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-   -   Trunk Fuel Resistor (https://www.subaru-svx.net/forum/showthread.php?t=64733)

theflystyle 11-21-2018 01:55 PM

Trunk Fuel Resistor
 
Hello,

I am having a hard time finding the Subaru part number for the trunk fuel resistor (the one with the two long white wires) underneath the rear deck. The part number on the unit itself is A15-000R20 but I couldn't cross reference it with any Subaru part numbers.

Thanks!

theflystyle 11-22-2018 11:21 AM

Re: Trunk Fuel Resistor
 
Finally found it listed under "Engine and Cooling" then "Relay & Sensor (Engine)" on the Subaru Parts website. Unfortunately the part is no longer available.

For posterity, here is the part number information:

Resistor Assembly (rear trunk lid) - 22654AA060
Fuel Control Module (rear trunk lid) - 22637AA000
Relay Assembly (round under dash) - 82501GA240
Relay Assembly (square under dash) - 25232AA020

For those wondering, my car died while driving. Had it towed to my garage and began chasing the issue. Fuel was not being delivered to the engine (past the fuel filter) so I then checked the relays under the dash. Followed by verifying power to the fuel pump. After that I tried disconnecting the rear deck Fuel Control Module and the car started right up. This leads me to believe the Fuel Control Module is to blame.

RedLionSVX 11-22-2018 11:29 AM

Re: Trunk Fuel Resistor
 
1 Attachment(s)
Wow, how many miles on your car?

theflystyle 11-23-2018 06:04 AM

Re: Trunk Fuel Resistor
 
She has 115K but is kept in the garage and never driven in any precipitation.

That attachment does not have the parts I listed in case you were wondering.

I would really like to find a test for the fuel tank resistor. I didn't see anything in the factory service manuals yet.

SacSVX 11-28-2018 10:04 PM

Re: Trunk Fuel Resistor
 
I’ve been having the same issue where the car dies. After long threads of MAF sensor, I "believe" I have traced it to a fuel supply issue (I still haven't tested it). There have been multiple threads on this peculiar problem.

The car starts normal from cold, but when it heats up (especially during the summer) after driving, it stalls out and cannot be restarted until it cools down. I've gotten good at stabbing the throttle to prevent it from stalling out when I sense a failure, which is what led me to look at fuel delivery issues.

Here's the weird part. When I got the engine running normal, I would unplug the fuel control module from under the deck lid, yet the car would continue to run normally. H Am I missing something? Can someone elaborate?

.

Trevor 11-28-2018 10:41 PM

Re: Trunk Fuel Resistor
 
Quote:

Originally Posted by SacSVX (Post 749770)

I’ve been having the same issue where the car dies. After long threads of MAF sensor, I "believe" I have traced it to a fuel supply issue (I still haven't tested it). There have been multiple threads on this peculiar problem.

The car starts normal from cold, but when it heats up (especially during the summer) after driving, it stalls out and cannot be restarted until it cools down. I've gotten good at stabbing the throttle to prevent it from stalling out when I sense a failure, which is what led me to look at fuel delivery issues.

Here's the weird part. When I got the engine running normal, I would unplug the fuel control module from under the deck lid, yet the car would continue to run normally. H Am I missing something? Can someone elaborate?

Several years ago I explained in a post exactly how the system works, but I no longer have the circuit diagram. If this can be provided I will again do so.

Sincerely, Trevor.

theflystyle 12-02-2018 12:17 PM

Re: Trunk Fuel Resistor
 
1 Attachment(s)
Quote:

Originally Posted by Trevor (Post 749771)
Several years ago I explained in a post exactly how the system works but I no longer have the circuit diagram. If this can be provided I will again do so.

Sincerely, Trevor.


Attached is the only circuit diagram I found with the resistor and fuel control module included. What really bothers me is that the resistance measured on the fuel resistor (R34 in the diagram) reads a resistance of 1.2 ohm (.2 is my multimeter’ss probe resistance). Yet when I unplug it, the car starts. When its plugged in it does not.

.

Trevor 12-02-2018 02:49 PM

Re: Trunk Fuel Resistor
 
Quote:

Originally Posted by theflystyle (Post 749780)
Attached is the only circuit diagram I found with the resistor and fuel control module included. What really bothers me is that the resistance measured on the fuel resistor (R34 in the diagram) reads a resistance of 1.2 ohm (.2 is my multimeter’s probe resistance). Yet when I unplug it, the car starts. When its plugged in it does not.

