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Old 10-21-2020, 05:33 PM   #15
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Get a couple cans, some fuel hose the same size as the one feeding the rail, one of those barbed tube things to join the hoses, blah blah... Jumper at the fuel pump relay. Profit.


Might take a while. ... clogged filter and all.
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Old 10-21-2020, 05:34 PM   #16
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If you disconnect the fuel lines before removing the pump assembly from the tank, the fuel will run up the narrow pipes connected to the pump assembly. I don't think you can remove the pump assembly before removing the fuel lines, but I could be mistaken.

Also, I'm pretty sure I saw this happen before, but I could be mistaken as to the physical cause if it.
You can purge the lines by disconnecting the fuel pump relay and turning the car over. If you don't then the line will be pressurized, so yes, when you pop off the lines you will spray fuel. A terrycloth towel around the connector should limit spray, but purging the line should limit the volume of fuel leakage to something fairly minimal.
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Old 10-23-2020, 06:10 PM   #17
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You can purge the lines by disconnecting the fuel pump relay and turning the car over. If you don't then the line will be pressurized, so yes, when you pop off the lines you will spray fuel. A terrycloth towel around the connector should limit spray, but purging the line should limit the volume of fuel leakage to something fairly minimal.
That's not the problem. Watch this. I basically need a hose and stopper anyway, but I have to drain the tank so it comes out slowly enough to put a hose on before it gets everywhere.

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Old 10-23-2020, 06:15 PM   #18
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New dilemma. Is the risk of the pump actually being messed up worth the ~$300 difference for just replacing the whole unit... and it would save me time...

(42072 vs 42021 or 42022)

https://parts.subaru.com/a/Subaru_20...10-421-03.html
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Old 10-23-2020, 07:04 PM   #19
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New dilemma. Is the risk of the pump actually being messed up worth the ~$300 difference for just replacing the whole unit... and it would save me time...

(42072 vs 42021 or 42022)

https://parts.subaru.com/a/Subaru_20...10-421-03.html
You would find out if you try using it to drain the tank. ...maybe. If it drains slowly and the filter is dirty, then... else if filter is clean and it drains slowly, then..
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Old 10-23-2020, 08:35 PM   #20
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You would find out if you try using it to drain the tank. ...maybe. If it drains slowly and the filter is dirty, then... else if filter is clean and it drains slowly, then..
It's a good thought but...

The filter looks to be sealed in a plastic case, you buy the case with the filtration element inside. I'm saying this because I don't think I can check the filter to see how dirty it is. Plus it would mean opening and resealing the tank twice because I have to wait for parts.
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Old 10-23-2020, 09:00 PM   #21
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I searched the usual places like Alldata and a few technician sites but only found one reference to anything like your problem and the cause was a dying battery.

It makes sense in a way. Most alternators reach max output somewhere above 2K rpm so if your main battery is shot, it might take that many rpm to feed enough current demands to make the engine run normally.

An electrical load test might help and imagine a DIY oriented auto parts store has a free tester.

If you do go with a fuel system repair, definitely do it outdoors and not in the garage.

Good luck.
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Old 10-23-2020, 09:36 PM   #22
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The filter looks to be sealed in a plastic case,...
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Old 10-24-2020, 11:40 AM   #23
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Garage
Most motorcycles with an in-tank fuel pump publish Gallons-Per-Minute rate in the repair manual.

Disconnect the fuel line and route it to a holding can.
Apply a known voltage to the fuel pump and it should move X amount of fuel in Y minutes.
Then you know if it's the pump and filter or something else.

Also gets fuel out of the tank in the mean time and don't have to break into the tank.
There should be specs for this available somewhere.

=========================

Looks like the 86 manual only wants you to use an in-line pressure gauge and Techstream.
Bleah.
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Old 10-31-2020, 05:28 PM   #24
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I searched the usual places like Alldata and a few technician sites but only found one reference to anything like your problem and the cause was a dying battery.

It makes sense in a way. Most alternators reach max output somewhere above 2K rpm so if your main battery is shot, it might take that many rpm to feed enough current demands to make the engine run normally.

An electrical load test might help and imagine a DIY oriented auto parts store has a free tester.

If you do go with a fuel system repair, definitely do it outdoors and not in the garage.

