Troubleshoot: Lost power...

[hefftone]

This is in essence a follow up to a previous post:
http://www.gmt400.com/forum/showthread.php?11542-Loud-whine-brand-new-fuel-pump

In summation: 1990 TBI 350....replaced dead fuel pump with ac Delco EP381 (07+ vortec), ran great then started to fall on face sooner and sooner after start up. At one point the pump was howling, the sounded like an electric drill. Would idle and run with very light throttle, but more than that it just bogged and did nothing, often stalling. Using the ill fitting rental fuel pressure test kits, i figured the fuel pump must have crapped out....got warranty replacement from R0CK-@UT0.

So now....
I just finished buttoning everything up. New Delco EP381 fuel pump is installed with new delco strainer, all on a (spectre fuel sender and fram fuel filter new as of Feb. 2012.) The TBI was cleaned, and the FPR rebuilt with new spring and diaphragm, adjusted to 13 psi. I also spent some time on the harness. There were a couple of wires that had worn off insulation. I cleaned the wires, heated and soldered them, and wrapped with tape. There is still some voltage drop to the pump....engine running Battery voltage is 14.44v and at the fuel pump harness (& chassis ground point) i have 13.44v.

So I take it out, and its running great. Then it starts to act up after i stand on the gas for a few seconds.....it accelarated fine, then conked out when i let off the accelerator. A few seconds later after shifting into neutral it restarted immeditately.

I continued to drive it around, idle and part throttle were fine, but getting into the 50% throttle range was showing signs of power loss....( I mean feels like fuel starvation). I stopped and popped the hood, all connections at map and sensor plugs where good. After a couple minutes i started it up and it drove better.....but the power still drops off with increased throttle.

I'm at the point now of frustration....these fuel systems are so simple....the pump and the regulator.......then there is the ecm stuff, map, tps, 02, knock, espark control.
The fact that only acts up while driving and at heavy throttle makes it hard to troubleshoot.

CLIFF NOTES:
Problem seems to be solved. It was the filthiness of he tank contaminating the gas, and clogging the fuel filter.After removing and rinsing the tank, new gas and fuel filter she's running awesome. Shoulda have replaced the whole tank when I first did the fuel pump. Worst looking gas I've ever seen. If your filter clogs up with rusty dust, ya gotta Yank the tank.

 

[1997chevydriver]

This is in essence a follow up to a previous post:
http://www.gmt400.com/forum/showthread.php?11542-Loud-whine-brand-new-fuel-pump

In summation: 1990 TBI 350....replaced dead fuel pump with ac Delco EP381 (07+ vortec), ran great then started to fall on face sooner and sooner after start up. At one point the pump was howling, the sounded like an electric drill. Would idle and run with very light throttle, but more than that it just bogged and did nothing, often stalling. Using the ill fitting rental fuel pressure test kits, i figured the fuel pump must have crapped out....got warranty replacement from R0CK-@UT0.

So now....
I just finished buttoning everything up. New Delco EP381 fuel pump is installed with new delco strainer, all on a (spectre fuel sender and fram fuel filter new as of Feb. 2012.) The TBI was cleaned, and the FPR rebuilt with new spring and diaphragm, adjusted to 13 psi. I also spent some time on the harness. There were a couple of wires that had worn off insulation. I cleaned the wires, heated and soldered them, and wrapped with tape. There is still some voltage drop to the pump....engine running Battery voltage is 14.44v and at the fuel pump harness (& chassis ground point) i have 13.44v.

So I take it out, and its running great. Then it starts to act up after i stand on the gas for a few seconds.....it accelarated fine, then conked out when i let off the accelerator. A few seconds later after shifting into neutral it restarted immeditately.

I continued to drive it around, idle and part throttle were fine, but getting into the 50% throttle range was showing signs of power loss....( I mean feels like fuel starvation). I stopped and popped the hood, all connections at map and sensor plugs where good. After a couple minutes i started it up and it drove better.....but the power still drops off with increased throttle.

