Ignition Problem

[bcoke]

When I turn the key it fires up, but when I let the key go it dies. It'll stay running if I back the key off just enough to have the starter motor stop, but as soon as I release it all the way the motor dies and there's a sound that sounds like the engine is slowing itself down (sounds like engine braking for those stick shift drivers out there).

I'm pretty hopeless when it comes to electrical wiring of these cars. I googled around about this and read about the ballast resistor burning up and causing that problem or an ignition switch problem. I checked for the ballast resistor wire but since none of the wiring is stock I couldn't find it. Don't see any burnt wires though.

For some context I have a 72 K5 with an IROC Z28 TPI engine. Lists of problems that I've fixed fairly recently that deal with electrical:
- battery drain - replaced a bad temperature sensor that was always going to ground with the engine fan (electric), fixed by replacing the sensor and putting the fan on a manual switch

- headlights blew out, replaced the fuze and the bulbs, no luck, had someone rewire the headlights (can't stay on hi beam too long though or the switch will get hot and the lights will go out)

- starter motor crapped out - replaced it with the standard one for an 89 IROC from autozone

This thing has been one problem after the other so trying to get this latest one solved. Any help would be greatly appreciated!

[billthompson]

sounds like a bad switch...how old is it? sounds like youve done a lot of electrical additions. do you have an hei or points distrib? if its hei, you could run a temperary wire from the battery to the hot side of the hei. if its got a coil you may need a resister in the wire so you dont burn the points. if it runs ‘hotwired’ then you know the problem in your switch circuit. not a lot to the stock wiring on our trucks but your mods might need to be looked at.

[A1971Blazer]

more than likely the switch is bad since it stays running if you're barely off the start position...or the connector on the back is bad....or a break in that circuit...
you can pull the connector off the back of the switch and take a look at it.....
to remove the switch...you need to turn it to acc mode.....push in the little hole with a paper clip...and the cylinder will come out.....
then unscrew the bezel off the front...that will let it come out...

[billthompson]

this might help

http://outintheshop.com/faq/wiring/wiring.htm

[paul mora]

The ignition switch is a switch that shuts all unnecessary power off and engages the starting system to crank the motor and get it started. Once you release the switch back to the running position it keeps all the same necessary stuff engaged to keep it running and stop cranking. Unless you have done some changes to the wiring system it sound like the ignition switch is bad. When you release the key to run the hot wire that keeps it running is not making contact. Before you replace the switch you should check to make sure all the wires are connected and if you have a volt meter check the switch in each position when turning the key it be sure it is the switch and not a back wire or connection downstream from the switch

[bcoke]

@billthompson - it's a 1972 but I'm not sure how old the switch itself is. Also not sure if I have HEI or points distribution...how would I go about figuring that out?

thanks so much for the help everyone! Okay so I'll take the switch out and check the back and check the connections. And if I don't see any problem with those I'll just order a new ignition switch offline and swap it. Sound good? I'll update soon

[billthompson]

its probably just a bad switch....hei dont have a seperate coil. as much as has been changes about your truck id be surprised if you didnt have one. i just bought a switch and key/tumbler from oreillys. together it was less than $30. let me know how it goes...lectrics is my thing...airplanes, cars, boats....if its got wires i work on it

[billthompson]

https://m.youtube.com/watch?v=XAn3RZvGufA

[RustyBucket]

disregard .... I took the time to read past your first couple of paragraphs.

[bcoke]

I pulled the switch and didn't look like anything was burned up or malfunctioning. It's hard to tell from the picture but it actually looks fairly new. Is there any way to tell if it's bad or do i just have to replace it and see?

It's hard to find the problem by chasing the wires to check down stream because the other picture is what it looks like under the steering wheel... the wires all look good themselves but it's a bird's nest

Does anyone know which of those wires in the first switch picture is the hot wire that is failing to make contact when i let the key snap back?

And dumb question: where in the engine bay is the starter solenoid? Is it on the starter motor? I'm trying to trace the wire from the switch all the way through to find problems elsewhere in the circuit

[82sdale]

Originally Posted by bcoke

I pulled the switch and didn't look like anything was burned up or malfunctioning. It's hard to tell from the picture but it actually looks fairly new. Is there any way to tell if it's bad or do i just have to replace it and see?

It's hard to find the problem by chasing the wires to check down stream because the other picture is what it looks like under the steering wheel... the wires all look good themselves but it's a bird's nest

Does anyone know which of those wires in the first switch picture is the hot wire that is failing to make contact when i let the key snap back?

And dumb question: where in the engine bay is the starter solenoid? Is it on the starter motor? I'm trying to trace the wire from the switch all the way through to find problems elsewhere in the circuit

yes the starter solenoid is the round thing on top of the
starter moter
Posted via Mobile Device

[82sdale]

red is hot from battery, purple goes to starter sol., brown/white stripe goes to the voltage reg or alternater (sense) depending on how your truck is wired (with all the mods im betting it isnt wired stock), the other brown is switched ignition witch runs stuff dependant
on the key via the fuse box. pink is probably the wire your after. it goes to the distrib. the stock config is though a resistor wire coming off the starter sol. but again im betting your engine has an hei and it probably isnt wired stock.
Posted via Mobile Device

[rpmerf]

Points or HEI:
If you have a square coil in the top of your cap, it is HEI.
If not, pull the cap and see if you have points in the front, or a electric sensor thing in the back. Guess you could look for the 2 wire connector in the back of the distributor also.

For the ignition switch:
Red should be full time power.
Purple should be for the starter.
From looking at the schematic, I think a pink wire will be for the coil / HEI.

