Holley Sniper 2 wiring

[Boiler Ben]

I’ve been waiting for Holley’s Black Friday sale to purchase the Sniper I want to use for the Roadster I am building with a FE engine. When I talked to their tech department they said I needed to use their fuel pump relay. But I want to make use of the inertia switch. Anyway I found that their power distribution module (PDM) option includes a harness that does not include a relay. It’s probably integrated with the PDM. Without the PDM, you get a harness that includes a relay in it and the heavy gauge blue wire is meant to go directly to the fuel pump. This would bypass the inertia switch though. I am wondering if I should try to modify the harness somehow or maybe order the PDM to get its harness but not use the actual box. I’m trying to study both the chassis harness schematic and the info from Holley but neither one really tells me the whole story of what’s going on.

Has anyone figured this out or knows of more detailed schematics that show all the relay connections?

[Papa]

You can put the inertia switch on the ground side of the pump and get the same effect as putting it on the ground side of the relay.

[Papa]

Looking at the Sniper 2 wiring instructions, there is a Fuel Pump (-) output on the main harness (Blue wire). You can simply run that to the inertia switch input instead of the chassis ground in the RF harness and then use the RF fuel pump relay as-is to control the fuel pump. The fan control would come off the 6-pin I/O harness (black/yellow) to the RF harness fan thermo wire (green - either one of the two available). You are then left with the two battery connections (+/-), a +12v switched connection, your specific ignition/coil connection(s), the tachometer connection, and that's it.

[rich grsc]

The inertia switch is not designed to handle the amp loads of a high output fuel pump. The best way to wire it would be to use the inertia switch on on the fuel pump relay switch wire. That is a low power draw, safe for the inertia switch, and still kill the power to the pump if needed.

[rickster991]

Here is what I did to keep the inertia switch.

https://thefactoryfiveforum.com/showthread.php?51417-Rick-s-Mark-V-Roadster-Build&p=589034&viewfull=1#post589034

https://thefactoryfiveforum.com/showthread.php?51417-Rick-s-Mark-V-Roadster-Build&p=589130&viewfull=1#post589130

Works great. I did not want to cut into the Holley harness which is the other option.

[Boiler Ben]

So the Sniper fuel pump trigger can go onto the orange wire on the RF fuel pump relay? Then the Sniper controls when the pump activates but the RF relay, harness, and inertia switch are all being used? The Sniper has a big blue wire that is power for the pump. I think I need the small blue trigger wire from the Sniper relay and basically not use the Sniper relay at all. Otherwise the relays may fight each other? I think it would be good if I could get the Sniper harness that normally comes with their PDM because that gives you the blue trigger wire itself and there is no rely. Doesn’t look like you can buy it this way unless you order the PDM (extra $100) just to get the harness. Does that make sense?

[rickster991]

I ran the blue wire straight. The relays will not fight each other. It worked for me.

[Papa]

So the Sniper fuel pump trigger can go onto the orange wire on the RF fuel pump relay? Then the Sniper controls when the pump activates but the RF relay, harness, and inertia switch are all being used? The Sniper has a big blue wire that is power for the pump. I think I need the small blue trigger wire from the Sniper relay and basically not use the Sniper relay at all. Otherwise the relays may fight each other? I think it would be good if I could get the Sniper harness that normally comes with their PDM because that gives you the blue trigger wire itself and there is no rely. Doesn’t look like you can buy it this way unless you order the PDM (extra $100) just to get the harness. Does that make sense?

This is what my comments were based on:

https://thefactoryfiveforum.com/attachment.php?attachmentid=221630&d=1763330408

You can create your own mating plug for the 16-pin plug and configure it to take advantage of the fuel pump ground (-) trigger. Note that the Holley harness with the fuel pump relay provides (+12v) out of the relay for powering the fuel pump.

[rich grsc]

It looks like the main harness connector 'R' is the ground side of a relay to control the fuel pump. The ECU does not switch high amp loads, they use relays, thus it's a ground. I think splicing the inertia switch in there would work. I had issues using the inertia switch to feed power to the pump.

[Boiler Ben]

Thank you for pointing that out. I need to use the blue trigger wire, not the large +12V blue wire. The chassis harness instructions talk about cutting the orange wire at the back of the fuel pump relay control wire and connecting the trigger there. But you are suggesting connecting the blue trigger wire to the ground side of the inertia switch instead of the chassis ground meaning the Sniper completes the path to ground rather than the chassis ground. Do I have that correct? That seems simpler. Is there any downside to not having a permanent ground on the inertia switch? Just thinking it through. Seems OK.

[Papa]

Thank you for pointing that out. I need to use the blue trigger wire, not the large +12V blue wire. The chassis harness instructions talk about cutting the orange wire at the back of the fuel pump relay control wire and connecting the trigger there. But you are suggesting connecting the blue trigger wire to the ground side of the inertia switch instead of the chassis ground meaning the Sniper completes the path to ground rather than the chassis ground. Do I have that correct? That seems simpler. Is there any downside to not having a permanent ground on the inertia switch? Just thinking it through. Seems OK.

You have the concept correct. All the inertia switch does is complete the ground to the RF fuel pump relay. By tying it to the ground output of the Sniper, it let's the Sniper turn the fuel pump on/off as needed. There isn't any need to modify the fuse block and there is no issue with the inertia switch not being grounded to the chassis.

[Boiler Ben]

Well that’s perfect then. Thank you for the help.

[Papa]

Well that’s perfect then. Thank you for the help.

You could buy the Holley PDM harness and get all the plug connections you need without spending the $200 on the PDM that isn't really that helpful in a car you are already doing all the wiring on.

https://www.summitracing.com/parts/sne-558-190?seid=srese1&gclid=Cj0KCQiArOvIBhDLARIsAPwJXOauI-f0_dK64fPfFia7F9qzJHlX23BALBt7q9T8HBEEoxYcSwUTXVEa Arl2EALw_wcB#overview

With this harness, you get the (-) fuel wire and plugs for the ignition - assuming you use the supported ignition.

These Holley Sniper 2 EFI PDM main harnesses includes the switched 12V power wire, main battery power and ground, coil input wire, and HyperSpark distributor connector. They feature a braided split wire loom to keep the wires protected and your engine bay clean! They are intended to be used on applications with a PDM, and do not include a fuel pump relay.

Holley Sniper 2 EFI PDM main harnesses include:

* One 5 ft. 12 gauge main battery power wire
* One 5 ft. 12 gauge main battery ground wire
* One 30 amp fuse
* One 20 ft. 20 gauge fuel pump trigger wire
* One 3 ft. 20 gauge coil input wire
* One 5 ft. 20 gauge switch 12V ignition wire