I'm at the point now of frustration....these fuel systems are so simple....the pump and the regulator.......then there is the ecm stuff, map, tps, 02, knock, espark control.
The fact that only acts up while driving and at heavy throttle makes it hard to troubleshoot.

Get a long enough fuel pressure tester and tape it to the windshield so you can see what the fuel pressure is doing when it acts up.

 

[hefftone]

I bought the same type of adapter off ebay, as what comes in the Fuel pressure test kit. First off, i could'nt get that f**ker to fit onto the lines at the TBI, The lines interferred all over the place (firewall,coil, throttle linkage). Second it leaks like crazy when the gauge is attached....it just altogther sucks. I had to attach mine after the fuel filter.

 

[Mik3]

Get the OEM fuel pump, clean the gas tank out with carb cleaner or brake cleaner. If you do use water to rinse it out, then make sure you rinse with carb cleaner, brake cleaner, or alot of gas. Using a large syringe or something similar (Even a turkey baster), flush out the fuel lines from the gas tank all the way to the throttle body. Clean the throttle body again and when you fill the gas tank, add a fuel system cleaner to it. I'm guessing there's possibly a restriction burning up your fuel pump.. or some sediment in the gas tank getting stuck to the filter and blocking it from getting fuel. Also clean the connector to the fuel pump and test the resistance from the pins to about 6in down the wire, make sure there's not excessive resistance in the connector.

 

[hefftone]

After some troubleshooting merely confirmed certain things that were unrelated to the problem... I put on a new fuel filter. The one that was on it had at most 1 tank of fuel through it......And it has rust all up in it. Couldn't believe it. I put a new one on and the truck seemed to run very good....for about a mile.
I'm going to take off the injector pod and open her up...see if it has crud built up inside....i had it clean as a whistle before. If there is crud in the pod there just might be too much in the tank....Removing it is about the last thing I want to do....but.....I'll do what I have to.
I also worry that I'm missing something, and it could be in the ignition, but my experience has been that ignition parts are rarely intermittent failures. Coils and modules usually crap out and they are done. Its the fact that even when it acts up, it will still idle just fine. There has been a couple times where it stalls out, and then it won't fire up. On the hard restart, it sounds as if either the fuel or the spark is completely absent.... Pretty hard to tell by myself, and usually it will fire quickly after it sits for a couple minutes....
is weird!

 

[shelbyt.67]

If yer filter is clogged w/ rust u can bet yer pump screen is too. Rust clumping onto the screen while there is suction, then fallin off when u shut down would cause the sporadic running problems.

 

[93 K1500]

Have you checked your Cat?

 

[hefftone]

I have not checked the catalytic, but it did pass emissions with it.

Android/Tapatalk

 

[93 K1500]

I dont know how strick your emissions are but I know that when a cat gets to hot( purple color) it can start to melt the "waffle" material inside, when its cool air still passes through when it gets hot and starts to melt it starts not letting air through. On mine it caused the truck to idle perfect as soon as I pressed hard on the gas bogged down exactly like youre discribing- I could turn the throttle by hand and about half throttle had the same problem and progressivly got worse. You dont have to cut the cat all the way out you can drill holes directly in front of it and see if that solves your problem and if not its easy to spot weld the holes.

 

[hefftone]

I pulled off the injector pod and opened it up. There was a little bit of particles in the pods, but did'nt seem substantial. I figured I'll probably be dropping the fuel tank, and I'd rather do that with less fuel than the 3/4 tank I had.

With a piece of clear plastic hose attached to the fuel line I jumped out the pump relay...The gas was coming out rather slowly i thought. Thinking the fuel filter might be clogged up, I took it off, at reattached the clear hose there.....just as slow.
For my own convenience sake, i reattached the filter and connected the hose in the engine bay. I timed it with a stop watch and it took 3 minutes to fill a 1 gallon jug......
If this pump puts out 155 lph, that equals about 40 gallons per hour...or about a gallon per 1.5 minutes....and that would be at a certain pressure. This has no pressure restriction, so technically it should push out even faster than that. It should flow pretty good.