Daughter's Subaru Will Not Start In the Morning

3,062 Views | 28 Replies | Last: 4 yr ago by fixer
TxTarpon
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8:53a, 2/12/20
She has a 2011 Legacy with 80,000 miles.
Starting in January it will crank, but not easily catch to start in the mornings.
Usual Subaru dash warning codes flash on the dash.
Cam position and crank position sensors replaced.
ECM replaced.
New Serpentine belt installed.
New battery installed.
Fuel pressure is fine.

Once it is started (pedal to the floor) is will drive the rest of the day without stalling, bucking or random revving. It will even restart without a problem for the rest of the day.
Then, the next morning same starting problem again.

Any ideas?
O2 sensors gone bad that do not register on the diagnstic?
Crap in the fuel tank? (I tell her not to fill up at HEB or WalMart, but...)
I am starting to think dump the fuel tank, clean it and reinstall.

I have two mechanics and myself baffeled at the next step.
Thank you.

----------------------------------
Texans make the best songwriters because they are the best liars.-Rodney Crowell

We will never give up our guns Steve, we don't care if there is a mass shooting every day of the week.
-BarronVonAwesome

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aggie_wes
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9:16a, 2/12/20
AG
I'd check the fuel pump and filter. I know you said it had fuel pressure, but is that while it's cranking to start in the morning?
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robertcope
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In reply to aggie_wes • 9:35a, 2/12/20
aggie_wes said:
I'd check the fuel pump and filter. I know you said it had fuel pressure, but is that while it's cranking to start in the morning?
Fuel is the first thing I though of, as well. Lots of modern cars will prime the fuel system when the car is unlocked or door opened or whatever. I wonder if that system is not working for some reason.
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Flaith
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9:45a, 2/12/20
AG
My guess is also fuel pump. Some of them (my Jeep included) lose prime when sitting overnight and have to be cranked and goaded to prime.

Have you tried to see if key-priming 4-5 times before cranking makes any difference?
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aggiedata
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9:59a, 2/12/20
AG
Did you recently give her a lecture about putting regular gas in your diesel truck by chance?
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TommyGun
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In reply to Flaith • 10:37a, 2/12/20
AG
Flaith said:
My guess is also fuel pump. Some of them (my Jeep included) lose prime when sitting overnight and have to be cranked and goaded to prime.

Have you tried to see if key-priming 4-5 times before cranking makes any difference?


Just had this issue in my Tahoe. It would lose prime while sitting overnight and not want to start in the morning. Look at your manual and see what the fuel pressure needs to be at while the engine is turned off and measure first thing in the morning or after it has been sitting all day. If the pressure is low then you know that it is the fuel pressure valve. Or you could try the priming trick and see if that works. Just had to replace mine in my Tahoe. Unfortunately for me, the valve is integrated with the pump in the tank and I had to replace the whole assembly which meant dropping the tank.

If pressure looks good on the fuel side, then you could potentially have a vacuum leak around the intake manifold. Basically, on a cold start the gasket will allow a little air to slip past making start-up difficult, and then as the engine warms the gasket will expand plugging the leak and the engine will run normal the rest of the day or as long as the engine is warm.
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Flaith
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11:06a, 2/12/20
AG
most of them are single units in the tank complete with pump, purge valve, sending unit, etc.

Fortunately, hers is probably fairly easily accessible below the back seat bottom without having to drop the tank like I had to do on my Jeep

$150 for an aftermarket brand

$250 for subaru brand
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Naveronski
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11:40a, 2/12/20
AG
Why not fill up at HEB?
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Mr. Dubi
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11:54a, 2/12/20
Oil pressure sensor
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EMY92
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In reply to Naveronski • 11:57a, 2/12/20
AG
Naveronski said:
Why not fill up at HEB?
25 years ago, I was a service manager for a company that installed and repaired fueling systems. I learned who and what to avoid.

In my case, I only fill up at my local HEB. If I do have a problem, it's the only station I have used.
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1agswitchin4lanes
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1:19p, 2/12/20
AG
Wonder if its bleeding down overnight.

What if you cycle the key to run a few times?
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TxTarpon
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In reply to aggie_wes • 3:00p, 2/12/20
Will check it again. Thank you.
----------------------------------
Texans make the best songwriters because they are the best liars.-Rodney Crowell

We will never give up our guns Steve, we don't care if there is a mass shooting every day of the week.
-BarronVonAwesome

A man with experience is not at the mercy of another man with an opinion.
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TxTarpon
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In reply to Flaith • 3:00p, 2/12/20

Quote:
Have you tried to see if key-priming 4-5 times before cranking makes any difference?
I think it does.
She cannot tell the difference.
----------------------------------
Texans make the best songwriters because they are the best liars.-Rodney Crowell

We will never give up our guns Steve, we don't care if there is a mass shooting every day of the week.
-BarronVonAwesome

A man with experience is not at the mercy of another man with an opinion.
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TxTarpon
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In reply to TommyGun • 3:02p, 2/12/20
Wonderful info.
Thank you.

Sorry your Tahoe was doing that.
----------------------------------
Texans make the best songwriters because they are the best liars.-Rodney Crowell

We will never give up our guns Steve, we don't care if there is a mass shooting every day of the week.
-BarronVonAwesome

A man with experience is not at the mercy of another man with an opinion.
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TxTarpon
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In reply to Naveronski • 3:05p, 2/12/20
Years ago I was told by a friend who worked at HEB that gas was wholesale yankee gas resold for cheap.
Same with Murphy USA.
The few times I bought gas there I experienced that "1980s Ford sputtering" in my Chevy and Jeep.
Moved back to Exxon and the problem was gone.

