2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

Has anyone ever had raw fuel come out thier exhuast pipes?

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Old May 16, 2002 | 03:16 AM
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Has anyone ever had raw fuel come out thier exhuast pipes?

That what mine is doing. My 90 GTU is barely running, and when it does fuel vapors and raw fuel are dumping out the back. I have spark, I have good compression, and my injectors looked fine(solenoids clicked nicely and I cleaned them).

PLEASE.....What could cause this much fuel to be getting into my engine???

Also, do to the fact that this is starting to look hopeless, any one know of a good rotary mechanic in Houston?

Thanks again to all who keep assisting me...

Cardio
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Old May 16, 2002 | 03:41 AM
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Following all your posts, it indeed seems like there is something seriously wrong with the car. Too many symptoms, and the facts are not conclusive (damn, I sound like a lawyer )

Since there doesnt seem to anything wrong with the engine itself (i.e housings, rotors, seals etc), a decent mechanic could find out what's wrong. Doesnt have to be a Mazda or RX-7 specialized one. However, if you can find a Mazda/RX-7 mechanic, then I'd say drop off your car for a couple of days, and then see what he has to say....
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Old May 16, 2002 | 03:46 AM
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injectors might be leaking
thats all i could think of
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Old May 16, 2002 | 10:37 AM
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Your injectors are leaking, BADLY

Does it flood easily?

You can put a fuel pressure gauge in after the fuel filter and clamp off the return line to the tank. Then start the engine, and then shut it off. Watch the gauge. The pressure should hold, with some bleed off. If it drops down very quickly, then the injectors are leaking like a ****!!!
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Old May 16, 2002 | 10:54 AM
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Alright, I guess iw ill borrow a fuel pressure gauge from the local auto shop.

But is there anything that could be telling my injectors to open to far as soon as i turn the key on? ECU, TPS, or something?

Cardio
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Old May 16, 2002 | 04:37 PM
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Re: Has anyone ever had raw fuel come out thier exhuast pipes?

Originally posted by Cardiovoid
My 90 GTU is barely running, and when it does fuel vapors and raw fuel are dumping out the back.
Are you sure that’s fuel? Water vapour is a product of combustion (a lot of it), and when the engine and air temps are low enough it will condense to a liquid within the exhaust. It will smell like fuel, because your mixture is obviously rich. Collect some and try to burn it. I doubt it will ignite.
When you say you cleaned the injectors, do you mean you cleaned them, or you had them professionally cleaned? Home cleaning won’t touch the really baked on stuff that may be stopping one of the pintles from sealing completely. This will cause a rich mixture.
Do you have strong spark at both leading plugs? Unless both are firing, unburnt fuel will be passing through the exhaust. What do the plugs look like after running the engine?
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Old May 16, 2002 | 06:02 PM
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I don't know of anything that would cause the injectors to open if you just turn the key to ON. The cas is monitored by the ECU and that determines when, if and how long the injectors are opened. No turning of the engine means no turning ot the cas means no injected fuel. Thats the way I understand things work. Might be a flaw there that I know nothing of. It is tough to believe raw fuel is pouring out of the exaust. Seems the engine would flood out prior to that ever happenig and if it did, it seems to me that you would have a FIRE! Then I could be WRONG.
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Old May 16, 2002 | 07:00 PM
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Hard to believe, but true. It barely struggles to a start, then goes to a weak, but high and smooth idle, with liquid fuel and vapor fuel pouring out the back.

This all happened when I had just replaced my oil metering pump. I am wondering of my ECU got hurt as a result of the O.M.P. and is now sending funny signals (i am sure there is a more technical way to say that). I guess I could replcae my ecu, the local junkyard has a few 7's laying around.

this is so frustrating...

