naimodo

Hello, I figured it would be better to post this in the 2nd gen forum rather then the first due to it being a FC engine. We have a stock 13BT, its an 87.5or 88 without the resistor pack for the injectors (factory turbo, ecu etc) S4 engine but we're getting a 'slow' injector pulse. or at least, it seems slow to us. lol. using 2 noid lights, one for each primary injector. They light up and alternative R1 and R2 but it seems kinda slow, happening with 1-2 second gaps between pulses. Also, we only get an injector pulse while the MAF is disconnected, if we connect the MAF, we get no pulse at all. The engine spinning over, we get fuel and Primary Coil spark, and T1 on the trailing coil fires but we're never gotten T2 to fire. We did a compression test and although its kinda low at 85PSI, my dad (he worked for Mazda from 78 to 90 as Master Tech) said Mazda had him install 'rebuilt' engines that only had 85 for compression. So, we're curious as to why we aren't getting T2 to fire, why connecting the MAF causes us to lose the injector pulse and if the injector pulse should be faster. We're replaced the ECU, Leading and Trailing Coils, and bought a reman MAF. We're also tested our wiring to verify we have everything as correct as we can. We would be thankful for any help we could get from ya'll. Thanks.

satch

iTrader: (1)

The Brown/White wire of the AFM should have 5 volts w/key to on. This wire runs to other engine sensors like the boost/pressure sensor and TPS (you could check for voltage on this wire at either of these sensors). If it doesn't have the 5 volts then the AFM is shorting out and that prevents the injectors from working properly.

naimodo

Thanks; I'll double check that today.

naimodo

We tested the MAF. We got 5V on the brown/white wire but on the Green/blue (Vs on the MAF, which goes to ECU 2E) we got a sporadic reading instead of 4V with KEY ON. Also, we don't have a knock control box, could that be causing any issue? The fuel almost seems if its in DECEL Fuel Cut, like the old 12A's had to prevent backfiring and help fuel economy but that's a guess on our part. Thanks again for the help thus far.

satch

iTrader: (1)

A remanufactured AFM is something to stay clear of as a used one would be a better alternative. And we're assuming that you had the AFM connected when you took these two readings?

Regarding the trailing coil a couple of possibilities are a poor plug or plug wire. You could switch things up between T1 and T2 to see if T2 still is problematic.

Acesanugal

iTrader: (5)

I've read a few comments that the knock box is not strictly necessary.

naimodo

Yeah I had it connected. We couldn't find a used one at our local junkyard (they haven't had a rotary car in a couple years) and the ebay used prices were higher then a reman one from NAPA; any reason why we should've avoided the reman AFM? I know some of them list the same part for the 929 and the RX-7 but our FSM says they're different internally. I reaplaced the plugs and wires while the engine was out of the car, but I'll swap in another set I have. Thanks.

ACR_RX-7

iTrader: (1)

The Reman units simply have a poor build quality. You get what you pay for.

The RX7 AFM is unique to the RX7. Have you verified all of the powers and grounds to the ECM, coils, and AFM? Checking for voltage with a volt meter is not good enough, you need to do a voltage drop test across the wires while you crank it over. A voltage drop can cause those symptoms. Also, are the CAS wires shielded? Is the CAS producing the correct signal? You can verify signal if you have access to a labscope, but many people do not have one.

The reason that T1 fires only, is probably because the engine is not running yet. The ECM uses a toggle signal from the CAS to make sure it fires the trailing coil on the correct timing. If it fires early, it can "kick back" the engine. It very much sounds like you have a power/ground issue and a CAS issue.

satch

iTrader: (1)

Once you clear the 10 post count you could use the classifieds within this site to source an AFM if need be. I've never heard of a reman unit working out well for the purchaser. Never.

naimodo

Oh I forgot to mention, the Trailing Coil Pack is what is giving us the problem. T1 fires but T2 never has, unless we switch the coil pack wiring, then T2 fires instead of T1

naimodo

Awesome! Only one post to go

naimodo

First off, thanks for you input, we appreciate it. The CAS wires are shielded and we OHM tested them. I've got a question, we only get an injector pulse when the T1 fires and the injector pulse does alternate between R1 and R2 but it seems slow. Like there's a noticeable gap between when R1 pulses and R2. Should they be super fast or is it ok that they appear slow to us?

satch

iTrader: (1)

What do you mean by switching the coil pack wiring?

naimodo

Nevermind lol; I got ahead of myself. We took the original 12A's twin coils and wired them so they would work like the FC's coil pack does to test if the pack was bad. Only T1 fired when we did that, then we switched the wiring and the other fired instead, it still didn't alternate. Sorry, ignore me lol.

ACR_RX-7

iTrader: (1)

Ugh, I hate it when people ohm test ****. You can have zero resistance through a single strand of copper wire in the exact same way you can have zero resistance in a 0/4 weld cable. You need to check to make sure the circuit can handle LOAD. You can simulate this with a sealed beam headlamp.

Disconnect the wires in question at both ends. Hook up the wire to power and ground the battery you would use to test the wires. I have a Mercedes Benz 12v Shift interlock battery that I use. It's about the size of a soup can. Hook up the sealed beam common to ground and hook the other end up to the other end of the circuit. So battery hooked up in passenger footwell where PCM is and sealed beam lamp at the connector you test.

