Dear Members,
Well, I did a good one on my 85 GS 1.1 liter with the manual trans. It was running perfectly until I wanted to check the rpm with my handheld analog tach. I hooked it up by placing its positive lead on the positive terminal of the trailing coil and the negative lead to ground. Started the engine and ...nothing! No electrical power anywhere, lights out on the dash and no engine start just one click heard coming from the starter solenoid, battery was fully charged...very sad! The fuses were checked and all was ok. Checked both coils for resistance, each approximately 1.3 ohms so all seems well. Leading and trailing high tension leads have continuity. Fusible links mounted on the left shock tower appears to have voltage through it and seem fine. Wires seem to be normal with no insulation burned. Trying all the electrical switches i was able to raise the headlamps and turn on the lights but upon attempting to start the engine all went dark again.
Attempted starting the next day, the engine turned briefly then cut out including all electrics again. I even pulled the ecu and visually checked for burned components but all looked fine physically but not checked electrically. Not sure where to turn at this point. Is there a relay or an other fusible link that could be the culprit? Any help would be greatly appreciated

 

Start by removing and cleaning both battery cables and battery posts til shiny metal,reattach and try to start again. No go,check battery positive and ground cables at starter for being clean and tight. Next check the fuselinks,all,especially the main. Use a testlight or a voltmeter with negative lead grounded and positive lead to either side of fuselink terminals while you manipulate the wire fuselink back and forth. Sometimes the link can melt(blow) and the two halves are still touching each other lightly which completes the circuit til a load is applied,manipulating the fuselink will find this. Regarding tachometer hookup... positive lead goes to ignition coil negative primary terminal and negative tach lead to ground. Good luck,report back findings/fix to help another down the road who may find this thread.

 

I checked out the fusible links on the left shock tower; cleaned all the contacts so they're nice and shiny, did a continuity test shaking the terminals as I did it making sure nothing was loose...all checked out ok. I went over to this other relay mounted nearby, I seen it described as a main relay and also hot start assist relay but am not sure which but its printed 'check relay' on top of the cover. Checked it according to the service manual and found it not having the continuity it should have with battery voltage applied. Could this part be causing the issues? I posted some photos, perhaps someone can recognize it for what it actually is and direct me to a parts supplier. Thank you for your help in advance!

 

Are your symptoms still the same? I think you're getting ahead of yourself looking at relays and such without proving out you do or don't have power reaching the things that need it. Need to start at the battery and work your way from there. The symptoms you describe are indicative of a poor connection that fails as a load is put on it. The fact you had lights-then didn't,the attempted start next day where you had electricity and then didn't-this is a poor connection. Something loose,corroded,broken. Focus on basic electrical system...battery,cables fuselinks fuses. Don't get pigeonholed into testing individual components like relays,none will work properly or at all without power and grounds. Focus on the headlights,all they need is power from battery to fuselink to headlight switch. Turn the headlights on to load lighting circuit-do they come on? Yes,leave them on. If they don't come on,leave them turned on anyway. When you find the no power fault they will blink on/off or just come on so you'll know where to concentrate your efforts. Start at the battery,put your voltmeter leads right on battery posts and read the voltage,should be 12.6 volts or so. Watching the voltmeter,move the negative voltmeter lead from negative battery post to negative battery cable terminal-voltage should be unchanged. Leave negative test lead there and now move positive test lead from positive battery post to positive battery cable terminal-again voltage should not change. If it does clean battery posts and cable terminals and retest. If everything tests ok at battery... leave negative meter lead on negative battery cable terminal,move positive lead of voltmeter to wire at main fuselink and look at voltage-should be same as at battery. If not,problem is in the wire coming from positive cable at battery that feeds main fuselink or the connection at main fuselink or fuselink itself. This is the point at which everything electrical in the car gets its power with the exception of starter motor. If you get to this point in underhood wiring and voltages are not consistent or present-no need to go further into power side of wiring at this point. Back to the battery,you have checked the power side of circuit that feeds car,now to test the ground side of circuit... put positive voltmeter lead on positive battery cable terminal. Follow negative battery cable from battery down left side fenderwell to engine side of strut tower where it is stripped and a clamp attached around it and bolted to the body. Put your negative voltmeter lead on the wire/clamp/bolt and read voltage on meter-should be essentially same reading as at battery maybe a tenth of a volt different-if its not same look at cable color,any corrosion,is it blue looking? Put your negative voltmeter lead onto a solid part of the engine and read the voltage,again should be same as readings at battery. The only connection left to check will be the end of the negative battery cable at the starter and which i recommend you loosen and remove both positive/negative battery cables at starter and clean the ends til bright/shiny as i recommended previously to cables at battery and reinstall. You should have seen your lights come on by now while working with all the connections. There is one last possibility,and that is the battery itself,it could be the culprit with a loose internal connection causing your symptoms. I believe if you follow my instructions in the order i've stated,you will find the problem(s). If not remove the battery and have it load tested,if it has the problem i spoke of it will be found

