Hello all,

I am new to the forum and a new RX7 owner. I just bought my 79 rx7. I am wondering if anyone can help me. It will run for about 15 minutes and just die. If I let it set for about 5 minutes it will start and run for another 15 minutes or so. Any help would be greatly appreciated. Thanks.

 

It could be several things. Bad gas tank or clogged fuel filter. Since it runs so long I'm saying it's not the carb.

 

Any idea of the condition of the inside of the gas tank? Your fuel pump could be drawing debris from inside the tank, clogging the outlet and cutting off the flow of fuel. With the car / fuel pump shut off, the particles are free to disperse until the suction from the pump draws them back. You might be in need of a thorough flush and clean of the tank and fuel system.

 

I just put a new fuel tank, fuel filter and fuel pump on it. I also have replaced the plugs, plug wires, cap and rotor.

 

Give more information about this "new" fuel tank.

 

Possible igniter heating up and shutting down? When attempting restart,does tach wiggle while cranking engine?
Soon as engine stops and won't restart,pull a leading and trailing plug wire off,stick a spare plug in each and ground wherever convenient. Crank engine and check for presence of spark on each.

 

Yes the toggle does wiggle when trying to start it back up. Something that I did is put the original plugs back in and it is running longer. The new one that I bought had a single prong and the original ones that were in it had 3 prongs. Does that matter? The gas tank came out of one that was running until it end up in a salvage yard about 2 months ago.

 

GSLSEforme is on to something with suspecting the igniter(s). Make sure they have dielectric grease on the backside. This is used to help transfer heat.

 

I will check the igniters tomorrow and post what I find.

 

Being a 79 it would have the "old" pre FB electronic distributor,or possibly has had an FB unit swapped in.
Perhaps op could post a picture of his distributor,could help in more specific suggestions,diagnostics.

 

Not dielectric grease, heat sink compound. Auto Zone carries some, part # SL203 .
The leading coil may also be suspect if the igniters are ok.

 

Plugs: Yes it DOES matter - use the 3 prongs only: BR8EQ14 NGKs
Tank: Sounds like you have no 'history' of the condition of your new-2-U tank. Just 'cause the Yard said it came from a running car means, well, nothing. This is, as others have said, a case of an old tank that sat for a long time and whatever gas/moisture inside sitting there has started to rust the inside of the tank. Your symptoms are a classic signature of a failing tank. You need to pull it, take to a quality radiator shop and have them dunk it in a chemical tank to clean out the insides. Then I highly recommend you SEAL the tank insides with a product POR15.com makes for sealing gas tanks.
https://www.por15.com/POR-15-Fuel-Tank-Repair-Kit
About $90 and will prevent this from happening again. $$ well spent. I went thru the exact same thing you are.

Stu Aull
80GS
AZ

 

 

With this dizzy pic, we can rule out ignitors since the 1979 has none.

 

After putting the original 3 prong spark plugs back in with the new cap, rotor and plugs wires. It has ran so far for an 1 in a half this morning with no problems yet.

 

There you go,nothing like right parts installed to make it run correctly. Check all pointset faces for burning,pitting and proper gap. Once you know all is good and point gap correct,check and set ignition timing. Set idle speed and mixture after that and all your tune up specs are covered.

A good upgrade for better spark and ignition timing that won't change is to swap in an 81-85 FB electronic ignition distributor. As the rubbing block/point faces in your distributor wear over time,the gap/point dwell changes which retards ignition timing.This is normal wear and tear and one of reasons tune ups had to be done so frequently on all cars 30-40 years ago. For the most part electronic ignition is set it and forget it as there are no wear parts that affect ignition timing settings.

 

I have developed a new problem. T2 plug seems to be loading up with oil. I know with a regular engine that means oil is seeping around the pistons and rings, but not for sure on a rotary motor.

 

Is T2 firing? It may just not be firing. The trailing really has almost zero affect on the power, so you won't know when its not firing. Do the other plugs look like this?

 

I had this exact problem happen on my FB when the fuel tank vent line was clogged. The tank would build vacuum as the engine ran and fuel drained, eventually the vacuum was enough to overpower the fuel pump. leave the gas cap loose or take it off to see if eliminates the symptoms.

Matt