soundquest

Need help pretty desperately -- indeed very glad for the existence of this forum and its members. I have seen/used many auto forums -- RX7club is indeed extremely intuitive and helpful; moderated by people that appear to know what they are doing (which cannot be said of all forums unfortunately).

Nuff prefacing...

my 1990 RX-7 convertible (non T, manual trans) has left me stranded once again. It has been doing this intermittently for the past few months; but this time it won't crank no matter what I do whereas before I could just wait a while and it would eventually ignite and turn over. Nnow... It will not turn over, won't even tease me that it might turn over. All cranking and no combustion. We are definitely getting spark as I have tested continuity at the plugs(even shocked myself to be absolutely certain ). I had an extra working ECU and an extra working CAS so I replaced both just to rule either/both out. That did not remedy the problem obviously. In most cars (I think this car is the exception), you can hear the fuel pump fire up when you move the key to the ON position. If I remember correctly, this car does not operate in this fashion, rather, the fuel pump does not fire up until you attempt to crank it. So here is my first question... IS THIS CORRECT, OR SHOULD I HEAR THE TYPICAL FUEL PUMP HUM AT CRANK? And my next question, related to same, what is the most efficient method for testing the functionality of the fuel pump?

And... lastly, if, after testing and confirming full functionality with ignition systems and fuel systems, what else shall I check in diagnosing and fixing this problem? WHERE SHOULD I LOOK NEXT in other words?

Thanks in advance.

Aaron Cake

iTrader: (1)

To get some terms straight, cranking and turning over means to rotate the engine with the starter. Starting, firing up, etc. means that the engine has started.

I am going to assume that when you say the engine won't crank, you actually mean it won't start. If the engine won't crank at all, then check the starter and main battery cable.

The fuel pump should run when the car is being cranked, but I doubt you will hear it. To test the fuel pump, jumper the yellow test connector by the passenger airbox then set the key to
"RUN". The pump should run.

RotaryRocket88

iTrader: (7)

I'm guessing that this happens when the engine is warm? The stock start map under warm conditions is excessively rich, which can lead to flooding. The EGI fuses can be removed to disable fuel injection and deflood the engine. Some people use a fuel pump switch to simply turn the pump off momentarily during cranking, others have tried this: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/looking-car-has-hot-start-problems-499744/. The true fix is to use an aftermarket computer that will allow you to change the amount of fuel injected on startup.

cab91089

iTrader: (3)

You can try the deflooding rotaryrocket88 is talking about by pulling the EGI fuse in the main fuse box and taking out the bottom two (Leading) spark plugs and crank the engine a few times for 5 or so seconds each and put alittle oil in the spark plug holes. Put everything back and try to start the car.

calpatriot

Sounds like a flooded start... especially given the season; they are more prone as the weather gets warmer... your S5 car has a 'flooded start' feature you can access by cranking with full throttle; it will cut off the fuel and you can give it a long crank that way to clear out all the raw fuel, then it should start normally. If that does not work:

pull the EGI fuse; press down and hold full throttle; give it a long crank to clear out all the fuel; put the EGI fuse back in; start normally.

If the problem recurrs, you may consider installing a 'hot start' button; use any momentary contact switch, and a relay; wire it to cut off power either to the injectors or to the fuel pump when the button is pressed AND the start circuit is energized. Then anytime this happens you can just push the button instead of getting out and pulling the EGI fuse...

Conventional wisdom says these cars are more prone to hot starts if the injectors are dirty... if your injectors have not been removed and professionally cleaned in the last 30k miles, you may consider doing that. I had mine done a month ago, and it has reduced (but not completely eliminated) the hot start problem. I am keeping my hot start button installed, and had to use it on a high-altitude hot start just a week ago...