Help! no start

[Z51JEFF]

Well,after bypassing the clutch switch I had a no start again so it's starter time. Not looking forward to it but gotta do it. Let the fun begin.

[Racinfan83]

Mine has started every time now since changing battery and wiring in the relay. Fingers crossed of course.... I have a set of plenum gaskets waiting because if it does it again I know where I'll be going...

[RussMcB]

Originally Posted by Z51JEFF

Well,after bypassing the clutch switch I had a no start again so it's starter time. Not looking forward to it but gotta do it. Let the fun begin.

Jeff, maybe you could do one last experiment before you dive in, and that would be to provide 12v directly to your starter motor (via purple wire) to see if it kicks over. That way you are bypassing several things (almost everything). It would be a shame to replace the starter if it is okay. Make sure the car is in neutral with parking brake on.

If it turns out you need to remove the plenum, it's not too bad. Plenty of help online if you have a question. Good luck.

[Z51JEFF]

Originally Posted by RussMcB

Jeff, maybe you could do one last experiment before you dive in, and that would be to provide 12v directly to your starter motor (via purple wire) to see if it kicks over. That way you are bypassing several things (almost everything). It would be a shame to replace the starter if it is okay. Make sure the car is in neutral with parking brake on.

If it turns out you need to remove the plenum, it's not too bad. Plenty of help online if you have a question. Good luck.

I would like to try the extra relay first,I have one just need to find it and I'd like to install this without cutting into any factory wires if that's possible. Where's exactly is the PURPLE wire in the bundle? Russ I've had the plenum off a few time so it's no big deal,just dont want to deal with it.

[Racinfan83]

I just did the relay - I didn't take any pictures unfortunately. There are some pics in Dynos DIY for it. The purple wire is in the bundle behind the computer, and it is one of the thicker wires. NOT one connected to the computer (there are purple wires connected to it too but they are smaller). And I did have to cut the purple wire per the DIY. I made up the wires beforehand so everything was ready and all I had to do was cut the purple wire, add the connections, and done. Follow the DIY deal - I had no issues and it works fine...

[Paul Workman]

I agree 100% with Glenn (aka gbrtng) far as troubleshooting to determine WHAT is failing. What he's said is sooo important to warding off gremlins in the future. (For example: How many times have you heard the story; "I replaced this or that and it ran great...for a while. Then it began doing "it" a gain..."? By replacing this or that without first confirming the problem leaves you wide open for "Murphy's Law" to intervene and future "NO START" failures...will again appear! (In my Navy days, we used to call 'replacing parts till the problem goes away "shotgunning".)

Electrical stuff like switches seldom fail completely - at first... Instead they often (usually) become intermittent before finally failing completely. (light bulbs being an exception) SO! Changing the clutch switch "just because" will do nothing for a starter solenoid switch that is in that early stage of "start, no-start, start" routine.

Several components are in series with the starter, including the starter solenoid, and ALL must function in order for the starter motor to work.

My point is, replacing the starter won't fix a clutch safety switch going bad. That clutch safety switch doesn't give a ratz azz how "heavy duty" the new starter solenoid is, or if there is an additional relay* installed to isolate the clutch safety switch from the full solenoid current, when the switch finally becomes intermittent or flat out fails...that's it. Replacing every other component in the chain will not fix that bad switch.

*(Note: Installing the relay to remove the high current load from the clutch safety switch is a good modification; essentially arriving at essentially the "same" solution used on the 93-95 ZR-1s: to isolate high solenoid current from the clutch safety switch. Also, installing the relay will tend to prolong the degradation of the (90-92) clutch safety switch; perhaps years, due to the reduction of current required to activate the relay. And, as Scottfab once pointed out, assuring the clutch is fully engaged before turning the START switch to START, and then first releasing the START switch BEFORE releasing the clutch will go a long way toward reducing or even eliminating much of the arching within the clutch safety switch [/U]when it is first closed, and (more importantly) opened!)

Refer to Marc Haibeck's web site for more detailed info on "Diagnosing Starter Issues".

[RussMcB]

I agree with Paul 100%, with these comments: I'd still do the "direct 12v to starter" test to confirm the starter is fine. It's free, not too difficult and will eliminate the starter (or identify it) as the problem.

And since you're already digging into the loom to find the purple wire, go ahead and do the relay mod because it's a good idea in itself - an improvement over stock and doesn't bypass any of the systems (clutch, ignition switch, VATS).

[Paul Workman]

Here is a schematic worked out by Marc Haibeck that has the approx. voltages you would expect to measure at the various locations between the battery and the starter. (This is for the 90-92 years only)



Oh, and I'm not meaning to imply one shouldn't take steps to also eliminate future potential problems, i.e., installing the relay, for example, but do it in conjunction with isolating the actual failing part (confirmed by actual testing to witness the failure before changing a part to fix the problem). Once the failure has been addressed and confirmed, replacing other related components is considered "preventive maintenance", but doing so is no substitute for actual measurements/witnessing the failure first to be completely sure the problem is fixed - verified by performing "before and after" measurements.

Please forgive me if all my blathering sounds like a "school marm" lecture. I used to travel the world to troubleshoot problems with communications equipment, and doing tech training, etc., and it's still in my blood, I guess. So, I hope I'm helping and not coming off otherwise. I wish to offend nobody.

PS: On my 1990 ZR-1, (S/N 1201) it IS a purple wire that runs to the starter from the clutch switch, for what it's worth. So, I gather it could be RED on some cars. So, there's that...

[Z51JEFF]

I would really like to isolate the problem but mine is so sporadic,7 times in eight years I have no choice but to just replace parts. So far I've replaced the OEM starter relay,tied Ina second ground coming from the factory starter relay and bypassed the clutch switch. Now I would like to look into the second hi amp relay but isn't this just a bandaid so to speak? And can somebody in this thread post a simple diagram of the hi amp relay wiring? Cliff has forwarded be some links but I'm not getting the right info.

[Dynomite]

Originally Posted by Z51JEFF

I would really like to isolate the problem but mine is so sporadic,7 times in eight years I have no choice but to just replace parts. So far I've replaced the OEM starter relay,tied Ina second ground coming from the factory starter relay and bypassed the clutch switch. Now I would like to look into the second hi amp relay but isn't this just a bandaid so to speak? And can somebody in this thread post a simple diagram of the hi amp relay wiring? Cliff has forwarded be some links but I'm not getting the right info.

The Starter Relay addition under the ECM is No Band Aid.....it is a Cure
In Conjunction with the Starter Solenoid Refurbishment of the Points (and checking the overall condition of the starter at the same time including armature bearings on each end)

I could just come up there Jeff and do it for you (fix your No Start Issue)

The 15 Minute Starter Relay Installation under the ECM and the Starter Solenoid Refurbishing with the 10 Minute Plenum Removal.
We could also do the Injector Housing TB Coolant Blocking (You will not be able to tell it has been done from outside appearance when I am finished).

But then again I am not sure of the condition of your Injector Housing Coolant Manifolds (May need heat to remove the bolts) .

It is a 3 hr drive from here in CA and too hot anyway and Acetylene Torch will not fit in the ZR-1 (with Cylinders)

I will leave it for Paul to help you and explain further....it is too complicated for me with all the diagrams

Good Luck Guys