 

Apologize for my "wall of text",something about this website,doesn't look like this til i hit submit-then all runs together and not all the time either. Seems only this site it happens on.

 

Thank you for taking the time and responding. I'll investigate further and let you know of my findings. Thank you again and best regards!

 

Good luck! Curious of your findings.

 

If you could take pics of the wires going into that relay I could tell you where each of them goes and what they're meant for. I can't remember off the top of my head what that relay exactly does but with the wiring plugs I should be able to tell you.

 

Though the area is a bit tight, I managed a couple photos. I suspect it's the hot start assist relay but not sure. Thank you for your help!

 

The hot start relay cannot cause a no-start situation. It's not a required circuit to start the car.

Like mentioned before, start at the battery and validate voltage at the required circuits to start an RX-7. Those are the starter, fuel pump, and coils/distributor circuits.

 

Picture 1:

Picture 2:


Alright, what you're holding in your hands there is the Choke & Check Relay on page A-1 of the 1985 RX-7 wiring diagram.

Starting with A-17, plugged into the back of the alternator:
B/W Black/White stripe - this is an ignition-switched wire, that should get 12v+ power when the ignition is turned on from a fuse in X-03 fuse box
W/B White/Black stripe - this is switched as well, coming out from the alternator and going to the C&C Relay, should also be 12v+ when the car is on if I remember correctly.

A-18 Plug 1:
B Black - Ground
L/R Blue/Red stripe - To choke switch and oscillator, shared function wire
Y/L Yellow/Blue stripe - From the warning light
B/W Black/White stripe - this is an ignition-switched wire, that should get 12v+ power when the ignition is turned on from a fuse in X-03 fuse box (same as A-17 actually)

A-18 Plug 2:
B/W Black/White stripe - B/W Black/White stripe - this is an ignition-switched wire, that should get 12v+ power when the ignition is turned on from a fuse in X-03 fuse box (same as A-17 actually)
W/B White/Black stripe - from the alternator in A-17

Which ones were you not seeing 12v+ at? I don't think this is causing your issue but may have a contribution if some of these wires aren't getting the right voltage.

 

Thank you so much for taking the time and posting this valuable info. I just had carpal tunnel surgery on both hands so will not be doing any testing until I'm able to but have time to study the diagram in the meantime. Again, thank you for the help, will keep updating when I can!

 

The no crank, no start, no lights electrical issue still persists when attempting to crank the engine but I'm still soldiering on checking grounds and continuity in the wiring. So far, all wiring checks out fine. I've been disconnecting and cleaning electrical connectors as I go along checking things but nothing obviously bad comes up. I even swapped a new ignition switch with the old, no difference.

When connecting a battery tender to the battery I get a warning light on the tender stating there's a problem. I disconnected the battery from the car and placed the tender directly to it and it charges and maintains it without a problem. I had the battery load checked along with the alternator, all was good. I attempted a parasitic draw test through the fuse box and found there's an issue with the 'hazard' circuit. Now the challenge is to find what components are associated with this and find the offending part. Is it possible a bad starter could be at fault causing the symptoms? In my experience when a starter goes bad there's just a click or nothing at all but never all the electrical cut out. Any ideas on this?

