1973 c20. . .Starting Difficulties

[A_Stranger]

So to start. I am not really a gear head. I am not afraid of turning a tool, but what I know is pretty limited to what I have tackled previously. I am sort of up against a wall on this one and was sort of hoping for some direction.

So I was supposed to make a drive from Phoenix to Bakersfield two weeks ago. The night previous, I went to fill up and it stalled at the light at the intersections a block from where I was staying and refused to start. The next day it started. It then refused to start again and would try to do so an additional couple times while I was trying to determine the precise nature of the problem but the third time it started after the initial failure would be its last and it has been dead ever since.

I replaced the starter and solenoid first since they seemed the most likely culprit but it improved nothing. Then the battery and cables upon advice from a friend. I am embarrassed to admit it, but it took me a entire week to mucking about to realize it isn't simply a starter issue, additionally I cannot turn on my headlights or even get a squeak out of my horn. So I suspect the issue isn't with the starting system.

From what I have perused online, it seems very likely I need to replace the electronic spark control. It had been running rather rough for a week before this all happened and all of the symptoms fit perfectly, I hadn't given that much weight since it had been sitting all summer and I expected it to be a little rough until I adjusted the idle and maybe gave it a tune up. However I cannot find any information regarding whether or not my year of truck even has such a thing as an electronic spark control and additionally where it would be located. Every reference I find to it concerns models from the 80s.

Also, it may bear mentioning my particular engine is a target master 350, a small block V6 I believe. Now you all know everything I know. Any help would be greatly appreciated. Specifically, information regarding the ESC, which may also be known as an ECM.

 

[1987 GMC Jimmy]

Okay, a lot to unpack here. The 350 is a V8, and the 262/4.3 is the truck V6, but that one’s ‘85 or newer. Your truck would have originally come with a point style ignition system, and high energy ignition (HEI) is what came later and some older trucks have been retrofitted. Unless someone swapped in the complete harness from an 81-86 truck, which is highly unlikely, there are no ESC or ECM. The first thing to do is post up a comprehensive picture of your engine bay and, more specifically, the distributor. There are diagnostics/parts replacement recommendations/maintenance procedures that are specific to each system.

Also, are your electrical gremlins there when the truck is working properly? If they are, that’s almost certainly a separate issue unless there’s a missing ground, or two, or three. That’s one of the first things I’d check. I’ll attach a diagram. Even if all three are there, poor contact on a ground is the same as not having one. You mentioned replacing the cables, but are the terminals new, as well? Those can cause random issues. You mentioned a tune up. What did that consist of? When you say it won’t start, do you mean everything’s dead, or it’ll just crank without so much as a cough or sputter? It sounds like possibly both have happened, but I’m not sure.

It sounds like it’s going to be something pretty general in the electrical system or a spark issue, but more info is needed.

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[A_Stranger]

Well, I may be an idiot, but the sticker on the engine says 350, but when you count the cylinders there are only three on each side. I didn't know enough for that to strike me as odd, but maybe that merits a closer look.

As for the issues being separate, that may well be the case. I never use the horn, but the headlights worked just fine until everything stopped working. I don't use a smart phone, I just don't use my mobile often, so I will grab my buddy's phone to get some decent pictures and throw them up in a couple hours when he stops by. Thank you so much.

 

[A_Stranger]

Alright so you were right, it is a v8. I just can't count. Two, initially when it wouldn't start there would be the gentle click of the solenoid, I assume, trying to engage the starter. Now it is complete silence. I have not given it a tune up yet, my garage and tools are in California, my plan was to do so upon arrival. All grounds are in place, and I replaced the terminals along with the battery and cables. I am not a big fan of leaving things to doubt. If you need further information or more specific pictures, I am your service, simply tell me what I need to do, just remember I am a strict amateur, just explain things to me as you would a very clever dog or a very dull child, please.

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[Snoots]

Get a Flat Head screwdriver (medium head)
See that little screw on the distributor cap (left side)?
Turn it 180 degrees ccw.
Do the same to the screw on the other side.
Lift the distributor cap.
DO NOT REMOVE ANY SPARK PLUG WIRES!!!
Look inside the cap at the connectors.
Are they white and chalky? If so go and buy a new cap AND rotor AND points.

Once you get that done, check back in.

 

[Charlie]

 

[1987 GMC Jimmy]

Yep, you have a points ignition, which is what it came with. I’d make sure the battery’s not dead first of all. I can’t tell you how many times I’ve assumed the most simple thing was working properly, and it wasn’t. There could be a parisitic draw, an alternator undervolt condition, or just a dead alternator. At the most basic, you’ll need a test lamp. You’re much better off with a voltmeter of some kind, though. Second, I’d make sure you don’t have a burned fusible link. If this is the case, I’d trace your wires leaving the positive of the battery and see if everything’s still there. @Charlie @73c20jim or @gmachinz would know if there was anything weird in the wiring harness that could be holding you back. The first thing is going to be restoring power, and then once that’s done, you can resolve your poor running, which I’m inclined to agree the aforementioned advice will be your first stop.

 

[A_Stranger]

I have a mulitmeter, battery is solid. And the solenoid reads the same voltage. Let me see about the fusible link

 

[73c20jim]

Cody, I also have a 1973 C20 with crate motor.

Just throwing a few things out there.

When it won't start does it go one umph to the starter and dead? Or does it crank freely.?

That could be bad corroded battery terminals and/or poor connection between battery and starter cables.

But you said you have a new battery, starter and battery cables.

That symptom means you got 12V but don't get enough amperage to starter. Recheck all connections at starter and battery, and negative side battery to alternator GROUND..

Even though new, is the battery fully charged?

When was the last time it started before the current problems. Did you do ANYTHING to the truck just before the problem started??

What is the voltage of the battery? Then what is the voltage while it is cranking? I am assuming that it cranks.

Disconnect wire to alternator.
Disconnect wire from left side of junction box.
This will disconnect ALL power to the truck. It should isolate the starting system.

IMMOBILIZE truck from moving.

This is the way we would start a car without the key in an "emergency" back in the day.

Run wire from 12V+ from battery to points side of coil. NOTE: The points are designed to run on 6V+. Don't leave the wire on too long as it might burn out the points. I don't think 10-15 minutes should hurt it. Since ALL other electrical circuits are OFF if you remove the wire the engine will stall.

You should be able to use a LONG screwdriver to reach non handle side of screwdriver to make contact between the LARGE bolt and the S lug on the solenoid. It might spark but it should start.

If it starts you have then tested the starter and run systems. Those vehicles without steering wheel locks could the be driven away.

 

[1979k10]

I'll be in Bakersfield on the 23 & 24 this month. If you still have the problem by then, I could swing by for an hour or so and help you with a voltmeter.

 

[Frankenchevy]

Since you’ve lost all power, this leads me to believe you’ve likely lost power to your main junction, which I’ve circled in red. Check continuity from those terminals to your battery positive. If that checks out, check voltage from the terminals to the negative side of the battery. If that checks out, take the pointy bits of your multimeter and stab on either side of anything that looks like what I’ve circled in yellow. Those are fusable links and fuses; they should have continuity from one side to the other.

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Check back with your findings.