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Component Matching #2
Sequence of Upgrades
In the previous article (component matching, sequence of upgrades #1) we addressed the first 5 things that should be done in order to your otherwise stock but good running TR. 1, Knock detector. 2, Scan Tool. 3, Fuel system verified to be adequate or upgraded. 4, Fuel pressure gauge with extension line for viewing at the windshield. 5, Adjustable fuel pressure regulator.
In continuing with the basics and the proper sequence of upgrades there is still one more thing that should be done with the fuel system prior to moving on to the next component. That is supplying your fuel pump the most electrical voltage possible from your system.
Typically the voltage at the pump will be lower than at the source of supply which is the alternator or battery. The reason for this is there is substantial resistance in the stock wiring.
This can be addressed by improving the wiring to the pump. Simply bypass the old wiring and leave it in place. Replace it with about 15 feet of 12 gauge wire.
This will require a relay triggered from the stock voltage signal to control the new circuit. The inexpensive 30 amp automotive relay along with the wire and crimp connectors can be purchased from Radio Shak or most hardware stores.
You will want to supply a good new additional 12 gauge ground path for the fuel tank as well. The tank is what the pump uses for a ground. Electricity flows like water and therefore needs a ground path to complete the circuit. Upgrading the supply without upgrading the ground would not be doing the job properly.
Some use 10 gauge wire for this, the difference in resistance is minimal between 10 and 12 but the degree of difficulty is greater. If you want to go with the thicker 10 ga wire you will need special connectors as well.
There are several well written articles out there for this procedure, so you may want to do it differently than how I will describe it here.
I like to mount the relay in the engine compartment and trigger it from the grey wire with the black female spade connector that is just behind the alternator and hangs down from the harness just below the valve cover on the drivers side. I like to use the battery power stud on the back of the alternator for my power supply and fuse it close to the source. I like to use crimp connectors and weather-proof them with both silicone and shrink tubing. I prefer to avoid cutting into the stock harness when I can.
There are sources for the GM / Packard connectors if you want to make a plug & play harness. There are small boxes of assorted connectors that also include a tool for disassembling the connectors. This will make for a more expensive set-up but will be the cleanest without cutting your stock wiring. There are pre made kits out there from aftermarket vendors that will allow you to install without fabricating. There are packages that include this “Hot Wire” harness with a pump purchase or at least add it at additional cost. If purchasing a pump upgrade you may want to consider this option.
I have checked the voltage at the pump connector, which is near the left rear corner of the car under the trunk. It’s grey with 3 wires. This is where you will connect the new wiring. The stock voltage at this location is lower by as much as 1 to 2 volts than it is at the source.
The reason for this is the stock wiring was adequate in the opinion of the engineers that designed the system. Obviously we would have done many things differently than the original GM engineers. Keep in mind they had a different set of guidelines than we do. Doing things in the most cost effective manner was most likely the primary consideration.
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