Ignition Switch Question ... 12v while cranking

[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....

[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.