Z51JEFF

Here's is my starter relay install I did recently. This modification isn't my idea,I believe TCCRAB came up with the idea,DYNOMITE changed it a bit and I simplified the explanation for dummies like me. I made a bracket for the relay to mount it out of view but it can be mounted anywhere. The reason for this modification is the starter circuit in the 1990-1992 LT5 is a poor design that was revised in model year 1993-1995 from what I understand. The high amp relay can be found on EBay. Under the ECM you will find the main wiring bundle,the PURPLE 12 GAGE WIRE FROM THE STARTER is in this bundle. You will be splicing into this wire and running it into the relay. The spliced PURPLE WIRE coming from the starter,left side of wire will go to terminal 30 on the relay. The other end of the cut PURPLE WIRE,right side will go to terminal 87. Terminal 85 going to go to your 12 volt power at the junction block down by the battery and terminal 86 goes to ground. Terminal 87A is not used,even though this isn't hot I used a piece of shrink tubing on it to isolate it. I picked up my ground at the AIRBAG SENSOR right next to the battery. The wires I have leading from the PURPLE STARTER WIRES to the relay are about 14 inches long. I routed these wires under the ECM and out of view. Elsewhere on the internet you will see these instructions stating a PURPLE WIRE comes from the ECM for this installation,NOTHING IS SPLICED INTO THE ECM,it's the wire bundle under the ECM is where the PURPLE 12 gage starter wire can be found.

Z51JEFF

Forgot a picture of the relay. All connections should be soldered and sealed shrink wrap. Depending on where you chose to mount the relay,In my case you would never know it was there unless I pointed it out.

Dynomite

See Item #2 for additional photos and information Electrical Ground Connections and Installing Starter Relay

Your installation/location of the Relay is a bit more professional than my installation
That is a very nice location and professionally installed Relay with bracket

In my case I just used black electrical tape wrapping the Relay and electrical splices (with Heat Shrink) into a single bundle under the ECM.



What is with the battery cloth cover? I may be missing something

I do have a Battery Disconnect Switch to conserve Battery Power when the ZR-1 is sitting for a while which may contribute to quick starting
The Battery Disconnect Switch and Having an Operational Secondary Full Power Switch

WVZR-1

Battery insulator/blanket would have been an OE part on '92+ cars.

ZR-71

Great job in mounting and hiding the new relay Jeff
When I did it I just stuffed it under the ECM and protected it.

But I did this modification without cutting or splicing any wiring as seen in my post here.

https://www.corvetteforum.com/forums...-splicing.html

Z51JEFF

Hey Cliff. I saw a 1996 years ago that had this battery cover,liked it and did some digging and found it was stock OEM so I got a few. Been meaning to pick up one more before they are NLA.

Z51JEFF

While you believe it may be wrong my not start issue went away once I put this setup in the car.

ccmano

Interesting it appears TCCrabs has a third way to wire it. Here is his post from 2010.
H

“SPDT Relay : (Single Pole Double Throw Relay) an electromagnetic switch, consist of a coil (terminals 85 & 86), 1 common terminal (30), 1 normally closed terminal (87a), and one normally open terminal (87) (Figure 1).

When the coil of an SPDT relay is at rest (not energized), the common terminal (30) and the normally closed terminal (87a) have continuity. When the coil is energized, the common terminal (30) and the normally open terminal (87) have continuity.

Pin #87: Purple wire to the starter
Pin #30: Battery positive 12v
Pin #86: Battery ground
Pin #85: Purple wire from ECM
Pin #87a: Not used


The purple wire lives in the big loom just after the ECM. Peel back the ribbed covering and dig around. There is only one purple wire.
Cut the purple wire carefully noting which end leads down to the starter and which end comes out of the back of the ECM.
Use similar sized wire (10 or 12 gauge if I recall correctly).
Black wire doesn't stand out like bright red or yellow.

I hid my relay under the ECM, Paul (in the picture above) hid his in the battery area.”

So we have...
TCCrabs
Pin #87: Purple wire to the starter
Pin #30: Battery positive 12v
Pin #86: Battery ground
Pin #85: Purple wire from ECM
Pin #87a: Not used

Ihatebarkingdogs
#30 - Purple wire TO starter.
#87 - B+ Hot at All Times from junction block
#86 - Purple wire FROM key switch
#85 - Ground.

Z51Jeff
#30 - Purple wire to starter.
#87 - Other end of Purple wire
#85 - 12 volt power at the junction block down by the battery
#86 - goes to ground.
#87A - is not used

Here’s Paul Workman’s nice diagram. Wish he would have identified the terminal numbers. Paul can you help us out here?
H

mhobtr

I wouldn't solder the starter terminal eyelets. Those are potentially high heat terminals and the solder can melt. A good solid crimp with a heat shrink cover is all you need. If you want to solder the control connections (the relay coil terminal eyelets) that should be OK.

My '91 had a red wire instead of purple. Almost went nuts looking for a purple then decided it had to be the red.

All corvettes with this starting circuit, because of all the connections and wire size, will eventually see the applied voltage to the starter decay to a point where these "No-start" problems occur. This is a great solution which should have been in the original design.

