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I just bought this '89 Turbo II which had been sitting for about 4-5 months before I bought it. The owner told me that the car used to start and then die out and its been sitting ever since. Currently it cranks but won't start. I checked through some other posts to try and track down the culprit but I got stuck. I checked for fuel and hear the fuel pump start up, and I cracked the bolt open on the fuel rail and saw some pressurized fuel come out so I am fairly sure the fuel is good. I bought an ignition test light and hooked it up to the newly replaced spark plugs (just replaced them once I bought the car) and there is no light indicating spark. I also 'checked' compression with the somewhat jank method of unplugging the trailing plug on one rotor at a time and cranking the engine over to listen for the 3 consistent "puffs" indicating compression was at least decent. Took a test light today and went through all the fuses inside the car under the dash near the dead pedal and they all checked out. I checked the fuses in the engine bay and all of them were normal except for the EGI fuse, which I noticed had voltage on both terminals of the connector. The way I tested was by removing the fuse, checked the fuse with my multimeter for continuity, and then used the test light to probe each side of the terminal the fuse plugs onto one at a time. The terminal on the fuse box closest to the front of the car had the test light turn on. Same as all the other fuses in the engine bay, but only the EGI fuse had the other terminal also give a dim light. I tracked the wires (white/blue and white/red) to the main relay, and I am not sure if the EGI fuse is supposed to work that way or if its even getting that voltage from the main relay or if either of these are even the problem. Also worth noting I put new gas in and premixed with some oil to try and help build compression. Any help would be greatly appreciated. I am fairly new to rx7s this will be my second one and I got it as a project to try and learn as much as I can about them.
I can’t comment on the egi fuse but I think you should definitely find out about that.
but….
Should keep spare spark plugs on hand, especially if it injects fuel but doesn’t start. They’ll get wet pretty fast and won’t spark correctly.
do you smell fuel out the exhaust? Try deflooding with spark plugs removed? Are fuel vapors coming out? Did you put a spark plug on the spark plug wire and visually verify spark?
does a connector on the engine harness show ~+12 v with ignition on. Verify this. This will indicate if the ecu is on. Does the car have a usdm n370 ecu? If so, the CEL on the idiot cluster should light up for a few seconds then turn off when switching to ignition on. All in this paragraph is to verify ecu is turned on with ignition on.
fuel pump primes fuel for a few seconds when switching to ignition on, then fuel pump shuts off. Fuel pump waits for maf signal to turn back on. If you have spark but fuel pump won’t stay on, there is a jumper connector you can use to manually turn the fuel pump on.
did you check the engine fuse under the dash?
CAS sends engine position to ecu to inject fuel and to fire ignition. Should verify timing by removing the cas cover and aligning it with the crank pulley at timing mark.
vacuum leaks?
I highly suggest you go through all of these questions. I’m forgetting some stuff but I’m at work atm.
I can’t comment on the egi fuse but I think you should definitely find out about that.
but….
Should keep spare spark plugs on hand, especially if it injects fuel but doesn’t start. They’ll get wet pretty fast and won’t spark correctly.
do you smell fuel out the exhaust? Try deflooding with spark plugs removed? Are fuel vapors coming out? Did you put a spark plug on the spark plug wire and visually verify spark?
does a connector on the engine harness show ~+12 v with ignition on. Verify this. This will indicate if the ecu is on. Does the car have a usdm n370 ecu? If so, the CEL on the idiot cluster should light up for a few seconds then turn off when switching to ignition on. All in this paragraph is to verify ecu is turned on with ignition on.
fuel pump primes fuel for a few seconds when switching to ignition on, then fuel pump shuts off. Fuel pump waits for maf signal to turn back on. If you have spark but fuel pump won’t stay on, there is a jumper connector you can use to manually turn the fuel pump on.
did you check the engine fuse under the dash?
CAS sends engine position to ecu to inject fuel and to fire ignition. Should verify timing by removing the cas cover and aligning it with the crank pulley at timing mark.
vacuum leaks?
I highly suggest you go through all of these questions. I’m forgetting some stuff but I’m at work atm.
