Ag_xterra

is it true that if you start up a rotary engine and dont drive it or let it run for about 10 minutes that the fuel remaining in the engine will cause it to hydrolock the next time you start it? i was told this by someone and just wondered if it was true.

Tireburner

I have not heard of it being hydrolocked. The Gen2's have a bad tenancy of going into what Mazda mechanics refer to as "garage mode"
It is caused by excessive fuel into the motor when cold to keep it running. When the motor is not allowed to run long enough to warm up and lean out. When you go start it again, the injectors are rich to start, plus the left over fuel in the motor creates a heavily flooded condition.

What I have observed Mazda tech's doing to correct this "garage mode", they pull the fuse for the fuel pump. One guy cranks the motor with his foot on the floor for about 30-45 seconds, then the other tech slams the fuel pump fuse back in and the car fires admist a huge cloud of smoke.

Ag_xterra

thanks for the reply. its sounds kinda fishy to me that a car maker would put out a car that would hydro lock like that.

Tireburner

I think it was one of those things they discovered after the product was released. I know the Gen 3 was not suseptable to it.

NathanRX7

Only the 1984-88 RX-7s had a real flooding problem, and that was fixed post-1988. All rotary (at least Mazda ones) engines can be flooded if the driver does not follow directions. The engine must be warmed up before being shut off, that's all there is to it.

On the 1989 and newer RX-7s, Mazda built in an easy way to unflood them. When the accelerator pedal is depressed to the floor, the ECU turns off the fuel pump. When the engine starts you let go of the pedal and you're good to go.

I would not consider the flooding condition "hydrolock" because the engine does not lock up at all, it simply loses some of it's compression because having all of that fuel in there dilutes the oil which makes the seal. The compression returns as soon as that extra fuel gets burned up and the oil metering pump injects more oil, thus the reason for turning off the fuel pump either manually or with the pedal on the newer cars.

__________________


Nathan Cowles
1990 Mazda RX-7 N/A

AOL IM: NathanRX7

My modification list and lots of pictures are on my Web site:
http://www.goldcoastinspections.com/nathanrx7/

Tireburner

Thanks Nathan. I was unaware when the problem was resolved. It is good to know about the gas pedal on the 89 and up models. You explained what I tried, but in better terms. Thanks.

Ag_xterra

thanks for everyones help.

DigitalBoy

This problem can also be fixed by yourself. The problem is with the cold fuel injection system. It was designed to inject extra fuel into the engine when it is cold so as you don't have to pump it to start it when it is cold outside. However, when it is cold out if you don't let it warm up all the way the computer senses it is still cold and injects even more fuel. It doesn't matter if you let it sit for 5 minutes after you shut it off or 2 months. The computer remembers what part of the cycle it was in and continues from there. The best way to fix it is to pull the fuse and hold the pedal to the floor while turning it over for about 30 seconds. Then putting the fuse back in and starting it. However, if this doesn't work after a few times don't keep trying. You can get too much gas in the engine and it will seep into your oil somehow and also foul your plugs. You then need to change your plugs and oil.