HELP. No start

[Ozruss90]

Originally Posted by Paul Workman

Before we start changing batteries, or even installing the auxiliary relay (never a bad idea, tho), Some basic troubleshooting is called for.

Check battery voltage. Fully charged it should read ~ 12.6 VDC at rest (!14.7 when being charged).

The two most common "NO START" issues on the 90-92s are either the clutch safety switch or the solenoid contacts within the starter itself. And, a third relay is commonly known as the VATS relay (but unless your security light is flashing when you turn the ignition switch to START, that is not likely the issue).

Use the schematic provided that was published by Marc Haibeck that provides common voltages along the circuit WHEN THE IGNITION SWITCH IS IN THE START position.

IF the purple wire between the clutch safety switch and the starter has voltage on it when the ignition switch is in the START position, then chances are the starter solenoid contacts need replacement (will cost you about $10-15 for the Denso Starter Solenoid kit (See Jerry's Gaskets for that or whatever else your LT5 needs, including plenum gaskets you will need when you pull the plenum - a "rite of passage" for all ZR-1 owners!). Also, Most auto parts stores have the kits. Many domestic and foreign cars use that Denso starter(s).

Well, I don't want to jump ahead too far. But, refer to the schematic and use your VOM and trace the voltage from the battery to the point where you loose it. That will be the location of the fault.

The BIGGER POINT I'm trying to make is, before you start changing parts, VERIFY that the fault FIRST! Otherwise you'll be headed for a lot of frustration AND expense TOO!

Thanks Paul for your input and advise, much appreciated and will follow if not the battery. I had already pulled the battery out (as it’s only a 5 min job) to take to battery shop to be tested,, AC Delco 650cca measured 24 cca when the load tester was applied. I’m going to put a new battery in tomorrow to hopefully solve the issue. My worst fear was mice damage under the plenum. I’ll be happy to part with $ for a new battery if that fixes it.

[Paul Workman]

Did the shop FIRST fully charge that AC Delco battery before load testing it? A couple or three years on a battery is unusually short.

In my experiences (I used to maintain dozens of lead-acid batteries, among other things, at remote microwave radio repeater sites (think mountain tops) and now have 7 lead-acid batteries of my own in various vehicles and equipment.) The average age is 10 years...and counting! So, unless you have an excessive parasitic draw that exceeds ~25 to a max of 50mA, your battery expiring so soon is unusual to say the least, OR it isn't charging as well as it should. (Corroded battery terminal connections??)

A cold battery should read 13.8 (hot) to 14.7 volts (cold) across the terminals with the motor running (w/o the lights or AC running) IF the alternator is working properly.

Not implying YOU or anyone who is not "anal retentive" (like me) go out and buy a BATTERY LOAD TESTER, but they are cheap enough and take all the guess work out of testing your lead-acid batteries (including AGM batteries). Since I have so many 'round the ranch, I decided I needed to have my own, and AutoZone was more than happy to feed my obsession with tools! Anyway, doing a home load test is a subject for another day.

[lfalzarano]

The warranty on the AC Delco 75PS with 650 CCA is 30 months. The model 75VPG with 700 CCA is 48 months. It is rare to hear someone post a “NO Start” when the battery was new. Just my personal observation.

Extremely hot weather and overcharging are the two main reasons for shortened battery life, according to the Car Council. The battery contains liquid and heat causes it to evaporate. Low fluid levels will damage the internal structure of the battery.

Always replace a battery with one that is of equal or higher quality than the one originally specified. A LT5 requires a minimum of 690 CCA according to the FSM.

I recently screwed up and bought the 650 CCA battery because I didn’t have the above information. I will be getting the 700 CCA next Summer for sure!

Sent from my iPhone using ZR-1 Net Registry

[Ozruss90]

Originally Posted by Paul Workman

Did the shop FIRST fully charge that AC Delco battery before load testing it? A couple or three years on a battery is unusually short.

