Resolved!
Dealer replaced PCM, problem resolved.

Hey guys, trying to diagnose my RX8 to see if I can get it started without taking it to the dealership. I have an 04MT with 57K miles and am familiar with the usual won't start because flooded or the standard dead battery/bad leads scenarios. I made sure my RX wasn't flooded (pulled all 4 plugs, took the fuel pump fuse/relay out and turned over, no gas/smoke etc). Also charged the battery to full, so it wouldn't appear to be these two common issues.

All seems well when trying to start the car, I get a nice strong sound and turn over, however the engine won't start. It would appear that the engine is not receiving any fuel. The fuel pump fuse and relay under the hood in the fuse box appear to be fine and using a voltmeter I was able to determine that the plug leading into the fuel pump was getting voltage (but only on one side of the plug). Should all 4 prongs of the plug be getting voltage, or is it normal for just 2 prongs to have voltage only?

If the pump is receiving power, my next guess is that the fuel pump is dead. Before going through the hassle of pulling the pump, I wanted to see if anyone here could tell me for sure what kind of readings I should be getting on that plug (the one leading into the fuel pump itself providing power).

This all began Monday morning. I drove the car home from work on Friday, parked it, no problems at all. After sitting out over the weekend (a nice rainy weekend) the car began experiencing the problem above.

In short:
-Car isn't flooded
-Battery is fully charged
-Leads look good
-Fuses/Relays under the hood look good
-Car turns over strong but won't start (appears to not have any fuel)
-Plug leading into the fuel pump has live voltage in 2 prongs, no voltage in the other 2
-And yes, the car has fuel in the tank

Any suggestions would be greatly appreciated.

Thanks guys.

 

if it's getting fuel and not firing the plugs will be wet and smell of gasoline no different than if it was flooded, that should tell you something

otherwise there are various fuel system tests listed in the service manual

 

How about coil and wire?

 

Probably violates several 'best practices' and numerous State codes, but I like to put a good shot of starting fluid - ether, into the air filter, then crank.

If it fires for ten revs then dies, you have good spark and a fuel problem.

If it doesn't fire at all you have no spark or a flood.

Then you pull a spark plug wire and put it on a used plug, see if it sparks as you crank - if there is a solid spark, you're flooded.

That covers all three No Start conditions.....

 

if you pump is working you should at least hear it prime when you turn on the ignition

 

Thank for the responses, I'll be looking into it further tomorrow. As for the plugs and wires, they seem fine. I had replaced plugs, wires and coils about 10k miles ago, shortly after my dealer replaced my engine due to low compression, haven't had any engine trouble since, just now with the start trouble.

As for the plugs, bone dry after many many start attempts. No fuel in the engine at all, definitely not flooded .

I'll check the manual for the fuel line tests, I probably should have looked into that sooner, didn't realize that information was so readily available.

Still thinking its the fuel pump, whether the wiring is bad (2 prongs with 12volts 2 prongs with no voltage) or the pump itself I'm not sure.

Actually, the pump is unresponsive when the key is in the "on" position or when attempting to crank.

 

2 of the 4 prongs on the FP are not used, sounds like a dead FP

 

Thanks Team, figured as much, just wanted to be sure before pulling the pump. Now to get it replaced.

Thanks everyone.

 

So I'm back and still having trouble.

I removed the fuel pump and bench tested it. The pump ran but I replaced it being it was out. After getting everything back together the new pump did not seem to run and there was no fuel transfer to the engine. When I tested the power leads going into the fuel pump assembly there was about 12v. So my question is, can anyone explain why the pump would not be running when there is power to the assembly? Also if the fuel pump relay was bad would there still be power to the leads going to the pump?

Thanks again.

 

Check the Eccentric shaft position sensor. Might be dirty on the trigger sensor surface. Connector disconnected? You can remove it from the bottom.

 

Finally ended up towing the car to my local dealer. After 3 days of diagnoses they determined that the PCM was in need of replacement. It doesn't appear that there were any other electrical problems with the car so not exactly sure why or how this was caused.

Although my car is out of the standard warranty, my dealer was able to replace the PCM (apparently under some extended warranty?) and diagnose the car for the flat $100 fee.

Car ran great on my drive home, hopefully there won't be anymore work needed any time soon

Thanks everyone for all the advice.