UnregisteredSA22C

Hey guys,

I once again must call upon the wisdom of the rx7club members... I'm pretty confused.
A few days ago I bought my first GSE SE, and it didn't run. It also had no exhaust at all (not even a manifold). I managed to get it going by bypassing the AFM using the fuel pump short plug. It was super loud, but i was able to drive it into my garage to continue working on it. I found that the air pump was gone, the air control/check valve was gone, and the blocking plate was held on by one screw and literally dangling. But it ran and I drove it!

Since then I've installed a racingbeat header and pre-silencer, and properly installed the blocking plate. But now the car dies immediately after starting! It goes up to 2k rpm and then immediately dies. The o2 sensor is wired up correctly, and I've tested that the BAC and Air Supply Valves work properly. I've been reading guides and whatnot on how to get a dead car going again, but can't seem to find one that references my situation.
Anyone have any tips/advice?

Roland

LongDuck

Hey, man - first off, the O2 sensor, BAC and ASV are unrelated to the issue at hand. The O2 sensor only comes into play in 5th gear to run closed loop fuel map dithering. The BAC and ASV are used as fine air bypass for idle control for electrical load and A/C, so they won't bypass enough air to cause your engine to die.

Therefore, this leads me to believe the (missing) air pump and/or the blocking plate are allowing for a large volume of inlet air that gets into the engine without the Air Flow Meter knowing it, and the engine promptly dies. The -SE doesn't fare well with emissions bypass steps, and oftentimes removal of the Rat's Nest results in incurable idle and acceleration problems. Aside from the air circuit which you seem to be focusing on, there are also fuel issues that you'd want to be sure are in order.

Based on what you posted above, I don't have much else to offer, but hopefully you can find the Air Pump and reinstall the air circuit valve on the Lower Intake Manifold to restore it to closer to stock condition.

UnregisteredSA22C

Thanks for the reply! I was hoping not to hear something like that, since I don't have the AC/CV valves or air pump... but all that's removed is what's needed for the racingbeat header according to their instructions online, so I'm still keeping hope I can still make it work somehow. Could a bad air flow meter (AFM) cause the problem? The fuel pump won't even run unless the "fuel pump short plug" is connected, bypassing the AFM - does this mean the AFM is shot?

Roland

LongDuck

Search on my username and Air Flow Meter for troubleshooting steps. Reply back if questions, and we'll get it sorted out.

UnregisteredSA22C

I've tested the MAF sensor mechanically (the door opens and closes smoothly and without restrictions) but couldn't find a way to check that the electronics are ok. However after doing a bunch of reading it seems like the MAF isn't usually involved with idling issues anyways because of the lower air flow at idle (also saw your name pop up a lot - you're a good guy for helping everyone out! I really appreciate your advice as well). So I'm thinking it might not be the MAF, which leaves me back at square one. I've just been looking for potential vacuum leaks.

Maybe I'll just give a more complete background of the car haha:
- The guy I bought it from said it was driving well a year and a half ago, and he parked it because it wasn't getting fuel. It had a RB header installed, but he removed it at some point after it died.

- I bought the car a week ago and it had only the stock exhaust manifold installed, with no air pump or air control valve/check valve assembly. It has the RB supplied plug for the airbox, and had a ACV/CV blocking plate loosely held on by one bolt.

- I found that the fuel pump wasn't getting any power, and narrowed the problem down to the fuel pump short plug; when I put a wire in each end of this plug, the car would start. I was able to drive the car in and out of my garage, and it would idle at about 1600 rpm - high, but I figured it was normal since it had no exhaust and an open hole where the ACV/CV assembly should be.

- I got a RB header and pre-silencer (with a bung for the o2 sensor and the tube for the port actuators) and installed them, as well as properly securing the RB supplied blocking plate. Thought I was good to go!

- I still don't have the line connecting the pre silencer to the port actuators or any exhaust after the pre-silencer, but my plan was to limp it to a nearby exhaust shop and have them weld up the rest of the exhaust. However once I installed the header and pre-silencer, the car would start but immediately die, even if I gave it gas. I couldn't drive it at all.

Again, I appreciate the help.

