No crank and no key on power

[fidelity101]

Okay I'm thoroughly stumped on this one:

It is an 87 TBI 3/4 suburban 350

I have a no crank and no power in my accy and key on position.

No fuses are blown in the fuse panel, things like the horn and power windows do not work.

I have 12.3v going to the both B+ locations on the ignition switch but only 1v coming out at the accy/on position when I turn the key, Makes me think that it is an ign switch, so I replace it - still nothing.

starter gets 12.3V, junction block gets 12.3v, I cleaned the grounds behind the dash, core support, alternator bracket (they weren't rusty or anything either) just to be safe.

I had the starter tested at advance auto and it passed, the fuseable links at the starter and alternator were good, i was able to tug on them pretty good.

I do hear the fuel pump run with the key on position.

I'm clueless.

 

[dyeager535]

Did the problem just start, or have the problems sort of compounded over time?

If it happened at once, then that likely narrows it down to one thing. When you replaced the ignition switch, did the 1V become 12V?

Horn is constant 12V, it SHOULD be an independent problem...

 

[Fordum]

Just throwing this out to start with.

You may be missing something basic. Don't know exactly how you tested, so I need to explain this.
A bad connection, under no load, will show full battery voltage.
This fools a lot of people.

Go back, and check the B+ to the switch again. If you have full battery voltage, turn the key on, and check the B+ again.
There is a good possibility you will lose battery voltage then.

If so, then you have a bad connection between the switch and the battery.

Next, turn on the headlights and see if they work. If so, then the battery clamps and cables are probably OK.

As a check, with the lights and as many loads turned on as you can, put the voltmeter on the lowest setting, and measure between the battery post and the clamp hooked to it.

Assuming its a top post battery. You should have much less than a volt between the two, both on the + and - posts.

If there is a significant voltage between the post and its clamp, you have a bad connection there.

 

[fidelity101]

Did the problem just start, or have the problems sort of compounded over time?

If it happened at once, then that likely narrows it down to one thing. When you replaced the ignition switch, did the 1V become 12V?

Horn is constant 12V, it SHOULD be an independent problem...

happened all at once, drove fine the other week. it sat for a week then went to move it and got nothing. headlamps still light up via the switch.

When I replaced the ignition switch it stayed at 1v in the acc/on position.

I checked the B+ points on the ignition switch with the key on and off, both positions shows 12.3v

 

[dyeager535]

Are you getting enough "throw" on the ignition switch itself? They are adjustable. I doubt it's the problem, but oftentimes you will get a low voltage reading even if the connection is not being made.

Headlights are unfused as I recall (switch has an internal circuit breaker) and lights are on one of the two fusible links...the other is ignition.

Is there/are there fusible links between the junction block and the engine side of the fuse panel connector? I'd pull the fuse panel connector and verify that the wires from the junction block to the terminals on the connector are allowing current to get through them.

If the starter is getting 12V from the battery, then the only reason (barring starter component failure) that the starter won't rotate, would be the purple wire not providing the starter what it needs. Either ground or 12V, I'm guessing 12V with key in "start" position. Since your power windows and horn don't work, but lights do, I don't think a ground would be your problem, but if it were, it would be the one from the body to the engine.

 

[fidelity101]

Are you getting enough "throw" on the ignition switch itself? They are adjustable. I doubt it's the problem, but oftentimes you will get a low voltage reading even if the connection is not being made.

Headlights are unfused as I recall (switch has an internal circuit breaker) and lights are on one of the two fusible links...the other is ignition.

Is there/are there fusible links between the junction block and the engine side of the fuse panel connector? I'd pull the fuse panel connector and verify that the wires from the junction block to the terminals on the connector are allowing current to get through them.

If the starter is getting 12V from the battery, then the only reason (barring starter component failure) that the starter won't rotate, would be the purple wire not providing the starter what it needs. Either ground or 12V, I'm guessing 12V with key in "start" position. Since your power windows and horn don't work, but lights do, I don't think a ground would be your problem, but if it were, it would be the one from the body to the engine.

Yeah the mechanical side of the switch is okay, the lock cylinder moves the rod and I can see the switch move. I didn't see any fuseable links by the junction block but I can double check.

I'm wondering if that ignition switch connector is garbage now. may have to re wire it or grab another connector from a junkyard and solder it back in.

 

[dyeager535]

I would be a bit surprised if that connector has issues, but I have seen other locking connectors have the lock portion fail, so when you plug it in, the terminal in the connector pushes itself out. Should be pretty easy to test that, disconnect it, see if any of them will pull out. Not too much force on the wire, you can break the locking portion.

With the diameter of some of those wires, if me, I'd prefer not to deal with soldering them.

When you say the switch moves, does it move to the proper position? Those switches aren't simply an on/off deal. The contacts must be in the right position for current to pass through them. There are detents in it's travel, but those can be hard/impossible to feel through the key.

 

[fidelity101]

I'd rather not solder them either, that is a last resort. The lock portion on the connector is good, the connector fits snug and is rather hard to R&R. The wires themselves are secure in the connector too.

I was able to move through all of the detents with the key as well as using pliers on the rod and actuating manually.

