Engine will not run with all plugs in?
 

hello i have a 12a in my 84 rx7

i was checking the compression w/o a compression tester when i removed my rear cylinder bottom spark plug the car would fire and blow flames out the spark plug hole, when i put the plug back it it would fire at all. all my plugs wear checked and had great spark can i get anyhelp, someone explain y

Check the leading ignition, your flame was started with the trailing plug that you left in. It might be tough to start on trailing ig alone.

can you explain that again ...please

I wouldn't do it that way, great way to burn something to the ground :)

Just take the plugs out and lay them on the fender. Spin it over a few times and check for spark.

is it possible that i could have the two plug wires mixed up

the bottom plugs should spark first or should the top plugs?

hI TEST THE COILS FIRST DO BOTH COILS FIRE WHEN GROUNDED ON THE LEFT STRUT,IF ONLY ONE IS YOU HAVE PULLED OUT THE WIRE FROM THE SMALL BLACKBOXES LOCATED ON THE DISTRIBUTER IF THE ARE PLUGED IN IT , COULD BE YOU HAVE A BAD BLACK BOX TRY THAT ALSO ,CLEAN OUT THE CRUD ON THE CAP iTS MOST LIKELY BEEN THERE FOR 20 YEARS,BETTER YET PUT ON A NEW BRASS POST. CAP(NOT ALUM) AND ROTOR AS WELL,PS i HAVE SEEN PLUGS THAT FIRE DOWN INSIDE THAT WILL NOT START YOUR CAR INVEST THE MONEY AND INSTALL NEW

He is saying your leading ignitor could be bad.

On the distributor, you should see 2 black boxes on it (assuming it is an 81-85 car). Those are your ignitors. One is leading, one is trailing. The Leading plugs are labeled on the housing with a L and the trailing with a T. On the dizzy cap, you should see L1, L2, T1 and T1 plug wires going to the engine. The 1's designate the front rotor, and the 2's for the rear.

Pull all the plugs out of the car and lay them on the fender. Have someone crank the car over and check to see if you are getting spark on them. I generally do both leadings on the fender, spin it over and check for spark, then put the trailings on the fender and check.

If your leading Ignitor is out, you will not have any spark. If your trailing was out, you would not have any tach (or any fuel pump if 84-85). Be sure to also check your coils, you could have a good ignitor but a bad coil.

I've managed to start and run my 12A off of the trailing plugs before....

First of all when performing a compression test you need to not only disable fuel but spark for safety reasons. Unplugging the trailing ignitor on your year model will disable fuel to the engine and spark to the trailing side plugs.

Removing the coil wire from the leading side coil will disable spark to the leading plugs.

Did your engine start and run before you did the compression test?

Copy and paste the link in my signature then go to that site and download a copy of your year FSM. That will have all the information as to where the ignitions wires are routed, the location of the trailing and leading ignitors and coils.

Deflood your engine. Search on how to do it. I bet $10 on it.

thanks u guys ill check this out this weekend