05-21-2019 | #1 |
Join Date: Jan 2012
Location: Wisconsin
Posts: 887
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Classic no start “relay fix” – what does it do?
Gurus,
How does adding the relay to the starting circuit help?* What is the issue we’re trying to solve? Is it low voltage to the starter solenoid or what? The purple wire to the starter solenoid is after both the starter enable relay and the clutch start switch, so do we think there’s a voltage drop through those? I want to understand the issue, so can you help me and explain the problem the added relay solves? Thanks, Gary *[a few recent threads for reference http://www.zr1.net/forum/showthread.php?t=30452 https://www.corvetteforum.com/forums...made-easy.html https://www.corvetteforum.com/forums...post1581564089 ] Oh, who want to read a thread without a pic in it, so here you go
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1990 ZR-1 #2180 Red/Black Many of the usual mods for 460HP, tuned by Marc Haibeck ZR-1 Net Registry Member #1548 |
05-21-2019 | #2 |
Join Date: May 2007
Location: Westminster, Maryland
Posts: 3,689
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Re: Classic no start “relay fix” – what does it do?
I believe that the relay is added to bypass all of the contacts in the start circuit that could cause a "no-start".
Jim
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If it isn't fun, you aren't doing it right! 1990 Black ZR-1 - sold 1993 Quasar Blue ZR-1 1994 Competition Yellow ZR-1 1995 Dark Purple ZR-1 Maryland State Coordinator WAZOO Member |
05-21-2019 | #3 |
Join Date: Aug 2009
Location: South Dakota/California
Posts: 3,797
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Re: Classic no start “relay fix” – what does it do?
As Jim suggests
The voltage required to trip the relay is considerably less than the voltage required to "trip" the Starter Solenoid. What you have left are the contacts of the Starter Solenoid itself which when closed send voltage directly from the Battery to the Starter Motor. I always refresh (wire brush) the Solenoid Contacts of the Starter Solenoid during a Top End Restoration of the LT5. This is described in several posts of the signature below. Relay Installation is also described (LT5 Added Systems).
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Left Clickable links -Solutions- LT5 Modifications/Rebuild Tricks Low Mileage ZR-1 Restoration 1990 Corvette (L98) Modifications LT5 Eliminated Systems LT5 Added Systems LT5/ZR-1 Fluids 1995 LT5 SPECIFIC TOP END REBUILD TRICKS Last edited by Dynomite; 05-21-2019 at 09:05 PM. |
05-21-2019 | #4 |
Join Date: Nov 2007
Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri
Posts: 6,493
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Re: Classic no start “relay fix” – what does it do?
Let me "splain" it this-0-way...
At issue (90-92 C4s) was the high current draw through the clutch safety switch necessary to operate the starter solenoid in the 90-92 circuit design. Arcing increases with current, and the clutch safety switch can't handle a steady diet of it! So, in 93 the circuit was changed by installing a heavy duty relay to service the solenoid. As result, the clutch safety switch now only has to carry a very small current - just enough to activate the relay: the relay now carries the relatively heavy current load required by the solenoid. The relay modification (addition) to the 90-92s essentially updates the starter circuit to that of the 93+ C4s. The life expectancy and reliability of the clutch safety switch is thus vastly improved. DIAGRAMS (BELOW)
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Good carz, good food, good friendz = the best of timez! 90 #1202 "FBI" top end ported & relieved Cam timing by "Pete the Greek" Sans secondaries Chip & dyno tuning by Haibeck Automotive SW headers, X-pipe, MF muffs Former Secretary, ZR-1 Net Registry Last edited by Paul Workman; 05-21-2019 at 11:58 PM. |
05-22-2019 | #5 |
Join Date: Jan 2012
Location: Wisconsin
Posts: 887
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Re: Classic no start “relay fix” – what does it do?
Thanks Jim, Cliff, and Paul.
So, Paul, the starter solenoid requires more current that can be supplied if the contacts and loads leading up to the solenoid introduce too much resistance. (true?) I have my clutch switch bypassed, but I still experience an occasional no start. I plan on doing the relay fix anyway. I'm also going to follow ZR-71's thread where rather than cutting the purple wire in the loom under the hood, he routed from the under the dash disconnecting wires from the clutch switch. Here's my plan mount new relay under dash -- pin 30 [high power in] -- new red 12ga wire from battery block pin 87 [high power out] -- purple wire at clutch switch pin 85 [low power ground] -- to ground ping 88 [low power trigger] -- yellow/black wire at clutch switch pins 30 and 87 are the "high power / battery voltage" legs of the relay pins 85 and 86 are the "lower current / trigger" legs of the relay So, the yellow/black wire which comes from the existing starter enable relay will send the signal to trigger the relay and provide battery power through the purple wire to the starter solenoid.
