Trying to convert

[Setter]

Hello, just bought a 1990 chevy 6.2 L diesel engine short bus. Put in new battery and starter but engine still will not turn over. There’s disconnected wires everywhere so is there possibly another wire somewhere that’s causing it not to start. Or what else could be wrong?

[PoppaSmurff]

You need to verify the starter exciter wire (small one on the starter solenoid) has power when turning ignition to start.

[Setter]

Absolutely will. Thank you!

[SDJunkMan]

Might be a safety switch such as a nuteral safety thats interrupting the current to the starter.

[Setter]

Ok will check that out. Thanks for the insight!

[HamSkoolie]

Originally Posted by Setter

Hello, just bought a 1990 chevy 6.2 L diesel engine short bus. Put in new battery and starter but engine still will not turn over. There’s disconnected wires everywhere so is there possibly another wire somewhere that’s causing it not to start. Or what else could be wrong?

That's the same engine that was in the military "CUCV" trucks. Are you sure it only requires one battery? In the CUCV it was a 2 battery system wired to 24 volts with a (crappy) step down to the 12 volt vehicle system. This was done just so that the jump starting was compatible with all other motor transport systems. I'm not sure if civillian version shad one or two batteries but they were wired 12 volts. Many diesels have two batteries because of the power requirements when starting in cold weather.


Have you checked for voltage to the starter?
Attempted to jumper the starter?
At the solenoid using vehicle power?

Bypasses start and safety switch circuitry.

With a known good power source?


Also, (not related to not turn over) there should be a heavy gauge pink wire at the top center front of the engine or that area.... it is the fuel solenoid. It won't prevent starter engagement but it will prevent fuel. I mention it because you said there were a lot of wires disconnected. If you get it turning over and it won't start it's going to be a fuel pump or that solenoid.

[Setter]

Thank you so much for that wealth of information. Will check all of those out over the weekend hopefully. As I am really excited to get this “Beast” on the road.

[SDJunkMan]

Originally Posted by HamSkoolie

That's the same engine that was in the military "CUCV" trucks. Are you sure it only requires one battery? In the CUCV it was a 2 battery system wired to 24 volts with a (crappy) step down to the 12 volt vehicle system.

The CUCV had 24volts to power radios and other military equipment. It was built especially for the military and the electrical system is totally different then civilian diesels. Most 6.2 and 6.5 diesels do run dual batteries to give them more cranking power, but it is 12 volts, not 24. The CUCV did not have a "step down" to 12 volts, it just ran 12 volts from one battery and 24 volts from the pair ( it ran 2 12 volt alternators, each powering one battery). The 12 volt wiring is the same as a civilian GM truck with the execption ovf the 24 volt starter and glow plug system.

[Setter]

Thank you for your help. I plan to work on it some over the weekend. I will check out everything youve mentioned. Thank you so much.

[Delos356]

Originally Posted by Setter

Hello, just bought a 1990 chevy 6.2 L diesel engine short bus. Put in new battery and starter but engine still will not turn over. There’s disconnected wires everywhere so is there possibly another wire somewhere that’s causing it not to start. Or what else could be wrong?

Hey man- this is a pretty common problem for busses after they've had their demo started. You start pulling out the "unnecessary" harnesses and stuff from the back of the bus and accidently trip the Interlock system. If you have checked the battery and starter and the obvious stuff, EXPESCIALLY if your bus used to start just fine, this is likely the issue. Basically your bus thinks you have an emergency door open, or the wheel chair lift down/out or something like that. Depending on the complexity of your bus, you may be able to find the relay responsible and trick it, buy providing 12v to the correct terminal. If your system is pretty complex (my daughters 04 shuttle was a series of relays) you will probably need to bypass the system entirely. You can search "vandelock" or "Interlock" and find tons of the threads on the various ways people have gotten around it. If you can provide pics of your breaker or relay panel we may be able to help?

Good luck!

[HamSkoolie]

Originally Posted by SDJunkMan

The CUCV had 24volts to power radios and other military equipment. It was built especially for the military and the electrical system is totally different then civilian diesels. Most 6.2 and 6.5 diesels do run dual batteries to give them more cranking power, but it is 12 volts, not 24. The CUCV did not have a "step down" to 12 volts, it just ran 12 volts from one battery and 24 volts from the pair ( it ran 2 12 volt alternators, each powering one battery). The 12 volt wiring is the same as a civilian GM truck with the execption ovf the 24 volt starter and glow plug system.

I was a 3521 motor transport mechanic in the Marine Corps. I went from mechanic to maintenance management officer of an entire motor pool with over 120 prime movers plus all the trailers, tools, mechanics, etc.
The GM CUCV's were commercial civilian heavy duty pickup trucks MODIFIED for military "administrative" and support roles, not combat. They were 5/4 ton (1 1/4 ton) capacity suspensions except the Blazer.
Under the hood was 24 volts except for some stupid reason the glow plug system which was 12 volts. Everything else was 12 volts as was all lighting, instrumentation, etc. There were two massive resistors on the passenger side firewall to drop the 24 volt system (required in order to be NATO "idiot proof" jumper cable compatible) to drop the 24 to 12. When one failed, the 12 volt glow plugs swelled up, expanded, and often broke when being removed thus necessitating removal of the aluminum intake manifold and the affected exhaust manifold and head. A REAL PAIN IN THE ASS.

[Setter]

Thank you so much