Cardio
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Old May 16, 2002 | 08:03 PM
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You're there seeing it happen, so its happening. Really strange. I'd get a fire extinguisher and keep it handy. I don't see the metering oil pump having anything to do with it, but then again, I don't have a 89 and newer car. Good luck and be careful.
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Old May 16, 2002 | 08:21 PM
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Originally posted by Cardiovoid
Hard to believe, but true. It barely struggles to a start, then goes to a weak, but high and smooth idle, with liquid fuel and vapor fuel pouring out the back.
Very hard to believe...
If there was truly that much fuel going into the engine, the exhaust gas would be black smoke. I still think it’s just condensing water vapour that smells like gas because the idle mixture’s too rich. Did you know that if you perfectly combust 1kg of fuel, 8-10kg of water is produced! Test it like I said.
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Old May 16, 2002 | 10:02 PM
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Hope this helps

When my AFM failed, I got lots of raw fuel smell everywhere. Strong gas smell, glowing catalytic, made me buy a fire extinguisher.....
When the car was cold, the condensation dripping from the exhaust smelled flammable.
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Old May 16, 2002 | 10:50 PM
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Thanks,
I am doing the fuel pressure test right now, that will be my next inspection...

Cardio
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Old May 17, 2002 | 09:10 AM
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When my AFM failed, I got lots of raw fuel smell everywhere.

NB: do check your AFM
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Old May 17, 2002 | 09:12 AM
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When my AFM failed, I got lots of raw fuel smell everywhere.

NB: Do check your AFM. It must slide in and out smoothly, and resistance values must be linear.
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Old May 22, 2002 | 12:13 AM
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From: Texas
Update...

K, i did a fuel pressure test and something interesting happened....

After cranking the engine (it won't start) the fuel pressure went up to 35 psi. My assistant stopped cranking the engine, turned the key off and I clamped the return line. The pressure dropped from 35 psi to 22 psi in about 2 minutes, but it held at 22 psi (within the FSM specifications).

Here is what is wierd. We did the test again, but instead of turning the ignition all the way off, the key was left in the on position. Immediately after the cranking I heard the fuel pump, the tester needle went to about 30 psi, then dropped straight to zero when the pump shut off. The return line was clamped, so it must have gone through the injectors into the engine, right?

The only thing I have not checked/replaced is the ECU, that is my guess as to what is wrong. Anyone else have any theories???

Super thanks again,

Cardio
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Old May 22, 2002 | 12:14 AM
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oh yeah, the AFM checked out fine....

Cardio
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Old Jul 18, 2002 | 10:29 PM
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Well,
My automotively inclined Uncle came in town this week. He was only here for a day before he brought my 7 back to life. Apparently my Metering Oil Pump Wiring Harness was bad. I happened to have a spare laying around (not perfect, but still a substitute), and after placing the new harness on, the car fired right up. NO SMOKE, NO FUEL COMING OUT THE EXHUAST. However it was severley out of tune from my frantic adjustments. An hour later, it was idling perfectly.

So, the good new is my engine is not blown. The bad news is, that I am still getting a code 27 after it idles for a while. I have trouble believing that the three MOP's I have used are all bad. They all pass the continuity tests, etc. So, I fear I have a long road of wiring tests in front of me.

If any one has had this happen to them (perfect idle, then a code 27), let me know your solution. I will be ordering a new Wiring harness for my MOP to eliminate that possibility.

MY CAR IS ALIVE!!!!------YAY!!!!
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Old Jul 19, 2002 | 01:45 AM
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Originally posted by Cardiovoid
Well,
My automotively inclined Uncle came in town this week. He was only here for a day before he brought my 7 back to life. Apparently my Metering Oil Pump Wiring Harness was bad. I happened to have a spare laying around (not perfect, but still a substitute), and after placing the new harness on, the car fired right up. NO SMOKE, NO FUEL COMING OUT THE EXHUAST. However it was severley out of tune from my frantic adjustments. An hour later, it was idling perfectly.

So, the good new is my engine is not blown. The bad news is, that I am still getting a code 27 after it idles for a while. I have trouble believing that the three MOP's I have used are all bad. They all pass the continuity tests, etc. So, I fear I have a long road of wiring tests in front of me.

If any one has had this happen to them (perfect idle, then a code 27), let me know your solution. I will be ordering a new Wiring harness for my MOP to eliminate that possibility.

MY CAR IS ALIVE!!!!------YAY!!!!
At last
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