Hey everyone. Maybe someones had this issue before and can give me some advice i have an 88 f350. Sat for over a year. Went to go start her up. Turned the keyto the on position. No lights nothing. Turned the key to the run position. All the lights come on but no crank. I have replaced the lock cylinder amd the ignition switch. When testing the wires that go in and out of the ign. Switch. The thicker gauge wires all test good. Out of the 4 thinner wires. 2 lit up my test light very dimly. The other 2 nothing at all. Key was in run position during testing. Ive replaced the switch twice and nothing same issue. I also replaced the neutral safety switch. That didnt help the issue either. What am i missing, any advice on what to check next? One thing that did give me hope at one point was before i replaced the neutral safety switch i was testing the wires to it. Must have touched 2 together or something because the motor started to crank. I assumed the switch or wireing was back so i replaced it. Only to find out im having the same issue. Any help is greatly appreciated

 

Have you tried jumping the starter solenoid or/and the starter itself? Can you crank and start the vehicle that way?

 

With the key in the run position i can jump start the solinoid. I tested the top terminal and wire going to it. There is no power to them when the key is turned.

 

Sounds to me like it’s an issue in the wires themselves. Did you check continuity of the wires? Specifically to the starter solenoid that you said didn’t have power

Im not familiar with the 7.3 solenoids. Is the top post to the ignition switch?

 

I pulled this diagram from google. You know that your switches and your solenoid are good so you just need to figure out why there isn’t power getting to your solenoid. Check your continuity through all these connections

 

Im starting to get into all the individual wires. I need an accurate wiring diagram to tell me what goes to what. I havnt been able to find one with the correct color codes. I think i said this already but i tested the wires going to and coming from the ignition switch.10 wires total. 6 (thicker wires) all have power going to them. Then theres 2 wires that had a very week signal. And 2 with nothing at all. Ive been at this for about a week now. Im not an electrition by any means but this doesnt make sense to me. Shouldnt i have power to all of the wires from the ignition switch. The ignition switch on this truck is not by the key its further down the steering column behind/ underneath the dash

 

I’m by no means an electrical guru either. But I have chased out my fair share of electrical issues in old trucks, usually without diagrams.

The four wires that are either weak or dead, are they all on the hot side of the switch?

 

here is the wiring for your 88 F250 7.3 starter circuit

 

What do you mean hot side of the switch? Where the power comes in? The weak or dead wires are on the opposite side of the switch compared to the two yellow power wires

 

If your ignition switch is down by the dash and not the column then it's been moved. Unfortunately, that's going to make it a bit more difficult to troubleshoot.

Instead of testing for continuity use your multimeter to test for 12V. Don't use a trouble light because it could be illuminated with >12V and you would never know the difference. You mentioned that you have 12V going into your ignition switch on 8 wires (6 of which are heavier gauge). The 2 other wires of the 10 should only have 12V depending on the key position (probably ACCessory/RUN and START). With the key in the START position you should have 12V at the Neutral Safety switch all the way to the starter relay. Once you test this let us know what you find.

 

That is the part where the OP lost me as he said he only has two wires going into the switch and ten coming out. The four wires that are not getting power are on the out side. If the wires in are hot and if with the correct ignition position the out wires are not getting power. Then it has to be a switch problem. But Op already replaced the switch twice correct?

 

yeah, and if you have had the Tumbler assy out and the ignition switch itself off for replacement then getting that Plastic Gear Rack right can sometimes be problematic

 

Which explains why he is getting no lights when turned on, lights at start but no crank. As if the key is just misaligned

 

the older ones probably not as bad as the 90's racks but still have to be right.... may not be the issue but Just Saying

 

Have had this trouble before, simple enough fix by pulling the ignition lock cylinder, realigning the flat gear in there and then properly adjusting the ignition switch itself.