I am looking for the fuel injector grounds on a GSL-SE. I have the wiring diagram, and I think I have them tracked down, but I would like some confirmation from someone who knows for sure.
They look to be under the dynamic chamber (or whatever mazda calls it) on top of the engine, on the left side. Near the oil filter and kind of under the solenoid rack. Is this correct?

I know where they are on a second gen, but not on an SE. I have 12V on the B and D connectors (which are the fuel injector grounds) of the ECU, which isn't right. I had the same situation on a second gen last summer, and once I cleaned up the grounds it started right up. It seems odd I would have the same problem again in a first gen car, but who knows.
I have a no start condition currently, but it will start momentarily with ether. Which tells me I have no fuel. The fuel pump is good, and I can hear the relay. So, I am thinking it is the injectors. They were just rebuilt by RC Engineering, so I am guessing they are good. That is why I looked towards the ECU.

Any help would be appreciated.
Thanks.

 

That is correct. There are 2 black wires w/ eyelets that are bolted down at the solenoid rack. These are the grounds you are looking for.

Also, do you have spark on trailing? Is the tach moving? If trailing is dead, there will be no signal to fire the injectors.

 

Ok, I found the grounds and cleaned them up. But, they were already immaculate. Which made me go back and examine my testing of the ECU. I was looking at it backwards, Doh! My grounds are fine.

So, I will try your advice. Don't know if the tach is moving or not, I will find out. I will test the trailing plug wires and see if I have spark. I am going to have to start the troubleshooting right from square one. I was really hoping to find this without spending a huge amount of time on it. I have so many other projects. Oh well.

 

Ok, no luck on the trailing ignition.
I have spark on both the leading and the trailing.

What would cause the injectors not to fire, other than the ECU, the trailing ignition, and the fuel injection grounds? I have checked all of these things.

 

Look at this for checking error codes (similar to the 2nd gen cars):

https://www.rx7club.com/1st-gen-archive-71/electrical-se-error-code-write-up-285461/

Hook up the tester and crank the engine. See if you get the trailing ignition code. If so, take a look at the trailing coil (-) terminal. There should be a blue spade connector connected to the trailing (-). If that checks out and still not getting signal to ECU, there is also a yellow connector under the windshield washer bottle (passenger side). That connector carries the tach signal and other improtant signals (pretty sure injectors are through that connector too).

Did you check voltage at all of the pins on the ECU (shown in Haynes manual and FSM)? The other possibility is that signals are getting to the ECU, the ECU is good, but signals not getting to injectors. Could be bad connectors on the injectors (they tend to crumble with age). Another option is that the injectors are just stuck closed.

- do code checker
- get trailing connector
- check yellow connector
- check ECU voltage
- check wiring between injectors and ECU

 

ok ive got a chore for you to do then pull the long plug from the ecu and check out what voltage you are getting from F and H and let us know and how is you rats nest. when you leave the ignition switch in the on position do you here clicking from under the uim. if not check the little bullet looking things on the driver side where all the relays are make sure they are connected properly. after that I'm not sure what to do was this an engine swap or something?

 

also B and D should get 0v for the ground dude thats so not good getting 12v

 

No, B and D are 0 volts, as they should be. My mistake in my earlier post.

 

I can hear the main relay kicking in, so it's ok.

But, I will follow addicts advice, and repost results this Sunday, if not sooner. Work keeps getting in the way of my RX repairs.

My wife keeps harping on the same thing over and over. "Would you just fix one of them completely before you start working on another one!"

That's no fun!!!

 

what about F and H?

 

Kent, is there anything you don't know about these cars? :-)

Mike

 

hehe.. Well, it is just experience of owning my GSL-SE for about 13 years now. I let a shop work on her once... that was such a mess.. too long and too expensive. Never again. Ever since, I have and will always do the work myself.

 

I am the same way, I do all of my own work.
Usually I don't need advice (notice the low post count), I can figure it out. But, this one is starting to get the best of me.

 

If the SE is like 99.9% of the other EFI cars in the world,then the grounds for the injectors are controlled by the ECU.
Thats how the injectors work.The large black wire to the injectors is a full time power wire that is fused from the battery,then energized by the ECU main relay when the key is turned on.The smaller wire from the injector runs to the ECU,which switches the ground on and off as needed to provide the correct amount of fuel to the engine based on input from various sensors.The reason the ECU controls the ground, instead of the power supply to the injectors is because in this configuration,the ECU doesnt have to channel much current.This keeps the drivers cool and reduces the chances of an overload or short.This is the same method used to control all the other sensors and solenoids on the engine that the ECU has direct control over.All the large black wires with white stripes that go to the various solenoids on the engine,are power leads.The smaller,colored wires that go to the ECU,are the grounds which the ECU switches on and off.

 

that ECU tester actually worked. very nice mod.

 

What ECU tester?

 

This one:

https://www.rx7club.com/showthread.php?t=285461

You make it yourself... very simple to do. Great tool for checking to see if major things are either not connected or are bad. I used this tool to find out my AFM was messed up.

 

i used it to make sure it was working right. thinking about mounting it some where

 

Ok, I have 12V to the fuel pump, but it's not running. I "assumed" I had fuel to the injectors, because I replaced my pump with a used spare that I just bought. But, I am thinking now that I have a fuel pump problem.

I have applied 12V to my old pump (out of the car), and it does not run.
I have 12V to the connector behind the drivers seat in the cubby hole that goes to the fuel pump, and it is not running.
Am I missing something, or are both of my pumps bad? To run the pump all you need is 12V correct?

 

12v and a ground is all you need. Relay could be bad fuse could be bad. But you could always disconect the plug going to the pump and splice them into alternate power source to see if pump works

 

I plugged the old pump straight in to the battery on my 80, no go.
And I have 12V at the fuel pump connector, with the jumper connected, when I pull the jumper, I lose the 12V as I should.

I am thinking of buying a Walbro and seeing if that will work. I need one eventually anyway, as this is to be my turbo project.