I have not hooked up a noid light to an RX7, honestly because I use a labscope to diagnose a car. I generally hook up an amp clamp to the power feed to the loads in question (coils, injectors, solenoids, pumps, etc) , hook up a lead to the power side of the circuit to measure voltage draw, and hook up a lead to the trigger side of said component. I also hook up a lead to the CAS, or cam sensor on piston engines, and sync the trigger on my display to cyl/rotor 1.


As far as the noid light "pulsing slow" I don't have a good answer, but it should fire once per e-shaft revolution. That's why I use a labscope. I can sync all events together and watch everything happen on the screen.

As far as it pulsing when T1 happens, the injectors are batch fired as far as I know. According to the factory diagram, they have discrete outputs from the PCM, so they may be sequential. They both should fire at the same time for R1 and R2 if they are batched.

naimodo

Thanks Ill try that headlamp test. Also, we're using the 12A starter, we're tested the draw at 155AMP. Could this be pulling too much and causing our issue? or could the starter just not be spinning the engine fast enough? I believe the FC came with a gear-reduction type. We tried pulling the car to start it but that was awhile back before we just getting an injector pulse with the CAS in the block. Can the car crank without the AFM installed? I wouldn't expect to run, but could it crank at all? Thanks again for all the info and help, we really do appreciate it.

ACR_RX-7

iTrader: (1)

That amperage draw is about right for that engine, but a 12A starter most likely might not have the juice to spin it fast enough.

Yes the car can crank without the AFM installed. It may start and run, but unlikely.

You may either need to get a rewound 12A starter, or figure out if there is a thread on the topic.

naimodo

k thanks; ill check everything ya'll listed and post what I find

naimodo

Sorry its been so long; been busy with work. Okay here's an update. we ran new wires from the CAS to the ECU. Got a gear reduction starter, and we still had the same problem. No injector pulse with the AFM connected. We did some checking and decided to connect the Water Temp Switch pin on the ECU and now we get the injector pulse with the AFM...which is a first. We installed a AEM/Bosch AFR gauge, fuel pressure and vacuum gauge. It has 40PSI fuel pressure, 80psi if we pinch the return. It runs about 4-5 inches of vacuum with no throttle while trying to crank. AFR runs off the scale into the red (over 20:1) but it probably doesn't read accurately until the car is running.
It kept sputtering and trying to start but then the engine flooded (ugh fuel injection). So we pulled the plugs and spun it to clean it out, and we couldn't get it to even try to start (though we still had spark, pulse) but the battery was really weak. Does the Clutch Switch needed to be connected?
Also when we were tracing back wires (this was several months ago), the CAS ran to a white/clear rectangular connector, maybe 16-20 pins. I've never seen a diagram that showed this connector. Everything I have shows it go straight to the ECU. I read one guy say his had this connector but he didn't know where it went so he just cut the CAS wires and wired them to the ECU (which is what we did). He had the same engine we did too, Japanese 13BT from an automatic, he also had dual TPS's like we do. Though only one of ours is connected because we don't see where the outer one goes, though we think it may have gone to the automatic transmission box. Does anyone have any more info on a S4 (it has the linkage for the oil metering pump) with 2 TPS's? Also, our injector pulse is once every 3 seconds on each primary injector. Shouldn't be pulse every spin of the eccentric shaft? i.e., 250rpm = 250 pulses?
Thanks again for reading my long post and for all the help.

ACR_RX-7

iTrader: (1)

Should be 3 pulses per revolution. Basically, it should as frequent as spark.

You may have a bum ECU

naimodo

It seems to pulse as often as the spark. But I've got a spare ECU so ill try it instead of the Japanese auto one. Thanks.

ACR_RX-7

iTrader: (1)

Without me getting my own eyes on it, I'm tossing ideas like I would try and toss paper ***** into a wastebasket across the room. I may be able to make something happen, but it is strange you are having so many issues.

naimodo

lol just the nature of engine swaps I guess. I ordered the engine from a guy who said it was a S5 with ECU and a complete wiring harness, when I got it, I realized it was a S4. We worked it out and then I realized we were missing the harness that goes to the 24 PIN on the ECU. So we've had to go wire by wire to get it to where it is now. Further checking and the fuel rails aren't the 'backwards' JDM ones, they're USDM because they match our FSM diagram, but it does have the injectors that don't need the solenoid resistor. Its been a pain but its been fun.

I The battery is on charge, so tomorrow we'll try to pull it with our truck to see if it fires off.

ACR_RX-7

iTrader: (1)

Oh boy, looks like you have had a swell time.

I know you're already deep into it, but I personally would have recommended going with a standalone into that chassis. Yes, I know you can wire it in properly and get it to work. Yes, I know standalones are pricey, but the way I personally see it. You're already there. You can get a fresh harness and guarantee it will be wired correctly.

If worse comes to worst, look at the Haltech SprintRE or the Megasquirt MS3X or MS3Pro. The SprintRE is specially designed by Haltech for the 13B (RE stands for rotary engine.)

The MS3X is a full sequential standalone that works very well.

I hope you get it up and running with what you have, though. That way, it will run and work and then you can enjoy it.

erick31876

iTrader: (8)

I just got my swap running,same engine except mine is usdm.and mine is a 85 . I was having similar issues like you are having, try checking if the wires going into the cas plug are fully seated,mine backed out of the plug slightly causing random spark and injector pulse,I fixed that and it started right up,in might also have a spare ecu plug that goes to the 3rd plug if you need it