The fuel pump plays a major role in keeping the engine of your vehicle running since it is one of the continuously running components of your vehicle.
Owing to the fuel pump durability life it may operate with reduced performance after the vehicle covers some mileage.
The life of the fuel pump depends mostly on the contamination level of the fuel being used, the fuel tank’s hygiene, and the level of fuel being maintained inside the fuel tank.
Poor quality of the fuel will try to clog the in-tank fuel pump strainer and it may start releasing unfiltered fuel to the fuel pump motor.
This causes clogging of the fuel pump impeller blades and damages the surface of the impellers as well which reduces its capability to deliver fuel to the engine.
Hence it is necessary to replace the fuel pump strainer after fixed intervals, otherwise, it would damage the fuel pump and it will lose its primary function of fuel delivery.
Once the fuel pump goes bad and fuel starvation takes place, you may start experiencing engine hesitation and sputtering issues, and then finally the vehicle comes to a standstill.
If you are already facing the vehicle stalling issue in your GM vehicle and thinking of replacing the fuel pump or the electrical connectors, then you shall first know the fuel pump wires color codes to ensure correct wiring harness connections to the intended parts, otherwise, you may not be able to supply power to the fuel pump and kick off the vehicle.
The GM fuel pump wires color codes typically used in the vehicle are grey, black and white strip, purple and black and it indicates power to fuel pump, ground connection to pump, power to fuel gauge, and ground to the fuel level sender unit respectively in that sequence.
If you are interested in knowing the fuel pump wire color codes of GM trucks, then you are at the right place.
Here, you will get to know everything about the fuel pump or electrical connector replacement and the color codes. So, stay tuned!
Table Of Contents
What are the GM Fuel Pump Wires Color Codes?
If you are replacing the fuel pump in your GM trucks, then knowing the GM fuel pump wires color codes is of prime importance.
The fuel pump module typically has both fuel pump and fuel level sender unit assembly built in one single module.
The problem arises when you confuse the wire color codes and there is no mention of color codes in the vehicle’s user manual.
Often, a lot of time is wasted in identifying which color wire goes to which part and at times it becomes annoying to do trial and error in matching the wires to their respective parts to operate the fuel pump.
In many cases depending upon the vehicle model and year of manufacturing, the vehicle wiring harness may have different colors than that of the fuel pump and it becomes tough to identify which color wire goes to which part of the fuel pump.
Also in a few cases, depending upon the vehicle model, the electrical connectors may need to be changed either to suit the mating connectors that come along with the new fuel pump wiring harness or the connector is damaged and worn out.
You may need to cut the old vehicle wiring harness as close as possible to the old electrical connector to ensure sufficient length is available when you connect to the new fuel pump.
Once you cut the old wires, you would need to splice the cut end of the wire to the new connector either by soldering or by twisting and taping it.
If the electrical connectors are damaged, then there would be either intermittent loose connection or a large voltage drop due to high resistance across the connectors.
This would cause the fuel pump to operate inefficiently and you may notice that the fuel pump primes but no pressure of fuel in such cases.
It is worthwhile to know the color coding of the fuel pump wires in your GM truck when you are replacing the electrical connectors as that would ensure that the correct wire is connected to the right parts of the fuel pump assembly.
The fuel pump wiring harness typically has a color code and each wire indicates either a current flow path or a ground path for the electricity flow to a particular part of the fuel pump module.
The typical GM fuel pump wires color codes are as follows; the grey wire indicates power feed to the fuel pump from the fuel pump relay, the black and white strip wire designates ground connection to the fuel pump, and a purple wire on the GM fuel pump module is typically assigned to power signal to the fuel level sending unit and finally a black colored wire code implies a ground connection to the fuel level sending unit.
If the color on the vehicle wiring harness doesn’t match the fuel pump wires color codes, then you may need to check each circuit with the help of a multimeter to arrive at which wires have a power supply and which wires have a ground connection.
What is grey wire on GM fuel pump?
The grey wire on GM fuel pump or the vehicle wiring harness connects the fuel pump to the 12 volts battery positive via. the fuel pump relay and is relatively larger in diameter.
When you put the ignition key in the ON position, the fuel pump would start running for 3 seconds and you would hear the fuel pump buzzing sound and after that, the fuel pump goes off.
