55-62psi no vac to the regulator. pressure should drop 3-10 with vac at the regulator. check if your regulator holds vacuum.
if you have fuel pressure that high and are not setting fuel trim rich codes....try a different fuel pressure guage...yours may be inaccurate.
February 23rd, 2023, 4:19 PM
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Your guess is as good as mine about the gas cap... I changed it, took a reading, and it held pressure for the first time since I've had the truck.. Go figure?
The point of the post was about what to do other than change the regulator... Cost and budget my friend. However, I was able to get the vendor to agree to send a replacement. It is on the way.
Pressure with vacuum removed is currently 74, so definitely high.
The point of the post was about what to do other than change the regulator... Cost and budget my friend. However, I was able to get the vendor to agree to send a replacement. It is on the way.
Pressure with vacuum removed is currently 74, so definitely high.
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