rough idle, p0300 after FPR replacement 96 5.0 vortec

[chevy in my blood]

Chevy in My Blood,
if you are going to work on vehicles especially computer vehicles, get at least the basic tools to diagnose. Guessing without testing is just a parts changer, and I'm sure you don't want that. Besides a fuel pressure gauge even at HF is only $19.00. If that breaks you or your customer won't spend the $$$ you don't need to working on diagnostics. Remember diagnostics is testing components to evaluate if they meet specs or nut.
As to your misfires, are you sure you don't have a pintle leaking? In that vehicle, they are not injectors at the end of the tube in the intake manifold they are pintles, and they give problems mostly carbon in them.

It's my dad's truck, I've asked these questions for him. He's stubborn and doesn't believe it's a fuel problem. Please understand I have tools, like a fuel pressure gauge, but it only fits my f150. I've not been wrenching on trucks in a couple years due to circumstances I'm not going to explain here, but I'm finally doing well enough to get back outside and do what I love. So please don't tell me what I need to be doing. I'm trying to help my dad get his truck running, all i can do is make suggestions to him but it's his to work on. Now that my f150 is toast I have my own problems to deal with.

Besides, where I come from tools means duct tape and an adjustable wrench I still mount tires by hand for God sakes. Which I'm actually doing on the Tahoe today. Enough rambling.

 

[chevy in my blood]

Chevy in My Blood,
if you are going to work on vehicles especially computer vehicles, get at least the basic tools to diagnose. Guessing without testing is just a parts changer, and I'm sure you don't want that. Besides a fuel pressure gauge even at HF is only $19.00. If that breaks you or your customer won't spend the $$$ you don't need to working on diagnostics. Remember diagnostics is testing components to evaluate if they meet specs or nut.
As to your misfires, are you sure you don't have a pintle leaking? In that vehicle, they are not injectors at the end of the tube in the intake manifold they are pintles, and they give problems mostly carbon in them.

To answer your question, I don't think it's a leaking poppet because it seems to be all four cylinders on the passenger side misfiring randomly. The main reason he's so stubborn about it is because he has access to nearly unlimited free parts from a junk yard, and he makes fairly good money so what he cant get for free he can buy new. He got two complete intakes from running and driving trucks for free. And if it was a leaking poppet, he replaced the spider injector assembly this past weekend. Idk if he ever fired it off or not though.

 

[chevy in my blood]

Got the tires mounted on the Tahoe so it's sitting on its own weight. And now once I go get a starter hopefully it'll fire and run. To my knowledge nothing is wrong with it other than it needs a full tube up. Thanks for the advice on my dad's truck guys, I've relayed it all to him.

 

[chevy in my blood]

Just an update, he got the "new" spider in and all put back together and now his truck won't fire at all. It tries, but wont start. He's rebuilding the old spider soon or replacing it with the upgraded one, we found a deal. I have a fuel pressure gauge coming in and I'll check his pressure for him. On a side note I discovered his 5.0 is a 4 bolt main. Nice info to have.

 

[chevy in my blood]

Okay, I tested his fuel pressure, its all over the place. First few times it would only build 30 ish psi and drop down to 20 after the pump stopped running. After that it would jump to 55 every time but as soon as the pump primes to 55 it drops to either 50 or 42 and then slowly drops over 20 mins or so. If I try to start it right as it jumps to 55 it tries to run but just dies. I'm thinking the new pump he bought and put in the hanger has a defectiv fuel pump. Thoughts?