Hello Gentlemen.
I have a 93 FD mostly stock, exhaust intakes and whatnot, doesnt really mater for this post...
My motor was working great no problems, UNTIL my diff seal went out and I put the car away for 2 months til I had time to work on it.. NOW IT DOESN'T START!!..
I am getting a CEL code 71 (seven long, 1 short) Which means Injector (front secondary) I don't understand y it wud go out for no reason at all, but whatever..
Questions is, how do I fix it? Where do I even start? And what do I test for?
I can take apart my whole motor to get to that thing and check to see if the connector is broken, but why would that happen for no reason?..
Also, I'm guessing you can test the injector from the ECU side, but I don't know how to do that.

How do you even get ECU readings with a multimeter if your ECU plugs need to be plugged in? Using the airplane wire method? And what readings would I be looking for to see what's going on with the injector. Sorry guys, I don't even know where to start looking for information on this. Been doing lot of searching but nothing that relates...
Looking forward to hear your tips. Thanks!

 

A secondary injector code won't keep the car from starting. Most likely the engine is flooded or the like, probably just need to de-flood and it will start up for you. That's usually the culprit if the motor sat for a long time and won't start. I would also be sure you have a strong battery.

Injector wiring is simple. Each injector has 2 wires going to it, one is 12v and the other goes to the injector driver in the ECU. The ECU taps that wire to ground, that is how the injector fires. Faster tapping, more fuel.

The stock ECU is SUPER dumb with the codes. When you have a circuit, you have resistance. It looks at that resistance to make sure the circuit is complete. In this case it's open circuit, no resistance, so it's giving you a code.

Fortunately the secondary injectors are MUCH easier to get to than the primaries. With a meter, test for voltage at the two wires. If one has 12v with the key on, then you know that wire is good. For the other, you can test continuity with the multimeter, but you will likely need an extension wire and maybe an assistant. Touch the non-12v wire on the injector plug with the meter and the other lead on the meter to the wire going into the ECU.

Most likely it's the connector itself, they crumble and get banged around. If so, go to the pick and pull junkyard and look for 90's Mazda Protege's. They have the same connector, and they're up high on the engine, takes 2 seconds to cut a few off and have some connectors.

If it's not the connector, you're going to have to find the break in the harness, or run a new wire back to the ECU.

Dale

 

Thank you Dale! Once again coming thru with the good info I need. Appreciate it much.
Yeah that's what I figured. Didn't think it would keep the car from starting, esp since it's not the primary inj... Okay, I'll do the de-flooding technique.
Still doesn't make sense to me why when I put the car away there was no inj problem, but now all of a sudden there is.. But yeah, I will check around like you suggested.
So yea I'll check for 12v for the first wire on the injector plug, and then for continuity at the second one.
So I would pull off the plug at the ECU right? And then find the wire that goes to the injector (via wiring diagram pin layout) and test the wire that goes from the ECU to the non 12v wire on the injector plug right?

What do you mean the ECU is super dumb with the codes? I thought it was pretty spot on with letting you know what the problem is? Does that mean that the ECU might be saying it's the injector when there is in fact no problem there?

 

Basically that's let's you know there is an error in the circuit with the secondary injectors. That doesn't mean the injectors are the exact problem per say; it could be a grounding issue, plug issue, spliced/frayed wires, etc...

 

Got ya, got ya. But as far as the testing techniques, I understand it correctly yes? I will do the testing hopefully today or tomorrow and I'll check back here with the results.

 

Oh, and Why is it that the motor would flood after a while of standing? I would figure even if there was any extra fuel, it would evaporate over time... So why then would flooding be possible?

 

First, I would try the de-flooding procedure to see if that even works. It may not be flooded at all so you may continue to diagnose the problem.

 

Okay, So I did the de-flooding procedure, let it sit with no spark plugs overnight and tried starting it the next day. It didn't do a great job, I had to crank it 6 or 7 different times, cranking for 10 seconds or so. It finally did start up and has been starting without hesitation since then.

