90 c2500 won’t start

[Kmoody528]

My truck (5.7 tbi 5 speed) died at the gas station when I tried to restart the starter sounded very weak like it had low voltage then stopped all together
I tested the battery 12.4 volts
Bypassed the clutch safety switch still nothing
Had the starter tested its good
I got it home by popping the clutch to start and it ran just fine 15 miles home
Now trying to restart I just hear an electrical click not a starter click
It does throw a knock sensor code when I drive

 

[Schurkey]

12.4 volts is way undercharged. A fully-charged battery will show 12.6--12.7 volts. Slow-charge battery, have battery load-tested. Does the alternator work properly? Why is the battery voltage so low?

HOW was the starter tested?

Did you clean the battery cable connections?

Did you check to see if the engine is locked-up? Moderate chance the alternator is seized.

You'll want to attend to the knock sensor code, but that's not why it doesn't start.

 

[Kmoody528]

I’ll throw the battery on the charger
The starter was tested at autozone they hooked it up on the solenoid like it gets wired on the truck
All connections are clean
I don’t believe the engine is locked up as it drove home just fine when I popped the clutch and the volt meter in the cluster shows charging

 

[DeCaff2007]

I’ll throw the battery on the charger
The starter was tested at autozone they hooked it up on the solenoid like it gets wired on the truck
All connections are clean
I don’t believe the engine is locked up as it drove home just fine when I popped the clutch and the volt meter in the cluster shows charging

The voltmeter in the cluster is not a reliable indicator of what your alternator is doing. Get a decent multi-meter and learn how to use it if you don't already know how. Test the voltage coming out of the alternator (should be 13.8V, give or take a few tenths of a volt) and then check for continuity between the alternator and positive battery terminal. Your multimeter should have an audible beep if the connection is good.

Let's start with that.

 

[Kmoody528]

I have continuity however I won’t be able to test the alternator if It’s not running correct? If the battery charges and I can start I’ll test otherwise should I have the parts store test it?

 

[DeCaff2007]

If that's an option for you, you should absolutely have the parts store test it. I don't know what the parts stores are in SoCal, but in NEPA we either get AutoZone or Advance Auto. Sometimes we even get a NAPA, if we are lucky.

Personally, I used to work for AutoZone so I'd take it there, but I digress.

 

[Kmoody528]

Alright so I charged the battery it reads 12.7 try to start same thing just clicking sound not the starter throwing the armature sounds like a relay clicking but this truck doesn’t have a relay just the solenoid when I had autozone test it they connected through the solenoid and it worked so any more ideas would be appreciated

 

[Erik the Awful]

All connections are clean

charged the battery it reads 12.7 try to start same thing just clicking sound not the starter throwing the armature sounds like a relay clicking

You have a connection problem somewhere. Side post or top post? If you have a side post, they can be finicky. Even if everything looks clean, get a wire brush and scuff up all the mating surfaces. It's stupid, but sometimes clean metal gets a layer of poorly conducting oxidation on the surface, and it looks great while limiting your current.

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[Kmoody528]

Yeah they’re side post I’ll clean them good tomorrow hopefully it helps

 

[Frank Enstein]

If that fixes it great but I have one more test for you;

Put a volt meter on the positive terminal of the battery and put the other lead on the large terminal on the starter. Have a helper crank the engine (pull the fuel pump fuse so it doesn't start).
Read the voltage on the meter. It should read less than .2 volts.

Do the same test on the negative post of the battery and the other lead on the starter case. It should be .2volts or less as well.

The battery cables were undersized from the factory and the negative cable is best on one of the starter mounting bolts.

The factory puts the ground cable elsewhere because it is cheaper to use a shorter cable and it was easier and faster on the assembly line to put it somewhere else, not because it was better.
Check out the Big 3 wiring threads for more info on this.