Engine will not crank over? No starter operation

Hi,

I attached the starting system wiring schematic below so that you have a reference.

First, are all the fuses I highlighted good? If they are and the relay is new, remove the relay. The pins the relay push into need checked. First, the ignition A fuse provides 12v at all times, so one of the pins will have B+. Confirm that first. If you look at the relay itself, there will be 4 different numbers, 85, 86, 87, and 30. Power from the ignition A fuse will be at either pin 87 or 30.

Next, is the primary side of the relay. I believe that is what you are questioning. Those will be pins 85 and 86. With the key in the start position, one of the two will receive B+ via the ignition E fuse in the under-hood fuse box. Have a helper hold the key in the start position while you determine which pin it is. Then, the opposite pin of the primary side needs to provide a ground path to complete the circuit and actuate the relay.

So, do this. Connect your test lamp alligator clip to the positive side of the battery. Probe the pin in the box which is the opposite of the B+. Have a helper turn the key to the start position. The lamp should turn on.

Let me know what you find or if you have other questions.

Take care,

joe

Hi,

Nice truck! As far as the numbers on the relay, the manufacturers determine them. However, they will always be based on the primary side (85 and 86) and the secondary side (87 and 30). If pin 30 has power, that means pin 87 goes to the starter motor. That happens when the relay is actuated. That is the only time when pin (87) will have power through it.

Everything you mentioned sounds like it is working. Pin 87 shouldn't have power but rather it should send power to the starter motor when the relay is actuated. That power is what comes from pin 30.

First, don't jump 85 and 87. That could cause other issues.

Next, will the starter engage if you jump 87 and 30? Also, you indicated pin 86 is ground. That pin should only be ground when the key is in the start position. Is that correct?

If you can't get the starter to engage jumping 30 and 87 but you can jumping 85 and 87, we have an issue at the box or the relay you have is no good. Everything other you mentioned is working.

Let me know.

Joe

Hi,

Once the engine starts, power is removed from the primary which disengages the relay. That eliminates power to the starter by releasing the relay switch. Are you saying the starter stays engaged with the relay installed?

Everything you showed in the video appears to be working correctly. When you install the relay, what happens? If it is nothing, switch that relay with a different one having the same part number. It should work.

Let me know.

Joe

Hi,

The primary side of the relay (pins 85 and 86) is what triggers the secondary side to send power via pin 87.

You have power available to one of the two pins on the primary side. When you turn the key to the start position, power is sent through the 10-amp crank fuse to the PCM crank signal which in turn provides a ground path via the PCM starter enable relay. That completes the primary circuit in the relay.

Once that happens, it energizes an electromagnet on the primary side which attracts the internal relay switch causing the circuit between 87 and 30 to be completed and power sent to the starter motor.

I attached what you mentioned before. Based on that information, it should work.

Let me know if this makes any sense. LOL Also, read through this link. It will likely be easier to understand.

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Take care,

Joe

See pic below.

Hi,

Thank you for the update and you are very welcome. I'm glad to know you got it running again. You did a great job because electrical issues are always a nightmare. LOL

Take care of yourself and feel free to come back anytime in the future.

Joe