So... I just installed a fresh motor in my RX-8 race car. It's a 100% stock motor using the stock ECU etc. (It does have a header, racing beat flash, light flywheel, AEM intake, no cats or smog equipment)

The motor will start and seems to run ok but after about 3-5 seconds it always dies - even if I bring the revs up with the gas pedal.

My first though was an air leak somewhere and guess what! I did have one (left the brake booster hose off - duh!). But this did not fix it.

Then I thought maybe I connected the fuel injection wiring harness wrong. So I got our a wiring diagram and guess what, I had two of the injector plugs swapped incorrectly. I fixed this and it ran better but STILL always died after 3-5 seconds of running.

I've tried deflooding, changing spark plugs etc.

Is this perhaps the fuel pump? Someone told me that the fuel pump has a mode where it is activated when you crank the motor but it's possible for it then to turn off after you stop cranking. If this is the case how do I trouble shoot this?

Any ideas?

 

Check the MAF's electrical connection. That could do it.

 

Well... I know it's plugged in correctly... maybe a wire is broken? Or maybe the MAF broke when I transferred it to the AEM intake.

 

Hmmmm. Hook up a fuel pressure gauge and see what it does when it dies or remove the seat and listen to the pump and see if it cuts out right before it dies.

 

I'll give that a try. Easy to check on my race car since the rear seat is already removed! I wanted to check just that the other night but I can't listen to the fuel pump and crank the car at the same time. I need an assistant!

 

I figured it out. I'm a moron. When I replaced the engine this time I also eliminated the air pump. Turns out the air pump has a resister attached to it that it part of the fuel pump electrical system. As I had thrown away the air pump I just jumped the connector in the wiring harness and that was good enough to get the car running... didn't want idle when hot but otherwise was fine.

 

Yeah I have received at least one phone call about this problem (I won't mention any names). No one would think it had anything to do with the fuel pump.