Power loss. Need help.
December 9th, 2021 | 5:20 PM
#1
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Joined: Mar 2021
Posts: 9
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Power loss. Need help.
95 GMC Sierra 4x4 5.7l tbi.
not certain of engine year as it may have been replaced or rebuilt.
The problem I'm having is that it loses power quickly after starting. Starving for fuel I think.Once started you can drive for a moment then it seems to be running out of gas you can then put in neutral key off for a few seconds then restart and power is back again for a few moments. Sometimes seconds sometimes minutes
This problem came when I purchased it and I did not get any info about it.
So far I have replaced the fuel pump and filter. Checked fuses and relays. Checked timing. Changed battery. Changed coil.Took a complete throttle body from a running truck and tried it on this one with no change.
The only improvement came when I changed the pump and battery the truck ran fine to work (45min) and about 2/3 of the way home before same problem started.Distributor and ICM appear to be new also MAP sensor IAC TPS look new but again, tried throttle body with known good sensors. I don't see any O2 sensors as headers have been added. There is a fuel pressure gauge added to the back of the throttle body, not sure of it's accuracy but at start up is says about 9psi and you can see it drop to five or so as it begins to lose power.
not sure what else I can add.
Any help would be appreciated
not certain of engine year as it may have been replaced or rebuilt.
The problem I'm having is that it loses power quickly after starting. Starving for fuel I think.Once started you can drive for a moment then it seems to be running out of gas you can then put in neutral key off for a few seconds then restart and power is back again for a few moments. Sometimes seconds sometimes minutes
This problem came when I purchased it and I did not get any info about it.
So far I have replaced the fuel pump and filter. Checked fuses and relays. Checked timing. Changed battery. Changed coil.Took a complete throttle body from a running truck and tried it on this one with no change.
The only improvement came when I changed the pump and battery the truck ran fine to work (45min) and about 2/3 of the way home before same problem started.Distributor and ICM appear to be new also MAP sensor IAC TPS look new but again, tried throttle body with known good sensors. I don't see any O2 sensors as headers have been added. There is a fuel pressure gauge added to the back of the throttle body, not sure of it's accuracy but at start up is says about 9psi and you can see it drop to five or so as it begins to lose power.
not sure what else I can add.
Any help would be appreciated
December 9th, 2021 | 6:47 PM
#2
Thread Starter
CF Beginner
Joined: Mar 2021
Posts: 9
Likes: 0
95 GMC Sierra 4x4 5.7l tbi.
not certain of engine year as it may have been replaced or rebuilt.
The problem I'm having is that it loses power quickly after starting. Starving for fuel I think.Once started you can drive for a moment then it seems to be running out of gas you can then put in neutral key off for a few seconds then restart and power is back again for a few moments. Sometimes seconds sometimes minutes
This problem came when I purchased it and I did not get any info about it.
So far I have replaced the fuel pump and filter. Checked fuses and relays. Checked timing. Changed battery. Changed coil.Took a complete throttle body from a running truck and tried it on this one with no change.
The only improvement came when I changed the pump and battery the truck ran fine to work (45min) and about 2/3 of the way home before same problem started.Distributor and ICM appear to be new also MAP sensor IAC TPS look new but again, tried throttle body with known good sensors. I don't see any O2 sensors as headers have been added. There is a fuel pressure gauge added to the back of the throttle body, not sure of it's accuracy but at start up is says about 9psi and you can see it drop to five or so as it begins to lose power.
not sure what else I can add.
Any help would be appreciated
not certain of engine year as it may have been replaced or rebuilt.
The problem I'm having is that it loses power quickly after starting. Starving for fuel I think.Once started you can drive for a moment then it seems to be running out of gas you can then put in neutral key off for a few seconds then restart and power is back again for a few moments. Sometimes seconds sometimes minutes
This problem came when I purchased it and I did not get any info about it.
So far I have replaced the fuel pump and filter. Checked fuses and relays. Checked timing. Changed battery. Changed coil.Took a complete throttle body from a running truck and tried it on this one with no change.
The only improvement came when I changed the pump and battery the truck ran fine to work (45min) and about 2/3 of the way home before same problem started.Distributor and ICM appear to be new also MAP sensor IAC TPS look new but again, tried throttle body with known good sensors. I don't see any O2 sensors as headers have been added. There is a fuel pressure gauge added to the back of the throttle body, not sure of it's accuracy but at start up is says about 9psi and you can see it drop to five or so as it begins to lose power.
not sure what else I can add.
Any help would be appreciated
I wanted to add I don't have a scanner but I only get the #12 code with the jumper method.
December 10th, 2021 | 6:42 PM
#3
CF Veteran
Joined: May 2011
Posts: 1,476
Likes: 287
From: Central Iowa
1) Verify the fuel pressure with a known accurate gauge.
2) If the pressure is accurate, inspect for kinks or other damage to the fuel lines.
3) The next time the problem is present, perform a current draw test on the fuel pump. This is easy to to at the fuel pump fuse or relay on the firewall - it should be 10 amps +/- 2.
2) If the pressure is accurate, inspect for kinks or other damage to the fuel lines.
3) The next time the problem is present, perform a current draw test on the fuel pump. This is easy to to at the fuel pump fuse or relay on the firewall - it should be 10 amps +/- 2.
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oilcanhenry (December 11th, 2021)
December 11th, 2021 | 7:26 PM
#4
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Joined: Mar 2021
Posts: 9
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Solved thanks
Gumby22.
thanks for the response. But I kept going back to it running for that day after changing pump thinking I must've done something wrong so I pulled it again and I would have sworn that I changed that little hose(still kinda think I did) but anyway that was it. It's running at 16/17 psi now and has full power. Also may have had a bad ground cause it didn't work at all when I put in this time and had to redo ground to frame.
Thanks again
thanks for the response. But I kept going back to it running for that day after changing pump thinking I must've done something wrong so I pulled it again and I would have sworn that I changed that little hose(still kinda think I did) but anyway that was it. It's running at 16/17 psi now and has full power. Also may have had a bad ground cause it didn't work at all when I put in this time and had to redo ground to frame.
Thanks again
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