Electrical problem

[MrMarty51]

Now my truck will only turn over when battery is hooked up to a power source engine acts as getting no spark

So, what You are saying is that, the starter will crank the engine over but, only if it is hooked to a charger ??? if so then, let the charger do its thing for like at least overnight, then see how it cranks over, without the charger and, if it does crank over without the charger, does it then get spark.
Might be that the battery is so low that, while cranking on the starter, it draws enough voltage that it robs from the ignition.

 

[chengny]

Or, there may be a dead short to ground in the main positive lead. That is draining the battery.

If you have a brand new, fully charged battery, it should crank the starter. There should be no reason to have to jump it (or use a heavy duty charger as the case may be).

The starter does not appear to be the issue - because it cranks the engine when additional power is available.

Assuming the extra power is a pair of jumper cables, and they are attached in the usual manner (i.e. to the battery's terminals) you can rule out a broken main lead to the starter.

But the insulation on that main lead could be worn off - allowing the copper wire to touch a ground point. This will cause at least two problems:

1. It can kill (drain down to 0 volts) a battery in no time - even a brand new one.

2. As a corallary to MrMarty's suggestion: a short to ground can shunt enough power away from the ignition system that the coil does not see the required 10 volts it needs to produce a spark. This applies even if you use jumper cables to create a back up power supply (or even if you put in another brand new battery).

A starter will crank on pretty low voltage but the ignition system needs a minimum of 10 volts. There may be power available at the battery and starter but it just never gets to the coil.

Another possibility - if the negative clamp of jumper cables is attached to the engine block (lots of people do this) and the starter cranks, but does not crank when hooked up to the negative post - look closely at the negative battery cable.

 

[89Suburban]

Could be a dud battery too.


Posted From Hell

 

[MrMarty51]

Could be a dud battery too.


Posted From Hell

That seems to happen way too musch.

 

[Chevyboy12]

I got the battery tested its fine , but ya when I put the jumper ground to frame it will turn over, it used to start but I spliced done wire where the fusable links are and it sparked up to the two wires that are to the left of the brake booster and now it won't start ill double check the fuses but don't think I blew one , are any of the two relays connected to starting ?

 

[chengny]

but ya when I put the jumper ground to frame it will turn over,


That's what I was talking about when I mentioned this:

Another possibility - if the negative clamp of jumper cables is attached to the engine block (lots of people do this) and the starter cranks, but does not crank when hooked up to the negative post - look closely at the negative battery cable.

When I say "look closely", I mean test/replace it.

If the starter cranks when the negative jumper cable is clamped to the engine block (and does not crank when attached to the negative battery post) - your battery grounding cable is probably NFG.

 

[Chevyboy12]

Hey guys replaced the battery wires + and - works fine now , only problem is that it will turn over strong just wont start Almost like it won't get spark

 

[89Suburban]

pull a spark plug wire off of one of the spark plugs and connect it to a spare spark plug, ground the plug to the motor and crank the engine and see if there is spark.

 

[77 K20]

Did they start using those ignition modules in the distributor in 1982? I think they did. If it went out you won't get spark and it will not start.


A mechanic back in high school showed me something involving the negative cable. He had a meter with him and went from the alternator bracket to the frame measuring the resistance in ohms. It was something like 500 ohms if I remember right. He said the puny little ground strap that they use doesn't last forever. He had a extra section of black battery cable there with large ring lugs on both ends. Ran that from the alternator bracket to the frame down below (it even had a hole already in it).
This made my headlights/off road lights brighter and even got rid of some stereo whine noise I had. Basically it just makes sure the whole truck is grounded better.

 

[82chevy350]

I bet its the ignition module test for power at the coil!

 

[Chevyboy12]

Just replaced ignition coil , still same thing

 

[Chevyboy12]

Also my truck has the decal electronic spark control so it might have the module

 

[89Suburban]

Courtesy of the man with the plan - Chengy

http://www.gmsquarebody.com/forum/showthread.php?p=173910&highlight=ignition#post173910

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imagur

 

[chengny]

What does your spark look like?

This is a basic test but can tell you a lot. Pull a plug and stick it back into the boot. Ground the plug to the engine block and have an assistant crank the starter.

Note the condition of the spark. It should easily jump across the electrodes. It must be a bright blue arc and emit an audible "snap" sound.

If it is a feeble yellow trickle and makes no sound the problem is with the ignition system.

Also watch closely when the assistant releases the key from start to the run position - does the spark suddenly become more intense? It may take several crank ups and releases before you get lucky and see what the spark looks like when the starter is released.

My point is this- if the spark improves dramatically when the starter circuit is no longer drawing power fron the battery, that could be the problem.

If the starter motor or the solenoid are shorted internally it can cause your overall system voltage to drop below 10.5 volts. That is the minumum required by the primary to produce the high voltage required in the secondary.

Check primary voltage at the pink wire with a meter while cranking the starter. Don't go by just static condtions (i.e with the key only in the run position) - you'll almost always see 12 volts.

To do a valid test of primary voltage, the starter has to be drawing power.

Without at least 10 volts at the pink wire during crank, you wont get a spark out of the coil that is strong enough to fire the fuel/air mixture.

Another way to check the starter motor as a voltage drain is to supply the coil with an outside source of power. Pull the pink wire from the distributor and in it's place, use a battery charger (or another/additional battery) to supply 12 volts to the coil primary.

Everything will act as normal - the only difference is that the ignition system will now have an exclusive voltage supply that is unaffected by the heavy draw created by the starter motor.

Even if the starter is pulling the entire system down while cranking, the coil won't see the voltage drop and should produce a good blue spark.

 

[Chevyboy12]

Thanks for all the advice but I'm done just bout everything , all my fuses are good replaced wires , distributor cap , rotory piece , coil , modulator , battery still no spark I don't know what else to do