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-   -   FC S4 NA Changed Alternator Now Won't Start (https://www.rx7club.com/new-member-rx-7-technical-256/fc-s4-na-changed-alternator-now-wont-start-994989/)

jharris2188 04-21-12 05:11 PM

Narrowed it down - not getting fuel from the fuel pump. Tried the jumper and still nothing. Is there a fuel shutdown / reset button on this thing?

satch 04-21-12 05:18 PM


Originally Posted by jharris2188 (Post 11063779)
Narrowed it down - not getting fuel from the fuel pump. Tried the jumper and still nothing. Is there a fuel shutdown / reset button on this thing?

At what spot did you check that wasn't receiving fuel as it should?

satch 04-21-12 06:06 PM

The Circuit Opening Relay powers the fuel pump. It is Yellow and Black and located under the dash and just to the right of the steering column. There are five wires in the relay plug with three of them on the top row. Far left spot (Black/Red on autos otherwise B/W) has voltage w/key to start. No voltage here and the pump will not turn on. The center position wire (Black/White) has voltage w/key to on. No voltage here and the pump dies immediately after starting. In either case, the Blue wire (far right spot) will have voltage when the relay is working properly, and this Blue wire powers the pump.

jharris2188 04-22-12 10:43 AM


Originally Posted by satch (Post 11063847)
The Circuit Opening Relay powers the fuel pump. It is Yellow and Black and located under the dash and just to the right of the steering column. There are five wires in the relay plug with three of them on the top row. Far left spot (Black/Red on autos otherwise B/W) has voltage w/key to start. No voltage here and the pump will not turn on. The center position wire (Black/White) has voltage w/key to on. No voltage here and the pump dies immediately after starting. In either case, the Blue wire (far right spot) will have voltage when the relay is working properly, and this Blue wire powers the pump.

Solid info - greatly appreciated. Checking this out today.

jharris2188 04-22-12 01:30 PM


Originally Posted by satch (Post 11063847)
The Circuit Opening Relay powers the fuel pump. It is Yellow and Black and located under the dash and just to the right of the steering column. There are five wires in the relay plug with three of them on the top row. Far left spot (Black/Red on autos otherwise B/W) has voltage w/key to start. No voltage here and the pump will not turn on. The center position wire (Black/White) has voltage w/key to on. No voltage here and the pump dies immediately after starting. In either case, the Blue wire (far right spot) will have voltage when the relay is working properly, and this Blue wire powers the pump.

Black / Red has voltage, black / white has none.

satch 04-22-12 01:42 PM


Originally Posted by jharris2188 (Post 11064501)
Black / Red has voltage, black / white has none.

The B/W wire should have voltage w/key to on. This wire is powered by the "15 amp Engine fuse." This fuse powers the B/W wire found at the back of the alternator and the B/W wire found in the two wire plug at the Main Relay as well.

If the Main Relay clicks w/key to on then the fuse is good. And that's the Main Relay clicking "and not" the Starter Cut Relay.

jharris2188 04-22-12 02:42 PM


Originally Posted by satch (Post 11064516)
The B/W wire should have voltage w/key to on. This wire is powered by the "15 amp Engine fuse." This fuse powers the B/W wire found at the back of the alternator and the B/W wire found in the two wire plug at the Main Relay as well.

If the Main Relay clicks w/key to on then the fuse is good. And that's the Main Relay clicking "and not" the Starter Cut Relay.

Oops - b/w is powered, b/r is not powered. had it reversed. ...with key on. Relay clicks with key on.

satch 04-22-12 02:51 PM


Originally Posted by jharris2188 (Post 11064558)
Oops - b/w is powered, b/r is not powered. had it reversed. ...with key on. Relay clicks with key on.

