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1992 AE100 Levin
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55 Posts
Discussion Starter #1
Vehicle is a manual 1992 Corolla with the 5A-FE engine, nearly identical to the 4A-FE.

Within the last week or so I've been having intermittent stalling issues. On two occasions, the car stalled within 5 seconds of starting, once when cold and once when already at operating temperature. On the third occasion, I was driving highway speed and the car just shut down entirely. I can swing the key and it restarts after one of two tries, but on one of those occasions, it took minutes of waiting before I could get the car started.

The interesting thing is that each time this happens, and with the key in the 'on' position, there is a loud buzzing sound coming from behind my radio, in the vicinity of the ecu. Once I get the car restarted, the buzzing goes away and the car drives perfectly fine. Also, I don't get a check engine light to indicate any issue taking place.

From my research, the 'circuit open relay' could be the cause of this issue or maybe even an ecu problem?

Does anyone have any experience with this issue or have any idea what may be the cause and how to go about testing? I'm quite mechanically inclined but am not too well versed on the electronics.


Cheers
 

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1997 Corolla
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5,658 Posts
Buzzing? Would that be a relay? Are there relays in our ECUs?
 

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1997 Corolla CE
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2,861 Posts
I didn't see any relays in my ECM, but the circuit opening relay is above it. It's behind that little storage cubby above the cup holders. I didn't hear any buzzing sounds when my ECM died either, for what that's worth.
 

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1992 AE100 Levin
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55 Posts
Discussion Starter #6
Okay so update. This evening when o got home o shut off the car. I restarted the car and it died within 2 seconds. The buzzing sound came on and I felt behind the radio area and touched the open circuit relay and I can confirm that it is the relay causing the buzzing and it was quite hot to the touch as well. Could this be a grounding issue ? I will remove the relay this evening and inspect for possible corrosion. Any other tips or things to look for ?
 

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1992 AE100 Levin
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55 Posts
Discussion Starter #8
This particular relay is located beside the ecu. It is not a part of the ecu.
 

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1997 Corolla
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5,658 Posts
I'd go ahead and replace it if you can source another easily and cheaply - like at the junkyard. I'd say to get two of them at the junkyard, but since it's not a common problem, you're probably safe with one.

I would not get another one if the only ones you can find are expensive. In that case, I would want to see further testing and a conclusive diagnosis before spending $$ or $$$ on parts.

You definitely want that old one out of there since it's making a lot of heat.
 

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1997 Corolla CE
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2,861 Posts
Yours sounds like it's probably bad, but if you want to check. . .Do you have an FSM handy?

This is from page EG-148 Circuit Opening Relay:

4. INSPECT CIRCUIT OPENING RELAY

A. Inspect relay continuity.
(a.) Using an ohmmeter, check that there is continuity between terminals STA and E1.
If there is no continuity, replace the relay.
(b.) Check that there is continuity between terminals +B and FC.
If there is no continuity, replace the relay.
(c.) Check that there is NO continuity between terminals +B and FP.
If there IS continuity, replace the relay.

B. Inspect relay operation
(a.) Apply battery voltage across terminals STA and E1.
(b.) Using an ohmmeter, check that there is continuity between terminals +B and FP.
If there is no continuity, replace the relay.
(c.) Apply battery voltage across terminals +B and FC.
(d.) Check that there is continuity between terminals +B and FP.
If there is no continuity, replace the relay.


I'll try to describe the pin locations.

If you're holding the relay with the metal bracket facing away from you:

It will look like this:

PIN PIN PIN
PIN EMPTY PIN

Which translates into this:

STA +B FP
E1 EMPTY FC
 

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1997 Corolla
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4,575 Posts
Just because the relay is buzzing doesn't mean that's the problem. It could be the ECU is not grounding the relay correctly. The ECU shouldn't ground the relay at all when the engine is not turning and firing the spark plugs, like when you just have the key at the ON position.

On the other hand, the switch inside the relay could have broken, so it's not springing back to the off position. Test it like Chris94 said.
 

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1992 AE100 Levin
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55 Posts
Discussion Starter #13
Yours sounds like it's probably bad, but if you want to check. . .Do you have an FSM handy?

