EFI / Circuit Opening Relay Questions (1 Viewer)

[IoN6]

I have been struggling with a random loss of power for a month or so now. Only when it is hot out and/or when up to operating temp for a while. Went through and replace the distributor cap, rotor, wires and plugs. She ran better, but issue still occurred. Though not as often since it is getting colder.

Well today on the way back from Home Depot it started doing it again. Got home and popped the hood and figured I would look at the EFI relay. Holy wow that thing was HOT. Looked in the FSM on tests and it says that there should be continuity across 1 and 3, but there was none. Napa down the street had one in stock (oh the sacrilege, I know) so ran down and picked it up. Threw it in right there and drove home. Did not act up on the way, but it was less than 2 miles.

Got home and pulled the relay, warm but not nearly as hot as before, and there is still no continuity across 1 and 3.

Like pringles, I had popped and I couldn't stop. So I pulled the Circuit Open Relay to test as well. STA and E1 have continuity, though it seems a bit delayed. +B and FC, no continuity.

So I have a few questions:

1) Is FSM incorrect on the EFI relay test or is the Napa relay DOA/FOA?
2a) For the Circuit Open Relay, STA and E1 give an audible continuity on my meter or 25.5Ω
2b) For the Circuit Open Relay, +B and FC give no audible continuity on my meter, but does show 137.7Ω

Any help or guidance is much appreciated.

 

[ppc]

l would reverse the leads from your meter on the pins of the relay. Some relays may have a diode inline to the coil which may explain the differences you have observed.

 

[IoN6]

l would reverse the leads from your meter on the pins of the relay. Some relays may have a diode inline to the coil which may explain the differences you have observed.

I am guessing you are saying the positive / negative? Tried both + to 1 / - to 3 and - to 1 / + to 3. Both the same on the EFI relay. Will have to pull the COR again in the morning to see what that one does.

 

[jonheld]

Putting a meter across pins 1 and 3 should see the resistance of the coil + the load resistor in the relay. The OEM EFI relay has no diode in place.
IIRC it should read about 4.6K ohms across the coil, so I suspect you are on the wrong pins or your meter is set incorrectly.
If the EFI relay was faulty, the engine wouldn't run.
If the CHECK ENGINE light is illuminated when you turn the key to the ON/RUN position before cranking the starter, then the EFI relay is good and the ECU is in a ready state.

 

[IoN6]

@jonheld so what you are saying is that the FSM is incorrect (which was one of my questions)?

 

[jonheld]

@jonheld so what you are saying is that the FSM is incorrect (which was one of my questions)?

It appears so. What does your multimeter say the resistance is across pins 1 and 3?
It's raining pretty hard right now, or I would check it myself.

 

[jonheld]

Allow me to eat some crow here.
I just pulled my EFI relay and spare relay out of the truck. Across the coil reads 65 ohms, so there is no current limiting resistor in place, nor is there a diode.
I'm not sure where I got 4.6K ohms from, but I'm sure something on the truck measured 4.6K ohms

In any case, the FSM is correct and I was wrong. Sorry for the confusion.

I did find something interesting. My spare EFI relay is a really old one from my 91 and the pinout drawing on the side of the relay case is wrong. Same Toyota part number as the current one, pins are identical, just the drawing is wrong. It shows the coil across pins 1 and 2 and the load across pins 3 and 4.

 

[jonheld]

More interesting tidbits.
I had an old EFI relay lying about the shop, so I took it apart. There is a 820 ohm resistor across the coil terminals, so there is some current limiting on the logic side.
That said, the resistance across pins 1 and 3 with the relay intact will be in the 65 ohm range because the resistor is in parallel with the coil. If the coil is open, it will read around 820 ohms or so.
If the coil is shorted, it will read less than 65 ohms.

We now return you to your regularly scheduled program already in progress.

 

[bicycleagent003]

If I recall correctly, the part number for the COR and the EFI relay are identical. No?
FWIW, my EFI relay also gets too hot to hold or pull by hand when I drive the truck. I never thought anything of it.
I think O2 sensors are suspects in situations like yours, unless they are known to have been replaced by good units. However, yours is a 1993 and I don't know if you have an upstream sensor. My intermittently failing upstream sensor caused me problems (occasional power loss under load) for a year before I figured it out. That was very frustrating.
Good luck.

 

[IoN6]

Yeah, the more I thought about it the more I realized I was barking up the wrong tree with the EFI relay. I replaced the O2's about a year ago. I checked the fuel pump relay and some other parts. I also disconnected my TOYODB1 connector. Which I think may have been causing it. Have not had any issues since, but have some driving in front of me today and it is warm out. So, we will see...