 

Was wondering what the problem turned out to be. I think you went off on a tangent with suspecting relays and such. Suggest you reread my post of 10/10/17 and follow the diagnostic path laid out there step by step. Post your voltmeter readings with each successive test to allow us to see what they are. I can say with certainty the starter is not causing "loss of power". To satisfy your suspicion,you could remove starter,clamp in bench vise and test operation with battery jumper cables and a jumper wire to verify operation...the "problem" will be a bad,corroded connection downstream from the battery as stated previously. Next time you look at car start fresh-don't try to crank it over at first. Turn headlights on,did they come on? Yes,walk around car and look at all lights,taillights,side marker lights,dash illumination lights. Are all these functional? Yes? Press on brake pedal,brake lights? Yes? Leave lights on. Turn key to run position,all warning lights at bottom of cluster illuminate? Actuate turn signals,get out and look to verify. Turn wipers on,do they work? Turn blower fan on,does it work? If all these things work,try to start the car,what happens,what do you lose? The starter is the biggest power consumer in the electrical system. All the other things i mentioned to test for operation are power consumers,all of them combined draw a fraction of what the starter motor draws when you turn the key to crank position so if this is when you lose everything,the starter circuit is where you should focus your efforts-from the battery to the starter and back-power and ground cables. Next is feed from positive battery cable to main fuse link. There's your homework. Reread chapter one and put it to use. Will look in on your thread periodically.

 

The battery tender warning light statement brings a couple questions to mind...what model battery tender is it,what color is warning light,is it flashing? Are you certain you have battery in car connected properly,positive cable to positve post(larger of two) negative cable to negative post?

 

BooBooBear,

I don't normally spend time in the 1st Gen forum but read about your wiring problems and wanted to offer some advice.

1. Do you have a copy (print or digital) of the Wiring Diagram Manual?

2. Roughly 90% of all electrical issues happen within 1" of a connector.

3. If you tested for parasitic draw at the fuse box then found the HAZARD circuit to be consuming power. If this is correct then your attention should be focused on the Turn & Hazard Flasher Lights circuit. Please refer to Diagram F in the Wiring Diagram Manual.

4. Does your car blow any fuses when you try to start it? If so, then what fuses blow?

5. According to Diagram F, I would argue that the Flasher CPU (aka Body CPU in the FC & FD world) would be the most likely culprit for failure. On the schematic, it is in the center of the page just below the Cluster Switch (Left Hand) for the Hazard lights. It is connected via X-11 and appears to be located adjacent to the fuse box. Make sure to check the two 15A fuses that directly feed the Cluster Switch AND the Flasher CPU. The 2nd culprit could be the Hazard switch itself.

6. It looks like B+ (12v) is split two ways, one through the ignition switch that leads to the Hazard Switch and the second through a fuse and then to the other side of the Hazard switch. Normally, switches are drawn in their de-energized state. This holds true for the Hazard switch which shows one segment of the switch drawn "normally closed". This passes B+ to the Flasher CPU at Connector E-26.

7. Did you verify the cable connections from the battery to the fuse box & ignition switch? Did you play with the fuseable links as GSLSEforme suggested? What was the result?

8. Use the Resistance (Ohm) function when testing de-energized wires, when possible. The Continuity function could give you a false indication because a short or open circuit may not be maintained long enough for the meter to properly respond. This may be the case with a fuseable link damaged by vibration.

I hope this gives you better insight to fix your problem. My recommendation is also based upon the presumption that the Starting/Charging system checked good.

Best of luck on your repair!
Cheers,
George

 

Thank you for your reply. It's a Griots battery tender and seems to be working fine. When hooked up to the battery while wired into the car the red light flashes, indicating a problem either with the battery, it's leads are reversed or an issue with the car's circuit. Disconnecting the battery from the car and hooking the tender to the battery, it operates normally, cycles as it should and shows the green light that all is well. The battery's cables in the car are correctly attached by polarity.
I'd like to reemphasize the electrical issue being experienced immediately surfaced after hooking up a tach to check the engine rpm. Prior to that the car ran perfectly. I can only conclude the way I hooked the tach up did something to the electrical system.

