13bbuggy

iTrader: (2)

I know there is a similar thread going on right now, but I didn't want to threadjack and my problem is a bit different. I have finished my wiring for my 1991 NA motor in my sandrail and to get the black and yellow wire from the main relay to the coils and injectors I used a junction box. I have checked with my voltmeter and I am getting 12V from the main relay into the box and it continues to the injectors, so that is all working correctly. The problem is the power to the coils is disappearing at the posts in the junction box. I thought it might be a bad post so I stacked the wires on one of the posts the injector was hooked to and it disappeared again and I can't figure out what's going on. I disconnected the connections from the coils and checked power to those wires and they are all within spec from the FSM so I'm stumped.

satch

iTrader: (1)

When looking at the leading coil only one of the two wires has battery voltage w/key to on. The other has 5 volts.

13bbuggy

iTrader: (2)

Do you mean 1 wire has 12 volts and the other has 5, or that 1 has 5 volts and the other 0?

satch

iTrader: (1)

First part.

13bbuggy

iTrader: (2)

If that's the case, then where does the ground come from to the leading coil to tell it when to fire? Isn't the ignitor part of the coil (or am I missing something)?

satch

iTrader: (1)

That would be from the ECU as it uses input from the CAS to trigger the coil. If you checked for voltage on the Green/Yellow wire at the leading coil it would be 5 volts w/key to on. Then rotate the alternator pulley which rotates the Main Pulley which then causes the ECU to ground the G/Y wire for a brief moment before returning to 5 volts. It does this over and over as the pulley is rotated, though the reading stays at 5 volts for most of the time.

13bbuggy

iTrader: (2)

So I checked again and with the key on I have no voltage on either wire to the leading coil, all the wires on the trailing coil match up with the FSM, except for the black/ yellow from the main relay which is at 1.0 right now. It was at zero but I tried stacking the wires from the injectors, which were at 11.5-12, with the ones to the coils, which weren't getting any power. When I stacked them it went from 11.5 or so down to 1.0 on both wires to the injectors and all 3 to the coils (since they're on the same posts now). When I move them back it goes back to full power to the injectors and none to the coils.

satch

iTrader: (1)

When you measure for voltage to the coils on the B/Y wires the wires are to be unplugged to the coils. Is this how you are measuring the voltage? Also, are your coils bolted to the metal body for grounding? They need to be.

13bbuggy

iTrader: (2)

Yes it was unplugged when I checked it, and they are bolted to the frame, that's why I'm totally stumped on this.

satch

iTrader: (1)

If the voltage drops on all the wires to the injectors and coils when before the voltage to the injectors was just fine then it is apparent that you have a short related to the B/Y wires to the coils. Besides the B/Y power wires running to the coils, if you measured for voltage at the leading coil w/key to on on the G/Y wire does it show 5 volts or close to zero volts as well? And you're using S5 wiring where you only have one EGI fuse in the Engine fuse box?

13bbuggy

iTrader: (2)

I'm not using a fuse box, but I do have the appropriate fuses for the main relay and from thee battery to the ecu (I just ran in-line fuses. I messed with it some more tonight and I unwrapped the 2 wires that go to the leading coil and separated them and redid the black and yellow wire and now with both coils unplugged I have 12 volts to all 3, then if I plug either one in I lose it back to around zero. I removed the coils and reattached them after grinding a bit off around the mounts to ensure a good ground and still get nothing. Also, I still haven't gotten any power to the green and yellow wire on he leading coil. I'll mess with the ecu wiring tomorrow and see if I find anything.

satch

iTrader: (1)

There's a Black wire, short in length, that is attached to each coil. This wire is for connecting to a tach for diagnostic purposes. Are you grounding this wire by chance. It shouldn't be. Pin 1B of the ECU is the pin which powers the ECU. It should have voltage w/key to start and key to on. And the Brown/White wires at the TPS, AFM, and Pressure Sensor should have about 5 volts w/key to on. This would tell you that the ECU is powered properly in addition to a couple of other things.

13bbuggy

iTrader: (2)

Ok, I checked the sensors you mentioned and the wires off the coils and here are my findings:
the Boost sensor and MAF had 5V to a brown and white wire on both and the MAF also had 5V to a Green and Red wire, the CAS had no power to any of the wires and the Green and yellow wire off the leading coil still doesn't have power.
I have 12V going from the main relay into the ecu at 1B and 12V from the battery into 1A. I moved the ecu ground from the frame to its stock location on the UIM and checked the #10 ground (up by the ecu) with my voltmeter to make sure it was grounded well enough. there is also a ground wire near the alternator/ water pump (I think it's the one for the MAF and boost sensor but can't remember what number it is). Any ideas on what could be causing this?

satch

iTrader: (1)

But what about the short Black wire eminating from the coils. It's not supposed to be grounded. Do you have it grounded??? Also, the wires from the CAS to the ECU are not supposed to have any meaningful voltage. Have you tried to turn the Main Pulley as suggested to see if there is any voltage on the G/Y with key to on at the leading coil. And ground point #10 is for the shielding found on the Oxygen Sensor, CAS and AFM (Green wire). You can also disconnect the plug at the ECU housing the CAS wires and take an ohm reading to make sure it is hooked up properly and within spec. Ohming pins 3G and 3H should show between 110 to 220 ohms and the same thing goes for pins 3E and 3H.