Great, exactly what I needed.

When the ignition is turned on the fuel pump is supplied with a positive supply via the fuel pump relay and fuses SB4 and No. 16 but overall switching of the pump relay and therefore the pump, depends on the ECU completing the negative ground circuit via d23.

The pump receives its negative supply via two alternatives, i.e. the resistor R34 or the fuel pump modulator switching transistors which are controlled via the ECU.

The resistor will provide a reduced voltage and therefore limited pump speed in the event of the pump modulator or its control failing. The resistor will also prevent full zero voltage in respect of pulse width modulation speed control of the pump.

Under normal circumstances pump speed and therefore pressure, will be controlled via the modulator and ultimately by the ECU by means of pulse width modulation.

The pump will run at a reduced speed with the pump modulator disconnected.

I presume that you are reading the value of the resistor with it unplugged. It would appear certain that the resistance value is too low but I do not have the specified figure. This would result in the resistor circuit overriding control via the modulator as would a short circuit to ground within the resistor housing.

Can you locate the correct specified value of the resistor?

theflystyle 12-04-2018 05:57 PM

Re: Trunk Fuel Resistor
 
Trevor,

All your information has been greatly appreciated. When reading your explanation it makes sense when paired with the diagram.

Regarding any specs or values for the resistor or the modulator, I have not been able to find anything. I would love to see if anyone had a stock unit they could test so that we could have a known good unit to compare to.

I am going to hopefully get a replacement used unit to test soon. I will provide updates as they occur.

Trevor 12-04-2018 08:58 PM

Re: Trunk Fuel Resistor
 
Quote:

Originally Posted by theflystyle (Post 749794)
Trevor,

All your information has been greatly appreciated. When reading your explanation it makes sense when paired with the diagram.

Regarding any specs or values for the resistor or the modulator, I have not been able to find anything. I would love to see if anyone had a stock unit they could test so that we could have a known good unit to compare to.

I am going to hopefully get a replacement used unit to test soon. I will provide updates as they occur.

I find this situation very sad, as years ago there would have been many members keen and able to assist you. There must be numerous parts cars out there with a resistor available for easy removal.

Furthermore, surely there is someone who can unplug and measure the resistor in their operational SVX. If I still had my car, doing so I would have involved less time than that expended in posting the required messages talking about the issue. LOL

Probably it would have been preferable for the post to have appeared in the Technical section, but this surely is not a real problem.

I would expect the resistor value to be in two figures but it can it not be estimated without full details covering the pump motor and its requirements.

THIS POST LAUNCHES AS A ROCKET OF DISTRESS!

svxcess 12-05-2018 07:28 PM

Re: Trunk Fuel Resistor
 
.
Moved to the Technical Q&A forum.
.

Trevor 12-05-2018 10:00 PM

Re: Trunk Fuel Resistor
 
Quote:

Originally Posted by svxcess (Post 749798)
.
Moved to the Technical Q&A forum.
.

Thanks friend, compliments of the season.

irox 12-06-2018 01:29 PM

Re: Trunk Fuel Resistor
 
If I get a chance this weekend, I'll throw a ohm meter across mine and see what it says.

What's the quickest way to access it? (I know the vague location.)

Cheers,
Ian.

theflystyle 12-06-2018 01:58 PM

Re: Trunk Fuel Resistor
 
Quote:

Originally Posted by irox (Post 749800)
If I get a chance this weekend, I'll throw a ohm meter across mine and see what it says.

What's the quickest way to access it? (I know the vague location.)

Cheers,
Ian.

that would be greatly appreciated. Its under the rear deck, behind the trunk liner between the two speakers. I ended up taking the pop-its off to allow the whole cover to come off. I don't know if there was/is an easier way.

Trevor 12-06-2018 04:49 PM

Re: Trunk Fuel Resistor
 
Quote:

Originally Posted by theflystyle (Post 749801)
that would be greatly appreciated. Its under the rear deck, behind the trunk liner between the two speakers. I ended up taking the pop-its off to allow the whole cover to come off. I don't know if there was/is an easier way.

Also special thanks from me Ian.

Please make sure that the resistor is disconnected when you measure it, otherwise existing circuitry in parallel could upset the reading. No doubt I am stating the obvious and asking you to suck eggs. LOL


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