Won't crank

[pk1993]

I am helping a friend work on a 1993 300ZX and am in desperate need for help. The car is a N/A 5-speed model and will not crank with the key turned to the start position and the clutch fully depressed.

After checking for voltage at the starter solenoid with a test light, it appeared that the starter/solenoid was the culprit. We replaced this assembly, but still have the problem. I can jump the solenoid trigger wire directly to the battery connection and the starter will engage (too bad I didn't test this before replacing the starter!).

Apparently we are getting a voltage drop in the circuit that enables the solenoid. We replaced the starter inhibit relay inside the LH fenderwell and the problem is still there. Does anyone have any other suggestions on this?

[gpelite]

What battery you running?

If your battery has been through a short or several rundowns it may read 12v and not carry enough under load to crank anything. If its not enough cold crank amps this process can be accelerated. Try a new batt to rule it out if you have one, or a working one from a buddy that is of the same type. If you have it warrantied, go have it checked for the hell of it.

Rear mount batterys and such need to be grounded correctly, and the grounding on stock Zs wears quite brutally. Not to mentione the placement of one of the grounding points is pretty openly exposed to elements.]

Have you tested all your terminals, cleaned them, etc. I know you would get a crank at least if this was the ONLY problem, but hey can't hurt

[tg]

Wouldn't be the battery if he can start it by straight-jumping it.

Sounds like a relay to be honest, is there NO voltage or just really low voltage?

Bust out the multimeter and go nuts, check the ignition wiring to see if its good too, somebody can probably fish up a wiring diagram for the car if you wait a bit.

[pk1993]

I didn't have a voltmeter at the time, only a test light (looks like an ice pick with a light in it). I agree that I will need to use a voltmeter to diagnose this problem. I was hoping it would be something simple.

A detailed wiring diagram would be helpful at this point. I am not familiar enough with these cars to know the entire path of the starter control circuit.

Since we already replaced the starter inhibit relay (blue relay in LH fenderwell - controlled by clutch switch), are there any other relays in the circuit?

[evildky]

so you didn't test the right thing with the test light?

have you checked the ignition switch?

if you can get the starter to engage by sending 12v to the trigger on the selenoid then you are nto getting signal to the selenoid, but your voltage cables and batt are all fine, you just need to get the signal working, and aside from the clutch swithc attached to the pedal ( or neutral safty switch on the side of an autop trans) and the relay underhood, the ignition switch should send the signal through, start there and work forward

[gpelite]

Wouldn't be the battery if he can start it by straight-jumping it.

dunno, but it did happen with me thats all I am saying

[pk1993]

so you didn't test the right thing with the test light?

Well the answer is yes and no. I tested the right thing (signal to the solenoid), I just used the wrong type of test procedure for the particular problem on this car.

With the solenoid wire disconnected at the connector near the starter, the test light would light up when the ignition switch was turned to the "start" position and the clutch pedal depressed. The light seemed bright enough to indicate 12V on the wire. This is where I made a bad interpretation that the signal to the solenoid was good.

The problem is that there is a very small load in the circuit with the solenoid disconnected. It only takes a few milliamps to light the test light. When the solenoid connector is hooked up, now the load is much greater thus requiring a lot more current. Whatever component or connection is failing is having a large voltage drop when trying to deliver the current required to engage the solenoid.

My next thing will be to get a voltmeter and start checking points along the circuit with the ignition in the start position and the clutch pedal depressed. I agree with what you said that the ignition switch is one of the first places I'll check. Other possibilities are in the wiring from the fusible link box to the ignition switch. It may be a few days before I can check this again, but I'll be sure to post my results.

Thanks for the responses.

[gaehrings13]

the starter is under the driverside fender i believe, try that!

[evildky]

the signal to the starter doen't need to be very strong it just has to energise a glorified relay, the batt cable does the heavy lifting, the starter trigger is just a low amp trigger

[93T0nyZx]

check you colum, and make sure your ECU is good, consider your cam sensors as well, but it could be jsut too weak of a batery, you may not be recieving a reference pulse though =\