Fuel gauge staying past full and sucking enough juice to make truck stall.

Tiny
TAKWAKIN
  • MEMBER
  • 1997 CHEVROLET BLAZER
  • 133,595 MILES
I had and erratic fuel gauge needle and truck was sluggish. Suddenly the needle went past full and stucked there. Later I got a check engine and truck stalled. After further tests the P0107 MAP low voltage code came out but the problem was not the manifold absolute pressure sensor. There is a 5 wires connector sticked to the driver fender that I unplugged and the engine started fine and ran fine. After further test the EGR and MAP voltage went back to 5 volts instead of 2.08v before I unplugged that connector also the fuel gauge went back to empty position. No more engine code, engine starts fine and run better but as soon as I plug it back the engine stall or perform sluggish and needle go back past the full position. The five wires are black, green, pink, white and grey. The grey give the 5 volts and the pink the 12 volts. Strange thing is that both side of the connector the grey wire give the 5 volts when grunded to the battery. I'm joining an image so you can help me identify this connector and what's for exactly. Thank you !
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Saturday, December 31st, 2011 AT 7:00 PM

23 Replies

Tiny
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Also you can see a free round connector in the picture. It's a big red wire and I don't know what it is used for because it was there when I bought the truck. Maybe the starter wire they changed and left the older there. Not sure.
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Saturday, December 31st, 2011 AT 7:08 PM
Tiny
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Shorted fuel gauge, wiring, or sending unit.
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Saturday, December 31st, 2011 AT 8:05 PM
Tiny
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I would need the location of connectors so I can test it. I have the full wiring diagrams but don't show the exact location of the connectors.
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Saturday, December 31st, 2011 AT 9:59 PM
Tiny
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Purple wire on instrument cluster connector, pin 29 to fuel level buffer module, pin L, under the cluster. The schematic I have doesn't show any intermediate connectors. Instrument cluster, fuel level buffer module, engine control, and pump. Pump is in the top of the tank.
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Sunday, January 1st, 2012 AT 1:26 AM
Tiny
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Ok thank you I will give it a try but before I will get the diagram location because pin L, pin 29 and purple. It don't give me the exact location. For now with the connector underhood unplugged the truck run fine. Also do you know what is the exact usage of this connector?
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Sunday, January 1st, 2012 AT 2:07 AM
Tiny
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I'm not sure about the connector. But, there is a set of wires that runs to the engine control module for the pump from the fuel level buffer module. I'm guessing this might be the wires/connector you disconnected.

Pin 29 is on the instrument cluster. The dash gauges. Where the speedometer and fuel gauge are.
Pin L is on the fuel level buffer module. It's behind the dash in the center.
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Sunday, January 1st, 2012 AT 3:38 AM
Tiny
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What is the usage of this fuel level buffer module? Nothing seems to change when its unplugged except the needle not showing the fuel level?
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Sunday, January 1st, 2012 AT 3:42 AM
Tiny
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I'm not sure, because there's nothing definitive in my reference, but I would say voltage stabilization. I think that's why when you unplugged the wires from it to the engine control, things went back to normal.
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Sunday, January 1st, 2012 AT 4:17 AM
Tiny
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I printed the 4 pages for wirings of engine but from a Jimmy 1997 instead of a Blazer so the wires are not the same color. I have to find what is where prior to further testing.
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Sunday, January 1st, 2012 AT 6:28 AM
Tiny
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Here.
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Sunday, January 1st, 2012 AT 8:51 AM
Tiny
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I finally found the connector usage. Partially. The wire go all the way to the back crossmember and plug onto the fuel pump. The problem I think is that the purple wire from the Fuel level buffer module gives only 2.2 volts. I will have to test further to see if it's still 2.2 at the exit of the module. If not then it will only means that the wire is shorted and the module is fine.
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Sunday, January 1st, 2012 AT 9:25 PM
Tiny
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Probably, yes. Let us know what you find out.
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Sunday, January 1st, 2012 AT 10:01 PM
Tiny
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Prior to that can you post me a picture of the location of fuel buffer and what it looks like? I've seen on the web that its under the glove box but not found it earlier today. Last step for the test and ill keep you updated. BTW do you know what voltage the purple wire is supposed to send? Thx and happy new year !
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Monday, January 2nd, 2012 AT 1:44 AM
Tiny
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My reference states the fuel level buffer is behind the dash above the steering wheel.

The schematic I have shows the buffer input power as being 6V and the buffer being below the instrument panel behind the dash.
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Monday, January 2nd, 2012 AT 2:02 AM
Tiny
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Yes for the 5 to 6 volts input on the gray wire but the output on the purple wire that goes to the fuel level sensor in the tank it's the one I'm searching for. I really need this voltage output on the purple so I can go further with the testing. If the voltae is wrong then I won't have to test the wire all the way to the back because I will know that its the buffer module that is defective. The 5 volts come from the VCM as an input to the buffer module and some sensors. That's why the power I'm losing make the engine run or not sometimes.
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Monday, January 2nd, 2012 AT 3:40 AM
Tiny
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Our reference doesn't list it.
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Monday, January 2nd, 2012 AT 3:58 AM
Tiny
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Ok. I will have to find it and continue later on. I'll keep you informed in a month only because I'm leaving out of town for work. Thank you for everything and keep up the good work guys :-D
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Monday, January 2nd, 2012 AT 4:24 AM
Tiny
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Have a safe trip.
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Monday, January 2nd, 2012 AT 4:38 AM
Tiny
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Plane delayed an hour for mechanical trouble. At least it was before taking off. Check engine code P01** ;) Just kidding about the code but not the mechanical trouble.
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Wednesday, January 4th, 2012 AT 12:23 PM
Tiny
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LOL. Cylinder misfire detected. Heheh
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Thursday, January 5th, 2012 AT 2:56 AM

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