 

[dyeager535]

If you've got 12V going in one side of the switch, but not coming out the other when it should be, I'd have to look at the switch, new or not. The switches are pretty robust, but I have seen them fail, and assuming the one you bought is aftermarket, I wouldn't rule out failure/improper manufacture out of the box.

 

[fidelity101]

If you've got 12V going in one side of the switch, but not coming out the other when it should be, I'd have to look at the switch, new or not. The switches are pretty robust, but I have seen them fail, and assuming the one you bought is aftermarket, I wouldn't rule out failure/improper manufacture out of the box.

Yeah thats all I can think of at this time, its BWD brand, I'm just going to exhange it and try another, I find it hard to believe that I would get 2 bad out of box switches.

The only other idea I have is disconnect the harness from the switch.

make a jumper from the harness connector to the switch in both B+ locations and then actuate the switch with the key.

measure the voltage at the pins that SHOULD be sending power in acc/on position.

If that shows that I'm getting key on power when I should I know its a connection issue in that connector or worse yet, the wiring going to it...

OR

with the harness disconnected just measure the at the switch the resistance across where the B+ and acc pins would go. It should read 0.0 ohms because they are connected with the key in the on position.

 

[4X4HIGH]

Does this vehicle have an alarm or did it at some point that might still be in the vehicle but "disconnected"? This is a common problem with alarm installs and their failure.

 

[fidelity101]

Does this vehicle have an alarm or did it at some point that might still be in the vehicle but "disconnected"? This is a common problem with alarm installs and their failure.

I doubt it but it doesn't hurt to check.

 

[454Sub]

Mine did something similar a while back, not sure of its official name, but there is a junction box above left of the vacuum booster. Its got 2 different (why I have no idea) nuts with wires hooked on both sides. Basically a fuse, well anyways one nut on mine was loose and it went all haywire until I happened to guesstimate that stupid little thing.

 

[neverdone]

Check your fusible links again. You said you tugged on them. They can fail electrically, but still be intact. Check voltage at both sides of the links. I've had them loose their connection inside, but look and feel OK. Hope this helps.

 

[pblaze725]

This sounds exactly like something that happened to me on the trail once.

It was a heavy gauge red wire on the firewall that goes into left side of the fuse box. It came loose. I actually have a pic of it too.



I hope it's something simple like that.

 

[fidelity101]

Mine did something similar a while back, not sure of its official name, but there is a junction box above left of the vacuum booster. Its got 2 different (why I have no idea) nuts with wires hooked on both sides. Basically a fuse, well anyways one nut on mine was loose and it went all haywire until I happened to guesstimate that stupid little thing.

Well I don't have a vacuum booster but and i checked the nut on it and it was tight
But anywhoo I "fixed" it.
Also I looked, there is no alarm on this vehicle.

I check the switch, measure both of them for resistance they had about 1.2 ohms in the on position so I know that the switch was good and should be sending power from one pin to the other.

The connector was a little corroded so I cleaned that up, no change

So after that I just removed the connector, cut the harness and made spade connectors to the switch thinking that the poor contact was the issue. I was able to get key on voltage back but no start still.

So I gave up and gave it a push button switch for starter cranking between the pins on the switch. I basically jumpered the constant power to solenoid wire with a momentary switch. fires right up.

 

[4X4HIGH]

Well I don't have a vacuum booster but and i checked the nut on it and it was tight
But anywhoo I "fixed" it.
Also I looked, there is no alarm on this vehicle.

I check the switch, measure both of them for resistance they had about 1.2 ohms in the on position so I know that the switch was good and should be sending power from one pin to the other.

The connector was a little corroded so I cleaned that up, no change

So after that I just removed the connector, cut the harness and made spade connectors to the switch thinking that the poor contact was the issue. I was able to get key on voltage back but no start still.

So I gave up and gave it a push button switch for starter cranking between the pins on the switch. I basically jumpered the constant power to solenoid wire with a momentary switch. fires right up.

Did you do this right at the wires from the ignition switch or did you run wires directly from the solenoid? If you jumpered these wires under the dash right at the switch then you're switch is bad.

 

[fidelity101]

Did you do this right at the wires from the ignition switch or did you run wires directly from the solenoid? If you jumpered these wires under the dash right at the switch then you're switch is bad.

Tried 3 switches, no change. Measured each of the switches too, they function and open and close as they should electrically, mechanical aspect is fine too, its getting the actuation needed to move the switch across the contacts.

I basically t'd in a momentary switch between the red wire and the yellow wire.

Trust me, it doesn't make any sense to me either, the switch SHOULD be the fault. But hey, at least it works now.

 

[4X4HIGH]

Tried 3 switches, no change. Measured each of the switches too, they function and open and close as they should electrically.

I basically t'd in a momentary switch between the red wire and the yellow wire.

This was under the dash at the ignition switch? If so then you may have a bad neutral safety switch which wont allow the engine to crank unless in park or neutral but doing what you have will basically bypass the switch.

 

[fidelity101]

This was under the dash at the ignition switch? If so then you may have a bad neutral safety switch which wont allow the engine to crank unless in park or neutral but doing what you have will basically bypass the switch.

Yeah the one on the steering collumn.

I jumpered the clutch switch a few days prior so I didn't have to press it all the time doing this diag.