Fuel pump or fuel relay fault?

[SonicHedgeHog]

My Subaru Outback has been reluctant to start over the last few weeks. Doesn’t burst into life like it used you. I assumed the three year old battery was knackered and so replaced it yesterday. After replacing it I tried to start the engine and it was still a bit reluctant but got going. Engine switched off and restarted a little better. Third attempt and it seemed fine.

This morning it would only turn over. Tried three times. Timing chain is fine. Spark plugs are top quality and all changed 20000 miles ago. Starter motor works. Battery is new. I reckon it’s a fuel problem. Question is, is it a fuel relay or a fuel pump - I have checked the fuel pump fuse. Neither are easily accessible items. When I turn the key one notch in the ignition and listen to the fuel pump which lives under the rear seat I hear nothing. Makes me think it is the relay as no power seems to be getting to the pump.

Can I have some thoughts from experienced mechanics please? Have a mechanic coming round with a diagnostic tool tomorrow but can’t stop thinking about the problem.

[SturdyHSV]

i'd expect a relay to either work or not, I'd be surprised if it was intermittently getting worse but would be fine once running, and ultimately failing completely. It's ultimately a pretty simple thing.

A fuel pump on the other hand will deteriorate, and I can well imagine it getting its standard priming signal from the ECU and not providing enough pressure in time for the car to fuel correctly upon starting, and take a few attempts to get itself going / get the pressure up etc. If you redline it for a while does it start to break up?

If it was vaguely accessible, you could hook 12v directly to the pump and see if it solved the problem

[GreenV8S]

Not obvious from your post but I guess that previously the engine was cranking over slowly and now it is cranking over at the usual speed but not firing as soon as usual.

Cranking but not firing might just be a consequence of the engine being harder to turn over in very cold weather and pulling the battery voltage down more than normal. You could monitor the battery voltage while cranking to prove/disprove that theory. It could also be a general reluctance to fire due to dirty plugs, weak plug leads or anything like that - these problems would tend to show up in cold damp conditions and be aggravated by a low battery voltage.

It could perhaps be due to lack of fuel pressure or the fuel pump not running at all for some reason, but there's no particular reason to expect that to be aggravated by cold weather or to fix itself within a few seconds so the symptoms don't particularly point to that being the problem.

[SturdyHSV]

As a second suggestion, once it's running, if you turn it off and immediately try to start it again, does it fire nicely?

Just thinking along the lines of once it's running with acceptable fuel pressure in the fuel rails, turning it off and back on means it'd crack on immediately and the pump would have a bit of time to get up to speed, whereas if it's a relay that always takes several attempts to work, then it likely wouldn't work upon the one off restart

[SonicHedgeHog]

The car is otherwise A1 and very well maintained. I don’t think it’s down to the battery not having enough juice to start as it’s a new battery. Once started the car drives normally which makes me think the relay is ok but the pump isn’t. £620 for a new pump with delivery MAYBE February. Breakers here I come…

[SonicHedgeHog]

Second start was better than the first and the third start almost normal. Engine was literally turned off then on quickly. Now, a day later, it won’t fire at all.

[Polly Grigora]

SonicHedgeHog said:

When I turn the key one notch in the ignition and listen to the fuel pump which lives under the rear seat I hear nothing

Do you mean the fuel pump isn't priming at ignition on before cranking yet it used to?

If answer is yes, this could explain why it doesn't start easily at first crank over

[stevieturbo]

SonicHedgeHog said:

My Subaru Outback has been reluctant to start over the last few weeks. Doesn’t burst into life like it used you. I assumed the three year old battery was knackered and so replaced it yesterday. After replacing it I tried to start the engine and it was still a bit reluctant but got going. Engine switched off and restarted a little better. Third attempt and it seemed fine.

This morning it would only turn over. Tried three times. Timing chain is fine. Spark plugs are top quality and all changed 20000 miles ago. Starter motor works. Battery is new. I reckon it’s a fuel problem. Question is, is it a fuel relay or a fuel pump - I have checked the fuel pump fuse. Neither are easily accessible items. When I turn the key one notch in the ignition and listen to the fuel pump which lives under the rear seat I hear nothing. Makes me think it is the relay as no power seems to be getting to the pump.

Can I have some thoughts from experienced mechanics please? Have a mechanic coming round with a diagnostic tool tomorrow but can’t stop thinking about the problem.

So is the fuel pump running or not when you key on ? Test, don't guess.

What sort of speed is the engine turning over at ? no sense changing batteries if that aspect is good.

You say timing chain, what engine is it ?

[SonicHedgeHog]

So, my mechanic friend turned up this evening and the car started after turning over for 5-6 seconds. Ran smoothly and no fault codes were showing on his pro fault code reader. Very much a conundrum. This engine does occasionally have a cold start problem. Every man and his dog has offered an opinion on an Internet forum somewhere in the world but no one has a definitive answer. The suggestion I like the most is that there is a sensor or setting somewhere in the engine that operates to a fine tolerance. During extreme cold weather this tolerance is exceeded causing the problem. One chap solved his cold start issue by changing the PCV valve. I’m going to do this because it’s a cheap part and a good one to change as part of general maintenance. But the mystery remains.

[Belle427]

It’s almost impossible to guess at faults like this really, most people end up just firing the parts cannon.
Fuel pressure checks are probably beneficial.
Two sensors I’d maybe check out are the coolant temp sensor and the crank position sensor, but again these are just guesses.

[SonicHedgeHog]

Those were ideas I read too. The crank position sensor would probably cause hot start problems too so less likely than the coolant sensor. I’ll take a look when I’m under the bonnet doing the pcv valve though. Main thing is it’s not the ferociously expensive fuel pump and the engine is still tip top. Such a shame Subaru no longer make a flat 6.

