1990 No Crank

[A26B]

Bill, I'm not sure when a relay was added to the start circuit, but someone else here will know.

[Dynomite]

Originally Posted by A26B

Bill, I'm not sure when a relay was added to the start circuit, but someone else here will know.

I install Relays in All 90's and 91' and touch up Starter Solenoid contacts in ALL ZR1s' as a standard restoration

[Paul Workman]

90-92 = NO start relay, ALL the starter solenoid current passes through the clutch safety switch . That is why it is especially important on 90-92 MY Z's to fully depress the clutch BEFORE turning the key: prevents arching on the switch contacts.

However, in 93-95 Z's the starter circuit was changed to include a seperate starter relay to handle the current. The clutch safety switch now only switches on that starter relay.

However, a relay can be added to the 90-92 Z's between the clutch safety switch and the starter solenoid, a relay like the 93-95 Z's have to carry the high current load of the starter solenoid. (So, having a 93-95 Z you DO NOT need to install an auxiliary relay!)

Dynomite included the relay mod procedure in SOLUTIONS (sticky).

[SAHall]

Originally Posted by Paul Workman

You mentioned the voltage gauge reacted slightly to turning the ignition switch. That could mean the starter solenoid is activated, but the high current contacts inside of the starter may need to be replace; a common problem with the Denso starters (with 20-30k miles).



Replacement contacts are easy for a DIY project, once the starter is removed, and cost under $10 for a kit with just the copper contact lugs. (NOTE: Some kits include a new armature and contact ring (attached). I caution you that the thrust pins on some replacement armatures are too short, resulting in the pinion gear not fully engaging with the ring gear. However, the copper contact ring can be resurfaced with a little emory cloth - and the armature reused, no problem!))

Thanks for the advice and information. I will run this down.


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[ghlkal]

Just to be clear ... there is a relay in the circuit for all ZR-1s


My 1990 has a "Starter Enable Relay" in the circuit.


On early Zs, the relay is before the clutch interlock switch


See this thread for some more information and wiring diagrams http://www.zr1.net/forum/showthread.php?t=30567

[Paul Workman]

Ah! youz guyz are over thinking this, methinks! (Refer to the 90-92 and the 93-95 diagrams)

And, because there is a common misunderstanding of different terms going on here (i.e., voltage vs. current [amperes]) and what the two entirely different terms/quantities refer to...descriptions get unnecessarily messy here.

Soze we don't get confused, VOLTAGE is analogous to water PRESSURE in a plumbing example. Voltage does not "flow". It is what it is at any point in the circuit.

CURRENT, electron FLOW measureD in "amperes" is analogous to water flow in our plumbing example. Current flows as result of differences in pressure (voltage); flows from high pressure to lower pressure in the circuit.

90-92 starter circuit:

Battery CURRENT flows through the start switch and then to the VATS relay (controlled by the CCM) and then to the CLUTCH START SWITCH before powering the solenoid actuator coils, and then returns to the battery (via chassis ground), completing the round trip circuit.
[B][COLOR="Blue"]

93-95 starter circuit:

Battery CURRENT flows through the start switch and branches through the VATS relay and through the CLUTCH START SWITCH to VATS actuator coil and then returns to ground through the CCM module.

CURRENT through the VATS (high current capacity) relay path goes directly to the starter solenoid.

AT ISSUE in 90-92 cars...

At issue is the relatively high current drawn by the starter solenoid itself and the limited inability of the CLUTCH START SWITCH to handle the relatively high (~10 amps) of the starter solenoid actuator coil windings, long term.

The voltages (seen on the 90-92 diagram) are from a presentation by Marc Haibeck. They (voltages instead of current readings) provide valuable troubleshooting information, being much easier to measure than a current measurement, far as tracing an open circuit goes. If you have voltage or you don't have voltage when the ignition switch is in START, you have a clue as to where to look next. No voltage (except at ground points) means NO pressure which means NO current. No voltage = NO current and NO current means whatever is next in the circuit = NO WORKIE!

