Bad fuel Pump? (Solved)

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steiny93

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2003 GMC Yukon XL 1500 5.3

Finally got a test kit to measure fuel pressure. When I initially put it on there was no pressure. I jumped the fuel pump and got up to about 50psi. After removing power, pressure fell to about 40 and slowly started falling.

I only jumped the fuel pump relay because it was easier, not because the key won’t activate it.
So if you try and start with just the key it doesn't have pressure. But if you jump the fuel pump it has pressure?

The pressure falling issue sounds like a different problem; it shouldn't drop super quick, their is a spec for it.

I just went through this on a 2007; mine was an intermittent pump that would get power but wouldn't run all the time. Validated via measuring pressure on the rail.
 
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WestCoastie

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So if you try and start with just the key it doesn't have pressure. But if you jump the fuel pump it has pressure?

The pressure falling issue sounds like a different problem; it shouldn't drop super quick, their is a spec for it.

I just went through this on a 2007; mine was an intermittent pump that would get power but wouldn't run all the time. Validated via measuring pressure on the rail.
Key and jumping cause pump to run and give pressure. When key to “on” pressure builds to about 50psi. Once you try to start the truck pressure drops to about 40.

When key is turned off, pressure begins to steadily fall.

Haven’t tried starting with pump jumped though, might try that
 
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WestCoastie

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When I removed the vacuum line from the pressure regulator it ripped the boot on it. So I got another one and figured I would try a new regulator as well.

They came in today. Replaced the pressure regulator and vacuum line.

Still no start, but every time I went to start there was a stumble like it wanted to.

Fuel pump came in today too. After replacing the regulator and testing I’m a little more convinced it’s the pump. Don’t have time to replace today, but when I do I’ll post the results.
 
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WestCoastie

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New fuel pump is in and truck fired right up!

Now I just have to patch the hole I cut to get to it…easier than wrestling with a 3/4 full tank by myself.
 

OR VietVet

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New fuel pump is in and truck fired right up!

Now I just have to patch the hole I cut to get to it…easier than wrestling with a 3/4 full tank by myself.
If you search, you can read how I feel about cutting an access hole. It is your vehicle though. Glad it is working though.
 
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WestCoastie

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If you search, you can read how I feel about cutting an access hole. It is your vehicle though. Glad it is working though.
Well as my father would say “any car over 20 years old is a project car, whether it is or not.”

I daily drive it and have no plans to sell, so not a big deal. Not sure if your dislike is from a structural standpoint, corrosion or whatever. I thought them all over and settled on it just being the best way to do it. Appreciate the input though.

- read your thoughts on the matter. I totally understand. If a time comes that I sell, I promise to disclose it. As for structural integrity, I’ve made my peace with it. Again, appreciate your input
 
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OR VietVet

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Well as my father would say “any car over 20 years old is a project car, whether it is or not.”

I daily drive it and have no plans to sell, so not a big deal. Not sure if your dislike is from a structural standpoint, corrosion or whatever. I thought them all over and settled on it just being the best way to do it. Appreciate the input though.

- read your thoughts on the matter. I totally understand. If a time comes that I sell, I promise to disclose it. As for structural integrity, I’ve made my peace with it. Again, appreciate your input
Just never let anyone you love ride back there.
 

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