In my experiences (I used to maintain dozens of lead-acid batteries, among other things, at remote microwave radio repeater sites (think mountain tops) and now have 7 lead-acid batteries of my own in various vehicles and equipment.) The average age is 10 years...and counting! So, unless you have an excessive parasitic draw that exceeds ~25 to a max of 50mA, your battery expiring so soon is unusual to say the least, OR it isn't charging as well as it should. (Corroded battery terminal connections??)

A cold battery should read 13.8 (hot) to 14.7 volts (cold) across the terminals with the motor running (w/o the lights or AC running) IF the alternator is working properly.

Not implying YOU or anyone who is not "anal retentive" (like me) go out and buy a BATTERY LOAD TESTER, but they are cheap enough and take all the guess work out of testing your lead-acid batteries (including AGM batteries). Since I have so many 'round the ranch, I decided I needed to have my own, and AutoZone was more than happy to feed my obsession with tools! Anyway, doing a home load test is a subject for another day.

Been on the charger over night. will go in this morning and observe whilst they do the load test

[Ozruss90]

Originally Posted by lfalzarano

The warranty on the AC Delco 75PS with 650 CCA is 30 months. The model 75VPG with 700 CCA is 48 months. It is rare to hear someone post a “NO Start” when the battery was new. Just my personal observation.

Extremely hot weather and overcharging are the two main reasons for shortened battery life, according to the Car Council. The battery contains liquid and heat causes it to evaporate. Low fluid levels will damage the internal structure of the battery.

Always replace a battery with one that is of equal or higher quality than the one originally specified. A LT5 requires a minimum of 690 CCA according to the FSM.

I recently screwed up and bought the 650 CCA battery because I didn’t have the above information. I will be getting the 700 CCA next Summer for sure!

Sent from my iPhone using ZR-1 Net Registry

The battery that l purchased 32 months ago is a S75-6MF It’s the only battery with the correct dimensions and side terminals in the AC Delco range according to the Aus./ NZ online catalogue. Rated at only 650 CCA. Only went for the AC Delco battery to keep the original look . They do list it as having a 36 month warranty, so I will follow that up. BUT l don’t want another 650 CCA if it’s not enough. Might have to look at other brands to get 700 or better CCA. Will know more after today. Will keep you posted

[TX '90 ZR1]

I put in a AC Delco Professional 75VPG. There is also a number on the tag that might be a part number. This might help you locate the correct one in case the listing criteria is different where you are.
Number is 88861746.
Here's the specs as listed by Delco.
Applications: Passenger Car / Light Truck / Commercial Batteries
BCI Group Size: 75
Volts: 12
Reserve Capacity: 95
AH@20: 52
Cold Cranking Amps: 700
Cranking Amps: 875
Length: 8.7
Width: 6.8
Height: 7.2
Weight: 33.7 Lbs
Hope this helps.

[lfalzarano]

Kenny has it right on!


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[Ozruss90]

Originally Posted by TX '90 ZR1

I put in a AC Delco Professional 75VPG. There is also a number on the tag that might be a part number. This might help you locate the correct one in case the listing criteria is different where you are.
Number is 88861746.
Here's the specs as listed by Delco.
Applications: Passenger Car / Light Truck / Commercial Batteries
BCI Group Size: 75
Volts: 12
Reserve Capacity: 95
AH@20: 52
Cold Cranking Amps: 700
Cranking Amps: 875
Length: 8.7
Width: 6.8
Height: 7.2
Weight: 33.7 Lbs
Hope this helps.

Thanks Kenny for that info, interesting.
I’m assuming the AC Delco range here in Australia 🇦🇺 is different to what is available to you over there. Only ‘2’ batteries available with side mount terminals.
S75-6MF, correct physical dimensions for the car but only 650cca
And a S78-6MF for later corvette and others l guess, at 770cca, BUT physical dimensions to big for the Z
I’ve looked at other brands and can only come up with the larger version for the later US cars with side mount terms. For now I’m stuck with a 650cca battery.
As it turned out, the faulty battery was 32 months into a 36 month warranty. They are replacing it free of charge. Hopefully will have a better run out of the replacement battery. Pick it up today and will put in and test tonight🤞