Have to bump throttle to keep running. Won't run at any steady RPM.

[Hoot Gibson]

Put 12v on the OBD1 G pin, and the pressure gauge still showed 0. I'm too far away to hear if the pump ran or not.

Went into the wheel well and disconnected the ground and wiring connector. Using a separate battery, I grounded the battery to the frame, and to the ground wire coming from the pump. I put 12v to the gray wire, and the pump ran. Still no reading on the pressure gauge.

I opened the fuel drain on the pressure gauge, and nothing came out. Then I connected the pump again, got it running, and the drain got fuel coming out, but it was weak. Drain open or closed didn't make a difference in the sound of the pump.

I'm guessing that I have a bad fuel pump. Or maybe a blockage in the fuel line somewhere, but I'm betting on the pump. Any thoughts before I throw money at it? I'm going to drop the tank before I order anything, just to see what condition it's in. Fuel lines look rusty too.

TBI, I got your recommendation for an EP381. I'm planning to replace the whole hanger assembly. Maybe buy the hanger seperate?

 

[PlayingWithTBI]

TBI, I got your recommendation for an EP381. I'm planning to replace the whole hanger assembly. Maybe buy the hanger seperate?

You may be able to get a complete sending unit from a 96 Vortec, I'm not sure, maybe someone else can jump in.

I wonder if the little hose that connects your pump to the pressure pipe inside hasn't split allowing fuel to blow by back into the tank?

When dropping the tank, make sure all your electrical connections are clean and solid, including the grounds. Good luck

 

[Hoot Gibson]

I'm going to drop the tank and check the whole kit and caboodle of stuff inside the tank before I buy anything. That little hose could be the issue.

I found a hanger without pump for about $80, and the EP381 for about $60, so that's probably what I'll go with if it's not that hose.

I'll be doing a bunch of cleaning stuff when I drop the tank. This was a work truck in Key Largo Fla and got lots of salt water immersion. Might replace the fuel lines while I'm at it.

Thanks for all your help and guidance! I'll come back and post my progress when I get done.

 

[thinger2]

It is a little more work but, with an AFPR and a gauge, you can get it dialed in plus, it's easy to verify whenever you want.

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Here's when I was running a 28LB spring on my 5.7L

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Thats awesome. I really like that whole setup.
fuel pressure at a glance.
Thanks Bud. Im doing that.

 

[PlayingWithTBI]

Thanks Bud. Im doing that.

Thanks! The only issue is, I got all the parts from RVMorseMachine.com but, he passed away this past summer. You should be able to build your own with help from here

CFM Technologies

CFM Technologies sells and manufacturers Magazine + TV Featured performance parts for GM TBI , Throttle Body Injection, along with custom carburetor spacers and the famous HVH Super Sucker Carb Spacers.

marine-performance-parts.com

 

[thinger2]

Another way to do it is to remove all the bed bolts on the left side, loosen the bolts on the right, unhook wire harness to the tail lights, fill spout and ground wire(s) there, then jack up the left side of the bed and block it up high enough so you can reach the sending unit on top of the tank. If/when you replace the fuel pump don't forget a new suction sock too.


And this could be contributing to your issue with fuel pressure if, as Schurkey said, you're not getting proper power and/or ground.

If you use the "bed tipping" method.
Drop the spare, disconnect all of the wiring and plan on repairing that too.
A good cordless impact will pull those bed bolts.
Ive done it by hand and it was a lot of work. They have some type of a thread compound on them.
Pull all of the passenger side bolts first and clean them up and use some anti-seize.
This is so you can decide if you can tip the bed at all.
One stuck bolt will stop this entire process.
You can use a 2x4 or 2x6 cut to the right length. It will fit at an angle between the rim and the frame and tipped inward towards the frame.
Take your factory screw jack. Run it up under the bed and crank it up.
Leave the far side bed bolts partially installed.
If you need more clearence, you can pull the far side bolts but if you do that, take a couple of ratchet straps from the far side of the bed to the nearside frame and keep them under tension as you tilt the bed.
If you dont, eventually the bed will slide away from you and dent the back of the cab and the bumper will dent the lower corner of the bed.
Once you have the bed tilted far enough, make absolutely sure that it is stable. Jackstands, firewood, whatever.
You are about to stick your neck under that bed so be carefull.
Get a new fuel pump lock ring.
They are about 4 bucks at NAPA
Clean the top of the tank where the pump goes in before you pull it and clean the bed above you before you pull.
No crud allowed into the tank.
The lock ring is sealled with an unknown GM mystery goo.
Ive always used the wax from a toilet bowl seal.
3 bucks, waterproof, and fairly chemical resistant.
You dont need the special tool to remove the lock ring.
Just work around the tabs with a drift and it will come loose.
(Preferably a brass drift but you already have your neck under the bed and supported by firewood and are using toilet seals Right?
Why stop now)
This is how I did mine in the dead of the night on the side of a mountain in the snow.
That was about 6 or 8 years ago.
Sometimes ya gotta improvise