WVZR-1

There are 'issues' with all of these descriptive instructions and 'Cliff' just copied without verification TCCrab who's mentioned here. I noted in bold the most obvious error in 2 and you could include Cliff's in TCCrab note. Your personal install seems to descriptively mimic TCCrab & Cliff. This isn't just an LT5 issue, it's actually an all including L98. An M6 issue but I believe I've actually seen a A4 mentioned a couple times through the years. Cliff in his images seems to actually ID the source of the wire but used at 85 which isn't ideal

Paul Workman's I believe was originally mentioned to have been done with a SPST which I'd think is promising with an appropriately rated Amperage of the relay. Paul's original image is also just a bit suspect but it requires interpretation by the user. I asked Z51Jeff if his might have been a 'typo' in his original description because it was (still is) a difficult read. If your descriptive text of his is correct then there's issues there also I believe.

If you're to believe DaveP(ihatebarkingdogs) wired as he suggests (from ignition switch) then the CSS is 'bypassed'.

I started a new thread where I believe it would be in everyones best interest to rethink their descriptive text of installs and maybe post there. Do the 3 mentioned work?

https://www.corvetteforum.com/forums...92-all-c4.html

WVZR-1

A 'teaser' for some maybe!

https://www.corvetteforum.com/forums...t-problem.html

WVZR-1

@Z51JEFF I'm sorry but if yours is wired as mentioned you've changed nothing from C100 F2 to the S terminal of starter and the coil would also be 'loaded' 100% of the time it would seem.

If someone was doing this going forward I'd think there's likely more appropriate ways to accomplish it. Pick your own relay But I can see absolutely no reason for the 5 terminal SPDT variety. No one has responded with reasoning so I'll guess there isn't reasaonable reasons why. Cliff?

Everyone mentions the use of 12 gauge wire, that just isn't correct. That circuit is 5 Metric wire which if you're sustituting AWG would require 10. Done with 12 AWG just don't make sense. A quick read of the FSM 8A-30-0. I believe that the relay if powered from the 'jump start block' should be fused. A 30 or 40AMP MAXi using a weather-proof affair. All SPST/SPDT relays suggest that the 'device' is nearly always 87, fused 12V is nearly always 30, 86 is nearly always the 'trigger' and 85 is grounded. Is it important? I'd think so because it would make all future diagnostics by anyone easier. There's procedures for 'load side' and also 'switched side'. The 'DEVICE' in this application is the starter solenoid'.

So my thoughts vs the others:
87 - S terminal starter
30 - Fused from Batttery Jump Block (other than that would do also so long as fused)
86 - Purple from C100 originating from CSS(Clutch Safety Switch)
85- Ground

That circuit (purple wire) should be more easily accesible than going into the wire bundle under the ECM which requires it's removal and also the mounting bracket. That wire is in the C100 junction lower engine harness connecter terminal F2. That connector generally isn't heavily taped like the upper forward lamp harness. I've borrowed a @Z51Jeff image and the connector is very visible. In the conduit the wire should be very accesible. I'd think the ECM and bracket could stay in place. Mounting it? Wherever you might want!

Jumpering the CSS I'd thhink a last resort. Carrying an appropriate 10G AWG Jumper? From the Ignition switch through the C100 block the entire circuit is 5M(10G AWG) The only wire that isn't is the .5M (20AWG) BLK/YEL to CCM that's the 'teaser' in post 11.

Z51JEFF

Dave regardless of how I have it hooked up I have had ZERO no start issues since I've had the relay hooked up. Now if it's wired wrong it's as easy as plugging in the terminals in the correct order at the relay.

WVZR-1

Yes and likely need to change the terminals on maybe two. 87 and 30 are generally different width on some configurations. Your location, the smaller diameter conduit and bracket is certainlly attractive. I've never needed to do it and aside from commenting on the 'blanket' I never paid attention. Your snapshot ID'd very well access to the C100 for those of us that haven't been there yet.

It would be very easy to confirm yours as it is with a meter first That's also why I mentioned the more frequently used terminations. Change nothing until confirmed. Have you 'jumpered' the CSS or is it still connected and functioning? Consider the fuse!

I spotted a post from many years ago where the fellow had a 'no start' and doing diagnostic to figure out what to do found the relay already done and just hanging at the ECM tray with either the splices or terminations failed. @DaveP85C4 (ihatebarkingdogs) posting/commenting then returning to delete certainly leaves much to be desired. He knows how I feel. I didn't mention 'liking' his termination configuration either! 30 & 87 identity is important I believe.

Cliff's 'descriptive text' is a damn mess - I assume it's a quick read for most and they sort it properly for theirs.

00Nassau

A couple of friends and I just performed this modification on a friends ZR1. We first installed the relay using J51Jeff's wiring:

Z51Jeff
#30 - Purple wire to starter.
#87 - Other end of Purple wire
#85 - 12 volt power at the junction block down by the battery
#86 - goes to ground.
#87A - is not used

We got the car to start once, and then it would not start again. So we then changed to:

#30 - Purple wire to starter.
#87 - 12 volt power at the junction block down by the battery
#85 - Other end of Purple wire
#86 - goes to ground.
#87A - is not used

And the car is now starting every time.

Basically, you need

#30 and #87 - Purple wire to starter and 12 volt power at the junction block down by the battery
#85 and #86 - Other end of Purple wire and to ground.
#87A - is not used

When you turn the key on, #85 and #86 activate the relay, which then sends full voltage to the starter from the block down by the battery thru #30 and #87.

Good Luck,
Allen