killalot13601

iTrader: (5)

Hi, my name is Chris
I have a little problem on my hands that I could use some help with.
The car is an 87' FC, spare parts are from another Series 4 that ran great.
When this car was purchased, the passenger side wire harness for the engine
was melted, burned, and even a little fried, but ran remarkably great.
This car is on its way to a Mega squirt 1 version 3 but before that happens the nasty burnt harness needed to be removed and replaced with a reliable (looking) OEM harness. Along with the harness being replaced, the OEM rats nest was put on the car according to diagrams, but taken in working condition from a parts car.

Now, the car has no spark. I have checked all the connections on the passenger side of the car under the dash, and in the engine compartment. The CAS and coils have been replaced from the running parts car.
For a moment when the key was in the on positions the spark plug which was resting on the alternator, plugged in was creating a steady spark, but the battery was to dead to turn the car over. We replaced the battery with a new yellow top optima and no spark nothing still.

I have 5 years of experience in the mechanical and electrical aspects of an FC, but everything seems to be hooked up properly. I can see how I may have missed something, since there is a lot of forgotten knowledge now days.

If anyone can tell me the proper order to track down spark issues on this particular car then I believe it can be fixed fairly simple.

-Checked-
*CAS
*Battery
*Fuses
*Plugs and connections

No matter how simple of an idea you may have, please let me know. People overlook small simple things sometime and I feel that is the case with this car.

Thank you very much
Christopher Stewart

satch

iTrader: (1)

Have you checked any of the pins on the ECU? Pin 3I, B/W wire, (main relay) should be 12 volts with key to on. Pin 3B, B/L wire (start signal)should be around 1.5 volts with the key to on and close to 10 volts with the key to start.

killalot13601

iTrader: (5)

I will as soon as I get the chance. Thanks.

satch

iTrader: (1)

While you are at it you could recheck the CAS at the ECU by getting an ohm reading and again see if it falls within spec. With no key in the ignition check the reading,ohms, between pins (1N and 1P) as well as (1T and 1Q). Both should be between 110 to 210 ohms. " Do this ohm check with the plug "removed" from the ECU."

Other pins to read are associated with the coils. Pin 1V, leading coil, should read 0 volts with key to "on." Trailing coil pin 1M (2 volts with key to on), pin 1U (4.5 volts with key to on) and pin 1V ( 0 volts with key to "on").

Lastly, check pin 2A for voltage. Should read about 5 volts with the key to on.

killalot13601

iTrader: (5)

Thank you very much for the input man. Exactly the type of reply I was hoping for.

satch

iTrader: (1)

No problem. I forgot to mention, when checking pin 3B it should be done with the plug removed from the ECU.

rx-7 obsessed

could also try to make sure you have voltage at your coils could be a ground issue (just a shot in the dark)

SirCygnus

iTrader: (1)

unplug your airflow meter and see if it fires up. a faulty airflow meter will do funky **** to the coils.

killalot13601

iTrader: (5)

A 12 inch 14 gauge wire is going directly from the battery's (-) terminal to one of the studs/nuts that mount the leading coil. I have checked for good grounded throughout the entire engine.

I just had a great idea of something I did not check for some reason. The ecu ground is in the engine harness, where it bolts up under the UIM. I will track them down and check for ground at the ecu. This is the significant source of ground for the ecu correct?

I will give that a shot.


Thanks for the assistance people. I can already tell this will be quickly tracked down.

killalot13601

iTrader: (5)

PIN 3I (Good)

PIN 3B (0 volts Wrong)

PIN 1V (0 volts Good)

PIN 1M (Started out with .02 volts, replaced the Trailing coil, received 1.11 volts but could not pull that reading up a second time so I do not know where I went wrong there. (Wrong))

PIN 1U (0 volts Wrong)

PIN 1V (0 volts Good)

PIN 2A (11 Volts Bad)(We tried a second AFM which gave the exact same reading) We are working from a shop manual which reads that this wire is for the AFM.)