OK cranked it without sparkplugs installed and with the EGI fuse pulled, I smelled some gas as expected and I am not sure of any fuel vapor. When we tried to crank at first it wouldn't do anything and I could just hear a relay clicking like crazy, but we gave it a second go and it cranked normal. After that I reinstalled the EGI fuse and I checked visually for a spark by connecting a leading plug to a leading wire and grounded it to the top of the intake manifold which I verified with my multimeter as a good ground source. Still no spark. Battery was low so I gave it a charge and tried a second time just to be safe and still nothing. Smelled some fuel at the exhaust also, but had to get right up next to it to smell it.
As for the ecu. I checked yesterday by back probing the connectors and only checked the first 2 or 3 meaning 1A 1B and 1C and I got 11.22v at 1A. 11.09v with ignition on and 0v with ignition off (battery was low because of trying to deflood and testing fuses with ignition on so battery voltage was at 11.22 or something close to that I checked it with the meter before I messed with the ecu) and then on 1C I was only reading like 4v while cranking which a lot lower than the approximated 12v value according to the FSM. I wasn't sure what to make of that and just called it a night and was planning to try again today. So now today I went to recheck these values and I cant get anything from the ecu. I am worried I fried it or something but I am not sure what I could've done to do that. I checked 1A the same as I did yesterday and when I turned ignition on I heard that relay clicking like crazy again so I am not sure if that has something to do with it or what, but I couldn't get anything from the ecu tonight. Also I remember a few days ago trying to pull engine codes and there was no check engine light, not even when I first put ignition on. So I wasn't able to pull the codes and I couldnt tell then whether it was burnt out or no power to ecu but now I am feeling like no power to ecu or I might've fried it somehow. Needless to say no check engine light came on today either while testing. As far as a connector on the engine harness showing close to 12v I wasn't sure exactly which connector you were referencing so I just thought I would try back probing again to verify my results from the other night.
I did the CAS stuff yesterday aligning the timing with the front cover pully and then removing the CAS itself, setting the gear on the bottom of that in line with the timing mark, holding it in place, and then reinstalling it ensuring the timing is still set, and I also should mention that the CAS connector wiring has been messed with by one of the previous owners because after the connector (on the wiring harness side if that makes sense--not the side of the connector coming out of the CAS, but the other side) the wires have been cut and then crimped into terminal connectors and I am not sure if that is compromising the signal or not, its a tight spot to get into with a soldering iron in order to fix it so I am not sure whether to leave it or find a way to test it somehow.
Also there's a relay under the gauge cluster above the pedals that has some alligator clips jumpering two of the wires together and I am not sure what that's all about either. That could be the relay clicking a bunch but its a little bit hard to tell and I don't know how to recreate the clicky relay circumstances.
Last edited by cereal; 10-26-21 at 07:19 PM.
Reason: clarification
OK cranked it without sparkplugs installed and with the EGI fuse pulled, I smelled some gas as expected and I am not sure of any fuel vapor. When we tried to crank at first it wouldn't do anything and I could just hear a relay clicking like crazy, but we gave it a second go and it cranked normal. After that I reinstalled the EGI fuse and I checked visually for a spark by connecting a leading plug to a leading wire and grounded it to the top of the intake manifold which I verified with my multimeter as a good ground source. Still no spark. Battery was low so I gave it a charge and tried a second time just to be safe and still nothing. Smelled some fuel at the exhaust also, but had to get right up next to it to smell it.
As for the ecu. I checked yesterday by back probing the connectors and only checked the first 2 or 3 meaning 1A 1B and 1C and I got 11.22v at 1A. 11.09v with ignition on and 0v with ignition off (battery was low because of trying to deflood and testing fuses with ignition on so battery voltage was at 11.22 or something close to that I checked it with the meter before I messed with the ecu) and then on 1C I was only reading like 4v while cranking which a lot lower than the approximated 12v value according to the FSM. I wasn't sure what to make of that and just called it a night and was planning to try again today. So now today I went to recheck these values and I cant get anything from the ecu. I am worried I fried it or something but I am not sure what I could've done to do that. I checked 1A the same as I did yesterday and when I turned ignition on I heard that relay clicking like crazy again so I am not sure if that has something to do with it or what, but I couldn't get anything from the ecu tonight. Also I remember a few days ago trying to pull engine codes and there was no check engine light, not even when I first put ignition on. So I wasn't able to pull the codes and I couldnt tell then whether it was burnt out or no power to ecu but now I am feeling like no power to ecu or I might've fried it somehow. Needless to say no check engine light came on today either while testing. As far as a connector on the engine harness showing close to 12v I wasn't sure exactly which connector you were referencing so I just thought I would try back probing again to verify my results from the other night.