This phenomenon is called fuel pump priming and it is typically designed to keep the fuel hose pressurized at the back of the fuel injector to keep it ready for fuel injection when the key is turned to start mode (engine cranking).
In some cases, it is possible that the wire that comes from the fuel pump relay to the fuel pump is broken in between while doing some repair work or the wire got damaged earlier but after some vehicle running it has given off.
So, in the above case, even after matching the wires considering the color codes, the car won’t start after fuel pump replacement as the fuel pump won’t get power due to broken wire.
What does black and white strip wire indicate?
The black and white strip wire on a GM fuel pump typically implies the ground connection to the fuel pump via. vehicle ECM (electronic control module).
Usually, the chassis frame serves the purpose of the ground connection. Unless the fuel pump is grounded, the power supply won’t flow to the fuel pump for its operation.
Typically, the vehicle ECM grounds the fuel pump for 3 seconds for fuel pump priming in ignition ON condition, and then the ECM removes the ground connection so the fuel pump stops operation.
When the key is turned to crank the engine, the ECM gets the input from the engine RPM sensor indicating that the vehicle has started running and this ensures continuous ground connection to the fuel pump from the ECM, until the vehicle stops running.
It is observed that people often complain about the fuel pump running continuously with the key in on position and not in cranking or start position, this may be due to the broken wires in between the ground connection point and the fuel pump.
The broken wire when it touches any part of the chassis frame, would establish false ground and bypasses the ECM grounding operation and the fuel pump would keep running continuously.
What is the purple wire on a GM fuel pump?
The purple wire on the GM fuel pump indicates +5 volts power signal to the fuel level sending unit.
People may identify purple color as violet, lavender, lilac, or mauve color based on different region practices.
Depending upon the fuel level inside the fuel tank, the float of the fuel gauge would send different resistance value to the instrument cluster via. a thermistor and this input are changed to either analog or digital signal on the dash panel depending upon the application.
What is black wire on a GM fuel pump?
The black wire on a GM fuel pump is typically assigned for a ground connection to the fuel sending unit.
In a few vehicles, the fuel level gauge may have orange-colored wire instead of regular black wires. This depends on the fuel pump and vehicle year of manufacturing.
What happens when you wire a fuel pump wrong?
While replacing the fuel pump on your GM vehicle, if the fuel pump wiring is done wrong then the fuel pump won’t get power since the power supply wire from the fuel pump relay will not get connected to the fuel pump.
Hence the fuel pump won’t run and discharge fuel to the engine and the vehicle won’t start.
If the fuel level sender unit is wired wrongly then the fuel level indicator on the dashboard will not reflect the fuel level inside the fuel tank.
The indicator may show zero fuel even though the fuel tank is completely or partially filled.
In some cases, if the harness colors are completely different than what we discussed so far, then taking picture of the fuel pump wiring harness before dismantling the parts would help to a large extent to reinstate the harness back to its original condition after the fuel pump repair operations to connect and match the correct wires to right fuel pump module parts.
Conclusion
The fuel pump wires color codes help in easy identification of the electrical connections going to various parts of the fuel pump module.
In modern vehicles, the electrical connectors are like plug and forget and there is no chance of doing wrong wiring since the connectors itself has foolproof arrangements.
But if the connector layout is altogether different or the connector has gone bad, then you may need to replace them considering the wiring color codes carefully.
If you are replacing the fuel pump or changing the connector of the wiring harness in your GM truck, then it is important to understand the GM fuel pump wire color codes for easy replacement.
The GM fuel pump wires color codes typically used are grey and purple color codes for the fuel pump and fuel level sending unit power supply respectively, black white strips and black color codes are for ground connection to the fuel pump and fuel level sending unit respectively.
Understanding the color codes makes the fuel pump replacement operation easy.
Hope the information discussed here helps you in keeping you updated about everything you need to know while doing the fuel pump repair or replacement operations.
Happy motoring!
References
https://www.s10forum.com/threads/need-a-color-code-wire-diagram-for-the-fuel-pump.861329/
https://www.GM-trucks.com/forums/topic/108359-fuel-pump-new-wiring/
https://www.camaros.net/threads/fuel-pump-wire-colors-help.41724/
https://www.astrosafari.com/threads/fuel-pump-relay-wire-color.147018/
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