Failing fuel pump symptoms? 96 Legacy

[Ravenwoods]

2.2 liter, MT, 119,000 miles.

No codes. It will run great for a day and now and then cut out intermittently. I borrowed a MAF sensor from a parts car and it did not solve the problem.

 I remember hearing that a Legacy fuel pump is prone to failure. Feels like sudden lack of fuel or suddenly no spark in all four cylinders.

It’s my daughter’s car. It seems like it never or seldom happens at highway speeds.

[lmdew]

I pull used pumps from the yard all the time.  Subaru pumps do fail, but are pretty darn good.

Can you hear it run when the key is first turned on?

When it will  not start put a cap of fuel in the throttle body and see if it starts and runs for a few seconds.  If so it's most likely the pump or relay.

Lots of fellows recommend checking the fuel pressure, but you need to Y into the fuel line and have a good gauge.

[Ravenwoods]

It always starts well. The MAF Sensor from the parts car could be bad. I just test drove it again and compared to my daughter’s description of the symptoms she experiences I believe it is worse. I’ll try the MAF off our 98 Forester when it gets home.

[lmdew]

If you have an amp meter, check the draw at the pump.  When the pumps are going out they sometimes run for a bit and then go out.  The amps will go up.

[mikec03]

I had a couple fail but not while the cars were running.  They are easy to change so you might want to get a used one and put it in.

Edited April 14, 2019 by mikec03

[FerGloyale]

Spark plugs?

when they get bad, they cause awful bucking/cutting out under load.

[Ravenwoods]

Plugs were replaced last September. Seems like plugs would cause a misfire code.

[el_freddo]

I doubt there’s a misfire code for the ‘96. 

What plugs did you use? 

Cheers 

Bennie

[Ravenwoods]

NGK plug, the recommended ones.  We did get a misfire code on the previous plugs so we changed them. No more misfire codes.

[idosubaru]

96 does have misfire codes and is OBD - read the codes first.  There could be pending codes.  

Clean or swap the idle control motor/valve if it’s usually cutting out when you take your foot off the gas....coasting, idling, etc. 

is it cutting out under load - while speeding up with foot on pedal or when coasting ?

[Ravenwoods]

4 hours ago, idosubaru said:

96 does have misfire codes and is OBD - read the codes first.  There could be pending codes.  

Clean or swap the idle control motor/valve if it’s usually cutting out when you take your foot off the gas....coasting, idling, etc. 

is it cutting out under load - while speeding up with foot on pedal or when coasting ?

We replaced the Idle Air Control Valve (with a used one) last November as we had been getting that Code from time to time and the engine would frequently stall when coming to a stop.

Now it cuts out under power and when you take your foot off the accelerator the engine is normally still running. It really reminds me of when another of our cars had a bad MAF. But I did some swapping and testing of the MAF on another vehicle and that car ran fine. But this 96 can go on a short trip and be symptom free. So I’m guessing we can’t rule out the MAF. I just got a 95 Legacy yesterday that I won’t be using and I could put that MAF in for a day or two.

[idosubaru]

Swap the coolant temp sensor next

There are three coolant temp components - one triggers the radiator fans, one is for the dash gauge cluster engine temp, and one is for the ECU.  Swap or replace the one for the ECU. 

 

When it cuts out to you get any symptoms just before or around that time such as: 
A. dash lights lighting up
B. drivability issues, engine getting weak
C. noises

Or it goes from perfect running to not at all instantaneously?

[el_freddo]

Fans are ecu controlled, so there’s two sensors - ECU and temp gauge. Unless that changed between the Gen1 and the Gen2.

As for weak, I can attest to that with my EJ22 converted L series - got a temp sensor code. Needs a new one. Fans don’t operate all the time so it’s not completely dead, and it’s not throwing a check engine light. I found it when I checked for codes. 

Cheers 

Bennie

[idosubaru]

29 minutes ago, el_freddo said:

Fans are ecu controlled, so there’s two sensors - ECU and temp gauge. Unless that changed between the Gen1 and the Gen2.

Oh right, I just meant "3 possible" coolant temperature devices - senders or switches.  I don't keep track of which engines have which ones because I know it varies some - I just keep in mind what to look for when I'm working on engine XYZ so to speak. 

