Subaru Outback Forums banner

1 - 20 of 20 Posts

·
Registered
Joined
·
48 Posts
Discussion Starter #1
I was just about done with my son's 2001 H6 engine swap/wheel bearing replacement. As I went to go get the alignment done the car refused to start. No fuel pump whine, fuel gauge pegged at full.

I did drop it off the jack quickly the last time down from the jack stands. Is there an inertia switch that could have been set off? Or would it be better to unhook the battery for a spell and see if it resets itself?

I was dangerously close to giving it a full viking funeral. I have another Subaru to work on. I need my garage back...
 

·
Brucey
'17 3.6 Limited
Joined
·
10,336 Posts
The O Ring on the fuel pump is known for cracking causing no start situations.

I would confirm that the crack isn't an issue before ordering a new fuel pump.

The tank doesn't have to be dropped. You can access it easily by lifting the rear seat up.
 

·
Registered
Outbacks, SVXs, XT6, 4Runner, Celica, Brat, E150s
Joined
·
523 Posts
No inertia switch. Continue your diagnosis elsewhere.

Check for codes. Use some starting fluid to verify spark and timing.
 

·
Registered
Joined
·
16,979 Posts
No fuel pump whine, fuel gauge pegged at full.
Fuel gauge pegged at full could be a short to ground in the wiring between the cluster and the fuel level sensors at the tank. That might also be related to the fuel pump not running. Was any work done in the vicinity of the fuel pump and/or the wiring harness to it?

Recheck any wiring and connectors in the engine and cabin area that were moved during the engine change.

Fuel pump power is from fuses 11 and 13 in the cabin fuse panel. Both are 15 Amps. If either is blown, the pump doesn't operate.
 

·
Registered
Joined
·
48 Posts
Discussion Starter #5
Thanks for the replies. I’m about to fire up the garage heater and work on fuel lines and gas tanks. What could go wrong here?

Car was running like a watch the day before. Jacked it up, checked the torque on the ball joints and brake hardware (because I thought I missed something), removed the jack stands, and with a flick of the wrist, dropped it to the ground.

Hopefully just a loose connection somewhere. I’ll probably run some Heet and a new fuel filter if I get it running.
 

·
Registered
Joined
·
48 Posts
Discussion Starter #6
Fuses are good.
No voltage at fuel pump.
No voltage across fuse 13
Battery voltage across fuse 11

So I guess I'm going up the food chain a bit on this one.
 

·
Registered
Joined
·
16,979 Posts
Need some clarification as I read the results:

No voltage across fuse 13
Is this when measuring [literally] across the fuse, i.e., between the two ends of the fuse?

Battery voltage across fuse 11
As above.

Should be measuring the voltage at each end of the fuse, using the meter positive test lead at the fuse, and the meter negative test lead to a good ground (two measurements at each fuse). The fuses have small openings in the plastic right above the fuse blade terminals. A fine test probe tip should be able to reach in through the opening to make contact. For fuse #11, there should be power at both ends when the ignition switch is at On, but not when it's at Off. Fuse #13 should have power at both ends at all times (ignition switch is not relevant).

fuse test points.JPG

Be sure you're checking the right fuses. The Owners Manual has a diagram of the layout in Section 12, "Specifications". Also, I believe the fuse panel itself is embossed with the fuse numbers.
 

·
Registered
Joined
·
48 Posts
Discussion Starter #8
I usually just pull the fuse out and put my leads into the holder to check for voltage. Was checking #13 and #11.

I had my assistant turn the key from off to on and the voltage to the fuel pump would blip for a second to 12V, then go back down to 0. It looks like the relay isn't working properly.
 

·
Registered
Joined
·
16,979 Posts
I had my assistant turn the key from off to on and the voltage to the fuel pump would blip for a second to 12V, then go back down to 0. It looks like the relay isn't working properly.
If I understand this correctly, that might be normal. When the ignition switch is moved from Off, to ON (not start), the ECM runs the pump for [only] about 2 seconds. It then remains off until the ignition is turned to Start at which point it should run while cranking and after the engine starts. So it's normal for the voltage to the fuel pump to "blip" when the key is turned to On. But it should hold for a second or two. Usually one can hear the pump motor run during that time even though a meter might not be fast enough to clearly display the voltage.
 

·
Registered
Joined
·
48 Posts
Discussion Starter #10
I’m being pretty generous with one second, is really a third to a half second. Enough for a spritz of fuel to come out of the filter. Carefully not to blow myself up.

My thinking was the fuel pump runs all the time until the key goes to acc or off. It should stay on long enough for proper pressure for injectors.

It just doesn’t seem to latch on. Off to the parts store for the relay to see if that could be it. Otherwise the seal gets broken and the pump comes out.

Thanks again for the help!
 

·
Registered
Joined
·
16,979 Posts
While at the parts store, see if they lend out a fuel pressure gauge kit (usually for a refundable deposit). Then see if the pump is developing required pressure in the system during the priming (turn the key to on, off, then back to on). As was noted earlier, that generation does have known fault in the fuel pump. If the pump motor runs, but doesn't develop the proper pressure, the engine won't start.
 

