No Power at All

[smoke'sDat's]

Good Morning Ratsun, I have a 78' 620 truck and a few months back I decided to remove and fix the cracks on my dash. After I had filled in the cracks and then decided to paint it. Before I installed the dash I then decided to mess with the wires and do a wire tuck. I completely pulled out the entire wire harness because from inside of the cab and cleaned it and re-taped it. I spend all day in the garage putting everything back together and connecting all the switches. After I was done I connected the battery and noticed that there was no power at all anywhere except for the battery. I then checked all the connections and everything was connected where it should be. The only thing I did changed was the fuselink. Can anyone tell me if I'm doing something wrong or all feed back will be more than welcome. Thank you.

 

Before

 

 

After

[Draker]

The best thing would be find a specific circuit that isn't working and then find the wiring diagram and trace it back to the power source. If you do that, then you will find out why it's not working.

[datzenmike]

The only thing I did changed was the fuselink.

 

I would start there.

[smoke'sDat's]

Thanks I will start with that first. The other thing that does have power is the starter motor cause I checked it with a light tester. This is the first time I've messed around with electrical. I did go over the Ignition System Circuit Diagram and all the wires are connected where it should be. One question, is there anyway to be able to check the transistor ignition unit with a ohm meter would this also be part of the problem ? I thought it was gonna be alot easier to do a wire tuck .

[datzenmike]

There's nothing to check on the dizzy.

 

The positive cable on the battery goes directly to the starter terminal so it will always have power. You need good fusible links to supply power to the ignition and the fuse box.

[smoke'sDat's]

Thanks

[DanielC]

You said you had power at the starter, and the battery, Start with this. Make sure the truck is in neutral. Connect a wire to the small terminal on the starter, and touch the wire to battery positive. Does the engine crank? It should. If not, fix that. Bad battery cables is a possible cause.

 

The engine cranks, that is good.

Take a test light, and connect the ground lead on the test light to body sheet metal. You may have to scrape off some paint, or find a clean bolt to attach it to. Touch the positive battery terminal with the test light probe. The light could light. If it does, you know the cab sheet metal is grounded.

 

Check for power on the fuseable link. Check both ends. check in the wire beyond the fuseable link by pushing the point of the test light through the insulation of the wire, after the connection to the fuseable link.

 

I believe this wire goes to the fuse box. You should have power there. If not, follow the wire from the fuseable link in to the cab, to where the fuse box is located. If there are any connectors in the wire, check for power on both sides of the connector by pushing the probe of the test light into the wire. Just keep following the wire until you reach the fuse box. Then check for power on both ends of each fuse. Do not trust a glass fuse looking good. Check for power on each end.

[smoke'sDat's]

Just wanted to thank each and everyone that tried to solve my problem and gave me feedback. Just to let you guys know that I did Find the problem and it was the fusible link. It did not carry the power inside the cab. Replaced it and now I have power everywhere. The only thing know is that the engine turns and sounds it wants to turn on but it don't. Any other feedback please. Thanks

[ggzilla]

Glad to hear the progress.

 

So now it cranks, but won't start? Get out your voltmeter or test light, and verify if there is power at the Ballast Resistor with Key On, Engine Off.

[smoke'sDat's]

Thanks, where would the Ballast Resistor be located ?

[ggzilla]

Under the hood. By the coil.

 

If you don't have a service manual, buy one. But only if your car is worth the $20 the manual cost. It shows where parts are and how to inspect/adjust them.

[q-tip]

'78 may not have a ballast ressistor, i think that was the first year of ei in the 620, would be the one with the big ignition controll box under the dash. check power on the positive side of the coil with the key on.

[ggzilla]

That's right, 1978 doesn't use ballast resistor. EI prior to 1978 (e.g. California models with EI) still used a resistor.

 

For 1978, make sure the coil has 12V with Key On, engine off.