84 720 will not turn over, I’m lost

[CharlieMurphy]

What’s up guys, new to the forum.  My 720 will not turn over.  I have swapped the battery, starter and ignition relay.  Starting to get bummed out...can someone please help me out.  When I turn the key, I hear the fuel pump and that’s it.

[captain720]

Do you have a DMM? (Digital voltmetter)

 

If no then get one, you won't regret it. Once you have one check for power everywhere! Check the battery, check the starter when you are trying to start it, check the ignition switch, check your fusible links (seriously check those, I have had this exact same scenario from bad fusible links and or loose terminal connections) 

[datzenmike]

There are at least 3 fusible links on the 720. One for the headlights and lighting, one for clock, brake lights, interior lights, horn... things you don't need the ignition ON for and then ther is one to the ignition switch tha routes to the fuse box, ignition and tells the starter to spin.

 

1/ If your headlamps work that is fine

2/ If you horn or 4 ways work then it's fine

3/ If the wipers, radio, heater do not work with the key on then I suspect that fusible link. Go to 5/

4/ If wipers and heater do work then maybe the start signal from the ignition switch to the starter is bad.

5/ All links are connected to the positive battery cable. There are 2 Green and a Black wire. One Green is by itself and the other is paired with the Black. This Green one powers the ignition switch. If it is blown it may appear melted or burnt. If you flex it it may have burnt crumbly wires inside.

 

If they all have power on the end farthest from the battery it can be assumed (for now)  that the fusible links are OK.

[CharlieMurphy]

I narrowed it down to the starter is not getting the electrical signal to engage.   Pulled the fuel pump relay where it was clicking, and just started playing electrician.  Are the 2 green wires connected together from the terminal but split when connecting with the black?

[datzenmike]

The start signal comes from the ignition switch and is a black wire. Don't know about any Green wires.

[banzai510(hainz)]

put truck in nuetral.

Take a wire say 16 ga. put on + battery then put it the starter selioniod tab and see if it cranks. or at least clicks

I hope the battery cables are good and not cracked.