I hope these readings can help you help us get headed in the right direction. Thank you very much for the help guys.

satch

iTrader: (1)

In making certain the tests were done properly I mentioned checking the CAS pins and pin 3B with the respective plugs "removed," but I didn't state to remove the largest plug which houses the other pins I mentioned that relate to the leading and trailing coils such as pins 1V, 1U, 1M, and I meant to type "1X" earlier but accidently typed pin 1V twice and I apologize for that miscue. Also, pin 2A should be read with the middle plug "not removed." So in retrospect the following pins should have been checked as follows;

Pin 1M key to on, below 2 volts,plug not removed
1U key to on, about 4.5 volts, plug not removed
1V key to on, 0 volts, plug not removed
1X key to on, 0 volts, plug not removed

2A key to on, about 5 volts, plug not removed
3B key to on, below 1.5 volts, plug removed
3I key to on, about 12 volts, plug removed

I am hoping you checked the pins at the largest plug (pins 1M,1U,1V,1X) were done incorrectly with the plug "removed." Say yes!

killalot13601

iTrader: (5)

The majority of the testing was done with the plug still in the ecu with the key in the on position.

I did check the CAS and it fell under 150-160 for both sets.

I tried the test with the plugs intact and removed.

I think PIN 3B is the beginning of the issue, since there is so start signal?

satch

iTrader: (1)

Does your car come equipped with an alarm?

satch

iTrader: (1)

If your car "does not" have an alarm then you could check as to why pin 3B (start signal) is not present. Between the main relay and the firewall, which is not much space, there lies a blue plug. When the key is turned to start the B/G wire feeding into the plug should have voltage and this voltage is passed onto a B/W wire withinn the same plug so check for voltage on both wires as the key is turned to start. The B/W wire goes to the starter but the wire splits off and goes to the FEM-02 harness where the B/W is fed into the B/L wire which shows up at the ECU at pin 3B.

killalot13601

iTrader: (5)

Thank you for the very clear instructions. When weather clears up a bit I will be tracking this down.

The wire diagram for what you explained was a bit confusing how they had it laid out. John, the owner of the car is very anxious to get this sorted out. A thanks comes from both of us for your detailed assistance.

We both have purchased parts cars, so like many rx-7 owners we have many spare parts, if there is anything you need for a project of your own please let me know so I can see if I have it and gladly ship it out free of charge (satch).

satch

iTrader: (1)

Does this car have an alarm? Also, I'd like to ask as well if when you're looking at the back of a plug at the ECU such as the small plug which houses the "3" pins and you look at the top right, what pin are you looking at. In other words what number/letter pin is it? Lastly, the wiring diagram assumes there is an alarm so it indicates a starter cut relay. On the other hand, if there is no alarm (factory) then there isn't a relay but a blue plug instead.

killalot13601

iTrader: (5)

No alarm.

To navigate the plugs/wires I use a pin out from the shop manual.


say it is number 3, 10 pin connector far top right is A bottom right is B.
But I am finding my way around with wire colors and counting, guided by the shop manual. I check everything 3-4 times for each wire to be sure I am in the right place.

satch

iTrader: (1)

Some more info. When you test for voltage at pin 3B (B/L wire) it much more relevant to take the voltage reading when the key is held to start as opposed to having the key to on. Pin 3B will receive the amount of voltage that is going to the starter and since the wire that leads to pin 3B is the same wire going to the starter you should get the same reading. If you check for voltage at the blue plug as mentioned in an earlier post, the B/W wire goes to the starter so that voltage "should" be the same as the reading at pin 3B. Again, this is when the key is held to start.

Since you have a parts car to work with then maybe you have an additional CAS to work with. What you could do is to unplug the CAS already in the car and plug in the backup CAS and with the key to "on" you could spin the wheel on the bottom of the CAS and you should hear the sparkplugs fire in addition to the injectors making a clicking sound. If you want visual validation of the spark plugs firing you could remove one of the plug wires from the leading coil and place the plug wire back into the bore slightly and then spin the CAS with the key to on and check if the coil/plug sparks.

killalot13601

iTrader: (5)

Ok, I was not sure if the wire had a resister somewhere to step it down to 1.5 volts at key on.
As long as it is above 45 degrees out I will post results tomorrow.


Also, the AFM readout on PIN 2A is 11 volts, not the 5 you specified, is this a sign of a faulty AFM?



Thanks for the pro tip on checking for spark with a spare CAS, we do have that option.

killalot13601

iTrader: (5)

ECU grounding turned out to be the issue.

satch

iTrader: (1)

Great to hear. It's nice when the fix involves something so simple. The high voltage reading at pin 2A was a red flag and the grounding issue would/could have been one of the issues.

killalot13601

iTrader: (5)

yeah, I would look further into that problem with the AFM, but we are switching the car over to megasquirt, boost and 4x 720cc injectors.