I would grab your test light and probe around, see what lights up when. Once you figure that out, you can pull the switch off and test for continuity in different positions. Might be able to pull it apart and clean up contacts or look for anything broken. Also, check for power at the coil when the switch is on and in it's 'running' position.

[82sdale]

Originally Posted by bcoke

I pulled the switch and didn't look like anything was burned up or malfunctioning. It's hard to tell from the picture but it actually looks fairly new. Is there any way to tell if it's bad or do i just have to replace it and see?

It's hard to find the problem by chasing the wires to check down stream because the other picture is what it looks like under the steering wheel... the wires all look good themselves but it's a bird's nest

Does anyone know which of those wires in the first switch picture is the hot wire that is failing to make contact when i let the key snap back?

And dumb question: where in the engine bay is the starter solenoid? Is it on the starter motor? I'm trying to trace the wire from the switch all the way through to find problems elsewhere in the circuit

yes the starter solenoid is the round thing on top of the
starter moter
Posted via Mobile Device

[82sdale]

billthompson is a automotive wiring guru. if you are still having problems i would highly recommend contacting him

[warrpath4x4]

my 72 had the same problem when i got it, mine was converted to HEI. when releasing the key the coil was losing power, the harness has been hacked by the previous owner so i just side stepped my issue by running a switched hot wire to the coil. worked for several years but now i am re-wiring the whole rig.

[WorkinLonghorn]

If you have electronic ignition (HEI or similar) you need to have 12 volts to the distributor. Coming out of a stock ignition switch I believe there are 2 different wires to the solenoid a purple resistance wire that reduces the voltage for a POINTS TYPE distributor and another one (orange and purple?) that supplies 12 volts during starting only. IF YOU HAVE HEI you NEED 12 volts constantly to run at all so you need to replace the purple wire (or whatever color the resistance wire is- look at the solenoid) with a regular wire that is not resistance wire . Very simple procedure. Check with a volt meter if you want to see what the voltage is to the distributor with the switch in the "run" position. Should be close to 12v not 9v.
I'm no mad genius with this electrical stuff but I think I have this right. It's what I have read and it worked on my truck. If you are getting 12v then you need a new switch. You won't see a problem from the outside. The contacts internally could be oxidized or burnt. -BA

[bcoke]

Update: replaced the switch and she fires up! Thanks for the help everyone! One more down in the litany of electrical problems.

So far:
- battery drain = fixed with bigger alternator, replacing bad temp sensor in engine that was always going to ground and turning the electric cooling fan on, wired a direct switch for cooling fan
- headlight blow = fixed with replacing fuse, bulbs, and floor dimmer switch. Now can’t use hi beams for any period of time without switch heating up and causing the lights to go out
- won’t turn over = replaced the starter motor (stock one for IROC Z28)
- won’t stay running = replaced ignition switch

Wondering what the next problem will be haha I feel like once I fix something else in the system, another thing pops up. Wish I could get ahead of it instead of putting out fires but maybe that’s how it has to be. If anyone has any advice for that (aside from spending thousands to completely rewire the truck), let me know!

Shoutout to Bill Thompson too for walking through things with me!

[rpmerf]

For the headlights, I would relay them. You can get a kit, or if you are handy with wiring, it isn't too bad to wire up. Use 2 relays, one for high beams, one for low beams. I put them on the driver side fender. Wire into the headlight wires before the drivers side headlight and grabbed power from that junction block.

For the drain, try a parasitic load test. You can google around, theres tons of write ups and youtube videos.

[billthompson]

Originally Posted by bcoke

Update: replaced the switch and she fires up! Thanks for the help everyone! One more down in the litany of electrical problems.

So far:
- battery drain = fixed with bigger alternator, replacing bad temp sensor in engine that was always going to ground and turning the electric cooling fan on, wired a direct switch for cooling fan
- headlight blow = fixed with replacing fuse, bulbs, and floor dimmer switch. Now can’t use hi beams for any period of time without switch heating up and causing the lights to go out
- won’t turn over = replaced the starter motor (stock one for IROC Z28)
- won’t stay running = replaced ignition switch

Wondering what the next problem will be haha I feel like once I fix something else in the system, another thing pops up. Wish I could get ahead of it instead of putting out fires but maybe that’s how it has to be. If anyone has any advice for that (aside from spending thousands to completely rewire the truck), let me know!

Shoutout to Bill Thompson too for walking through things with me!

glad you got it fixed. your truck has a lot modifications...break it
down one at a time....youll bag it....

light problem sounds like large ampere draw problem. things to look for are wrong light bulbs, too small or damaged wiring.
Posted via Mobile Device

[bcoke]

Update: the headlights can't be used at all now (even on low beam) without overheating. Attached is a picture of the wiring from above (facing the engine) and pictures of the two relay boxes.

But that's unfortunately the least of my worries....now the truck will crank but won't start. It was starting fine with the new switch, but now it just cranks forever and won't fire up.

From the reading I've done it seems like it's either not getting fuel (clogged fuel filter) or spark (bag plugs). not too sure how to check either of those on an IROC Z28 so if someone has advice lemme know.

This also feels like it could be something else weird since it comes on the heels of replacing the ignition switch ....thoughts?

[rpmerf]

Go under the hood. Remove the air cleaner. Move the throttle all the way open. See that the choke sets. Watch for the accelerator pump to spray fuel into the carb.

Could dump some fuel in the carb. If that gets it going, you have a fuel issue. If not, it's ignition.

Look for power at the coil.

Could use a timing light to see if the plugs are firing. Or take a wire, pull the boot back and hold the connector about 1/4" from an unpainted part of the engine while someone cranks.

[litebulblsc]

If I read correctly, you have a tuned port injection setup on this truck. If so, please post a picture of it so others can see what you are dealing with