2001 Impreza - Will Crank But Not Start

[Mike_44]

I have a 2001 Subaru Impreza GG9 2.0L EJ201 that's able to crank but doesn't start. This would happen from time to time if you hadn't driven the car in a while but lately it'll only fire when it's hot outside, if it's cold or at night forget about it. Currently it doesn't start at all. I did take the car to the mechanics a month ago complaining off the intermittent start but since the car was working at the time and zero codes, they sent it on its way.

Things I've checked:

• Sprayed starting fluid straight into the intake and it fired up
• Fuel pump relay has continuity and audibly clicks when engaged.
• Back probed the connector going into the fuel pump for power. Wouldn't get power when the ignition was in the "ON" position but would get 12v when I cranking the car over. Currently it doesn't get any power when I crank over.
• The fuel pump itself works when manually hooked up to 12v
• Replaced fuel filter, old one was filthy
• Battery connections are solid, grounds all look good.
• Checked all fuses and they're fine

Interesting things to note:

• I do have an immobilizer but if that was the issue I doubt I'd be able to turn the car over. However, usually if I disconnect the battery the immobilizer will continuously blare a horn at you every 5s or so for hours. It didn't when I disconnected the battery this time.
• Obviously the fact I was getting 12v to the fuel pump when cranking over but not anymore.

I'm not really sure what to do/where to go from here. I fear it's some sort of weird intermittent electrical issue and don't really want to spend $$ towing it somewhere and even then there's no guarantee they'll fix it. Not to mention i'm frugal af and that would hurt my soul.

Granted, I could jerry rig up a 12v battery directly to the fuel pump connector but if that's not getting the correct signals from the ECU/MAFS would car even run? What about the fuel pump itself, does that normally run continuously when the car is in operation or just stop when it reaches the correct fuel pressure? I guess excess fuel will just be fed straight back into the tank regardless.

Edit:
So the jerry rig situation did work, hooked the fuel pump connector straight to an external 12v and she fired right up.

I would like to improve this temp arraignment by hooking the fuel connector up to something that gets power when engine is spinning.

Cheers.

 

[Mark Monte]

That is a very interesting problem. I'm glad you devised a work around. It sounds to me like a fuel pump relay
has "bit the dust" and has quit working. A relay/solenoid can be intermittent until it fails completely.
One way to think of the fuel supply is this: it is like a river that keeps flowing back to the gas tank. The fuel pump is only activated when the engine is running. The fuel injectors work on a "duty cycle" that controls how much fuel is sprayed out. I once had a car with an anti-theft device. The alarm and wires were removed and then the car started without hesitation. Maybe your Immobilizer is malfunctioning.

 

[Mike_44]

That is a very interesting problem. I'm glad you devised a work around. It sounds to me like a fuel pump relay
has "bit the dust" and has quit working. A relay/solenoid can be intermittent until it fails completely.
One way to think of the fuel supply is this: it is like a river that keeps flowing back to the gas tank. The fuel pump is only activated when the engine is running. The fuel injectors work on a "duty cycle" that controls how much fuel is sprayed out. I once had a car with an anti-theft device. The alarm and wires were removed and then the car started without hesitation. Maybe your Immobilizer is malfunctioning.

Replaced the fuel pump relay and still have the same issue, no power at the fuel pump connector.

 

[Mark Monte]

Did you check the immobilizer? I wouldn't worry about the Mass Air Flow Sensor or any other sensors that feed back to the ECU. They are independent and spraying in starting fluid and wiring directly to the fuel pump proves that everything else is O.K.
I had a Mazda once that wouldn't start because of the clutch pedal interface. The clutch pedal had to be fully depressed in order to activate the starter. It turned out that it was corroded connections near the battery.
The ECU controls the access to Ground via a "gateway." The Immobilizer interupts the circuit by denying the pathway to Ground. As strange as it may seem, you may have an issue relating to a ground wire. Are your battery connections clean?
A dirty fuel filter could be a sign that indicates tthe fuel pump is getting old and overworked. It is weird that it is related to the weather, unless that is just a coincidence. a weak fuel pump may only work when it wants to, until it fails completely.

 

[Mike_44]

Did you check the immobilizer? I wouldn't worry about the Mass Air Flow Sensor or any other sensors that feed back to the ECU. They are independent and spraying in starting fluid and wiring directly to the fuel pump proves that everything else is O.K.
I had a Mazda once that wouldn't start because of the clutch pedal interface. The clutch pedal had to be fully depressed in order to activate the starter. It turned out that it was corroded connections near the battery.
The ECU controls the access to Ground via a "gateway." The Immobilizer interupts the circuit by denying the pathway to Ground. As strange as it may seem, you may have an issue relating to a ground wire. Are your battery connections clean?
A dirty fuel filter could be a sign that indicates tthe fuel pump is getting old and overworked. It is weird that it is related to the weather, unless that is just a coincidence. a weak fuel pump may only work when it wants to, until it fails completely.

I'm thinking it could be a bad ground but from all the ground wires I've found, I tested them and they're all good. I replaced the fuel pump too, the car actually runs really well (it used to surge a lot but doesn't anymore) even though I'm powering it off another battery. I'm not entirely sure how I go about checking the immobilizer. I've also never been able to hook an OBD2 reader to it(never can connect), tried different models and they all worked on different cars but not this one. I would have to manually read the codes via blinking lights. However, I currently have zero codes.