Help! intermittent no crank at start up

[ernbuild]

Hi Guys, need help. I have an intermittent no crank at start up. I have a 1991 ZR1. I know about the clutch start switch, but it seems that when it was converted to right hand drive the switch has been changed. I just cannot find the switch as described in the manuals. The car will clutch start every time I have had to do it ,without hessitation.
It starts first time also when it does start. I have a new ignition switch and key which has been installed and it hasn't made any difference. What else can it be. I am not an auto electrician but know my way around the old girl pretty well, so if you can speak in plain english I should be able to find it, whatever it is.
Looking forward to some help, cheers Ernie.

 

[John Robinson]

I am sending a couple of pages from my 93 service manual on the clutch switch location I don't know if they will help you or not. If the clutch being moved from the left side to the right side conversion used the original parts from GM then this might be of use to you.

 

[ernbuild]

Thaks John, The diagrams are the same as my GM manual for the 91. Its the actual switch I cant find, it just seems to be missing or changed. Dont suppose you know what color the wires are coming out of the switch?
Cheers Mate.

I am sending a couple of pages from my 93 service manual on the clutch switch location I don't know if they will help you or not. If the clutch being moved from the left side to the right side conversion used the original parts from GM then this might be of use to you.

View attachment 13020View attachment 13021

 

[John Robinson]

I am unable to find the color of the wires. Since you have a manual have you checked the section for Intermittent Hard starts? In my manual it is section 6e3-B. It mentions there several other possiblities for the symptoms you have. Hope this helps you find the problem. Please let us know when you get it all sorted out what you found.

 

[ecss]

The starter circuit is very simple.

When you turn the ignition On if the key pellet matches what the CCM was programmed for it grounds the Starter Enable Relay.

When you turn the key to Start.
The relay closes. 12 volts from a Yellow wire from the
ignition switch passes thru the relay and out of the relay via a Yellow/Black wire. The 12 volts then passes thru the Clutch Safety switch if closed and out of the switch via a Purple wire which goes to a push on lug on the Starter Solenoid.

If you have to engage the clutch pedal to start the car there must be a Clutch Safety switch some where around the clutch linkage. In the US cars the two wires at the Clutch Safety switch are a Yellow/Black wire and a Purple wire.

The most common problem is the Clutch Safety switch can't handle the current the Starter Solenoid draws which causes the switch contacts to pit. In the latter model C4's the Clutch Safety switch was moved to the primary coil side of the Starter Enable relay.

The Starter Enable relay location is identified in the diagram I posted. It could be in a different physical position because the relays are mounted on a slide on mounting bar so the relays themselves can be moved around on the bar. To identify the correct relay you need to look at the relay socket wiring. There should be two yellow wires, a Black wire, and a Yellow/Black wire.

To gain access to the relays you need to remove the panel holding the footwell lamp, remove the carpeted panel and then the metal panel below the steering column.

The relays in that location are all the same so you can swap them around if you think the relay is bad.

 

[boomdriver]

This is most likely a VATS problem and the key is rarely the way to fix or bypass VATS.

The starter enable relay is most often what fails. Next would be the VATS module under the breadbox.
You can buy new relays, $9 and you can buy new modules on fleabay for $100 or a good module bypass for $15.

Every once in a while you see a starter solenoid that sticks and hangs due to worn internal contacts or corroded connections. That causes confusion in the diagnosis. Thats not as common as the relay or module failure.

 

[ernbuild]

Well finally got the Z started with the key. For what its worth I ended up pulling the plug on the clutch start switch and connecting the purple wire from it to the powered yellow wire on the starter enable relay. Removed relay altogether. Started up straight away first time. Dont need the clutch pushed in any more, but thats ok for me as have a dicky knee joint on clutch leg. I dont know if VAT's still works but dont care about that either.
Thanks for the help guys, most appreciated. Cheers Ernie.

 

[vetteoz]

Removed relay altogether. Started up straight away first time.
I dont know if VAT's still works but dont care about that either.

All you have done is remove the starter enable relay operated by VATS ; the fuel injector cutoff feature is still active
You will still care about VATS because if you have a key reading problem ( the most common VATS fault with age )
you will have crank ( because you removed the relay ) but a no start condition because VATS ,in not seeing the correct key resistance will disable the injectors