Thread: Ignition Woes - Low Starter Signal Voltage

I'm starting to get really frustrated with this no start issue. I go to start the car and all I get is a single click from the starter solenoid. I can jump the starter signal right from the battery and it will start up and run fine so I know it has something to do with the ignition circuit. This issue seems to be rather intermittent, decides when it wants to start and when it does not. Car is a 91 240SX, ABS/HICAS, power options, 5 speed from factory, SR20DET. When testing the voltage on the starter line when it is disconnected from the starter I get a good 12.5 volts, when it is connected to the starter it drop to 8.5v with the key in the start position. When load is applied to the circuit is when I get my voltage drop.

What I have done:
- Tested battery
- Bypass the clutch interlock relay
- Bypass the ignition switch
- Had the starter tested
- Resistance over the circuit is around 3ohms
- Replaced fusable link

The thing that is throwing me off is the fact that I can jump the signal line right from the battery and the car will crank, all I'm down to is the line running from the fuseable link to the ignition switch or the line running from the ignition switch to the clutch interlock relay. I would assume if those would were bad why would they only show 3ohms of resistance? Any help with this would be greatly appreciated!

The circuit will behave differently when loaded, so a static ohms check might not find the voltage drop.
Use a voltmeter to check availible voltage at the solenoid signal terminal while holding the ign switch in "crank" position. A good circuit will show 12v(or so)to the load(the starter) under operation. You will see much less than that here due to a voltage drop in the signal circuit.
Work your way back toward the ign switch with the voltmeter,checking availible voltage during cranking attempt.
The drop could also be in the supply upstream(toward power supply)of the ign switch. You can voltage drop test at the white wire into the ign switch, again under load(holding the ign in "crank" position)

The first thing to check for this always seems to be the ground from the engine to the chassis to the negative battery terminal.

Next time you do your jumper cable thing, put the jumper cable on the engine block near the starter and put the other end on the negative battery terminal. Don't jump anything on the power side. If the car cranks over, you've likely found your issue. The engine-to-chassis grounds on these cars regularly fail with age.

I started to do this and when it will not crank I only see about 8.5v when trying to crank the car at the starter signal lead, also tested this on E19 and had the same 8.5v when trying to crank the car. Didn't get the chance to work back to the ignition switch.




I have ran a ground from the starter body to a chassis ground with the same issue, I don't believe it is a grounding issue due to the fact that I can jump the starter signal with 12v right from the battery and it will crank without issue.


Thanks for the suggestions!

hobbs, you've only eliminated the possibility of a bad engine-to-chassis ground. You have not eliminated the possibility of a bad chassis-to-battery ground connection.

If things work when you bypass the starter power cable, then I would look into replacing that (including all junctions), no?

On the chassis ground that I added the starter body to, this chassis ground also has a line running to the ground on the battery. Also when I said I can jump the starter I am jumping the starer solenoid signal line to the battery, not the 12v constant that goes to the starter.

If that is a new wire, then good. If you're re-using the old corroded wire, then you know the drill.

Oooh.

But you still hear the solenoid "click" when you turn the key (and the starter doesn't spin)? Or maybe that's a relay you're hearing?

New wires, not old OEM stuff. It's the starter solenoid clicking, I guess I should see if the solenoid is sending power to the starter motor when it clicks. The PO said the starter was rebuild a couple months ago but this is the same guy who didn't disclose that he had this issue the entire time he owned the car...

Have had same problem before. Outcome: Loss of hair (from pulling it out) and replacement of the ignition switch.

Tried that aswell, no dice, same issue even when I bypass the ignition switch all together.