KamRx7

Hi
My 86 stopped running. It's got fuel and spark but the injectors are not tuning on. There are no readings from the diagnostics. I think I have traced it down to the ECU. There was a fried solder joint around resistor number 951.

The problem is that the resistor is open circuited. The resistors around the same area are 3R9J that converts to a 3.9 Ohm resistor. But that does not mean this one was.

Is there anyone out there that could tell me the Ohm value of this resistor?

KamRx7

Here is where the resitor should be. See the attached file.

misterstyx69

iTrader: (142)

a used Ecu is Fairly cheap.if it is N/a I have a Couple 326's.
I just don't see the "Logic" of Farting around with a Fried Ecu,.it may be more than just that Resistor.and you have to find out Why that resistor popped in the first place.,But Good luck to ya.

KamRx7

I thought it would be like the rest of the soldering problems. A high resistance, poor solder, causes the heat and fries the component. It would be an easy try. I did not realize that a 323 had the same ecu. You don't see to many Rx7's in this area. What do you have to look for in a replacement? A particular number or year? This one is an 1986.

Thanks for the reply.

Dale

RotaryRocket88

iTrader: (7)

When misterstyx69 said "326", he was talking about the model number for the ECU, which is N326. This doesn't mean a Mazda 323 uses the same ECU.

You can use an N326, N327 or even N338 (S4 vert) ECU as a replacement. Check the 2nd gen classified section to pick one up.

KamRx7

I'm going to try a new/used n326. It's funny one out of 10 tries it starts and runs just fine.
I think I'll hook a scope up to the injector output from the ecu and see if the signal is there when cranking. The other thing is if the fuel pump is running in the start\crank.

ProChemBroTCM

What is the number on your ECU Kam? From my limited understanding on the topic, I thought that you can only use an ECU that shares the first three characters as the one installed by the factory. For example, my convertible has/had an N338, and if I want to replace it, I'll need to find another ECU with N33_ on the sticker. I could be wrong; I'm actually trying to research the topic more, but it's slow going slogging through all the unrelated topics brought up by my search... I had the same thing happen to my ECU - one of the resistors burned up, so now I'm on the hunt for a new ECU.