Ignition Switch Question ... 12v while cranking

[55mike]

I'm installing a Sniper fuel injection system on my 55. The main power (positive/negative) are hooked directly to the battery.

There is also a 12v "trigger" wire that is attached via the fuse-block that MUST have 12v while cranking and when in the run position.

My testing indicates no 12v when cranking on my fuse block. I have 12v when in run.. no problem.. it's the 12v when cranking/starting that I'm challenged with.

I've been given solutions such as a separate circuit utilizing a relay, which is not an option I really want to do.

I understand a simple jumper wire can be installed at the back of the ignition switch between #1 and #2 terminals, which will then provide 12v and both "run" and "Crank" positions of the switch. Has anyone here done this modification? Did it work ok?
Thanks
Mike

[Rick_L]

Yes, jumper the IGN1 and IGN2 terminals. It's been done forever when using electronic ignition and needing to eliminate the ballast resistor. Works equally well for an EFI retrofit. This applies only to 55-56 cars.

[55mike]

Thanks Rick!! That’s the answer I’m hoping for…

[55mike]

RickL … ok I did a temp jumper wire between ign 1 and ign 2 on the base of the terminal . Turn the key to “on” (not start) and the engine cranks…. Yikes! Not what it should do. I double checked the markings on the switch and am sure I’m jumping #1 with #2.
What am I doing wrong??

[chevynut]

ok I did a temp jumper wire between ign 1 and ign 2 on the base of the terminal . Turn the key to “on” (not start) and the engine cranks…. Yikes! Not what it should do. I double checked the markings on the switch and am sure I’m jumping #1 with #2.
What am I doing wrong??

There are "IGN1", "IGN2", "ACC", "BAT" and "SOL" terminals on the stock switch. The IGN1 and ACC are only supposed to be hot in the "run" mode. SOL and IGN2 are hot in the start mode. SOL and IGN2 are connected together during cranking, so if you jumpered IGN1 to IGN2 it would crank as soon as you turn on the key.

I used a diode on mine between IGN1 and IGN2 to prevent this.

http://67-72chevytrucks.com/vboard/attachment.php?attachmentid=1887328&stc=1&d=1553205670

http://www.567chevyclub.com/images/56_Chevy/Ignition-Switch-3.jpg

https://www.classicchevy.com/amfile/file/download/file/154/product/3220985/

[55mike]

I’ll check again

[55mike]

Yes sir. I double-dog checked. I jumped ign 1 to ign 2 …. I’ve never wired a diode in my life. Fact is wiring is my least favorite thing to do.
Is there an alternative?
If not …… what sort of diode?

[55mike]

Did some googling on diodes, appears an “in line” would work… still not sure when end would be + and which would be - in relation to #1 and 2 terminals…

[chevynut]

I researched the stock ignition switch thoroughly and made notes on what was connected to what in all positions. Unfortunately all my notes are at home and I’m in Montana this week.

Based on the way I think the stock ignition switch works I’m pretty sure yours is defective. It looks like IGN2 and SOL are always shorted together. They’re only supposed to be shorted together through the BAT terminal while cranking. Unplug everything and check if they’re shorted.

You can fix it without a new ignition switch by using a relay and a small diode if you want to. The nice thing about a relay is it takes the load off the ignition switch. I used one on my SOL terminal too.

[55mike]

Thanks for the responses and research. I think I’ll call American AutoWire next week and see if they can also shed some light. They sell a universal switch that might work, or perhaps I’ll get a new stock-style switch and jump #1 and #2 terminals. As a side note the old switch works just fine, it’s getting that 12v on cranking that’s kicking my tail.

[chevynut]

perhaps I’ll get a new stock-style switch and jump #1 and #2 terminals. As a side note the old switch works just fine, it’s getting that 12v on cranking that’s kicking my tail.

im pretty sure the ignition switch is just a 4 pole three position switch. I don’t believe your switch is working properly or the solenoid terminal wouldn’t go hot when the IGN2 terminal is shorted to IGN1. I think there’s something wrong with the switch contacts internally. If IGN2 and SOL are shorted together when in off or run then the switch is bad. I’ll post some schematics tomorrow if I can. Happy New Year!!!

