Having trouble with a '90 rx7 gtu. Engine will spin, but not start.

Thought it might be flooded, so we took out the old plugs and spun the engine with the ECU fuse (30A on driver side strut tower) pulled. Waited a while, installed the new plugs, and it still didn't start.

Then, we checked the spark with a timing light. When cranking, only the front leading plug is firing.

Any ideas?

 

Does the rear plug fire? If not your trailing coil might be dead. I have the how-to for checking the front coil but the rear is slightly different so maybe you could grab one at your local junkyard and test it with that one.

You could also pull the fuel pump fuse and then pull out the rear leading plug and put it next to the shock tower, or something metal, and then crank just to make sure there is no spark.

 

Only one leading plug fires. Neither of the trailing plugs fire.

Where is the fuel pump fuse located?

 

If only 1 leading plug is firing, you have an electrical short someplace. The reason I say this is there is only 1 leading coil, and it is working, otherwise no plugs would fire. Here is the circuit:

[Coil] -- wire -- spark plug -- ground --spark plug -- wire -- [coil]

For one spark plug to not fire when the other one is firing, there is some other way the current is getting to ground besides the other spark plug. This could be either a very bad plug wire (arcing to ground) or the spark plug itself shorted by dirt/cracked insulator or some such thing. In your position, I would replace the leading plugs and leading plug wires. Good luck!

Irv, Keith's dad

 

What about the trailing plugs?

 

I just went through this whole thing not too long ago... What I do know for sure is that if one of your coils is bad, they both are and both need to be replaced ( I am talking about the set either leading or trailing). When i had my starting problem, I checked each plug wire for spark individually, and I didnt use and inductive timing light (although a good idea). I just unplugged the spark plugs, and ran the end of the wire close to something metal. what you will discover is that the leading and trailing plugs fire in an entirely different order. Remember, sometimes an inductive timing light doesnt always catch the spark. If you have spark, and timing is good, you have the problem I had. And that is that the motor just sat too long and was way too flooded. The only thing that got it to crank was the ATF trick. I got that from talking to the guys here. The other thing I know is that there is an underhood fuse named ENG INJ. That controls your fuel pump. If you pull the ECU underhood fuse, you disable EVERYTHING (including the SPARK). And you could definately use the spark to help clean out the gas in the motor.

Rat

 

Where is the ENG INJ fuse? It's not in the same box as the EGI fuse on this car...

 

Okay the better way is to disconnect the relay under the dash. It should be on the right hand side of the steering column and it has yellow coloring. The only other thing you can do is disconnect the fuel pump at the left hand pillar in the rear of the car. But thats a lot of work. The fuses in your box in the engine bay may be different then mine. But thats where the injection fuse should be. They are labeled different things in different models of 7s. Ask someone about thier 90 model and see. Did the car sit a while? Did you not let it warm up before shutting it down?

 

Got the car running. Sprayed starter fluid in the leading plug holes. I think it flooded because it was shut down too soon.

Now, it's missing on both the leading and trailing plugs for the back rotor. The trailing plug is firing once every 10 or 15 seconds at times.

 

Slasher, this thread and the posts by HAMMOND: https://www.rx7club.com/forum/showth...t=timing+light