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1990 ZR-1 #2180 Red/Black Many of the usual mods for 460HP, tuned by Marc Haibeck ZR-1 Net Registry Member #1548 |
05-22-2019 | #6 | |||
Join Date: Nov 2007
Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri
Posts: 6,493
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Re: Classic no start “relay fix” – what does it do?
Quote:
Quote:
And, if you've bypassed the clutch switch, there's NO advantage to installing the relay mod. (In fact, if you don't intend to remove the clutch switch bypass, installing the auxiliary relay would serve no purpose and actually decrease reliability by introducing an additional (do nothing) component that could fail. Quote:
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Good carz, good food, good friendz = the best of timez! 90 #1202 "FBI" top end ported & relieved Cam timing by "Pete the Greek" Sans secondaries Chip & dyno tuning by Haibeck Automotive SW headers, X-pipe, MF muffs Former Secretary, ZR-1 Net Registry |
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05-22-2019 | #7 | |
Join Date: Jan 2012
Location: Wisconsin
Posts: 887
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Re: Classic no start “relay fix” – what does it do?
Quote:
I suspected the starter solenoid, but I replaced the starter solenoid and I still have the occasional no start ... So, I guess I'm stuck
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1990 ZR-1 #2180 Red/Black Many of the usual mods for 460HP, tuned by Marc Haibeck ZR-1 Net Registry Member #1548 |
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05-22-2019 | #8 |
Join Date: Jul 2016
Location: Greater St. Louis
Posts: 488
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Re: Classic no start “relay fix” – what does it do?
Had an odd starter failure on my 94 with intermittent no start. Marc found a coolant leak from the water pump gasket. Shape of the plenum allowed coolant to flow back to the starter and puddle underneath. Starter solenoid was newer but starter couldn’t survive sitting in stale coolant. Only hint of coolant leak was an occasional few drops of what looked like hydraulic/clutch fluid on the floor seemingly under the slave cylinder. It was discolored after its journey through the plenum valley and didn’t look green at all. I checked the clutch fluid reservoir several times but it was always full. The color change fooled me.
Anyway, Marc’s opinion before nailing down my problem is the purple wire tricks treat a symptom, not the problem. Usually the starter or at least solenoid needs to be replaced. |
05-22-2019 | #9 | |
Join Date: Aug 2009
Location: South Dakota/California
Posts: 3,797
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Re: Classic no start “relay fix” – what does it do?
Quote:
Does starter solenoid click when you turn key? Does battery voltage drop when solenoid clicks? Are your battery hot wire and ground clean and tight? The issue could be internal to the starter electric motor but I have found that the Solenoid points were the most often issue. You may just have to recondition the starter. Photo provided by mgbrv8 Complete starter rebuild by mgbrv8 (Dave) |
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05-22-2019 | #10 |
Join Date: Oct 2004
Location: Folsom CA
Posts: 1,653
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Re: Classic no start “relay fix” – what does it do?
Since I did the "Dreaded No Start" relay mod, I've never had a no-start.
It's been a good 10 or 12 years since I did it. No regrets. 'Crabs As Paul Harvey (God rest his soul) said, now it's time "For the Rest Of the Story". I didn't invent the DNS Mod (Dreaded No Start). I did popularize it, but the inspiration was not mine. After too many DNS events to count I went looking. The absolute worst DNS event was at the parking lot of a local BlockBuster Video store, which was about 10 blocks from my home, on a 115 degree day. I walked home. I had found mention of installing a relay in an obscure forum somewhere, but no details about what it was, where it was, or how they did it, and I was unable to find anyone who would educate me. So I dug out the wiring schematics and re-invented the wheel. Necessity is the Mother of Invention. It's taken a life of it's own, and I'm proud and humbled to have had a small little part of it.
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TomC '90ZR1 #792 Honorary Pirate [B]If it ain't FUN, you're doing something terribly WRONG. [/B] |
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