[SonicHedgeHog]

Interestingly, it’s -4C here this morning and the car just started on the button. One thing I did differently was turn the key two notches in the ignition, much like you do when cold starting a diesel, and waited maybe ten seconds for most of the dashboard lights to go out and what is probably the fuel pump going through some sort of cycle.

So, I’m well chuffed this morning. This car need to keep me going for the next 40 years so I need to keep it tip tip.

[eliot]

fuel pumps will usually prime for a few seconds on key on - try keying on/off 4 times then actually starting. If it starts, then it means your fuel system is loosing it's static pressure when off.

[SonicHedgeHog]

eliot said:

fuel pumps will usually prime for a few seconds on key on - try keying on/off 4 times then actually starting. If it starts, then it means your fuel system is loosing it's static pressure when off.

I’m just thinking about what you’ve said. This is a very cold weather problem only. Not sure why the fuel system would be losing residual pressure when it’s very cold. Maybe a rubber seal contracts somewhere? There is definitely no fuel leak anywhere because both I and my mechanic friend checked.

Reading lots of Subaru forums this issue dates back a couple of decades to when the first flat sixes were installed in Outbacks. There genuinely does not seem to be a fix although the problem does seem to be more common in older/higher mileage cars.

My car wants for nothing so I’ll change the PCV valve and I’ll have a look at changing a few of the sensors people have mentioned as well. These are inexpensive items and worthwhile changes as part of a thorough maintenance schedule. If find a definitive answer I’ll update this thread.

[Unweder]

Sounds like your going to fire the parts cannon shortly get a hand held diagnostic scanner that can read live data inc someone who can interpret said data to see whats going on exactly, a mechanicl gauge on the fuel rail for this long cranking period check wouldnt go amiss either failing that your just pissing in the wind IMO

[SonicHedgeHog]

Unweder said:

Sounds like your going to fire the parts cannon shortly get a hand held diagnostic scanner that can read live data inc someone who can interpret said data to see whats going on exactly, a mechanicl gauge on the fuel rail for this long cranking period check wouldnt go amiss either failing that your just pissing in the wind IMO

Last night’s expensive fault reader showed nothing whatsoever. Zero faults. I understand the pissing comment but what you have to remember is the number of these cars that live in the most extreme parts of North America and are maintained by sharing information on the internet. None of these sources have a definitive answer. I could spend forever trying to track down the culprit and get nowhere. In fact, unless I can find an industrial freezer to work in it’ll be impossible to fault find because the issue only happens at about -6 degrees and lower. It’ll be a tiny, tiny thing akin to a microscopic adjustment of a carburettor that causes the issue. Our family has had this car from new since 2006 and this is the first it has done this. I’m more than happy to change a few inexpensive parts on the off chance that the next time we have super cold weather it isn’t a problem. Although it’s no longer a problem because a small change to the way I start the car fixes the problem.

That reply might come across as a bit shirty but that wasn’t the intention. If I sent the car back to Subaru HQ they might be able to work it out. But I doubt it. I reckon they’d just say it’s an old car and we recommend changing a load of stuff just because of its age.

Anyway. Thank you everyone for your help. Very much appreciated.

[stevieturbo]

SonicHedgeHog said:

So, my mechanic friend turned up this evening and the car started after turning over for 5-6 seconds. Ran smoothly and no fault codes were showing on his pro fault code reader. Very much a conundrum. This engine does occasionally have a cold start problem. Every man and his dog has offered an opinion on an Internet forum somewhere in the world but no one has a definitive answer. The suggestion I like the most is that there is a sensor or setting somewhere in the engine that operates to a fine tolerance. During extreme cold weather this tolerance is exceeded causing the problem. One chap solved his cold start issue by changing the PCV valve. I’m going to do this because it’s a cheap part and a good one to change as part of general maintenance. But the mystery remains.

That aul crystal ball just doesn't work the same these days. How on earth would you expect anyone to diagnose it over the internet ?

I've stated clearly some basic first steps to test which it sounds like have not been done.

Comments like it's more likely crank sensor than coolant temp sensor, are just pure garbage. And any half witted mechanic would simply test either component during the non start to see if it is behaving normally.
They wouldn't simply guess or blindly read a code reader as if it is some miracle worker.

I just cannot grasp why so many so called garages, mechanics, or whatever you want to call them have no understanding whatsoever of how either any of the systems work, how to do basic testing, etc etc etc

Only idiots simply read a code reader then come off with "well it has no faults". These people should not even be attempting to work at cars.

If you suspect a component, test the f'ing thing. It's not rocket science, it's just very basic diagnostic work.

[camel_landy]

SonicHedgeHog said:

Second start was better than the first and the third start almost normal. Engine was literally turned off then on quickly. Now, a day later, it won’t fire at all.

That could also be something like a poor earth connection.

M

[GreenV8S]

SonicHedgeHog said:

I could spend forever trying to track down the culprit and get nowhere.

If you can reproduce the problem, it should be straight forward to diagnose it systematically and not involve the parts cannon. If you can't reproduce it then it can't be causing much trouble, so leave it until it you find it happening again. Replacing random bits of the engine management system on the off-chance it somehow fixes the problem is a waste of money that's as likely to make it worse as better.

[SonicHedgeHog]

Who knows what it is. It may never reappear. The car has been awesome today in some pretty grotty conditions. The suggestion that it is probably best to leave the engine alone rather than needlessly change parts is probably a wise idea. If I’m honest I’ll probably go down that route with the exception of the easy-change PCV valve that is now ordered.

To everyone else who offered supportive advice I really appreciate it. The last thing I need right now is to have to buy a new car. My original post was a nerve-settler while I scoured the internet for an answer and waited for my mechanic friend to turn up.