[Ravenwoods]

I put in the MAF sensor last night from my new 95 Legacy and she said there were no issues on her trip home. But that was the initial result for the first trip when I borrowed the MAF from the 99 Outback. The second trip is when it started acting up again. Then I tested that sensor in our Forester for a short trip and it was fine. But I did not leave it in for additional trips. So I didn’t do a thorough job eliminating the MAF as the culprit.This time I’ll leave the MAF from the 95 Legacy in for as long as needed as I’m doing some work on it for the next few weeks.

 

 

[Ravenwoods]

2 hours ago, idosubaru said:

Swap the coolant temp sensor next

There are three coolant temp components - one triggers the radiator fans, one is for the dash gauge cluster engine temp, and one is for the ECU.  Swap or replace the one for the ECU. 

 

When it cuts out to you get any symptoms just before or around that time such as: 
A. dash lights lighting up
B. drivability issues, engine getting weak
C. noises

Or it goes from perfect running to not at all instantaneously?

It goes from perfect to cutting out on all four cylinders instantly. So none of your ABC options.

[idosubaru]

40 minutes ago, Ravenwoods said:

It goes from perfect to cutting out on all four cylinders instantly. So none of your ABC options.

When it cuts off - it restarts immediately?
There's no patterns (hills, cold start, highway, coasting...)? 

Test or swap the CTS?

What would the pro's do here - log data so they can see what happens just before it cuts off?

[Ravenwoods]

16 minutes ago, idosubaru said:

When it cuts off - it restarts immediately?
There's no patterns (hills, cold start, highway, coasting...)? 

Test or swap the CTS?

What would the pro's do here - log data so they can see what happens just before it cuts off?

It doesn’t usually die. You take your foot off the accelerator and put the clutch in and it is idling.

 

No detectable pattern 

What is CTS?

[1 Lucky Texan]

if you were to rev in N, is there a point at which it would start missing?

some older soobs would have crank pos. sensors that would get intermittent at temp....I've also seen at least one post where cleaning debris from a cps helped it!

any association with rain/dew/moisture? how old are the plug wires?

 

Edited April 16, 2019 by 1 Lucky Texan

[Ravenwoods]

We haven't tried anything in Reverse but we can give it a try. Where is the Crank Position sensor?

[1 Lucky Texan]

no, increase engine rpms - revvvv.....

 

cps is just above the rear of the crank sprocket, below the alt. It senses pulses from the tabs on the sprocket and is used by the ecu to fire the spark. (well, basically)

Edited April 16, 2019 by 1 Lucky Texan

[el_freddo]

If it were the crank angle sensor the engine wouldn’t idle. Same for the cam angle sensor. 

I had my cam angle sensor back out of its mount after putting my engine back together because I didn’t nip up the retainer bolt properly.  This initially created an intermittent issue as hills were climbed until the engine finally cut out and wouldn’t start again until the issue was found. 

I’ve not heard of crank or cam angle sensors going bad. They’re just a magnet and a big pile of fine copper wire wrapped around it to pick up a signal, the one I pulled apart was very well sealed, so I can’t see the weather busting into one of these. 

@Ravenwoods - after the cutout, what is the “quality” of the idle? Is it smooth, rough, miss firing, high/low, does it create a vibration, will it rev freely with the clutch in - and with the clutch engaged does it take up the load or die again? 

I think @idosubaru has raised a good point - time to start data logging and taking a closer look at the situations when it happens, how long into the drive that it happens, what the rough ambient temps are - and even things Ike fuel tank level according to the highly accurate Subaru fuel gauge <insert sarcasm here>.

Cheers 

Bennie

[FerGloyale]

8 hours ago, idosubaru said:

Swap the coolant temp sensor next

There are three coolant temp components - one triggers the radiator fans, one is for the dash gauge cluster engine temp, and one is for the ECU.  Swap or replace the one for the ECU. 

 

 

This is incorrect.

There are only 2 temp sensors.  

The one for the gauge is a single prong.

The 2 prong one is for the ECU.  ECU controls fans based on this signal.

EA cars have a thermoswitch in the radiator for fan control but EJ car that's been handed to the ECU to control via relay.

[1 Lucky Texan]

any other problems of an electrical nature? maybe refreshing some grounds would be helpful

[Ravenwoods]

Two days ago I swapped out the MAF sensor and put in the sensor from my currently idle 95 Legacy. My daughter reports the car behaved much better but was not symptom free. Maybe there are two issues: 1. Failing MAF Sensor; 2. And something else. We got a used MAF sensor from the junkyard about five months ago for $50 and seems like it has already started to fail. Maybe it’s time to get a brand new one.