No cranking issue, please advise 78 Birchaven 454 carb na

[Ken B]

You have been chasing this long enough.

Right now, do not worry if the voltage is 12.2 or 12.8 volts. When you turn the key the solenoid should click. If it is not doing it, then go get a
reliable meter or better yet a 12 volt automotive test light.

https://www.harborfreight.com/612v-circuit-tester-with-5-ft-lead-63603.html?_br_psugg_q=12+volt+tester

Look at the wiring diagram and start diagnosing the problem. Forget adjusting things until you prove with your meter or test light the absence or
presence of +12 volts at the various points along the circuit.

You have already determined the absence of +12 at the solenoid on the small wire. So back up from there until you find the =12 volts.

If you do not have the wiring diagram go to www.bdub.net and download the diagram for your year coach.

http://www.bdub.net/wirediagrams/

You should be able to find this problem with a test light or meter and a diagram in 30 minutes or less. Once you find the failing component we can
find out what is wrong with that component.

I am looking at the diagram right now. It says:

1. the wire on the solenoid is 12 ga. purple and goes to the neutral safety switch.

2. from the neutral safety switch the circuit then goes back on another 12 ga. purple wire goes to the ignition switch.

3. going back from the ignition switch the circuit goes on a red 12 ga. wire to a terminal on the horn relay located under the passenger side hood.
This is the same terminal where the fusible link black 16 ga. wire is located.

4. The circuit then goes through the fusible link wire to the "Battery Pick Up Junction Block" which is 4 to 6 inches away from the horn relay
terminal.

That that is the entire circuit. I do not care if you start at the "Battery Pick Up Junction Block" and work forward or start a the solenoid terminal
and work backwards. Either way should lead you to where the circuit is open / failing.

Keep in mind that you may now have more than one failure because you have been removing plugs and adjusting switches. That is why we say diagnose
first and prove the failure before trying randomly to fix something.

Ken B.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[toastedpoboy]

I adjusted the ignition switch in both directions, no change.

dash.[/quote]

 

[toastedpoboy]

Thanks. I'm going to look at pulling that switch. It's probably available at a parts store or a day away on order.

Adjusting the switch did help nor did moving the told wheel in either extreme direction.

I've adjusted the switch position on the steering column, tried to tilt the wheel and nothing so perhaps it's in the switch.

Thank you.

way towards the windshield. If it starts, then you have found the problem.
The operating link between the ignition key and the start switch at the
base of the column is out of adjustment, OR, the switch itself has failed.
Easy fix. Readjust, or replace.
Jim Hupy
Salem, Or

On Tue, May 26, 2020, 7:34 AM Carl Stouffer via Gmclist <

> Do what Chuck Boyd suggested, adjust the ignition switch on the lower
> column below the dash.
> --
> Carl Stouffer
> '75 ex Palm Beach
> Tucson, AZ.
> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive,
> Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
> Eagles,
> Solar battery charging. GMCSJ and GMCMI member
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
_______________________________________________
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[/quote]

 

[toastedpoboy]

Still nothing

Headlights do not come on. Amber parking lights do come on however.

I pulled off the ignition switch. With a small screw driver inserted into the unit to simulate the key lever rod, I probed for continuity on the
spring loaded ignition end and that seems to be working fine and switching open closed as designed. I looked for the pin connected to the purple wire
that goes to the safety switch. Switch seems fine. I also metered the jumper I made for safety switch and my jump is making a solid connection.

Where is this "fusable link" I hear about? Where does it live physically? What color, what size is it? I don't see anything that looks special going
between the horn relay and relay and anything else.

Can anyone post a photo of the fuseable link?

Yes I'm getting electricity to what appears to be the horn relay based on the thickness of several positive wires leading to it with two really small
wires of pink and green wires coming out of the rear of the relay.

Now if there was a voltage drop and if the charging voltage wasn't at or over 13 volts, wouldn't that all be negated once a secondary vehicle
connected with jumper cables with KNOWN acceptable voltage to start a similar size truck engine? That eleminates low voltage as a culprit.

If I read correctly, if the fusable link was bad, there would NOT be electricity at the horn relay? Yes? No? There is 12v there.

Thanks again for all your help.

 

[Bruce Hart]

The fusible link looks like an ordinary wire nothing out of the ordinary.
In this picture look on the left side and middle of photo. You will see a
large diameter red wire that connects to a post with other wires. There is
a small black diameter wire (16ga) that gets lost under the group of wires
to the right. This is your fusible link. It connects to a separate stud
that is part of the horn relay.

www.gmcmhphotos.com/photos/combiner-to-diode-isolator/p24994-adding-a-combiner-to-a-stock-diode-isolator.html

Fusible link
https://www.napaonline.com/en/p/BEL784695?partTypeName=Fusible+Link&keywordInput=gm+fusible+link

Horn relay
https://www.napaonline.com/en/p/ECHHR133?partTypeName=Horn+Relay&keywordInput=horn+relay