As originally stated, the B/R wire should have power w/key to "start" which is different than "on."

jharris2188 04-22-12 03:03 PM


Originally Posted by satch (Post 11064566)
As originally stated, the B/R wire should have power w/key to "start" which is different than "on."

b/w is 12v at key on and b/r is at 7.5v at start. blue (double blue) is reading 0.0v at key on and about 0.25 at start.

satch 04-22-12 03:12 PM


Originally Posted by jharris2188 (Post 11064573)
b/w is 12v at key on and b/r is at 7.5v at start. blue (double blue) is reading 0.0v at key on and about 0.25 at start.

With key to on, the reading of the Blue wire is normal. The reading w/key to start on the Blue wire is not normal as it should read basically the same voltage as the B/R wire has w/key to start. It appears the relay is faulty or the solid Black wire in the bottom row far left position of this relay, which should be a constant ground, is not grounded properly. You could jumper a ground wire to the solid Black wire in the relay plug to see if the fault lies within the wire or the relay. So jumper a ground to this bottom row far left position wire and w/key to start try taking another reading on the Blue wire.

jharris2188 04-22-12 03:34 PM


Originally Posted by satch (Post 11064584)
With key to on, the reading of the Blue wire is normal. The reading w/key to start on the Blue wire is not normal as it should read basically the same voltage as the B/R wire has w/key to start. It appears the relay is faulty or the solid Black wire in the bottom row far left position of this relay, which should be a constant ground, is not grounded properly. You could jumper a ground wire to the solid Black wire in the relay plug to see if the fault lies within the wire or the relay. So jumper a ground to this bottom row far left position wire and w/key to start try taking another reading on the Blue wire.

Satch the Saint! Ground is solid, fuel pump relay is bad. Had pump running by bypassing the relay with 12v to pump for a couple os seconds and then it started for a few seconds. Thank you for all of the help. If the relay is bad i will be back...

jharris2188 04-23-12 03:50 PM


Originally Posted by jharris2188 (Post 11064597)
Satch the Saint! Ground is solid, fuel pump relay is bad. Had pump running by bypassing the relay with 12v to pump for a couple os seconds and then it started for a few seconds. Thank you for all of the help. If the relay is bad i will be back...

Spoke to soon - not 100% that this car has a Fuel Pump Relay & Resistor. It is not on the wiring diagram. Best to just rewire the fuel pump?

jharris2188 04-23-12 03:54 PM


Originally Posted by jharris2188 (Post 11065761)
Spoke to soon - not 100% that this car has a Fuel Pump Relay & Resistor. It is not on the wiring diagram. Best to just rewire the fuel pump?

http://www.invensoftlabs.com/rx7/Untitled-1.jpg

satch 04-23-12 03:57 PM


Originally Posted by jharris2188 (Post 11065761)
Spoke to soon - not 100% that this car has a Fuel Pump Relay & Resistor. It is not on the wiring diagram. Best to just rewire the fuel pump?

Your car does not have that resistor relay as those are found on S4 turbos and not autos. It is your Circuit Opening Relay which is in question.

jharris2188 04-23-12 04:29 PM


Originally Posted by satch (Post 11065772)
Your car does not have that resistor relay as those are found on S4 turbos and not autos. It is your Circuit Opening Relay which is in question.

So, get a new one of these: http://lh6.googleusercontent.com/pub...p_ymZdL1CeZCSY

satch 04-23-12 04:33 PM

You stated the Black ground wire in that relay was solid. Not sure how you checked, but if you used the Black wire as the ground source for the multimeter when measuring for voltage on the top row center wire (Black/White) w/key to on and if you get the same reading as before,12 volts, then the Black ground is good thus the problem is the relay itself.

jharris2188 04-23-12 04:39 PM


Originally Posted by satch (Post 11065826)
You stated the Black ground wire in that relay was solid. Not sure how you checked, but if you used the Black wire as the ground source for the multimeter when measuring for voltage on the top row center wire (Black/White) w/key to on and if you get the same reading as before,12 volts, then the Black ground is good thus the problem is the relay itself.

