Upgrading the OEM Wiring for the New High Power Fuel Pump
You've just installed an upgraded in-tank Low Pressure Fuel Pump (LPFP) in your factory fuel sender basket. You have your Torqbyte PM3 pump amplifier or your Torqbyte CM5 ready to power the new pump, but there is a problem:
The OEM wiring harness that plugs into your fuel sender most often uses very thin 16AWG wires that the manufacturer found appropriate for the amount of current drawn by the factory LPFP that comes with the car. The manufacturer should have anticipated that you will need a larger in-tank pump to fuel your out of control boost addiction and should have installed larger 10AWG fuel pump power wires - but they didn't.
Now what? Leaving those thin factory wires in place will create a bottleneck that will, at best, prevent the you from getting the most out of your new pump and quite possibly cause a fire hazard if the new pump draws more current than those 16AWG wires can safely handle causing them to overheat.
What can you do?
You could simply purchase our VAG Plug-n-Play Adapter Harness or make your own DIY PM3 P-n-P Harness or your own DIY CM5 P-n-P Harness, but given access to the right contact removal and crimping tools you could also rework your factory wiring to achieve the same result.
The male connector on top of the fuel sender is molded into the plastic top of the fuel sender assembly so you can't change it. You also can't drill into the fuel sender cover to pass larger diameter wiring into the tank as you'll never be able to make a safe and reliable seal around the wires. This is clearly an _extremely_ bad idea and should never be entertained.
The issue must be addressed at the connector that normally plugs into the fuel sender. To illustrate the proceudre we'll use the VW/Audi connector Part No. 1K0 919 231 that is found on a large number of VAG vehicles.
This is a hybrid 5 position (aka 5-way) connector made for VW by TE Connectivity (aka AMP / Tyco). Positions 1 and 5 supply the power to the fuel pump.
Step 1 - Remove the old wires from the connector housing
Before attempting to remove the contacts, first remove the plastic retainer (aka Terminal Position Assurance or TPA lock). This is a small pink, U-shaped piece of plastic that is snapped into position around the contacts. You can disengage it (which will allow the contacts to be removed later) by using a very small tipped screw driver and gently pushing it out towards the slot in the side of the connector until it clicks once. Don't remove the TPA from the connector housing or you won't be able to re-insert it once the contacts are put back in the housing. It only needs to disengage one click.
Now you'll need a contact removal tool TE Connectivity Part No. 1-1579007-3 available from many online suppliers such as digikey.com, mouser.com, newark.com, e-sonic.com, verical.com, itt.com, etc. This tool is shown below.
When you insert it through the front of the connector, this removal tool will simultaneously compress two spring-loaded tangs that hold the connector in the housing and allow you to (gently) pull the wire and contact out from the back. If you don't use the proper tool at this step you will likely damage the contact and probably damage the plastic housing preventing the new contact from locking in.
Step 2 - Install larger wires into Positions 1 and 5
Here you are faced with two options:
Option A: Quicker and cheaper but with some compromises depending on what you are doing.
You can just buy a wiring repair kit from the dealer that comes with the right terminals and pre-crimped 4mm^2 (i.e. 12AWG) wire. The VW/Audi Part No. 000 979 308 E provides you with a single wire with two terminals (one on each end), so all you need is one of these because you can cut it in the middle which will provide two pieces for the two positions you are trying to fill.
The first compromise with this approach is that you are limited to about 25A of peak current by the wire supplied with this kit. If you are using something like a TTRS pump this wiring will be fine, but if you are using something exotic it may not be enough.
The second compromise is that for whatever reason VAG doesn't include integrated pre-crimped silicone wire seals with this kit. Just look at the wires you pulled out in Step 1 and you'll see they each have a silicone wire seal that is "clasped" and held by the metal at the end of contact that you pulled out. However the VAG wire repair kit provides no silicone seal on the wire provided. We are not sure why VAG supplies these kits without the integrated wire seal, other than that there are many housings these can go into and each housing may require a different seal, but the manufacturer TE Connectivity states clearly that you should never add the seal onto the wire after it's been crimped. Anyways, if you chose to do it the VAG-way you can ask the dealer for a couple of wire seals and and slide them on from the cut wire side after you cut the provided wire in half. DO NOT slide the seal over the crimped metal contact as you will stretch and probably tear the seal.
Option B: MUCH more expensive but without any compromises, this option is probably the right way to go for dealers or shops that might perform this work on a regular basis.
Positions 1 and 5 accept terminals from the AMP MCP6.3/4.8K FLATCONTACT family. These contacts are shown below.
The manufacturer product family drawing can be downloaded HERE.
You can see in that drawing that there are two contacts that will fit into this housing AND accept a single wire sealing system (i.e.a silicone seal).
If using 12AWG wiring you'll need Qty 2 Contacts, TE Part No. 1241416 or 1241417
If using 10AWG wiring you'll need Qty 2 Contacts, TE Part No. 1241418 or 1241419
In either case you'll need a couple of silicone wire seals for the 8.5mm cavity (which is the cavity size of the VW connector at Positions 1 and 5) TE Part No. 1719043-1, but since these TE seals are rarely available anywhere, you can use a Delphi (GM) Part No. 15324990 instead.
To crimp the contacts and the seals onto your wiring you'll need the TE manual crimper Part No. 539635-1 shown below.
However this crimper is supplied blank and you'll need to purchase the crimping dies separately.
For the 12AWG wiring using contacts TE Part No. 1241416 or 1241417, you'll need crimping dies TE Part No. 539956-2.
For the 10AWG wiring using contacts TE Part No. 1241418 or 1241419, you'll need crimping dies TE Part No. 3-1579021-7.
You can get all these parts from your favorite online supplier such as digikey.com, mouser.com, newark.com, e-sonic.com, verical.com, itt.com, etc.
The manufacturer crimping specification can be downloaded HERE.
Once you've crimped the wires and seals as per above specification, insert the contacts into positions 1 and 5 tug on them gently to make sure they are locked in place. Make sure the seal is firmly in the cavity and then re-install the pink plastic TPA lock by applying pressure on it through the slot in the side of the connector until it snaps/clicks into place.
That's all - now you have an adequate wiring connection from the PM3 to the top of the fuel sender. We'll address the upgraded wiring on the inside of the tank in the next blog.