I did the CAS stuff yesterday aligning the timing with the front cover pully and then removing the CAS itself, setting the gear on the bottom of that in line with the timing mark, holding it in place, and then reinstalling it ensuring the timing is still set, and I also should mention that the CAS connector wiring has been messed with by one of the previous owners because after the connector (on the wiring harness side if that makes sense--not the side of the connector coming out of the CAS, but the other side) the wires have been cut and then crimped into terminal connectors and I am not sure if that is compromising the signal or not, its a tight spot to get into with a soldering iron in order to fix it so I am not sure whether to leave it or find a way to test it somehow.
Also there's a relay under the gauge cluster above the pedals that has some alligator clips jumpering two of the wires together and I am not sure what that's all about either. That could be the relay clicking a bunch but its a little bit hard to tell and I don't know how to recreate the clicky relay circumstances.
So you know your issue is spark. There's only 3 components here, so it shouldn't be too difficult to track down. You've got the actual spark plugs. Make sure they're not fouled or wet. If those are good, check your plug wires. Check for resistance from one end to the other. I don't remember the spec off the top of my head, but it's in the FSM. Last component is the coil. If both the plugs and plug wires are good, this is the last thing to check. There is also a procedure for checking this in the FSM.
So you know your issue is spark. There's only 3 components here, so it shouldn't be too difficult to track down. You've got the actual spark plugs. Make sure they're not fouled or wet. If those are good, check your plug wires. Check for resistance from one end to the other. I don't remember the spec off the top of my head, but it's in the FSM. Last component is the coil. If both the plugs and plug wires are good, this is the last thing to check. There is also a procedure for checking this in the FSM.
Went through and checked the wires which are good. checked coils and ignitors which are also good and getting battery power. Was worried about the ecu and checked again but took the connectors out this time instead of back probing (which seemed to be easier because it was hard to get to the wires while back probing) and I checked 1A, 1B, and they were normal and had power so I know the ecu should be getting power. I checked 1G and 1H and they were good. But 1J and 1V which are ignition trailing select signal and ignition trailing confirmation signal respectively, I read like 0.03v which is supposed to be 4.4v on 1J and 0.03-0.04v compared to the 2v on 1V according to FSM. I think that is my problem but I'm not sure how to follow those wires and see what's wrong. Could it be a bad ground causing that much voltage drop? How do I go about finding it?
Went through and checked the wires which are good. checked coils and ignitors which are also good and getting battery power. Was worried about the ecu and checked again but took the connectors out this time instead of back probing (which seemed to be easier because it was hard to get to the wires while back probing) and I checked 1A, 1B, and they were normal and had power so I know the ecu should be getting power. I checked 1G and 1H and they were good. But 1J and 1V which are ignition trailing select signal and ignition trailing confirmation signal respectively, I read like 0.03v which is supposed to be 4.4v on 1J and 0.03-0.04v compared to the 2v on 1V according to FSM. I think that is my problem but I'm not sure how to follow those wires and see what's wrong. Could it be a bad ground causing that much voltage drop? How do I go about finding it?
Do you have a spare ECU you could swap in to see if there's an issue there?
If not, I would honestly try giving the ECU ground a good cleaning. It sits under the dynamic chamber on top of the keg, close to the slave cylinder. You'll have to remove the UIM to do this.
With the key on run, check for 12v on the small black check connector on the leading coil harness. Its right next to the leading coil. This will verify you're getting 12v to the coils.
If this unit came with a security system you might try bypassing that relay. Its located next to the Main relay on the driver side fender wall.
Also, does your tach bounce when cranking? If not, and you have verified 12v to the coils, you may have a bad ECU or an issues with the CAS.
With the key on run, check for 12v on the small black check connector on the leading coil harness. Its right next to the leading coil. This will verify you're getting 12v to the coils.