Post #2 in this link shows some of the relevant wiring diagrams.

https://www.rx7club.com/2nd-generati...lowing-750202/

13bbuggy

iTrader: (2)

The black wires from the coils are not grounded. I have tried turning the pulley a bit and don't seem to be getting anything from the green and yellow wire. If I plug the connectors into the coils that come from the main relay then I still lose the 12V, so I've been trying with them unhooked until I figure out what's keeping the 5V from getting to the other wire before hooking it back up.

13bbuggy

iTrader: (2)

Thanks for the help, I really do appreciate it. Those wiring diagrams are the same ones I printed out to wire this, along with the page that gives the breakdown of which wires are what, and how many volts they should have with key on and idling. The good news is the more stuff I eliminate as being the problem the closer I should be to finding it.

satch

iTrader: (1)

Have you checked pin 1H at the ECU w/key to on as that is where the G/Y wire connects to. Also, there is a wire that splits off of the Black/Yelllow wire at the leading coil which connects to a condenser which is grounded. The condenser looks like a computer chip. Sometimes the chip falls off of the B/Y wire and people will then ground the wire itself, which is a no no. Did you perhaps do this? And when turning the Main Pulley via the Alternator Pully you have to end up turning the Main Pulley more than just a little such as at least a full revolution. And this is important, how are you measuring for voltage on the wires when they are connected to the coils? Are you pricking the wires with a pin and then taking the erading from the pin? The plugs are not condusive to backprobing so I wonder how you are doing this.

13bbuggy

iTrader: (2)

I didn't have a chance to check the wire at the ecu today (but will tomorrow after work). I've been testing it while it's not plugged in to the coil because when it's plugged in I've been losing the 12V on the B/Y wire and thought that would be best until I get power to the G/Y wire. I don't have a condenser on mine and don't have it grounded or hooked up to anything (I was told I shouldn't need the condenser but that could be wrong). The weird thing is when I check the power to the trailing coil from the ecu everything seems to be good but as soon as I hook up the connector with the 2 B/Y wires I loose the power to them (that's true of either coil so maybe the coils are bad or something?). I have turned the pulley a few times around and still wasn't getting anything on the G/Y wire.

satch

iTrader: (1)

Do you remember what voltage readings you were getting from the ECU that related to the trailing coil? It seems odd that both of your coils are bad. Could you possibly jumper a wire from the leading coil B/Y wire to its correct spot at the leading coil thus leaving the G/Y wire out of the mix to see if the voltage still drops out.

And are you sure you have the CAS wires connected to the ECU properly?

13bbuggy

iTrader: (2)

I just checked the 4 wires on the other plug to the trailing coil and I had 5V to the br/y and l/g wires and 12V to the y/l wire with nothing to the l/y. I ran ground wires directly from the battery to the coil brackets to make sure that isn't the problem (it isn't) and I checked the g/y wire at the ecu and it isn't getting any power there either.

13bbuggy

iTrader: (2)

Because everything else seems to be working I am wondering if I could just swap out the cas for a distributor setup and run that thereby eliminating my only problem? If so would I need to do anything other than swap it and use my Msd coils (I was running a dizzy setup previously so I have almost everything still)?

satch

iTrader: (1)

In looking at the pinout specs the G/Y should have 0 volts w/key to on but turns to 5 volts as the pulley is rotated (sorry). So I was mistaken that it should be 5 volts w/key to on but as the Main Pulley is rotated the voltage changes briefly to 5 volts then back to 0 volts. If yours does not do this then you need to focus on the CAS. You can pull the CAS and w/key to on when the CAS wheel is spun you should heat the injectors click along w/the spark plugs should spark. Now you should disconnect the electrical plugs to the coils to prevent the plugs from firing but while spinning the CAS you should measure the voltage on the G/Y wire to see if it changes from 0 to 5 volts or not. If it doesn't and the primary injectors don't click then you need to focus on the CAS and its wiring.

Br/Y (pin 1J) is 4.4 volts spec
L/G (pin 1V) is below 2 volts w/key to on
L/Y (pin 1G) is 0 volts w/key to on

13bbuggy

iTrader: (2)

I just checked voltage with everything hooked up and now instead of zero on the tracking coil b/y wires it is at 1.8V while hooked up and remains the same while turning it over. The b/y on the leading goes to zero still and stays there. Could it be a short inside the ignitor or coil itself? It has to be something with the coil itself I think (that's the only thing that makes any sense since it looses power only when hooked up to the coil), everything else seems to be right until those wires are connected.

satch

iTrader: (1)

EDITED:
Your conclusion seems right on, but it's strange that it occurs to both coils. Did you buy these coils from the same person/Car? Your other issue would be if the G/Y wire does not go from 0 volts to 5 volts and back to 0 volts and if it doesn't behave as necessary then that issue is from something other than the coils. Also, a wire that is multi threaded but has all threads severed except for one will still pass 12 volts. But that voltage might get pulled down when trying to power up an item. You might want to bypass the Main Relay by jumpering the White/Red wire in the four wire plug at the relay to the B/Y wire to see if this makes any difference. Also jumper the White/Blue wire and the B/W wire in the same plug. Also, the White/Blue wire and the White/Red wires eminating from the EGI fuse are spliced together. If this splicing/connection is rather poor then this could also pose a problem.

13bbuggy

iTrader: (2)

I did buy both coils from the same person and assume they came from the same car (maybe they fried something that messed up the coils?). The wires on the main relay are all new since I just bought a main relay for this and had to wire it up and I considered the possibility of there being to much draw on it so I unhooked both injector wires and tried it and still got the same results. I am getting 12V from the main relay under all tested conditions consistently and it drops from 12V to 1.8 on trailing as soon as plugged in, and from 12V to 0V on leading as soon as hooked up, that's why I wonder if it's the coils.