Hi, I just bought an old 88 rx7 in pretty ragged shape. It has sat for the last 7 years because the engine will not get spark and the shop couldnt figure out why... Anyways, I figured I would buy it and get it running. Its not turning out to be very easy... I have been reading posts all night, and trying EVERYTHING.

I have checked both fuses that have to do with the engine (40amp under hood, and 15 amp in fusebox). I have tried a different computer, a different crank angle sensor, and the car has a new coil (the one closest to the firewall). The main relay has power and allll the wiring (black w/white stripe) is getting 12v as it should. at one point out of nowhere the engine started firing.. I got excited and put the plug wire back on, and tried to start it... It wouldnt start so I went back to make sure it still had spark and it was gone!! I have been trying for 4 hours to get it back with NO luck. anyone have ANY other ideas? This car is driving me nuts! It almost seems like a crappy wire somewhere but I dont know where to look. The coils are getting 12v, but which wire triggers them to fire? What reading should I get from the wire when I turn the engine over? Thanks to anyone that may be able to help!!

 

Concentrate on the LEAD COIL assy. lThe one near the battery.

When you turn the engine over, does the tach needle move just a touch? Jump a touch? If it does then there is spark on the trails at least.

The ECU gets its ground from a *ring* terminal under the intake manifold. No ground there results in no spark. Pull the ECU plugs off and look at pins 3G, 3A, and 2R on the plugs for a good ground to chassis. I think they are all three solid black wires. The first two on the small plug and the other on the middle plug.

Some don't like the following: Pull the cas out. Leave the connector on. Turn the key ON. With your fingers spin the gear on the bottom of the cas. You should see spark at the plug wires if they are laying on the fender or near the strut tower studs/nuts. You should also be able to barely hear the injectors click.

That method is no good if you don't know how to install a cas. If leary....don't do that then. I personally think its the best method of seeing if you have spark. I don't trust looking for spark with a slow starter that's dragging the battery voltage down.

I'd look for the 12v on the small white , two socket plug at the LEAD coil assy. The black/yellow wire there. You said it had 12v I THINK. The other wire should have 5vdc coming and going as the engine is cranked.

 

Hi, Thanks for the reply. When I turn the car over the tach doesnt move at all. Just sits there dead as can be. I will check out the grounds you talked about here in a little bit. I will post the results. Thanks alot for the help!!

 

Oh yeah, also did check for 12v at the black/yellow wire and it has juice. The ground on the engine that your talking about... Does it just have a ground wire going from the engine to a bolt on the firewall? Thats the only ground I can find back there. It appears to be in good shape but it just looks like a body ground. Not a ECU ground. Is this the right one?

 

Its a little ground on the rats nest that gets held down by one of the bolts that the rats nest is held down by. You have to unbolt the whole UIM to get at it. I missed that one when I did my install. Im fixing it as we speak lol.

 

If the tach does not move when you crank then it could be two things.

The CAS is not sending the signal to the trailing coil or the trailing coil is not working. The trailing coil sends the TACH info to the tachometer.

Also, buy a timing light...nothing fancy just the 20 buck one....your going to need it.

Also, once you get the rpm showing up ....don't forget to try a fresh set of plugs.

James

 

Ok, the coil closest to the front of the car has 3 wires coming off it. It has a black/white stripe, showing 12v with key ON, or cranking. It has a solid black wire thats not hooked up to anything showing 12v with key on or cranking. There is a green/yellow wire that shows nothing (not a ground or +) with key on or cranking. I would imagine that the green/yellow is the signal wire to tell the coil when to fire. What is this wire suppose to show for voltage? I regrounded all the ground wires at the ECU and that didnt help - all the solid black wires that ground the ECU were already showing good ground.

The ecu does get pretty warm on one side. so it has to be getting power. Anyone have any ideas, or know what the green/yellow wire at the coil should read, or what its there for?

when you say you have to remove the Upper intake manifold, do you mean the rubber inlet hose, or the actual aluminum manifold. I am having serious problems finding this grounding point. Is it toward the front or back of the motor? Offset to either side? Thanks

Im tinkering on it right now so any quick help would be greatly appreciated!!

 

You have to take off the whole aluminum manifold. the connection in towards the rear of the engine and it looks like 2 black wires going into one ring connection. A bolt is used to hold this connection AND part of the rats nest to the engine. I just hooked mine up, but now Im running super lean. Trying to find out why.

 

Just did some more testing... NONE of the 4 wires to the Crank angle sensor are getting 12v. Anyone know what these wires should be showing? Thanks

If anyone knows what each of these wires do, I could rig up the CAS without the wiring harness. Like if the wire are 12v, neg, trailing signal, and leading signal (just a guess), I could wire each wire directly where it needs to go. Im guessing there is a problem in one of my harnesses somewhere. So, if anyone knows what each of these wires do, or where they route to, That would be great! Thanks

 

im kinda having the same problem with my swap...check the fuses inside the car also. that was the reason my tach didnt work

 

The cas wires should not show voltage at the cas. What happens is that the CAS outputs ac voltage TO the ECU when the cas is turning.

You should reconnect the cas plug, then go to the ECU and ohm out the cas two coils FROM the ECU. I can't attach pictures right now but if you have a manual you'll see what I mean.

If those ground wires on the ECU plug show a good ground, then the ground ring connector on the top of the engine is good.