If this unit came with a security system you might try bypassing that relay. Its located next to the Main relay on the driver side fender wall.
Also, does your tach bounce when cranking? If not, and you have verified 12v to the coils, you may have a bad ECU or an issues with the CAS.
Coils have power I checked from that check connector. No spare ecu but I cleaned the ecu ground and battery ground to see if that would help and it didn't do anything. No tach movement at all. Thinking it might be a CAS problem because the wires have been cut by the previous owner and have some sort of terminal connectors after the existing connector from mazda so I'll go through and fix that by soldering the wires together and eliminating the terminal connectors.
My car had a wiring issue years ago. I believe I ended up rewiring the cas straight to the ecu. Could possibly do a test by wiring the cas to the ecu…?
check the wiring diagram first though. I’ve since replaced all harnesses so I can’t verify my proposed solution.
by the way, I have a thread calling out the correct replacement ecu pins for a s5 ecu. Possibly could but a few of those and properly wire it into the harness connector in the ecu or use them to test with.
My car had a wiring issue years ago. I believe I ended up rewiring the cas straight to the ecu. Could possibly do a test by wiring the cas to the ecu…?
check the wiring diagram first though. I’ve since replaced all harnesses so I can’t verify my proposed solution.
by the way, I have a thread calling out the correct replacement ecu pins for a s5 ecu. Possibly could but a few of those and properly wire it into the harness connector in the ecu or use them to test with.
I am about to do this today. Your idea gave me some inspiration last night about testing with the leading coil by wiring it directly to the ecu which I triple checked the fsm and made sure I was doing it all correctly. So I tried that which essentially cut the leading coil out of the equation with a "second" wiring harness if you will. Still got nothing. I'm gonna try what you proposed today and get some more wires to create another 'second'wiring harness to wire the cas to the ecu on its own outside of the original wiring harness but ill be sure to check the fsm to ensure I have the connections in the right places. I'll attach an image of my own wiring diagram I created that depicts what I tried yesterday. I only directly wired the B connection on the leading coil directly to pin 1H on the ecu. I know the main relay is working because I have battery voltage (12.7v at battery and 12.2v at coil test connector with key to on position). So I didn't mess with anything on the trailing coil because I thought Id read somewhere that the engine can function on leading coils only? Also wasn't necessarily expecting it to start but was mainly just trying to see if I could at least get spark at the coil which did not happen.
I am about to do this today. Your idea gave me some inspiration last night about testing with the leading coil by wiring it directly to the ecu which I triple checked the fsm and made sure I was doing it all correctly. So I tried that which essentially cut the leading coil out of the equation with a "second" wiring harness if you will. Still got nothing. I'm gonna try what you proposed today and get some more wires to create another 'second'wiring harness to wire the cas to the ecu on its own outside of the original wiring harness but ill be sure to check the fsm to ensure I have the connections in the right places. I'll attach an image of my own wiring diagram I created that depicts what I tried yesterday. I only directly wired the B connection on the leading coil directly to pin 1H on the ecu. I know the main relay is working because I have battery voltage (12.7v at battery and 12.2v at coil test connector with key to on position). So I didn't mess with anything on the trailing coil because I thought Id read somewhere that the engine can function on leading coils only? Also wasn't necessarily expecting it to start but was mainly just trying to see if I could at least get spark at the coil which did not happen.
Instead of making test harnesses why not just use a meter to check continuity between each wire ends?
Did you fix the CAS wiring yet? You should do that first, as you're going to need to fix that anyway.
Instead of making test harnesses why not just use a meter to check continuity between each wire ends?
Did you fix the CAS wiring yet? You should do that first, as you're going to need to fix that anyway.
I fixed the CAS wiring a few days ago. Before it had some spade connectors and they were pretty jank so I cut them off stripped the insulation and soldered the wires. How should I test continuity? Set to continuity setting on multimeter and put negative probe on the ecu side of the wire and the positive probe on the CAS connector?
I fixed the CAS wiring a few days ago. Before it had some spade connectors and they were pretty jank so I cut them off stripped the insulation and soldered the wires. How should I test continuity? Set to continuity setting on multimeter and put negative probe on the ecu side of the wire and the positive probe on the CAS connector?