Good luck.
Good thoughts. Brought the battery to AutoZone to get tested. Read as having a low charge and they charged and tested it. It "tested bad" as in it probably wouldn't hold a full charge. It was 5 years old in a car that doesn't get driven much so I got a new one.

New battery installed, took like 10 seconds to start the car which I found a little odd. It cranked fine. High idle on startup was fine, but when it warmed up a bit and lowered the idle the same issue started happening.

I'm thinking taking a while to start might further indicate fuel flow problems? Alternatively, the alternator could have an issue resulting in a similar situation to a bad battery causing low fuel pressure...
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Old 10-31-2020, 06:33 PM   #25
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Disconnect and plug the vacuum to the pressure regulator. See if it changes how it idles. If Tcoat's theory holds, high manifold vacuum at idle increases return flow above the pump's ability to maintain pressure. It makes sense. Best thing would be to actually measure rail pressure.
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Old 11-06-2020, 11:11 PM   #26
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Disconnect and plug the vacuum to the pressure regulator. See if it changes how it idles. If Tcoat's theory holds, high manifold vacuum at idle increases return flow above the pump's ability to maintain pressure. It makes sense. Best thing would be to actually measure rail pressure.
So, let's pretend I don't know what vaccum to what regulator you are talking about (it's the internet therefore I really know everything right? )

Are you saying that the fuel pressure regulator is controlled by some air vaccum line to the manifold? Not familiar with how fueling systems work so sorry if I misunderstood.

Assuming that is true, if I disconnect the regulator from the line, I need to plug the end of the line to maintain correct manifold pressure, and leave the regulator open to the atmosphere to see what that does to idle. What would you expect it to do if Tcoat is correct, versus some other problem?

Also, is it safe to start and run the engine this way? I would think there is a reason they need the fuel pressure regulator in the first place?
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Old 11-07-2020, 03:46 AM   #27
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So, let's pretend I don't know what vaccum to what regulator you are talking about (it's the internet therefore I really know everything right? )

Are you saying that the fuel pressure regulator is controlled by some air vaccum line to the manifold? Not familiar with how fueling systems work so sorry if I misunderstood.
Yup, but I was wrong. Just looked it up. They went to a returnless system before 2008. Oooooops.

I'm pretty sure it also blows holes in Tcoat's theory. The only way to tell for sure is to test fuel pressure real time.

To answer your last question, disabling the pressure regulator would raise rail pressure but not to some crazy unbounded level. It would be the same as when manifold vacuum is lowest - at initial startup and what would be delivered near to full throttle. It would run rich at the low end. Not a showstopper, and would confirm the issue.
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Old 11-07-2020, 07:56 AM   #28
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Yup, but I was wrong. Just looked it up. They went to a returnless system before 2008. Oooooops.

I'm pretty sure it also blows holes in Tcoat's theory. The only way to tell for sure is to test fuel pressure real time.

To answer your last question, disabling the pressure regulator would raise rail pressure but not to some crazy unbounded level. It would be the same as when manifold vacuum is lowest - at initial startup and what would be delivered near to full throttle. It would run rich at the low end. Not a showstopper, and would confirm the issue.
I don't see how it invalidates the theory that a clogged fuel filter is preventing flow at lower pump settings.

Possible culprits:
1. Fuel filter is clogged
2. Fuel pump is dieing
3. Some fuel pressure regulation device is malfunctioning.
4. Coils/plugs
5. Alternator (possibly also the reason the battery was shot?)

I can probably check the the Alternator voltage output pretty easily, (obd readout or multimeter) to make sure it's at 14V+ right?

That just leaves 1-4. I think it's going to be more cost/time effective to just replace the filter and pump together than try to rig something together to figure out how to measure fuel pressure in a running engine and fi more diagnosis. If that costs me $300 and an afternoon to learn that wasn't it, well I learn better the hard way anyway lol. Plus, the filter at least is overdue for replacement anyway.

If that doesn't solve the problem, the plugs are due for replacement, and then coil packs. If I am still in the dark after that, well, it might be time to pay somebody to fix it...

Edit, first, I'm going to inspect the fuel lines under the car. I wonder if they may have been damaged when I got the cat inspected...
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