bassplayer27360

Here is a puzzler for you. I can drive my '91 ZR1 for 5 days straight, or let it sit for 2 weeks, and it will start every time. And then, like today, I drove it to work, drove it a half a mile to lunch and it wouldn't start. The dash lights up like normal, it just won't fire. A month ago the very same thing happened. It wouldn't start after driving it to lunch, so I waited about 45 minutes, tried it again and it cranked right up. It has a brand new battery and alternator. Do you guys have any idea what's the problem? Thanks for your help.

zr-1 guy

sounds like the clutch switch, which is always my first response

Peter Mahr

This is a common problem. It can be the clutch switch or other causes. I suggest that you call Aaron at South Georgia Corvette and describe the problem. 729 226-4447. He installed a starter relay on my car and several others and this seems to be a cure all if the simple stuff fails.

whichvette

starter is old and needs replacing just did mine and a vats overide switch should help

Peter Mahr

You could look at http://www.zr1netregistry.com/ that has comments about this problem or search this site. It comes up regularly.

Coupe89

Mine was the clutch switch. I by passed it

dbriana

Same for me. If it doesn't start the first time but it does on the second try after waiting it could be the VATS. If it doesn't start on the second third fourth tries, probably the clutch switch. You can also lock and unlock the drivers door with the key to bypass the VATS instead of waiting 10-15 minutes.

Fred Frazier

Is there any good way to determine if it is the solenoid in the started that is too hot or if it is the clutch switch? Seems like if it is the clutch switch it would not start after cooling down or the next day, etc. Those of us that have had these intermittent issues get nervous about trips, especially with wives and it doesn't start.

zr-1 guy

the problem with the switch is that the wire is too small a gauge, over heats, and won't conduct properly to close the circuit

ccmano

Have you washed your engine recently? If so, it's the starter. Otherwise there a multiple possibilities as was already noted.
Check out this thread over at ZR1.net
http://www.zr1.net/forum/showthread.php?t=11619
H

Paul Workman

No...The resistance of the wire is not the issue - and it doesn't change over time, but the resistance that builds up across the contacts of the interlock (clutch) switch does result in heat and may be conducted to the wiring. But the resistance/heat is due to the deterioration and eventual destruction of the switch contacts.

Bypassing the interlock allows the starter to be activated without the clutch being engaged. (Some like it that way as it results in no load to a (dry) thrust bearing in the motor if the clutch pedal is not pressed.)

The contacts are eroded as a function of cycles and current; high numbers of either and/or both = faster erosion. Some want to keep the interlock feature and simply replace the switch. However, some have modified the start circuit so the interlock switch only activates a high-current capacity (and easily replicable) relay (usually mounted under the ECM and above the battery).



However, as our long lost buddy CCmano says, it could be the starter, especially if you got it wet! Try tapping the (big) purple wire (located in the harness) that leads under the plenum. If you have battery voltage (at least 12.2+ volts) with the clutch depressed, and still "no start", then the starter is going to need to be investigated, and a plenum pull is in your stars. A plenum pull...It's the "right of passage" for a ZR-1 owner!!

P.

JThomas

For me, it was replacing the starter and since, no problems.

zr-1 guy

I stand corrected, thanks for the informative post.

Z51JEFF

Ive had one instants of a no start situation.I started looking for a new switch and nobody has,only used.Because this has only happened once I cleaned the battery contacs,die electric grease,nice and tight and started using my new ignition key.I did notice the pellet in the old key was worn alot compared to the new key.I did find one guy that had a new switch,$280.

Fred Frazier

Thanks Paul, good information. My car only has 25,000 on it, so seems like the clutch switch should not be worn out already. (For that matter neither should the starter). Aren't the clutch switches for the Z's, the same as all C-4's, or is this another GM "let's make them different"? Can't believe they are all gone.

Never washed the engine, heard about that back in mid-90's. Are there starters out there available or any place that does a complete rebuild, perhaps with improvements to the existing starter?

Good discussion, know this comes up almost annually.

gbrtng

Hi Fred - your 93 has a different circuit from the early (90 and 91, I think) vehicles where the clutch switch carried the current to the solenoid. Later ones used a relay to switch current to the solenoid so the clutch switch carried only the current for the relay. I'm not sure what year the change was made - either 92 or 93. Someone with a 93 FSM please jump in here.

Fred Frazier

Glenn and others

"your 93 has a different circuit from the early (90 and 91, I think) vehicles where the clutch switch carried the current to the solenoid. Later ones used a relay to switch current to the solenoid so the clutch switch carried only the current for the relay. I'm not sure what year the change was made - either 92 or 93."

Would this change to a relay, result in a lower current needed from clutch switch to relay and lessen the likehood of this burn-out issue with the clutch switch?? Would a by-pass on the newer models be the same as diagramed above?

Thanks............any starters or rebuilders out there, just in case?

dbriana

O'Reillys and Autozone both have rebuilt ones. $120 plus $45-70 core.