Exactly. Most meters have a "beep" function that beeps when the wire has continuity. Ideally you want close to 0 resistance. You can even use a copper wire as an extension if the leads dont reach. Makes it easier if you have a helper.
Ok basically I tested continuity with a multimeter and it checked out for the CAS so im sure it isn't a wiring problem, at least from the CAS. Kinda stumped at this point and don't really know what else it can be besides a bad ecu. Which would make sense because the CEL idiot light never shows up, not when key is turned to on or while cranking or anything so at this point I feel like I've ruled everything else out that I can and will probably have to pick up a working S5 TII ecu to test with. If that doesn't work I might have to bring it to someone to take a look and see if an extra set of eyes can identify whats up. Thanks for everyone's help, and if anyone has other ideas let me know.
It's been a while but I took it into a shop nearby and we are working together to figure out what in the world is going on. For a few weeks we went through all the things I've tried again and looked for ways to solve the problem of no spark and we decided its time for a new wiring harness. Almost every wire we checked out on the car had cuts and splices in it so it had been messed with before. Just time for a fresh start. Also checked compression and its got 60psi in the rear housing and 75 psi in the front housing but that was using a normal compression tester through the trailing spark plug holes so idk how accurate it is, but figured if the compression isnt great, might as well take out the engine, renew the wiring harness, and pop a new clutch on there too, just to get everything done for the next good while so I can just have a solid FC to drive around. I've spent the past 2 days getting the car ready for the engine/transmission removal and it is just about ready to come out, just has a few more hoses, wires, and other random things keeping it in and it should come out tomorrow if all goes well. Very excited because I've never taken an engine out before or put in a clutch so its cool to be able to learn to do this stuff but dang am I slow with doing the work on this. I'll update again soon once I have a more clear understanding of what is wrong with the harness exactly to hopefully help someone else out who is having the same problem. Thanks everyone for your help, will probably need it again so thanks in advance too, haha
Found out the engine is an s4 engine, meaning the UIM, LIM, OMP, TPS and throttle body are all s4 parts, so currently assessing the situation and seeing what the best course of action is on another thread.
OK I am picking up on the spark issue again in preparation for getting the car all put back together. I have the engine out and stripped down, and I am wanting to test for spark by spinning the CAS by hand. I am able to get the lights and everything to work with the battery plugged in and the alternator terminals/starter terminals isolated (note I do not have the grounds for those plugged up to the chassis somewhere they are unplugged) and I started going thru the wiring on the ECU again and found out I am getting voltage outputs from every single pin on the ECU, ranging from 9.3-9.5v, some pins 11.7v and some pins battery voltage at a little over 12v. Even on pins I should have 0 volts on or like 2v on. This was all tested with the ignition in the on position. I noticed that even my emissions harness grounds are carrying 9.5v and that makes me think I have some short somewhere. I have a second emmissions harness so I plugged up my second one and found the same results which leads me to believe that either
1) The other harness (I suppose would be the body harness? the one that starts with pin 1A) has a short somewhere on the driver side of the engine bay, or somewhere on the connector where it goes thru the firewall, or somewhere behind the dash.
2) Both of my emmissions harnesses suck and have a short somewhere.
I know that pin 1A and 1B function as they are supposed to as 1A has constant 12v and 1B gets it when the igntion is set to on. Would like to hear from other ppl to see if my understanding of this situation is correct. Seems to me like the next course of action is to start testing the body harness and make my way from the end of the harness ( starting from the front relays), back towards the firewall. If I can't find anything there, I will make my way back through the firewall and take the dash out. IDK exactly what I am looking for, obvious signs like cut wires, melted wires, that sort of thing, but I would think since my ground is getting power from somewhere I will follow the grounds, and follow the Black/White wire that carries 12v and go all the way to pin 1A on the ecu and see what I can see... any insight would be greatly appreciated, kinda worried how I will sort thru all the wires to find a short without any of the obvious signs, any tricks with a multimeter to make things a little easier?
Pin 1C which is the Ignition switch is not behaving properly, with ignition off it is normal, 0v then with it in ON position it gets 1.8v and while cranking it retains the 1.8v where it should be 12v. Probably going to take out the dash and get access to more of the wiring back there to see what is going on
10-25-21, 10:30 PM