 

[thinger2]

Thanks! The only issue is, I got all the parts from RVMorseMachine.com but, he passed away this past summer. You should be able to build your own with help from here

CFM Technologies

CFM Technologies sells and manufacturers Magazine + TV Featured performance parts for GM TBI , Throttle Body Injection, along with custom carburetor spacers and the famous HVH Super Sucker Carb Spacers.

marine-performance-parts.com

I think I can. Back when I was young I spent a whole bunch of time drilling and machining and tapping and inspecting threaded holes.
I have buckets of taps and dies.
Sometimes, late at night.
I can still hear that awfull screeching noise of a Tapco head with a smoked clutch.
We ran 9/16- 28 bone dry through copper extrusions by the tens of thousands a month.
All of the old school attenna conections are 9/16-28
And they would only pass the go/no go
if you dry tapped them on a Bridgeport with a Tapco head.
I really cant describe that screech to you.
It took awhile for my wife to understand that I wasnt ignoring her.
I just have tinnitus and sometimes I cant tell who or what is screaming at me.

 

[Hoot Gibson]

If you use the "bed tipping" method.
Drop the spare, disconnect all of the wiring and plan on repairing that too.
A good cordless impact will pull those bed bolts.
Ive done it by hand and it was a lot of work. They have some type of a thread compound on them.
Pull all of the passenger side bolts first and clean them up and use some anti-seize.
This is so you can decide if you can tip the bed at all.
One stuck bolt will stop this entire process.
You can use a 2x4 or 2x6 cut to the right length. It will fit at an angle between the rim and the frame and tipped inward towards the frame.
Take your factory screw jack. Run it up under the bed and crank it up.
Leave the far side bed bolts partially installed.
If you need more clearence, you can pull the far side bolts but if you do that, take a couple of ratchet straps from the far side of the bed to the nearside frame and keep them under tension as you tilt the bed.
If you dont, eventually the bed will slide away from you and dent the back of the cab and the bumper will dent the lower corner of the bed.
Once you have the bed tilted far enough, make absolutely sure that it is stable. Jackstands, firewood, whatever.
You are about to stick your neck under that bed so be carefull.
Get a new fuel pump lock ring.
They are about 4 bucks at NAPA
Clean the top of the tank where the pump goes in before you pull it and clean the bed above you before you pull.
No crud allowed into the tank.
The lock ring is sealled with an unknown GM mystery goo.
Ive always used the wax from a toilet bowl seal.
3 bucks, waterproof, and fairly chemical resistant.
You dont need the special tool to remove the lock ring.
Just work around the tabs with a drift and it will come loose.
(Preferably a brass drift but you already have your neck under the bed and supported by firewood and are using toilet seals Right?
Why stop now)
This is how I did mine in the dead of the night on the side of a mountain in the snow.
That was about 6 or 8 years ago.
Sometimes ya gotta improvise

Thanks, I appreciate the info. I'm convinced that dropping the tank is right for me. There are some fuel lines and wiring I want a closer look at.

 

[Hoot Gibson]

You may be able to get a complete sending unit from a 96 Vortec, I'm not sure, maybe someone else can jump in.

I wonder if the little hose that connects your pump to the pressure pipe inside hasn't split allowing fuel to blow by back into the tank?

When dropping the tank, make sure all your electrical connections are clean and solid, including the grounds. Good luck

Ding ding ding!!! We have a winner! That was the problem. Easy to see when the hanger came out of the tank. The hose was, well, hosed. Cracked and in place, but obviously not able to hold pressure.

I dropped the tank. It wasn't as bad as I thought it would be.

Unfortunately, the fuel lines on the hanger were so rusted that I had to twist them off to get them disconnected. Yes, I was using flare nut wrenches, and yes, I was turning them the correct direction. There was so much rust I couldn't get the nuts to turn even after I separated them from the lines.

Good news is that after replacing the hanger and pump, everything works again. 12-13 psi, and the fuel gauge on the dash reads right. I can successfully run a scan with my cheapie Bosch OBDI-II scanner. Now I just got to figure out what it's telling me. At least I have readings now, and I'm sure I can decipher them.

Thanks a bunch for all the help from you guys! I appreciate the time you took to share your knowledge, and it truly made my life much easier.

 

[Silverado1994]

That’s crazy about the amount of rust. Glad you got er goin