Roland

LongDuck

Okay - let's give this another shot from a different angle. Recognize that the -SE uses the Air Control Valve on the lower intake manifold to do 2 things; A) to route backpressure from the rear-most Cat (or RB Presilencer specific to the -SE) back to the lower intake manifold to operate the '6'-port actuators, and 2) feeds fresh air into the 3rd Cat (or Presilencer) to help burn unburned fuel which gets through the 2 prior Cats to clean up the emissions on deceleration. The ACV is a critical component to route air the right direction when needed. Here's the picture from Jim Rothe's pages:<img>http://www.jimrothe.com/mazda/mygslse/efiparts.jpg</img>

The Air Control Valve is in the lower part of this picture and you can see the pressure diaphragms which include an electric pressure solenoid to actuate the internal diaphragm. On the side of the Lower Intake Manifold is the location where it bolts, along with the vacuum lines which are used to offset the pressure on the diaphragm with intake air vacuum. Technically speaking, if your block-off plate is sealed properly, it should prevent any air getting into the Lower Intake Manifold and fooling the Air Flow Meter (*air getting around it somehow, and NOT getting metered for proper Air/Fuel Mixture). If this isn't sealed properly, it will pose a significant vacuum leak at a site very close to the engine ports, which could result in symptoms of stalling, as once the air velocity picks up and volume increases after startup, the air will choose the path of least resistance, which bypasses the Air Flow Meter. As soon as your AFM door closes, the circuit to the fuel pump is shut off, and no fuel is supplied, stopping the engine.

The fact that it starts and runs for a moment tells me that you have good fuel pressure, good spark, and you're dealing with the only remaining component to combustion; air. Focus on the vacuum lines and what may be open to atmosphere and you'll be on the right track.

Also, don't forget to remove your Fuel Rail Test shunt at the AFM when you get done with this.

UnregisteredSA22C

Ok! That's some good info. I'll keep tinkering and hopefully find where it's leaking. And maybe I didn't understand earlier but does the fact that the car won't start at all without the shunt at the AFM mean anything? Without it installed, the fuel pump gets no power when I turn the key.

Roland

LongDuck

The -SE fuel pump will to turn ON unless there's air coming into the engine as measured by the Air Flow Meter. This is why the Fuel Injector Test plug is located at the AFM; it fools the ECU into thinking the AFM air door is open, and engages the electricity to the Fuel Pump. What you described is normal operation for the Fuel Pump to only come on when the engine is cranking or running. This helps to prevent flooding.

That the car won't START without the Fuel Injector Test shunt in place is not normal. You'll need to track that down, because leaving it 'shunted' all the time could lead to flooding,

UnregisteredSA22C

I got it to run! I capped the port actuator (since it is missing the connection from the exhaust) and it idles at 1000. Probably should have tried that sooner. Thanks so much!!

That leaves me with a question that I havent been able to find though: what does having to shunt the fuel injector test plug actually mean? Like what needs replacing?

Roland

Monte0704

which port actuator? If you mean the 5/32" vacuum line, that shouldn't have made any difference... Unless you mean the bigger line above that.

EDIT: Now that it runs, try it with the shunt out, and the AFM hooked up.

LongDuck

Glad you got it figured out. As Monte says above - try running the engine and then removing the Fuel Injector Test shunt from over by the Air Flow Meter. If the engine dies immediately, then you have a problem with the Air Flow Meter switch (*which you bypassed with the shunt in the plug). I would bet you $$$ that the engine continues to run just fine. As long as air is coming into the Air Flow Meter, it pushes the Air Door open and completes the circuit, powering the Fuel Pump.

Explained a different way, the Fuel Injector Test shunt and the plug it goes into were put there by Mazda to allow mechanics to test the fuel pressure at the rail after working on the Fuel Injectors or performing any fuel system work on top of the engine. By installing the shunt, this tells the ECU that air is coming into the Air Flow Meter (either by cranking the engine, or from the engine running normally), and to power up the Fuel Pump. With the Upper Intake Manifold off, and the shunt in place, you can turn the key to Run (NOT Start), and the Fuel Pump will be powered up. This pressurizes the fuel system and allows you to check everything for fuel leaks before you install the Upper Intake Manifold and all the vacuum hoses and such. It's there to save you time and effort as a mechanic.

Also, know that if you cap the '6'-port pressure line, your '6'-ports obviously won't open. You'll lose a lot of power on the top end, and your torque curve won't be nearly as flat (*or as high).

UnregisteredSA22C

Oh ok. Thanks! I'll try that. And yes it is definitely not going to be capped forever. Love me that smooth torque curve.

Roland

tallbozo

iTrader: (5)

I love me some GSL-SE torque. It's a strange sensation coming from a 12A