Holley Sniper fuel pump relay and coolant temp sensor questions

[TMartinLVNV]

I think that I have my EFI all hooked up. I was following Dave's (Papa) instructions that he so graciously provided.

My main question is the Sniper fuel pump relay. Since the Sniper setup uses its own fuel pump relay (I have it mounted in the right rear of the engine bay on the firewall), should I take the relay out of the RF fuse block? I ran the blue wire back behind the dash and connected it to the tan wire that is in the "rear harness" bundle. Since I want to still use the inertia switch, so do I splice this into this blue wire? phileas_fogg in one of his posts says for the inertia switch to be in-line with the Holley Fuel Pump power circuit (I'm hoping that this fuel pump power circuit is the blue wire).

I have the Sniper pos/neg wires going directly to the battery.
The RF orange EFI/Coil is connected to the Holley pink switched ign.
The Sniper yellow wire is on the Neg of the coil.
The Holley light blue fan control wire is run to the RF dark green fan wire near the radiator.
O2 sensor is hooked up. Coolant Temp sensor is hooked up.

Do I connect the Sniper dark brown tach output to the RF purple coil/tach wire?

Do I connect the 3/16" Vacuum Advanced Distributor on the Sniper to the nipple on the cone shaped part on the distributor (don't laugh, I have never had one of these before).

I have a de-pin tool set on the way. When de-pinning a harness, are you just doing the downstream side of the connector?

If you see something else that I'm missing, please let me know.

Go easy on me guys, I am a wiring dummy!

Terry

[FF33rod]

Inertia Switch - as you suspect, you're not using the RF fuel pump relay anymore and have bypassed the inertia switch (which controlled the ground to the RF fuel pump relay). To get the inertial switch back in the circuit, you can as you suggest splice it into the Sniper blue wire. But I'm a bit concerned about current rating - has someone done this and no problem? On my setup, I kept the RF relay and didn't use the Sniper relay.

Tach - yes, Sniper dark brown goes to RF puple coil/tach wire

Vacuum advance - you have that correct

Depinning the harness - correct, just the downstream connector so that the wiring from the Sniper still goes to the first connector but that the connector that mates to it no longer has a wire for the unused signal.

Question - the water temp sensor for the Sniper, you used the Holley supplied sensor and put it on the manifold?

Steve

[Papa]

Terry,

No need to do anything with the RF fuel pump relay if don't want to. It won't be powering anything now that you've connected the Sniper to the fuel pump as you describe. On the inertia switch, yes, just connect it in-line with the blue wire that's providing power to the fuel pump. You'll want to tie the ground wires, the ones currently running through the inertia switch together to complete the ground circuit that will be cut when you re-wire the inertia switch. Don't forget to run +12v switched power to your coil(+) post. I recommend using the same orange EFI/Coil wire to power the coil and the ECU's pink wire.

I didn't use the brown tach wire in the Sniper connector, but connected the tach wire in the RF harness to the coil.

On the vacuum lines, connect both the vacuum advance on your distributor and the vacuum reference on the Sniper to the available vacuum ports on the Sniper's mounting flange.

That should be about it,
Dave

[TMartinLVNV]

Inertia Switch - as you suspect, you're not using the RF fuel pump relay anymore and have bypassed the inertia switch (which controlled the ground to the RF fuel pump relay). To get the inertial switch back in the circuit, you can as you suggest splice it into the Sniper blue wire. But I'm a bit concerned about current rating - has someone done this and no problem? On my setup, I kept the RF relay and didn't use the Sniper relay.

Tach - yes, Sniper dark brown goes to RF puple coil/tach wire

Vacuum advance - you have that correct

Depinning the harness - correct, just the downstream connector so that the wiring from the Sniper still goes to the first connector but that the connector that mates to it no longer has a wire for the unused signal.

Question - the water temp sensor for the Sniper, you used the Holley supplied sensor and put it on the manifold?

Steve

Thanks Steve. The Holley supplied sensor was installed already in the intake manifold by Forte.

[TMartinLVNV]

Terry,

No need to do anything with the RF fuel pump relay if don't want to. It won't be powering anything now that you've connected the Sniper to the fuel pump as you describe. On the inertia switch, yes, just connect it in-line with the blue wire that's providing power to the fuel pump. You'll want to tie the ground wires, the ones currently running through the inertia switch together to complete the ground circuit that will be cut when you re-wire the inertia switch. Don't forget to run +12v switched power to your coil(+) post. I recommend using the same orange EFI/Coil wire to power the coil and the ECU's pink wire.

I didn't use the brown tach wire in the Sniper connector, but connected the tach wire in the RF harness to the coil.

On the vacuum lines, connect both the vacuum advance on your distributor and the vacuum reference on the Sniper to the available vacuum ports on the Sniper's mounting flange.

That should be about it,
Dave

Ok, so I must have missed the part about the RF orange wire going to the positive side of the coil. This means that I will have distributor neg and the Sniper yellow wire on the neg side and the distributor pos and the RF orange wire on the pos side of the coil?

[Papa]

Ok, so I must have missed the part about the RF orange wire going to the positive side of the coil. This means that I will have distributor neg and the Sniper yellow wire on the neg side and the distributor pos and the RF orange wire on the pos side of the coil?

Correct.

[TMartinLVNV]

Ok, one more question after thinking about this for a bit. The coolant temp sensor in the intake manifold is going to the Holley Sniper so that it can kick on the fan. How do I get a signal to the Auto Meter gauge? Do I need a second sensor installed in the motor (where?)?

