Is fuel pressure flow chart wrong?

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_rgk

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Pressure bled off slowly with the valve in place of the fuel filter, and stopped around 48 pounds. Did the same thing whether valve was open or closed. Because it bled off so slowly I'm not too concerned.

Truck will start with starting fluid, so I'm pretty sure it's not a spark issue. At this point it can only be fuel delivery.

I checked the wiring diagrams again and saw that there is a fuse going to the injectors. Checked this fuse, and it appeared to be black with grime. Cleaned it and tested voltage, good voltage. Checked voltage at injectors, good voltage.

Ran a fused jumper wire at fuel relay terminal to run fuel pump indefinitely and tried starting the car, no change. This tells me it's not a wiring or relay issue.

Removed the bolts from the bed and lifted it enough with a jack to get in there. Removed the wiring to the pump and tested voltage. Good voltage.

Removed clamp from fuel pump and lifted it out of the tank some. It looks like the hose going from the pump to the sender is pretty dark, so the assembly might have gotten gummed up and restricted.

When I first rebuilt the engine I removed the fuel lines from the injectors and ran the fuel into a container to remove any bad fuel from the lines. The fuel that came out was dark at first but cleared up. What I didn't realize was that I very well might have gunked up the fuel pump at this point.

Additionally, I saw that I have an Airtex pump installed, so it's not surprising if it failed. I ordered a GM pump.

My only hope now is that the remaining fuel has not gummed up the lines and doesn't gum up the new pump. Unfortunately I'm not really equipped to drain the tank and get rid of the fuel. Judging by the look and smell of the fuel coming out of the lines right now, I think and hope I'm in the clear.

I couldn't remove the quick connect fittings to the pump and am waiting on the tools to come along with the new pump. There is not a lot of clearance between the lines and the plastic molding at the sender. I'm hoping the tool does the job and I don't have to do something drastic like cut the plastic fittings at the sender.
 

Schurkey

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Truck will start with starting fluid, so I'm pretty sure it's not a spark issue. At this point it can only be fuel delivery.
Seems reasonable.

I checked the wiring diagrams again and saw that there is a fuse going to the injectors. Checked this fuse, and it appeared to be black with grime. Cleaned it and tested voltage, good voltage. Checked voltage at injectors, good voltage.
Pretty-sure the injectors are triggered by the ECM supplying intermittent ground. If the injectors have power, do they get grounded by the ECM? Does a 'noid light flash when connected to the injector harness? Do you hear the injectors clicking when the engine is cranking?

Removed the bolts from the bed and lifted it enough with a jack to get in there. Removed the wiring to the pump and tested voltage. Good voltage.
If the pump wasn't RUNNING when you checked the voltage, you don't know that the pump has adequate power.

With no current flow, (pump not running) even a hugely-corroded harness will show proper voltage.

Test for voltage again, with the pump running and moving fuel at whatever pressure the regulator is set for.

Better still--verify voltage AND amperage with the pump running. Ideally (but not generally practical) is to use a low-amps probe connected to an oscilloscope, so you can verify amperage on each individual bar of the fuel pump motor's armature.

My only hope now is that the remaining fuel has not gummed up the lines and doesn't gum up the new pump. Unfortunately I'm not really equipped to drain the tank and get rid of the fuel. Judging by the look and smell of the fuel coming out of the lines right now, I think and hope I'm in the clear.
Bad fuel plugging the filter sock on the end of the pump? Sure.
Bad fuel plugging the fuel filter? Sure.

Bad fuel "gumming up the lines or the pump"? Not so much.
 

_rgk

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Does a 'noid light flash when connected to the injector harness? Do you hear the injectors clicking when the engine is cranking?

What is the difference between a noid light and voltage from a multimeter?

I can hear something clicking when I install fuse ECM1, but it's before I crank the engine, so I'm not sure it's the injectors. I've removed the spark plugs before and they were wet with gas.

But yes, I realize that this issue could be a bad pump or injectors not firing.

Copy the bad fuel, that's a bit of a relief.

Copy the amps. What value amps should the pump be?
 
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Schurkey

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What is the difference between a noid light and voltage from a multimeter?
You'd have voltage to the injectors all the time the ignition is on. What you don't have all the time is a ground to complete the circuit and trigger the injector.

The noid light illuminates when the ECM grounds the injector. It should flash if the computer is trying to fire that injector.

I can hear something clicking when I install fuse ECM1, but it's before I crank the engine, so I'm not sure it's the injectors. I've removed the spark plugs before and they were wet with gas.
Be worth checking out what clicks when the ECM1 fuse is installed.

There was a guy on this forum some months ago that had injectors firing when the ignition was turned on, before the engine cranked. Had a failed ignition module. First I'd ever heard of that.

What value amps should the pump be?
Usually around 6--7.
 

_rgk

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Whoa, good to know.

I've got a noid light on the way. I haven't been aware of this tool before, but it will make a great addition to the arsenal.

I'm assuming a failing or failed pump will work harder and draw more than 6-7 amps. But it won't draw more than ten or it would blow a fuse. So I'm not really sure how to troubleshoot that aspect.

I assume if my injector module is toast the noid light will blink before I crank. Or I can remove a plug in the morning and insert the ECM1 fuse to see if a gassy smell comes out of the plug opening. But again, the fact that it starts so easily with starter fluid doesn't support this theory.

Thanks for all your help. I'll keep you updated.
 
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PlayingWithTBI

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I'm assuming a failing or failed pump will work harder and draw more than 6-7 amps.
Maybe yes, maybe not. If the impeller in the pump is worn, it'll draw less amperage since it isn't pumping as much volume as a new one would.
 

_rgk

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Same thing with the new pump. Pressure gets up to 58 pounds, then as soon as pump stops running it drops down to 52. No change in engine behavior. It sputters, runs for a minute, then dies.

A friend came up with the brilliant idea to use the old pump to deliver fresh fuel out of a separate container to rule out bad gas. The gas in there is about a year old.

Does anyone know how much volume per minute the pump should deliver? I'd like to rule out a line restriction.

Also, the truck has a new crank sensor. Would I be able to tell if it needs to be programmed? Would this show up as poor spark?
 
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_rgk

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Ok, I took Schurkey's advice and verified spark again after the engine dies. I definitely have an intermittent spark! I checked it at the coil and yep same thing. I ran through the enhanced ignition troubleshooting flow chart and it points to a bad coil. On my way to pick up a replacement.
 

_rgk

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After much messing around with checking spark, checking injector pulse with a noid light, and cleaning grounds, I finally got the truck to run. It was the crank sensor. The RPMs were erratic on the scan tool while cranking, which I should have recognized sooner than later.

I still don't know whether the CPS is good or whether it's the wiring - whether I had it installed or torqued incorrectly or whether I need a different spacer. What I do know is that it is not new like I stated above. I didn't get a chance to warm the truck up yet (it's late), but while revving it cold it didn't want to get up above 2000 rpm. It felt as if it had a rev limiter. I'll look into this more tomorrow. For now I'm just glad it will start, run, and idle.
 

_rgk

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I buttoned everything up today and removed the spacer from the crank sensor. Someone put in a weird half-metal half-rubber "spacer" that I just removed. I'm hoping that with this aftermarket cover I dont need a spacer. Truck is running good and revs above 2000 rpm. I warmed it up and checked for leaks.

Unfortunately I have a leak at the block heater ... from the terminals. It just keeps getting better folks.
 
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