Now.. I've only driven this car for <2k miles since I got the motor rebuilt, so the plugs are brand new almost. They had a lot of black buildup on them and I was wondering if this is normal or not.. Sure seems far from normal.. I attached pictures, lemme know.

AND: I have a ECU code question. Now that the car runs, the check engine light does not come on. Everything seems normal and CEL is never on. But when I run the diagnostic, the CEL still shows code 71. Is this normal that there would be no CEL but there would still be a code? Still get a 71 when checking.

 

You should clear all the codes by disconnecting the positive battery cable and then pump the brake pedal a few times to rid the system of residual voltage. Do this and then check to see if you still get the code. I doubt you will.

Good luck!

 

If it's a new motor, those plugs look about normal. You get a LOT of oil, assembly lube, etc. the motor is burning off initially. Either scrub 'em clean or throw a new set in.

Also, don't forget your anti-sieze on the threads when installing.

Dale

 

That depends on the spark plug brand being used:

http://www.ngksparkplugs.com/pdf/tb-...1antisieze.pdf

 

If you don't know how to install plugs and use a 5 foot cheater pipe, sure. Install by hand and install to snug every time.

I always use anti-sieze, I've changed plugs on cars that didn't have it and had to fight the plug the whole way out. With, they unthread by hand after being broken loose. I've NEVER had a problem breaking or damaging a plug.

Just a little dab is all you need.

Dale

 

Disagree all you want, I'm just pointing out that NGK suggest not using anti-seize with their plugs. Call them up and argue with them.

 

I squirted antisieze under my neighbor's door handle on april fools day. He HATES the stuff. I love it and think it works great!

I got a flooded RX7 First gen running that sat up for a few years. I put a few drops of MMO into the engine and pulled it around with the 4 wheeler. As soon as the engine starting spinning 3,000 RPMs that baby fired right up. I sure there was some reason why I'm not supposed to do that but my neighbor was going to throw it away because the engine had no compression. His son drives it everyday to school.

 

UPDATE:
What's up guys. So I had time to work on my car today and I tested the injector wiring like you described Dale.
With the key to ON I tested the injector plug and basically, both of the wires had 12v power. Yeah, both of the wires on the plug read 12v.
Then I pulled off the plug from the ECU and tested the LG/W wire that goes to the secondary front injector for continuity. It read 0.5-0.7 resistance. Is that a good reading or should it not be having any resistance at all?
Anyways, help is appreciated, thank you guys.
While I wait for replies I will just go run a separate wire to the injectors and see if the code disappears.

 

Is only the one injector plug messed up like that? I would test a "known good" plug too.

That resistance should be fine. You'll probably have some from the old wiring.

Dale

 

Well is it normal that I am getting 12V from both of the wires on the injector plug?
From what I understand I should only be getting it on one of the wires right? and the other should give no voltage? If they're both putting out 12v then the wire somewhere is touching another positive wire right?
Yeah, I'll check the other secondary injector. But it's more of a pita to get to..

 

So the secondary rear injector is also showing 12V at both wires at the injector connector.

 

Any input on this? Why are both wires to the plug showing 12V? There should be only one wire giving 12V right? Anybody that knows FD electrical well?

 

So.. Talked to a very knowledgeable technician, a guy who used to work for team Falken and built Calvin Wan's RX-7 drift car.
So basically, It is normal to be getting 12V at both of the wires on the injector plug. When the plug is disconnected you get 12V at both wires. When the plug is connected to the injector then you would be getting 12V ONLY at the B/Y wire and not the wire that goes to the ECU.

Opened up the ECU to see if all the resistors were good and if the injector drivers were toast.. everything inside looked and smelled mint.

I will keep testing and trying to figure out this problem. Will post updates when I figure it out.

 

Important Question:
If the injector itself is bad, will that trigger a CEL or not? Can this code also mean bad injector?
In the forum-famous diagnostic document, it says that code 71 could be bad connector, broken wiring, or resistance.. but it doesn't say that it could mean faulty injector. So will a faulty injector or will it not trigger the code?