The LEAD coil plug should have but two wires in it. The small one I mentioned. WHATEVER YOU DO, do NOT ever ground that single black wire bullet connector. That is a diognostic plug for rpms.

 

all fuses are good. I still think that CAS should have voltage shouldnt it? Im hoping someone here will know which wire does what on the CAS. Thanks

 

CAS has NO voltage. 4 Wires, 2 for Lead, 2 For Trailing. When the cas hits a certain point, it sends a signal to the ECU, which does the rest.

 

I found out why its not firing... I started a new thread about the new cause. The ECU has 3 wire harnesses plugged into it. The center Medium size plug is causing it not to fire. If I unhook the center harness from the ECU the ignition sparks fine. If i plug it back in, NO spark. Any idea what would cause this? Thanks

 

The things in the middle plug that effect the operation of the car are: Pin2A which is ref voltage to the afm. Pin 2B wheich is the output FROM the boost sensor, Pin 2C which is a ground for the ECU, Pin 2G which is the output FROM the TPS, Pin 2E which is the output from the afm, Pin 2J and 2L which are air intake inputs, 2I which is the water thermo sensor, and pin 2R which is another ECU ground. I dismissed the other *2* piins as the cause of the problem.

ADVICE: Get the fsm which is free and online. Go to the Fuel Section. In that section there is a list of all the pins on the ECU. With the engine at idle OR off, you can back probe each pin to see which is the culprit. There is a given value for each pin. My advice is DO IT.

THE CAS DOES NOT GET AN INPUT VOLTAGE. THE CAS OUTPUTS A VOLTAGE. PERIOD. IT GENERATES VOLTAGE.

 

Oh ok... Ive been downloading every section of the FSM besides the fuel section trying to find what each pin of the ecu does! I will go download it and see what I can get figured out. Thanks alot!!!

 

http://www.teamfc3s.org/info/articles/demystifying.html

 

You might make the AFM and the BOOST SENSOR your prioritys. You might try disconnecting the afm's plug from the AFM and the boost sensors plug. Then see if you have the spark you had when the middle plug was disconnected but this time with all three plugs installed.

If it sparks like you think it should, then reinstall the afm plug first then look for the spark. If it's one of those two items then you should be able to figure it out right off.

Make sure nobody has unscrewed the JACK for the afm instead of just pulling the afm plug off. Unscewing the JACK on the afm will destroy the afm and MIGHT cause the problem you have right now.

 

HAILERS - You have been a great help!! I went and downloaded the fuel section of the manual. I tested each terminal and NONE of the center "B" harness terminals were reading the correct voltages. So, I pulled a wire out of the harness one at a time and figured out that its the 2A *V Ref* wire that is causing the problem. With this wire unhooked i have spark at the plugs. BUT, I dont have a fuel pump in it yet to see if it will actually run on its own. I did hose some gas in the throttle body and it fired up and ran for a sec. What is the V ref wire for? Is it needed for anything important?? I greatly appreciate everyones help and ideas! With your help I have finally made some progress on this problem!!

 

HAILERS - You are the man! I probed all the wires on the "B" center harness at the ECU. ALL of them were showing the wrong voltage. So, I pulled one wire out of the center harness at a time and figured out it was the V Ref wire that was causing it not to spark. So, I noticed you said this wire had to to with the AFM. I pulled out the airbox and took the harness of the AFM and the plugs are getting spark WITH the V ref wire hooked up to the ECU. Plugged the AFM back in and NO spark... So, i guess there is something wrong with the AFM. What should I do to it to try to fix it? There are NO rx7's in any local junkyards here, so Im kind of limited on getting used parts. If the old one can be fixed that would be great! Thanks to EVERYONE that helped troubleshoot this issue. I have fixed MANY cars and have never ran across a problem this goofy, and time consuming to narrow down. You all have been great!!

 

Ok, things just got wierd. I pulled out the airbox/AFM so I could check it out... When I pulled it out of the car I accidentally dropped the whole assembly on my garage floor. I looked at it, and then figured I would wait for your (HAILERS) response before I dug into the AFM. So, I hooked it back up and... I HAVE SPARK!! The AFM is plugged in, the V Ref wire is plugged into the ecu... Whats the deal? Could dropping the AFM knocked something to where it was suppose to go? I poured more gas in the throttle body and it just fired right up! I need to go buy a new Fuel Pump and see if the car will run on its own. The fuel had been in the tank for 7 years and had turned the pump into a glob of crap. I syphoned the tank (the old gas smells horrible!) tonight so it should be ready for a new pump and hopefully it will run!! Anyhow, any insight on how dropping the AFM would make everything happy?? Thanks for your help!!

 

bump

 

Got a new fuel pump today.. installed it and had no fuel pressure. I took the pump back out and the little section of hose that connects directly to the pump was clogged up. Cleaned it out and it started right up. Smoked like hell, and stunk but its running! It hasnt been started in 7 years so its probably got alot of crap to burn off... It seems to idle pretty high. I only ran it for about 5 minutes but the idle never dropped down. The temp gauge got about 1/4 of the way up. Is this normal?

Again, Thanks to everyone that helped me out with this!! I would have NEVER figured this out on my own. You guys are great!

 

This thread helped me some too. I managed to solve my spark issues and hunt down all but 1 vaccuum leak somewheres. Now for that nasty header leak.....

 

WTH, you started two threads on the same thing???


-Ted