On Tue, May 26, 2020 at 1:36 PM toastedpoboy--- via Gmclist <

> Still nothing
>
> Headlights do not come on. Amber parking lights do come on however.
>
> I pulled off the ignition switch. With a small screw driver inserted into
> the unit to simulate the key lever rod, I probed for continuity on the
> spring loaded ignition end and that seems to be working fine and switching
> open closed as designed. I looked for the pin connected to the purple wire
> that goes to the safety switch. Switch seems fine. I also metered the
> jumper I made for safety switch and my jump is making a solid connection.
>
> Where is this "fusable link" I hear about? Where does it live physically?
> What color, what size is it? I don't see anything that looks special going
> between the horn relay and relay and anything else.
>
> Can anyone post a photo of the fuseable link?
>
> Yes I'm getting electricity to what appears to be the horn relay based on
> the thickness of several positive wires leading to it with two really small
> wires of pink and green wires coming out of the rear of the relay.
>
> Now if there was a voltage drop and if the charging voltage wasn't at or
> over 13 volts, wouldn't that all be negated once a secondary vehicle
> connected with jumper cables with KNOWN acceptable voltage to start a
> similar size truck engine? That eleminates low voltage as a culprit.
>
> If I read correctly, if the fusable link was bad, there would NOT be
> electricity at the horn relay? Yes? No? There is 12v there.
>
> Thanks again for all your help.
>
>
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class

 

[toastedpoboy]

Thank you for the links to the parts in question. That's a big help and I appreciate it!

Horn relay
https://www.napaonline.com/en/p/ECHHR133?partTypeName=Horn+Relay&keywordInput=horn+relay

On Tue, May 26, 2020 at 1:36 PM toastedpoboy--- via Gmclist <

> Still nothing
>
> Headlights do not come on. Amber parking lights do come on however.
>
> I pulled off the ignition switch. With a small screw driver inserted into
> the unit to simulate the key lever rod, I probed for continuity on the
> spring loaded ignition end and that seems to be working fine and switching
> open closed as designed. I looked for the pin connected to the purple wire
> that goes to the safety switch. Switch seems fine. I also metered the
> jumper I made for safety switch and my jump is making a solid connection.
>
> Where is this "fusable link" I hear about? Where does it live physically?
> What color, what size is it? I don't see anything that looks special going
> between the horn relay and relay and anything else.
>
> Can anyone post a photo of the fuseable link?
>
> Yes I'm getting electricity to what appears to be the horn relay based on
> the thickness of several positive wires leading to it with two really small
> wires of pink and green wires coming out of the rear of the relay.
>
> Now if there was a voltage drop and if the charging voltage wasn't at or
> over 13 volts, wouldn't that all be negated once a secondary vehicle
> connected with jumper cables with KNOWN acceptable voltage to start a
> similar size truck engine? That eleminates low voltage as a culprit.
>
> If I read correctly, if the fusable link was bad, there would NOT be
> electricity at the horn relay? Yes? No? There is 12v there.
>
> Thanks again for all your help.
>
>
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

[/quote]

 

[charles boyd]

Sir, maybe try flipping the dimmer switch and see if that does any stuff for the headlights. The purple wire you have jumped on the neutral safety
switch is the wire coming from the ignition switch and goes to starter. Should be 12v in start position and activate starter. Trace the wires.
--
C. Boyd
76 Crestmont
East Tennessee

 

[RF_Burns]

I believe you said the parking lights do work, so power is getting through the Fusible Link. Have someone watch the parking lights and then pull ON
the headlights... do the parking lights then go OFF or stay ON. They should stay ON... Otherwise you have a high resistance in the circuit feeding
power from the battery. This could indicate a bad Fusible Link or it could be elsewhere.

Do the same thing again with the starter, watch the parking lights then try the starter, the parking lights should stay ON.

You may still have an issue in the starter circuit, but this eliminates bad battery, fusible link, poor connection to the switch etc.

FYI, the starter solenoid takes a lot of power to pull in, on the order of 30 Amps, which is why the purple wire feeding it is 12ga.

I agree with Ken Burton. Get a meter or a test light and download the wiring diagram and start troubleshooting. Start at the battery and follow the
power until it disappears.
--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

 

[toastedpoboy]

Thanks for all the wunnerful ideas!

I metered 12v through the ignition switch and through the safety switch and through my safety switch bypass. When they key is turned momentarily,
there is 12v out the purple wire down the back of the steering column, yet no voltage to the starter wire on the solenoid. Which is not purple at the
starter. It's old and faded and I haven't got a positive color I'd yet. It just doesn't look purple.

I read there is nothing between the safety switch and the starter but a purple #12 wire connecting them. So there should be voltage at the solenoid
pulse momentarily in unison with the turn of the key the way the switches meter out correctly.

There is however a "CY" box in the middle of the pure wire between the safety switch and the starter. What is a "CY" in that location on the wire
diagram? Could that be where the electrical flow is broken? CY=_?

As time permits, I'll keep plugging away. I appreciate your suggestions.

Thanks again!

voltage.

There is a fusible like that all power to the chassis goes through... including lights and ignition (starter solenoid too). It looks like about a #12
wire going from the chassis Battery Terminal Block on the aluminum plate to the large terminal on the horn relay to the upper right of the terminal
block.

Check that you have power at the horn relay terminal. If you have no voltage there, but you have voltage at the Battery Terminal Block, then the
fusible link wire is open. This is a special fuse wire, so don't replace it with regular wire. Replacements are available at the auto store. Wiring
diagram shows it as being a #16 fusible link wire.

[/quote]