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Old 12-18-2024, 12:52 PM   #1
FCguy
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Default Rough running then no run shortly after

So my wife's '18 Impreza (50th AE) started running rough as we pulled into the driveway the night before last. It wasn't crazy rough but I decided to see if it would continue or clear up by driving it a short distance in the neighborhood. I only got a few hundred feet before it shut off completely. I tried to rank it, it coughed a few times and then just cranked with no sign of it firing at all.

My first suspicion is the fuel pump. But I can definitely hear it run (pulled the starter relay and back seat and put my head up to the fuel pump access hatch and I'm fairly certain I heard it run). So maybe not fuel pump.

But then I saw there was a previous recall on fuel pumps and the impellers. So maybe it still is the fuel pump - it runs but it isn't pumping.

Then I discovered that these motors might be direct injected - are they really? I don't know much about direct injection.

In any case is there some place in the fuel system that I could test for fuel flow?

Is it actually direct injected?

Does it sound like it could be something else to you guys and gals?

Thanks!
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Old 12-19-2024, 10:40 AM   #2
Charlie-III
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Default

You could pull plugs and see if they're wet with gas.
Direct injection is into the combustion chamber instead of just upstream of the intake valves. It needs a much higher pressure to work than port injection, so a weak fuel pump kills the engine.
I can't help beyond that.
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Old 12-19-2024, 01:40 PM   #3
TurboRev
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Your '18 Impreza is indeed equipped with a direct injection engine, so it's a bit different from traditional fuel injection systems. The fact that you can hear the pump running doesn't entirely rule it out, as the fuel pump could still be malfunctioning even if it's making noise, sometimes they fail to maintain the proper pressure or volume. To check for fuel flow, you could hook up a fuel pressure gauge at the fuel rail to see if it's within spec (usually around 50-60 psi for Subaru DI engines). If the pressure is low, even if you hear the pump, that would point to a pump or fuel delivery issue. Another possibility is a faulty crankshaft position sensor, which can cause no-start conditions, so it's worth checking that too.
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Old 12-30-2024, 09:52 PM   #4
FCguy
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Just an update - it ended up being a coil. When the coil shorted it blew the few for all the coils so that helped track it down. One new coil and it purrs like a kitten.
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Old 12-30-2024, 11:21 PM   #5
Charlie-III
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Quote:
Originally Posted by FCguy View Post
Just an update - it ended up being a coil. When the coil shorted it blew the few for all the coils so that helped track it down. One new coil and it purrs like a kitten.
Glad you fixed it!

Really glad you posted back with the resolution, I really HATE dead end threads.
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Old 02-05-2025, 04:54 AM   #6
EdwardTurner
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Quote:
Originally Posted by FCguy View Post
So my wife's '18 Impreza (50th AE) started running rough as we pulled into the driveway the night before last. It wasn't crazy rough but I decided to see if it would continue or clear up by driving it a short distance in the neighborhood. I only got a few hundred feet before it shut off completely. I tried to rank it, it coughed a few times and then just cranked with no sign of it firing at all.

My first suspicion is the fuel pump. But I can definitely hear it run (pulled the starter relay and back seat and put my head up to the fuel pump access hatch and I'm fairly certain I heard it run). So maybe not fuel pump.

But then I saw there was a previous recall on fuel pumps and the impellers. So maybe it still is the fuel pump - it runs but it isn't pumping.

Then I discovered that these motors might be direct injected - are they really? I don't know much about direct injection.

In any case, is there some place in the fuel system that I could test for fuel flow?
games aussie at https://goldenstarcasino.co.com/
Is it actually direct injected?

Does it sound like it could be something else to you guys and gals?

Thanks!

Sounds like a frustrating situation! The '18 Impreza does have direct injection, so you won't find a traditional fuel rail with a test port like older port-injected systems. Even if you hear the fuel pump running, it could still be failing to deliver adequate pressure due to the impeller issue from the recall. You might want to check for spark as well-if there's no spark, it could be something like a crankshaft position sensor failure.

Last edited by EdwardTurner; 02-07-2025 at 12:19 PM.
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