So, when you first attached the gauge, before even touching the key, it had 46 psi showing? And then when you shut the engine down and watched the gauge it dropped to 4 psi? How quick did the pressure drop?
03 tahoe flex fuel intermittent no start
- Thread starter Monk17
- Start date
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46-48 when? First attached? Or after you shut off and it held at 46-48? Please be more detailed with your answers.
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Monk17
TYF Newbie
When i attached it before even putting in a key it was zero. Put in key turned to on position without start it did 46-48 multiple times
Engin on it jumped to 54 and settled down to 48
When i turned off the engine it dropped to 40.
Im currently doing the timed test as requested
After it's been sitting for a while, connect the fuel pressure gauge and write down the reading. Make sure the gauge is connected tightly to the schrader valve on the fuel rail. Note any changes over a minute or two.
Now turn the key to ON WITHOUT starting the engine. The NBS KOEO (key on, engine off) Flex Fuel pressure spec is 48 to 54 psi, and it should hold within that range. Note the reading and write it down.
Start the engine and observe variations in pressure; there will be some but check the running pressure at idle and maybe 1,500 or 2,000 rpm. Write them down.
(I think you're doing this now) Turn off the engine and the key, and observe every few minutes over an hour or so what the psi reads. This will tell you how long it takes the pressure to leak down.
If you had zero to begin with, it's apparently leaking down, indicating a faulty fuel pump or a leaky injector, or something else in the fuel line that is allowing leakdown.
Now turn the key to ON WITHOUT starting the engine. The NBS KOEO (key on, engine off) Flex Fuel pressure spec is 48 to 54 psi, and it should hold within that range. Note the reading and write it down.
Start the engine and observe variations in pressure; there will be some but check the running pressure at idle and maybe 1,500 or 2,000 rpm. Write them down.
(I think you're doing this now) Turn off the engine and the key, and observe every few minutes over an hour or so what the psi reads. This will tell you how long it takes the pressure to leak down.
If you had zero to begin with, it's apparently leaking down, indicating a faulty fuel pump or a leaky injector, or something else in the fuel line that is allowing leakdown.
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Monk17
TYF Newbie
After 13 minuets no drop it actually climbed about 3 psi ill check it again in 30 min
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Monk17
TYF Newbie
The zero pressure to start may have been my fault
How many miles on this truck, and do you know if the fuel pump has ever been replaced?
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Monk17
TYF Newbie
Almost 200k no idea if pump or fuel filter has ever been changed
https://www.rockauto.com/en/moreinfo.php?pk=356952&cc=1412244&jsn=3423
https://www.rockauto.com/en/moreinfo.php?pk=7056044&cc=1412244&jsn=3454
And 13500114 AC Delco fuel pump relay.
I see these in your future. With that kind of mileage and no history and the fact that the pressure is bleeding off and not knowing how long that old fuel filter has been there causing the pump to work so hard to push fuel to engine, these are likely the culprits, but, and I mean BUT, like Steve said, you may have leaking injector(s) allowing the pressure to bleed off. Before you replace the fuel pump and the other components, try just turning the key to the on position and not cranking the engine, for about 10-15 seconds before you actually turn the key to crank the engine. It may start way easier after you have allowed the fuel pump to build pressure before you crank the engine.
https://www.rockauto.com/en/moreinfo.php?pk=7056044&cc=1412244&jsn=3454
And 13500114 AC Delco fuel pump relay.
I see these in your future. With that kind of mileage and no history and the fact that the pressure is bleeding off and not knowing how long that old fuel filter has been there causing the pump to work so hard to push fuel to engine, these are likely the culprits, but, and I mean BUT, like Steve said, you may have leaking injector(s) allowing the pressure to bleed off. Before you replace the fuel pump and the other components, try just turning the key to the on position and not cranking the engine, for about 10-15 seconds before you actually turn the key to crank the engine. It may start way easier after you have allowed the fuel pump to build pressure before you crank the engine.
wildcatgoal
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Sort of right behind that little red power junction box on the side of the engine is a small sensor plug. Is that plugged in tight? If it isn't plugged in, you get these symptoms exactly.