Terry

[FF33rod]

I put it in the radiator. Make sure you use the sensor that comes with the gauge
Steve

[Big Blocker]

Terry,

Don't confuse the Temp gauge feed with the temp sensor for fan operation - two different animals. One is a grounding switch for the fan relay, other is a resistive element that provided a variable voltage to the gauge.

Doc

[TMartinLVNV]

Terry,

Don't confuse the Temp gauge feed with the temp sensor for fan operation - two different animals. One is a grounding switch for the fan relay, other is a resistive element that provided a variable voltage to the gauge.

Doc

I'm using the driver's front NPT fitting for the Sniper (Forte installed it there already) reading. The passenger front NPT fitting will be for my heater hose.

[TMartinLVNV]

I put it in the radiator. Make sure you use the sensor that comes with the gauge
Steve

Did you use the threaded bung that the top left petcock valve went into? How accurate is this location compared to the temp of the coolant in the engine?

[FF33rod]

BB should answer the bung question, the 33 radiator is a bit different. As for accuracy, it isn't giving you engine temp obviously but once the engine warms up and the thermostat opens it shows the water temp just fine. As the fine goes on and off in the hot rod the measured water temp on the gauge reacts accordingly.
Steve

[CraigS]

I would prefer both the Holley and gauge sensors in the engine manifold. You know about the two bungs in the intake left and right but there is a 3rd option. The t-stat housing. Naturally I can't find a link now so here is a pic of mine. You can see the brass nut on the sensor,
20191225_080657 by craig stuard, on Flickr

[phileas_fogg]

The thermostat housing (https://www.napaonline.com/en/p/BK_6051080) is where I put the sensor for my temperature gauge. Yes; it reads cold until the t-stat opens, but that's less than 5 minutes run time here in Northern VA.


John

IMG_3449 by jhsitton, on Flickr

[rich grsc]

You need the temp gauge in the engine. You want to know what is going on with engine temp. If the thermostat fails, and the gauge is in the radiator, all you're going to see is radiator temp, and over heat the motor even though the fan is running. Much safer to have the fan switch in the radiator.
If you have the gauge in the thermostat housing, again, if it fails and it doesn't open you won't know till the engine is dangerously hot. An OK place for the fan switch.

[Norm B]

I agree with both in the manifold. If the EFI temp sensor is already mounted on the drivers side then the gauge sensor should be on the opposite side in the manifold behind the thermostat. Here are a couple of pictures. I am running a heater so mine is in a T that connects to the heater line. This configuration requires the use of a bypass heater valve to ensure coolant flow past the sensor. If you are not running a heater then Breeze Automotive has a fitting for this port. Here’s a link https://www.breezeautomotive.com/ect-sensor-elbow.

On my pictures you can see the sensors just above the power steering reservoir cap and in the T beside the distributor.

HTH

Merry Christmas

Norm

[TMartinLVNV]

Thanks everyone for your suggestions and examples of what you have done. My thermostat housing does not have a port to insert a sensor. So basically, I have two ports and three things to go into these ports. I feel like the electric fan turn on sensor for the Sniper is the least important to have in the intake manifold coolant flow. I was thinking about finding a "T" NPT fitting to try and get the gauge sensor and the heater line to use the right side port. But, this would take the sensor out of the direct flow and would probably look ugly. I'm not a big fan of having the sensors in the radiator. I think that this is what I am going to do.

Buy a thermostat housing with a port. Remove the Holley sensor for the cooling fan from the left side of the intake manifold and move it to the post thermostat port. Use the right side intake manifold port for the heater line. Use the left side intake manifold port for the gauge sensor.

Does anyone see any issues with this plan? Best part is that the thermostat housing is cheap.

Terry

[Norm B]

A Holley Sniper EFI system is one of my planned winter upgrades. As such, I have been doing some research and believe there is only one temperature sensor associated with this system. It is critically important that this sensor be located in a constant coolant flow and that is why Forte installed it in the driver’s side intake manifold. The primary purpose of this sensor is to provide the unit with accurate engine temperatures to properly set mixture and timing. A secondary function is to provide a programable temperature to activate the rad fan. According to the Sniper instructions I have, there are two fan control circuits available, both designed to only handle the low amperage from the ground side of a relay. The temperature at which this circuit grounds is setup by following the instruction manual.

The thermostat housing is not a good place for this sensor because the unit will sense cold engine temps until the thermostat opens. This is the same reason it is not a good place for your temperature gauge sensor but, it will work for a fan temp switch.

My suggestion is to leave the Sniper sensor where Forte put it and find a way to provide constant coolant flow at the other manifold port for your gauge sensor.

Maybe I don’t understand the system correctly and someone with first hand experience will correct me.

HTH

Norm

[FF33rod]

What Norm said. The Sniper temp sensor is not just to trigger the fan so make sure it has an accurate read of engine temp. Forte put it where they did for a reason. Speaking of which, you could discuss your options (and compromises) with either/both Holley or Forte.

Steve

[Norm B]

Here’s the heater control valve you need and the one I’ll be using for this mod.

[TMartinLVNV]

Thanks Norm and Steve. I didn't know that it did more than just trigger the fan. I haven't removed anything yet. Because of your last few posts, I didn't get the thermostat housing. I just put the temp sensor for the gauge in the unused (passenger side) so that I can get to the first start. I will not hook up the heater until I'm ready to put the body on. Then I'll have to figure out the best course of action. I will have to get Forte a call too. I can keep doing some research until then.