[55mike]

Thank you Chevynut….. I’m looking forward to what you come up with

[55 Rescue Dog]

I don't know how you are testing it, but an ohmmeter will tell you how it works and if it works without even powering it up. That's how I checked mine, and I also used a relay for power on and another one for the starter solenoid. The original switch wasn't designed for any additional current which wasn't much when stock. The switch will only have to carry less than 1/2amp using relays can handle 30amps and the switch will last indefinitely.

[chevynut]

Pretty sure this is how the ignition switch works. Notice that each output terminal is independent of the others. You can short IGN1 and 2 together and SOL isn’t hot when in run mode. That’s why I think your switch is defective.

13150

Here’s a couple of ways to address it without a new switch.

13151

13152


The first way still uses the switch as a power source. It powers the relay output while in run or start position. The second takes the load off of the ignition switch. You could also run the solenoid off of another relay to take virtually all the load off the switch.

[55mike]

Thanks CN.

Seems like a relay is the way to go

[55 Rescue Dog]

Thanks CN.

Seems like a relay is the way to go
You need to figure out how and if the switch works first and foremost before hooking up relays. It's pretty simple to do with a meter if you know how to use one? I could explain if needed.

[chevynut]

Seems like a relay is the way to go

Whether you get a new ignition switch or not, a relay is a good idea to take the load off the switch. Pretty much all of the switched power in your car goes through the ignition switch to the fuse panel. So the switch will last longer and you won't be dropping voltage across it with the relay, if you use the 2nd schematic I posted where the 12V source doesn't go through the switch.

If you get a new switch, the diode isn't necessary because the IGN2 and SOL terminals would be independent (I think they're shorted together on your switch based on your symptoms). The diode can be small in this case because the relay coil only draws maybe 1/4 amp and the diode drops 0.7V so you can get by easily with a 1/2W diode, which is available in any electronics supply store like Radio Shack. Don't use a zener diode. This shows the polarity and how the current flows through it....



https://www.powerelectronictips.com/wp-content/uploads/2018/08/Fig-1-diode.jpg

[55mike]

I’m buying a new Optima battery (old one is over 7 yrs old)… and when I put my meter directly on it, and had a friend crank over the starter the voltage dropped to about 9.5. I reason full volts will help me find the best connection to the relay (trigger). Then I’ll pull power right off the battery (clean) for the Sniper

[chevynut]

I’m buying a new Optima battery (old one is over 7 yrs old)… and when I put my meter directly on it, and had a friend crank over the starter the voltage dropped to about 9.5. I reason full volts will help me find the best connection to the relay (trigger). Then I’ll pull power right off the battery (clean) for the Sniper

I'm not an expert on batteries but from googling a few sites it doesn't look like 9.5V while cranking means it's bad. It also depends on the type of starter since an geared starter will have less current load. Did you measure voltage directly on the battery terminals, or on the cable clamp?

A friend of mine has a Sniper on a 502 and he's had nothing but trouble with it. It literally would not shut off and filled his engine with gas three times when they were installing it at a reputable local shop. They had to pull the plugs and drain the cylinders and change the oil three times. They spent a lot of time with Holley on the phone but they weren't much help, but Holley finally sent them a new Sniper. He still had problems with the new one. Once when I was at his place he tried to start it and it wouldn't run. He disconnected the battery connection and re-connected it and it started. I have read that they have a major problem with EMI. He was using some high energy Holley ignition system so they changed it out and he's had no problems since but is still nervous about it happening again. Holley should have done a better job shielding sensitive wires. Just an FYI.

[55mike]

Yes sir, EMI is certainly a “thing” on Sniper. I’m concentrating on how I run the wiring with that fact in mind. Perhaps to this end, using a relay for the Sniper trigger is prudent to insure as clean of a signal as possible. I’m also adding some ground wires etc
CN thank you for all your help!
m

[chevynut]

Got to looking at your problem again and one thing doesn’t make sense to me. You said that you’re getting 12v on IGN1 while in run. You also said you’re not getting 12v on IGN2 in start. But you connected the two together and the engine cranks in run. So that implies that IGN2 and SOL are shorted together in run, but not in start like they’re supposed to be. I’m not sure how that can happen but it has to be a problem with the ignition switch.

It just occurred to me that you said you weren’t getting 12v when starting so my diagram is wrong. It says to connect the diode to IGN2 OR SOL. It would have to be connected to SOL to work since IGN2 is dead. Sorry about that.