 

BooBooBear,

You are probably correct that the external tach was improperly connected and caused some damage. However, advice was given by GSLSEforme, DreamInRotary, KansasCityREPU, and me. When you ask for help and help is offered, it is customary to follow through and provide feedback. I spent a few hours reading this thread, researched the schematics for your FB, and I gave a methodical process for you to follow; as other members offered similar suggestions. If you want to fix this problem then please follow the advice offered above! Otherwise, quit your complaining or taking wild stabs in the dark at the problem. That approach will not help!

Again, please follow the advice given then provide the necessary feedback.

Cheers,
George

 

First let me say I appreciate all the help and have been looking at the various things suggested and thought I was giving feedback on my findings. If I haven't posted complete responses is because I'm working slowly and find all this overwhelming as I don't work on cars often. Patience is appreciated.

Yes, I've a copy of the wiring diagram and have been studying to the best of my abilities. There are no blown fuses. Cable connections to the battery are correct. The fusible links were checked as the wires are moved about, all is fine. Continuity in the wiring I can access seemed okay. The hazard circuitry and starter have yet to be investigated. And my last point, I'm not complaining just informing and doing the best I can!

 

Unbelievable as it sounds, the issue turned out to be an intermittent connection where the cable attached to the negative battery terminal even though battery posts and connecting terminals were shiny and clean. Even past voltage and testing verified all was well in those departments making this a very confounding problem to resolve. I found this out by accident, the door was open actuating the buzzer which was making varied sounds from weak to strong as I moved negative cable. It was found voltage was fluctuating as the cable was moved about and continuity between the battery connection and ground point varied in resistance all due to corrosion that wasn't visible but hidden internally within the connecting terminal. It appears that when a load applied there wasn't enough of a ground connection to give what the starter required which also caused the overall power loss issue. The starter and electrical system now functions as it should after replacing the negative battery connector. Thanks to all that chipped in on this and hope this helps anyone experiencing a no start/ complete electrical failure issue.

 

If you still have the original battery cables you should think about swapping them out for new ones. You might also think about adding an aftermarket volt meter.

 

This - after burning myself touching one of the (original) battery cables on my '85 after cranking it for no more than 20 seconds, I promptly replaced both main cables - made a huge difference, starts quicker, starter spins faster, voltage is more stable, etc etc.

 

Replacement cables sounds like a good idea at this point, God only knows what's going on within those things after 34 years. Thanks for the recommendation!

 

Hello Everyone,
First timer writing on the log...
I own a 1985 GSL-SE...
Early symptom: went to warm up the car and when activated the ignition switch, you could hear a "clack" (single sound) which I guess is from the starter, then the car would be dead, but I could still see the interior lights on. Proceeded to buy a new battery. Like 5 weeks later, it did the same behavior, checked the battery and was 10% weak; charged the battery and try to crank again; once again one "clack" and dead, but interior lights still on. I kept unplugging the negative from the battery and it was like resetting the ignition switch. I was able to get the ignition switch to activate and was able to make only one contact with the starter and then dead... continued this method for 3 or 4 more times and kept doing the same, until suddenly, all interior lights went off.

Read this log and followed your instructions:
1) re-charge battery, 2) checked all fuses on the fuse box (all good), 3) checked volts from battery (good), 4) changed both battery cables and the car is running.

Observations:
1) when the car started (new battery cables installed), it sounded different, it sounded in synchronization, accelerated with more energy, it felt different.
2) I am the second owner of the car, bought it a year ago, so not sure if the positive cable was original; did notice the cable was light weighted and seems to be made of aluminum.

The new battery cables are 4 gauge copper: Autocraft AC154 (positive-red) and Autocraft AC144HS (negative-black) - cables are long but I recoiled them to reduce the length; had to add one 8 gauge cable to each battery cable; the positive which connects to a fixture next to the coils (don't know the name) and for the negative which connects to the fender.

Hope this will help !!

 

Something in the charging system isn't happy.