What's a "circuit opening relay" and how do I replicate it?

Thread Starter

strantor

Joined Oct 3, 2010
5,331
I'm trying to restore a '94 Toyota Celica that got flooded in Harvey. The ECU was submerged and I already replaced it but the car still won't start. There's a relay hanging off the side of the ECU which I didn't replace yet which also got submerged. I think this relay is preventing me from starting the car. P/n: 85910-20050. I can't find it for sale anywhere, because it's discontinued. I only found it for sale a couple places and it was about $130. I'm not going to pay that amount for a relay.

My internet searches indicate that it's either for the fuel pump or the ignition . It's not an ordinary relay. It has two coils. " circuit opening relay" would indicate to me that it is a normally closed relay, but it is not. I don't understand how the two coils interact with each other. I have a box of 12 volt relays in my garage, and I would like to figure out how to replicate this one relay with two separate relays to perform the same function. Does anyone know how this relay is supposed to work and how it can be replicated?

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ericgibbs

Joined Jan 29, 2010
10,776
Is it possible to apply 12V to the 'keeper' coil, check that it holds On and then apply 12V in the opposite sense to the release coil.?
 

Thread Starter

strantor

Joined Oct 3, 2010
5,331
There is a whole raft of schematics if you Google 'circuit opening relay bypass'
Max.
Thanks for the buzzwords. I put that into my googler and got a lot more practical i6nfo that what my searches revealed. So apparently it's an OR configuration. Either the mass airflow sensor or the ignition switch. When you're starting the car, the ignition keeps it on until the car starts to suck air, and then the MAF keeps it on. This will be super easy to do with 2 relays.
 

debe

Joined Sep 21, 2010
1,185
That same relay is used in several model Toyot Corola, Shouldn't be to hard to find in the wreckers or scrap yards cheap.
 

Thread Starter

strantor

Joined Oct 3, 2010
5,331
I love that feeling when they start after a major issue or tear down/rebuild.
Yeah me too. This one was especially momentous because the car hasn't ran since 2013. It's my stepfather's car and he had loaned it to my (at the time) brother in law who ran it with no oil and threw a rod through the block. I was in school and had spare time so I told my stepfather I would replace the engine. He ordered one off eBay and it showed up looking like it had seen better days; couple of decades worth of crusted oil/grease/grime caked all over it. So I told him it would better to go ahead and rebuild the donor engine before installing it so that I wouldn't have to take it out again a few months/years down the road. I ordered the rebuild kit and got half-way into the project when life happened. I started my own business and dropped out of school and no longer had time to mess with it.

Fast forward to 2017, I reconnected with one of my Navy buddies who is a certified mechanic. He said he was looking for side jobs and I told him about the car. He took the project on, worst possible scenario, finishing what I started, bolts and parts now lost after being kicked around my stepdad's garage for 4 years. He worked on it a little bit here and there in the evenings and a couple months later it was ready to go. He drove it around the block and then called my mom to come pick it up. She was busy that day and couldn't make it. The next day Harvey hit, and the car was submerged. My stepdad was heartbroken. He loved that car. He was going to write it off but I snagged it and started fixing it up. He said i could have it and he thinks I'm fixing it up for myself, but once I'm done, I'm giving it back to him. I just want to drive it around a few thousand miles to make sure it's 100% and no gremlins, because if I give it back to him and it immediately craps the bed, that's going to be a roller coaster of emotions for him (he's a sensitive guy).

So when i got it running again, that was the first time it had seen the open road in 4 years. Thankfully the registration laws are temporarily suspended due to Harvey while I drive around with a 2014 sticker. It passed a safety inspection yesterday with no airbag module installed LOL.
 

Lyonspride

Joined Jan 6, 2014
137
TBH My immediate thought was it's relay designed to maintain state when the voltage drops during cranking. One 12v coil and one lower voltage coil maybe.

In much the same way as old school ballast ignition systems worked, ignition coil had a 1-2ohm ballast in series, this was shorted during cranking, to account for the voltage drop, but once running it switched back in the 6ohm resistor to avoid frying the coil.
 
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