·
Registered
Outback 2011 3.6R Premium
Joined
·
971 Posts
My thinking was the fuel pump runs all the time until the key goes to acc or off. It should stay on long enough for proper pressure for injectors.

It just doesn’t seem to latch on. Off to the parts store for the relay to see if that could be it. Otherwise the seal gets broken and the pump comes out.

Thanks again for the help!
The fuel pump definitely does NOT run like this. As Plain OM suggests the fuel pump runs momentarily, to add fuel pressure to the system, and then stops until a signal is received by the ECU to confirm the engine is running. Once the signal is received by the ECU the fuel pump runs continuously as needed.

To test the fuel pressure you will need to turn the key on and wait for the fuel pump to stop, and then turn the key off and on again and continue this until the fuel pressure peaks in the gauge. You should be reading between 45 and 55 PSI as a peak reading.

Seagrass
 

·
Registered
Outback 2011 3.6R Premium
Joined
·
971 Posts
Thanks for the fuel pressure correction a Plain OM
 

·
Registered
Joined
·
48 Posts
Discussion Starter #15
I’ll plumb up some of my lab gear from work and see what happens. I have no reason to doubt anyone here, but that seems to be an odd way to run a pumping system. I design sanitary clean in place systems that flow 75-150gpm at 75psi. Bump starting isn’t my preferred way of getting the job done. But I have learned something new today.

Sometimes you are hindered because of what you know. I’m much happier troubleshooting 10hp VFD controlled pumps. That and it’s much easier, because you can see PLC program and know what’s going on.
 

·
Registered
Joined
·
16,979 Posts
I have no reason to doubt anyone here, but that seems to be an odd way to run a pumping system.
I think there's good reason for not keeping the pump running while the ignition switch is at On but the engine isn't running; primarily there's no need (i.e., the ignition could be at On for some purpose other than to run the engine), but also as a safety factor.

As for starting the engine, if the fuel system is in good shape, the one-time prime (in your case say at 25-30 psi) will be retained for some time if the engine isn't then started.

The initial "prime" ( i.e., if one pauses at On) is more than sufficient to establish readiness to supply the injectors. When the ignition is turned to Start, the ECM receives battery voltage at a starter switch sense terminal (this is the same voltage that is going to the starter solenoid). This signals the ECM that "engine start" is being initiated. At this point, I believe the ECM looks for a signal from either the camshaft or crankshaft sensor to confirm that the engine is actually being turned, at which point the fuel pump motor is started again and the injectors and spark plug firing begins. (Some time ago I was doing some tests on my 07 that involved disconnecting the single wire to the starter solenoid to prevent the starter from running when the switch is turned to Start. I recall that when the switch was turned to On the pump prime could be heard, and although I wasn't focussing on this, I don't think I heard the pump running when the switch was subsequently held at "Start", because the engine wasn't turning.)
 

·
Registered
Joined
·
48 Posts
Discussion Starter #17
On most days, my 05’s fuel pump doesn’t make much noise at all when the key goes to on. Daily use seems to keep adequate residual pressure in the fuel rail. After a week long business trip, that pressure is gone, and you hear the pump whirring away for a second or two before shutting off.

It’s quite natural to assume there is a pressure signal latch on the fuel pump on initial startup. But on a fuel system that is just a pump and regulators (no check valves or pressure switches), I scratch my head a bit. They don’t give you a fuel system P&ID in the manual to figure these things out.
 

·
Registered
Joined
·
48 Posts
Discussion Starter #18
Bad relay (iffy), bad o-ring. When I removed the return line I broke the line at the housing. One new fuel pump assembly later, good as new.

Time to walk the malamute. No snow days for me.
 

·
Registered
Joined
·
16,979 Posts
Bad relay (iffy), bad o-ring. When I removed the return line I broke the line at the housing. One new fuel pump assembly later, good as new.
Bad relay led to there not being power at the pump; classic bad o-ring on the cap meant low pressure when the pump did work. Unexpected combination.

In terms of identifying the problem(s), which was first? Did you find the bad o-ring, replace the pump assembly, then find the flakey relay, or the opposite?
 

·
Registered
Joined
·
48 Posts
Discussion Starter #20
Based on my experience troubleshooting pumping systems, I choose a top down approach. Start at the source of the pump signal and work your way down to the pump. So fuses, then relay, then pump. Fuses were good, but the pump didn't make any noise we going from off to acc. Checking the voltage on a start up situation, the voltage at the pump would only blip voltage momentarily then return to zero (when connected the fuel pump was silent). Relay switches get carbon buildup over the years and prevent the contacts from touching. So for 13 bucks a relay is a cheap first fix point. After the relay change, you would then hear the pump whirling, so on to the next point of failure. Felt like the pump was rotating but not making pressure (a feel thing). That's when I went in to pull the pump and see what was going on. That's when I snapped the return line of the pump housing. At that point a new pump housing assembly was ordered. I haven't done the full postmortem on the old assembly, but the o-ring was not looking good. But on the bright side the tank was completely full of gas, so no shorts from the sender to the cluster.

New pump, new filter, sound and pump fury, and it started right up. Now to get all the gas fumes out of the car and garage...
 
1 - 20 of 20 Posts
Top