agentruley

Information on the problem was originaly posted here

https://ls1tech.com/forums/generatio...-problems.html

So does anyone have any Ideas?
Am I going to have to reprogram again?

agentruley

I have checked everything except the fuel pump in the tank.
Doesn't anybody know if the ECU will cut off the pump then cut it back on?
Nothing?

Ed Wright

iTrader: (1)

I have seen a few PCM fuel pump drivers fail.

agentruley

??????
If the driver was bad, wouldnt the pump not cut on at all?
And I can cruise all day long, just anything more than 1/4 throttle and I can feel the reduced power big time and anymore throttle than that, fuel cuts on and off.

I was told that its all in the ECU and I need to get it (or a new one) reprogrammed.

What am i suppose to tell my programmer?
That I have a 4.8 with a nv3500 and want all vats, emissions stuff deleted?

I didn't know the ECU had the ability to cut the fuel pump off.
Is there a way I can force the pump on and see if its just the fuel cutting off and not the spark too?

Im so confused. I can't find anyone else with this problem.

Ed Wright

iTrader: (1)

So, your not logging data when this happens? Not logging fuel pump voltage or fuel pressure? If not you don't really know what is happening.

Drivers often open when hot, cool off then work again.

And, yes the PCM controls the fuel pump.

agentruley

I dont have all the money in the world,(a broke teenager, I am So all the computer tuning and logging stuff I can't do.

I did hook up a fuel pressure guage and when the engine cuts off (the on and off behavior at heavy throttle situations) the fuel pressure drops to twenty or so psi.

Can the driver really heat up and then cool off that quickly though?
And this only happens WOT or more than half, If i drive like I have some common sense it drives normally.

How am I suppose to log voltages at the pump?
Can i just bypass a the relay and send 12 volts right to it for just a quick test drive to see if actually the ECU cutting it off, or the driver or the tune?

Ed Wright

iTrader: (1)

I doubt your fuel pump is cutting off. More likely weak pump or your fuel filter is dirty. The fuel pump driver in the PCM does not know if or when your WOT.

agentruley

Changed the pump AND the filter 2 days ago.
Still happens.....
Same pressure issues

I have no idea if the pump is actually cutting off but the pressure drops off completely.
Maybe the computer just holds the injectors open?
Cause if I hold it to the floor and not let off when it (cuts on and off), it will back fire violently.

Ed Wright

iTrader: (1)

Connect a volt meter to the pump's power supply wire. If it stays at 12 volts or more, you probably have a linked or partially plugged fuel line.

agentruley

'Hot wired' My fuel pump and it still cuts off.
So it has to be something in the fuel system.
Regulator is fine.
So the pump is either bad or having a voltage problem.
Will do a voltage-drop test on the lines to confirm either or.

agentruley

So I finally figured out why the fuel pressure was dropping and figured if anyone had a similar problem, this could be documented for future reference.

So after many doughnuts, and launches with the fuel pressure dropping, I took the tank out to check the pump and low and behold, I figured it out.
When going WOT in first, from a stop or slow roll, unless i had half a tank of fuel, all of the gas in the tank would slosh away from the pump and baffles.
Yeah, weird right?
The TBi gas-tank didn't have good enough paths and baffles to stop fuel from going from one side of the tank to the other one.
Went and bought a late model tank 2007+, 26 gallons and then boom, it never happened again, even when running on fumes.
Not trying to revive old thread, just documenting the actual problem, although I still need to reprogram my ECU....

gagliano7

Glad you came back to let us know what fixed the problem. This will definitely help someone in the future.