Solutions (to the limitations of the CLUTCH START SWITCH):

1) BEFORE you have trouble with that switch (90-92 cars primarily), as Jerry Downey said, always depress the clutch pedal completely BEFORE turning the ignition switch. And, RELEASE the START switch BEFORE releasing the clutch peddle. This may avert you ever having to replace that CLUTCH START SWITCH or take other measures...to follow.

2) (90-92 only) Install an auxiliary (high current capacity) relay between the CLUTCH START SWITCH and the starter (see wiring diagram below).

3) (90-92 only) Bypass the (nanny) CLUTCH START SWITCH. The "nanny" part of the CLUTCH START SWITCH is without that switch, the starter can be turned over with the transmission still in gear and the car will lurch when the key is turned to START (which has some advantages too, but a topic for another time).

That only leaves the VATS relay to cause a problem, but that relay is very robust and is seldom the cause of the NO START syndrome.

AND, of course any attempt at troubleshooting begins with verifying that all connections are making good contact - again, the reason for including the typical voltages is provided to aid in the assessment of connections (starting with the battery terminals), among other things.

I created the RELAY diagram back when I first bought my Z and almost immediately experienced NO START issues. As it turned out tho, it was the STARTER SOLENOID contacts that were worn out and needed replacing. But, I then began to have intermittent issues with the CLUTCH START SWITCH.

NOTE: Installing an auxiliary relay (90-92 ZR-1s ONLY) won't fix a bad CLUTCH START SWITCH, nor will it fix BAD starter SOLENOID contacts if either is the problem. The relay will only preserve that switch by vastly reducing the current through the internal switch contacts. IOW, if your CLUTCH START SWITCH is already going bad, adding a relay will not fix it. It either has to be replaced and then install the relay (90-92 only), OR bypass that switch and forget too about adding that auxiliary relay al together!!

Anywayz.... I sincerely hope I didn't confuse the topic further. My intent was the opposite, to "unravel" it (as it were).

[SAHall]

So, i started this thread with a no crank situation in my 1990 z. Thanks for all of the advice.

I found the purple wire behind the ECU in the engine compartment, cut a small flap in the wire jacket, turned the ignition key to “on” and applied power directly from the positive battery terminal to the purple wire-and- the starter cranked. I then tried to start the engine with the key and it now starts the engine. All appears fixed, for now.

Glad it started-but still not sure what caused the starter to not crank in the first place?


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[Dynomite]

Originally Posted by SAHall

So, i started this thread with a no crank situation in my 1990 z. Thanks for all of the advice.

I found the purple wire behind the ECU in the engine compartment, cut a small flap in the wire jacket, turned the ignition key to “on” and applied power directly from the positive battery terminal to the purple wire-and- the starter cranked. I then tried to start the engine with the key and it now starts the engine. All appears fixed, for now.

Glad it started-but still not sure what caused the starter to not crank in the first place?


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The Starter Solenoid contacts are burnt a bit and a HOT start with purple wire is enough current to overcome the Solenoid contact issues.
It may start easily for a few times then back to no start once the Solenoid contacts are burned a bit more.

Best to Remove Starter and Solenoid cover. Then remove the plunger and wire brush the contacts on the plunger and fixed contacts within the Solenoid.

Post 52 - Starter, Starter Relay, Wiring Harness, Battery, and Plugs Tricks

[Ccmano]

Originally Posted by Dynomite

The Starter Solenoid contacts are burnt a bit and a HOT start with purple wire is enough current to overcome the Solenoid contact issues.
It may start easily for a few times then back to no start once the Solenoid contacts are burned a bit more.

Best to Remove Starter and Solenoid cover. Then remove the plunger and wire brush the contacts on the plunger and fixed contacts within the Solenoid.

Post 52 - Starter, Starter Relay, Wiring Harness, Battery, and Plugs Tricks

Listen to what Cliff is telling you. It’s time for some under plenum maintenance. If not now it will be in the near future.
H

[SAHall]

Originally Posted by Ccmano

Listen to what Cliff is telling you. It’s time for some under plenum maintenance. If not now it will be in the near future.

H

Seems odd that solenoid contacts would burn after only 16,000 miles. Poor design? On that note, why put the starter under the plenum anyway?


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