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Fuel Pump Question

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Old Jun 9, 2022 | 11:13 PM
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kiddoh's Avatar
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Fuel Pump Question

Hello peeps, finally got the fd started today after a while, added more fuel, heard fuel pump turn on and started right up, let it idle for a bit and turned it off. Tried to turn it back on and I don't hear the fuel pump start and the car wouldn't turn on. I was wondering if this would mean the fuel pump is bad or the fuel pump relay is bad, since it turned on the first time I tried I was thinking the fuel pump is still okay and maybe just need to replace the relay? Can't tell if the relay is bad though so if anyone else had this problem before if you could pass on some knowledge, thank you!
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Old Jun 10, 2022 | 02:55 AM
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I wouldn't write off the fuel pump or relay as bad just yet, it sounds like you may have just mildly flooded it. Let it sit overnight and try again.

The fuel pump starts when you crank the engine on the starter, it doesn't prime on accessories.

If you had it running, turned it off, then tried to start it again afterwards, you may not hear the pump because it's already primed.

The best way to test is to bump the starter by turning the key quickly so it cranks once, you should then hear the pump run for a second.
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Old Jun 10, 2022 | 05:24 AM
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Originally Posted by Axton
I wouldn't write off the fuel pump or relay as bad just yet, it sounds like you may have just mildly flooded it. Let it sit overnight and try again.

The fuel pump starts when you crank the engine on the starter, it doesn't prime on accessories.

If you had it running, turned it off, then tried to start it again afterwards, you may not hear the pump because it's already primed.

The best way to test is to bump the starter by turning the key quickly so it cranks once, you should then hear the pump run for a second.
Okay, will try again today after work and give an update and see if it primes at the start and try to do the test, thank you!
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Old Jun 10, 2022 | 08:15 AM
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You can also jumper the F/P and GND pins in the diagnostic connector and turn the key to On. This will run the fuel pump continuously.

The fuel pump relay is pretty hardy and doesn't typically go out.

It does sound like you flooded it. You NEVER want to start a rotary cold, run for a bit, then shut it off. Really sucks in an RX-8 when you foul $80 worth of spark plugs....

Anyhow, typically the fuel pump does a quick prime (like 1 second) when you turn the key. With stock and some aftermarket pumps you really can't hear it. I have a Walbro 255 and I can barely hear it prime.

Dale
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Old Jun 10, 2022 | 09:59 AM
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Originally Posted by DaleClark
You can also jumper the F/P and GND pins in the diagnostic connector and turn the key to On. This will run the fuel pump continuously.

The fuel pump relay is pretty hardy and doesn't typically go out.

It does sound like you flooded it. You NEVER want to start a rotary cold, run for a bit, then shut it off. Really sucks in an RX-8 when you foul $80 worth of spark plugs....

Anyhow, typically the fuel pump does a quick prime (like 1 second) when you turn the key. With stock and some aftermarket pumps you really can't hear it. I have a Walbro 255 and I can barely hear it prime.

Dale
Ah gotcha, okay I’m going to try and deflood it later on today, what’s the proper thing to do before shutting it off so it doesn’t flood? Get it to running temp? So I don’t flood it again haha
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Old Jun 11, 2022 | 08:55 AM
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If I have to move the car quickly or something, I do a quick lap around the block to put some heat in the engine. You don't have to get to full operating temp but a good 1 mile or so lap is sufficient. That puts a LOT more heat in the engine than just letting it idle. If you can't drive it for some reason (like the car starts but you are working on the drivetrain or something) just let it idle for 10-15 minutes until operating temp and shut off.

Matter of fact I just had to move cars to make room for the carpet installer at our house this morning. Drove the RX-8 around the block and just pushed the FD where it needs to go. Later when I put things back I will drive the FD around the block to warm it up to drive it back into the garage.

This is Rotary 101. Having a strong healthy motor, a strong battery, good starter, etc. all helps but rotaries HATE being started cold and shut off. You can get away with it some times but it will get you at some point.

Dale
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