Should the EFI relay get hot

[Randy87T]

Have got the ms3/ms3x installed and car is running on E85. Have noticed that after some idling time that the efi relay gets very warm. I don't remember it ever doing that before but then again maybe I just never noticed before.

Can someone tell me if that's normal or do I have a problem.

Thanks
Randy

 

[Poodles]

Yep, normal.

 

[Randy87T]

Thankds. Had me worried.

 

[MightyAl]

Get it on the road Randy!!

 

[Crypton2006]

Yep, normal.

Actully no, you might need to replace it. Some heat is normal, but if you think it has gotten hotter sense the build there may be a problem.
Did you rewire anything possibly drawing more current they you should be through that relay?

Here is a simplified lesson in DC theory.

Heat coming from a component is expressed in Watts. Formula is Watts = Voltage X Current. Voltage would be the voltage drop across the relay. There would only be a voltage drop across the relay if there is resistance in the relay. So it would go something like this. (these are just made up numbers)

Perfect Relay 0 ohm's of resistance

10amps X 0 ohm's = 0 volts....... Watts = 0 X 10 Amp's = No heat.


Bad Relay .5 ohm's of resistance


10amps x .5 ohm's = 5V............... Watts = 5V x 10 Amp's = Something catching on fire.

Of course there is never going to be ZERO ohm's but you can see that a little bit of resistance in that relay will cause a lot of heat. Most likely you wired in something and now your pulling more current.

 

[suprarx7nut]

Mine gets burning hot. Never had a problem. A new relay may not get as hot, but it's certainly not unusual for them to be very warm.

Sent from my ADR6400L using Tapatalk 2

 

[Poodles]

They do get burning hot (there's a reason they're metal cased...)

 

[Crypton2006]

Well i guess that stupid ohms law thing is just hear say.
The metal case is to help dissipate heat from the field winding. Not really to dissipate heat from a 20 + year old contact. These are fused at 15 amp's. I have never felt a 30amp Bosch relay (with a plastic case) get to the point of burning me. All im saying is that you would never know if you had a big problem unless you threw a meter on it. Just because everyone's 20+ year old relays are getting hot does not mean its "normal".
This is a tech section nonetheless so we should look at it at a technical level, not just a "don't worry about it".

 

[IBoughtASupra]

I trust Peter Griffin on this one, he knows his stuff.

I have never had one of those relays get burning hot. I can hold them without any issue.

 

[Poodles]

I've replaced mine thinking it was bad because it was hot...yes it was still burning hot after a longish drive. I also know how to use a meter (hint: electromagnets get hot)

 

[IJ.]

Relay or Resistor?

 

[Crypton2006]

Thanks for the hint.
Guess i missed that in the last 60 credit hours of my EE program.
Field winding is the wire portion of the electromagnet

 

[NashMan]

hahaha i have new favoit thread


i have this issue in my truck cause of old shitty wiring relay would get hot and then stick open or closed and then poof my injectors don't fire

I used to bomb start my truck when this happend and when the truck had gas in ti it fire since on the 22re the ing system was not controlled buy the efi part of the ecu and every timei blind the thottle the relay would click back and froth make the relay hotter and hotter



20 year old cars do this whne they wer brand new they never did

 

[jetjock]

Crack me up. So many experts, so little time...

 

[Randy87T]

Thanks for the replles everyone. The reason I was asking the question was that the car is running lean and the MS3 Autotune is trying to add in way too much fuel to compensate. I thought that maybe there is too much current draw through the circuit showing itself by overheating the efi relay and creating the lean condition somehow. I did replace the relay but had the same result.

One more thing to ask... What should the voltage be to the injector. I am reading 9v roughly with the key on but not running and still using the stock resistor bank. They are 120lb low impedance peak and hold. Had them flow checked and they were all good so how do those big boys run lean?

Need to add that Autotune is trying to add too much fuel even at idle. Maybe some of you e85 megasquirt guys can help me out.

 

[Randy87T]

Get it on the road Randy!!

It is Al just not doing anything more than puttering it around until I can get this problem solved. Been working on it everyday.
Want to say thanks for coming down to get me going on this project. It was/is greatly appreciated. The texting was a big help
also. Beers are on me.