This is from page EG-148 Circuit Opening Relay:

4. INSPECT CIRCUIT OPENING RELAY

A. Inspect relay continuity.
(a.) Using an ohmmeter, check that there is continuity between terminals STA and E1.
If there is no continuity, replace the relay.
(b.) Check that there is continuity between terminals +B and FC.
If there is no continuity, replace the relay.
(c.) Check that there is NO continuity between terminals +B and FP.
If there IS continuity, replace the relay.

B. Inspect relay operation
(a.) Apply battery voltage across terminals STA and E1.
(b.) Using an ohmmeter, check that there is continuity between terminals +B and FP.
If there is no continuity, replace the relay.
(c.) Apply battery voltage across terminals +B and FC.
(d.) Check that there is continuity between terminals +B and FP.
If there is no continuity, replace the relay.


I'll try to describe the pin locations.

If you're holding the relay with the metal bracket facing away from you:

It will look like this:

PIN PIN PIN
PIN EMPTY PIN

Which translates into this:

STA +B FP
E1 EMPTY FC
 

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1992 AE100 Levin
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55 Posts
Discussion Starter #14
Thanks for the in depth instructions Chris. I carried out all of the tests you recommended. Everything checked out except for 4Ab. There was no continuity between +B and FC terminals.
Is this a situation where something internally has broken ?
Also, I will try to source a relay locally in the morning.
 

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1997 Corolla
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4,575 Posts
FC is the pin that gets grounded by the ECU. +B to FC has a small solenoid and resistor in the relay, so it may have a small amount of resistance. The multimeter may not detect it as continuity if the resistance is too great.

If 4Bc-d tests good then the relay should be turning on the fuel pump.

If you can find a cheap and/or used relay it might be worth throwing it in to see what happens.

If the relay turns out to be good, then you might also have low voltage at the relay or a bad ground down the line. I say this because the solenoid from +B to FC and the power to the fuel pump from +B to FP both get power from +B, so you might be getting a situation where the solenoid pulls the contact closed from +B to FP, then the extra current draw to the fuel pump (FP) causes the solenoid to lose power, so the contact opens from +B to FP, then the solenoid gets more power so it pulls the contact closed again, etc, etc. That could explain the buzzing or humming.
 

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1992 AE100 Levin
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55 Posts
Discussion Starter #16
Ohh interesting. I think I’m beginning to understand. I also looked at a diagram to get a better jist of the switch operations etc.

I think I need to amend my last comment. When testing the +B to FC terminals for continuity, the multimeter did not beep like usual, however, it did show a reading of 132. The other tests for continuity gave much lower readings and the multimeter beeped. So I’m assuming there is high resistance issue going on here
 

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1995 Toyota Corolla
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1,661 Posts
This is a Japanese Levin? It might have different parts than a regular Corolla, check replacement parts in a Japanese catalog if you change anything to be sure.
 

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1992 AE100 Levin
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55 Posts
Discussion Starter #18
Yes it is the Japanese Levin. The price for a new one is ridiculous so I will be getting a used one this evening. Will update if it solves the issue.
 

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1992 AE100 Levin
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55 Posts
Discussion Starter #19
Update:

I bought the used relay pretty cheap, which I tested to be sure it was good and it was. Unfortunately it didn’t fix the issue.
However, reading through everyone’s replies, I decided to heed DrZ’s advice, so I made a new ground for the relay. Snipped the ground wire, crimped on a ring terminal and bolted it down. It’s been two days and about 100km of driving and I haven’t had a single issue. No random stalling, no starting issues, and no crazy hot buzzing relay. In addition, since making the new ground, this is the first time that I have actually heard my fuel pump prime in the three years that I’ve had the car. It never made a noise with the key in the “on” position before. Thanks a ton!
 

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1997 Corolla
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4,575 Posts
Unfortunately, you just made your car a lot more dangerous if you ever got in an accident. The ECU only keeps the fuel pump running if the engine is running. If the engine stops running because a fuel line gets broken in an accident, then the fuel pump shuts off. The way you wired it it will just keep pumping out fuel and potentially cause a big fire (as long as the key is ON).

I would have checked the ground from the ECU to the back of the engine block under the intake manifold. It's possible it's loose or corroded and not allowing enough current to get through to activate the relay.
 
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