Regarding the B/W wire, I had a reading of 12v using the black wire and a reading of 12v after I grounded the black wire to the battery.

On a side note, a jumper on Yellow two prong by the passenger strut tower did absolutely nothing.

satch 04-23-12 04:45 PM


Originally Posted by jharris2188 (Post 11065834)
Regarding the B/W wire, I had a reading of 12v using the black wire and a reading of 12v after I grounded the black wire to the battery.

On a side note, a jumper on Yellow two prong by the passenger strut tower did absolutely nothing.

Then the relay is your problem. If you look at the diagram you provided the wire that goes to the relay at the top left of the pic shows the wire that provides voltage to the relay w/key to start and yours was about 7 to 8 volts. The Black wire at the bottom of the diagram feed the ground for the coil involved. When both these elements are present the relay closes and the voltage from the B/W wire is able to pass on to the Blue wire. You said you had a quarter of a volt when this happened.

jharris2188 04-23-12 04:51 PM


Originally Posted by satch (Post 11065840)
Then the relay is your problem. If you look at the diagram you provided the wire that goes to the relay at the top left of the pic shows the wire that provides voltage to the relay w/key to start and yours was about 7 to 8 volts. The Black wire at the bottom of the diagram feed the ground for the coil involved. When both these elements are present the relay closes and the voltage from the B/W wire is able to pass on to the Blue wire. You said you had a quarter of a volt when this happened.

Yes, key to start was one quarter of a volt.
Key to on was one tenth of a volt.

jharris2188 04-23-12 04:55 PM

Is there a way to bypass this temporarily? I would imagine that a constant 12v to the pump would deliver more fuel than the engine could burn and flood. Could be wrong...idk.

satch 04-23-12 04:58 PM


Originally Posted by jharris2188 (Post 11065847)
Yes, key to start was one quarter of a volt.
Key to on was one tenth of a volt.

The important number is the key to start. The relay requires the car to start for the AFM to supply a ground to the other coil located within the same relay. Since your car is not running you have no ground on the Brown wire and thus the relay does not close which is why the voltage off of the B/W wire does not pass onto the Blue wire so this is normal as can be, but the voltage on the Blue wire w/key to start is the problem w/the relay.

satch 04-23-12 05:02 PM


Originally Posted by jharris2188 (Post 11065851)
Is there a way to bypass this temporarily? I would imagine that a constant 12v to the pump would deliver more fuel than the engine could burn and flood. Could be wrong...idk.

The injectors are responsible for how much fuel gets dumped into the engine and not whether the pump was constantly on or not. You could try providing constant voltage to the pump and see what happens.

jharris2188 04-23-12 05:09 PM


Originally Posted by satch (Post 11065860)
The injectors are responsible for how much fuel gets dumped into the engine and not whether the pump was constantly on or not. You could try providing constant voltage to the pump and see what happens.

I can apply a constant 12v to the pump and (with a jump start) the car will start and idle. When I put into drive it killed (with out the cables hooked up though).

That could be the battery for sure. FYI - New alternator is hooked up but the battery is probably toast, or really drained. Will make sure battery is good and retry.

jharris2188 04-23-12 05:17 PM


Originally Posted by sickwithit46 (Post 11065880)
That sucks

The price you is never the price you pay :)

jharris2188 04-23-12 06:33 PM


Originally Posted by satch (Post 11065860)
The injectors are responsible for how much fuel gets dumped into the engine and not whether the pump was constantly on or not. You could try providing constant voltage to the pump and see what happens.

OK - sending a constant 12v to the fuel pump starts it.

Park to Reverse dies.
Park to Drive dies.
Park to Neutral runs, and then Neutral to Drive or Neutral to Reverse stays running.

When it was a 'cold' pressing the brake killed it.
Let it warm up for 2-3 minutes and pressing the brake did not kill it.

BAC needs cleaning, idle adjustment and/or weak tranny...?

Getting about 13.9v at battery right now while running.


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