----------------------------------
Texans make the best songwriters because they are the best liars.-Rodney Crowell

We will never give up our guns Steve, we don't care if there is a mass shooting every day of the week.
-BarronVonAwesome

A man with experience is not at the mercy of another man with an opinion.
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TxTarpon
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In reply to aggiedata • 3:07p, 2/12/20
Her last BF had a diesel.
After he "smoked" some people at a bus stop for fun she made a change.
----------------------------------
Texans make the best songwriters because they are the best liars.-Rodney Crowell

We will never give up our guns Steve, we don't care if there is a mass shooting every day of the week.
-BarronVonAwesome

A man with experience is not at the mercy of another man with an opinion.
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drumboy
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In reply to TxTarpon • 3:19p, 2/12/20
AG
Lol at him rolling coal on the poors. I want to get a TDI sportwagen w/ a tune to roll coal on fools.

Does she ever smell gas when it's cold? My 04 WRX had an issue w/ fuel lines near the manifold leaking a little gas when it was very cold but it always started fine.
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Tim Weaver
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6:23p, 2/12/20
Rolling coal is dumb and is not only bad for the environment, it is the result of a really bad tune. That's unburnt fuel you're spewing out into the world.

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DeWrecking Crew
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8:37p, 2/12/20
I too am inclined to think the prime on the fuel line is bleeding...but another thing to just consider is faulty battery cables, if there is a problem with them it tends to show on cold mornings
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TxTarpon
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In reply to DeWrecking Crew • 8:53a, 2/14/20
Thank you
----------------------------------
Texans make the best songwriters because they are the best liars.-Rodney Crowell

We will never give up our guns Steve, we don't care if there is a mass shooting every day of the week.
-BarronVonAwesome

A man with experience is not at the mercy of another man with an opinion.
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JamesPShelley
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9:16a, 2/14/20
Have you ruled out a faulty coolant temperature sensor?
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TxTarpon
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In reply to JamesPShelley • 8:06a, 2/17/20
No. Thank you for that idea.
When it is bad, does it not start the engine, but after it warms up it works well?

I am going to check that out since whatever this problem is, it trips the warning lights on the dash.

----------------------------------
Texans make the best songwriters because they are the best liars.-Rodney Crowell

We will never give up our guns Steve, we don't care if there is a mass shooting every day of the week.
-BarronVonAwesome

A man with experience is not at the mercy of another man with an opinion.
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TxTarpon
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In reply to TommyGun • 8:06a, 2/17/20
Did that trip warning lights on your dash?
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Texans make the best songwriters because they are the best liars.-Rodney Crowell

We will never give up our guns Steve, we don't care if there is a mass shooting every day of the week.
-BarronVonAwesome

A man with experience is not at the mercy of another man with an opinion.
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evan_aggie
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In reply to TxTarpon • 8:22a, 2/17/20
AG
TxTarpon said:

Quote:
Have you tried to see if key-priming 4-5 times before cranking makes any difference?
I think it does.
She cannot tell the difference.


Hi. Why do you think it does but she does not? I figured it either turns over more easily or doesn't.

One way to rule out fuel pressure is to simply buy a mechanical gauge that goes inline. My Ford had some sort of check valve return flow spring all as part of the pump. First prime would only get it to 25psi and fuel was dumping too fast back into the tank. Then is prime 2-3 times and it would go to 55-60 and start up and no issues running after.

Why was the ECM and crank sensor replaced btw? Was this to solve a separate problem?
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TxTarpon
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In reply to evan_aggie • 3:53p, 3/24/20

Quote:
Hi. Why do you think it does but she does not? I figured it either turns over more easily or doesn't.

Think of it churning to catch.


Quote:
Why was the ECM and crank sensor replaced btw?

The codes pointed to that.

Quote:
Was this to solve a separate problem?
No, the computer pointed to it.
----------------------------------
Texans make the best songwriters because they are the best liars.-Rodney Crowell

We will never give up our guns Steve, we don't care if there is a mass shooting every day of the week.
-BarronVonAwesome

A man with experience is not at the mercy of another man with an opinion.
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TxTarpon
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3:56p, 3/24/20
The verdict:

The aftermarket cam position sensor was +/- 800omz less than the bona fide Subaru part.
The bonafide Subaru sensor was installed and it has worked flawlessly.
@#%@#$ paid some "stupid tax" while trying to solve this problem.

Thank you everyone for you helpful input.
----------------------------------
Texans make the best songwriters because they are the best liars.-Rodney Crowell

We will never give up our guns Steve, we don't care if there is a mass shooting every day of the week.
-BarronVonAwesome

A man with experience is not at the mercy of another man with an opinion.
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DeWrecking Crew
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In reply to TxTarpon • 5:01p, 3/24/20
Thanks for posting the fix. Wonder why that was only a problem in the morning? Seems like that would have been an ongoing anytime problem.
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TxTarpon
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In reply to DeWrecking Crew • 10:42a, 3/26/20
When the car "got hot" in the afternoons it seemed to start better.


----------------------------------
Texans make the best songwriters because they are the best liars.-Rodney Crowell

We will never give up our guns Steve, we don't care if there is a mass shooting every day of the week.
-BarronVonAwesome

A man with experience is not at the mercy of another man with an opinion.
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DeWrecking Crew
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In reply to TxTarpon • 10:59a, 3/26/20
Yeah, I understood, I was just polling the others as to why that would be the case. From my experience a faulty cam sensor doesn't care what time of day it is. My only theory is that the warmer temperatures expanded the metals making everything come into spec, but I acknowledge that's a stretch in terms of theories, so was just wondering what others thoughts were.
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fixer
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In reply to Flaith • 7:08a, 3/28/20

Cool deal. Glad it was just a crank sensor.
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