Fuel Pump - Symptoms?

[vkykam]

Hi all,

What are the symptoms of a failing fuel pump?

For the past several months, the SVX has been misbehaving, with the occasional stalling at idle, as well as what I would describe as the engine "skipping a beat", where when cruising the rev would all of a sudden drop a few hundred revs, followed by a feeling of "slam" where the engine re-engages.

Over the past several days, it's gotten progressively worse, with a frequent erratic idle, frequent stalling, frequent slight hesitation when accelerating (a go-pause-go-pause-go feeling), and the occasional severe hesitation (pedal down half way, car won't go). The car is starting to feel like my friend's Colt, when the distributor went south on him, except there's no distributor in the SVX. When the severe hesitation happens, it almost feels like I've run out of gas, but eventually the car does pick up and go.

There's no tranny slippage of any sort (revs would not rise without a matching speed), I've recently cleaned the throttle body, the TPS, the MAF, and new spark plugs (NGK Iridiums) were installed today. Fuel filter was replaced after the initial symptoms appeared, but did not help in the situation.

I'm scratching my head over this. Any ideas?

Thx.

VK

[kuoh]

Could it also be a bad coil?

KuoH

[Beav]

Uh...that would be six bad coils (o.k., they wouldn't all have to be bad, but from the story it would seem so.)

Have someone test the fuel pump pressure, at this point it's as good of a place to start as any. The problem you're having could stem from many things but the pump pressure is one of the easier items to check. It should only take someone with a gauge 5-10 minutes to check.

[vkykam]

5 or 10 minutes to check IF it acts up...

At least it's misbehaving much more frequently over the past few days. Maybe it'll actually give a rough idle when I take it to my mechanic...

I went to the local parts shop today, to see what a fuel pressure gauge costs. $60USD! I'd figure for something I'd probably only use once, for $60USD, I'll take my car to my mechanic instead to have him give me an expert opinion.

Besides, for $60USD, I might as well just BUY the fuel pump. Autozone has one for not much more than that.

Thx for the advice. I'm changing out an O2 sensor tomorrow, and if that doesn't help, then the car goes to the shop on Monday.

VK

Originally posted by Beav
Uh...that would be six bad coils (o.k., they wouldn't all have to be bad, but from the story it would seem so.)

Have someone test the fuel pump pressure, at this point it's as good of a place to start as any. The problem you're having could stem from many things but the pump pressure is one of the easier items to check. It should only take someone with a gauge 5-10 minutes to check.

[Beav]

Uh...just how many times do you want to change that fuel pump? Buy a decent one somewhere that sells decent parts would be my best advice. I wouldn't buy a gallon of windshield washer fluid at the 'A' place. Have you ever wondered why their prices were lower than other parts stores? There's a reason....

[vkykam]

There ain't much aftermarket parts for the SVX. Either $2XXUSD thru subaruparts.com, $400USD from the local dealer , or maybe $80USD on a used one around here.

I'd gather that you'd rather go used Subaru than new from the 'A' place?

VK

Originally posted by Beav
Uh...just how many times do you want to change that fuel pump? Buy a decent one somewhere that sells decent parts would be my best advice. I wouldn't buy a gallon of windshield washer fluid at the 'A' place. Have you ever wondered why their prices were lower than other parts stores? There's a reason....

[Ovidiu STAN]

I would suspect also a bad coil.

The problem is that you can not be certain about the problem until something is dead. A device that is acting up ocasionally is difficult to pinpoint.

I had (my wife not me.....!) a Pontiac with an engine with electronic coils and also I suspected the fuel pump. Several times I had to call AAA to get home the car. Stupid car was stoping and starting at her discretion.
Finally it died and I identified as the problem the electronic coil. Before that I spent 2 days, in 2 different occasions trying to see what is wrong with the fuel pump (took out injectors, fuel line....anyhow not the fuel pump).

Fuel pump can be very difficult to change (because it is in the gas tank). You have to remove a lot and in your case you are not sure that it solves 100% the problem.

If I would be you I would buy an old coil and I would start to swap it around the 6 cylinders.
I think is the easiest and cheapest way to attack the problem.

Another way to see if there is something wrong with your fuel pump is to insert an Amp-meter in series with the pump. The pump should suck almost constant current except the cases when is not working (stuck or simply dead). The current would go to almost 0 or would surge to an unususal high value if is something wrong. When the car is acting take a look at the reading (better get a friend!). It is changing to unusual value that's your problem, if not look somewere else.

I would recommend to use an analogic meter (with needle). It will give you better readings (in this case) than a digital one. I think you can get one at less than $20 (if you don't have one).

I suppose that the pump sucks about 1-2 amps normally.


Good luck.

[vkykam]

Thx for the advice.

I might try out the ammeter idea. I only have a digital one, but I might put that on anyways just to see what's happening.

The fuel pump I don't think it is that hard to get to. I think it can be pulled out through the access panel in the trunk. It did mention a special tool, but I haven't looked to see if I can work without one.

I'm wondering whether it could be a coil, as it doesn't have that "one-lost-cylinder" feeling, where the engine wallops roughly. The revs are erratic, but the engine remains very smooth.

At least it's acting up to be a persistant problem now that I can just drive it to the mechanic to have him look at it.

VK

[oab_au]

Originally posted by vkykam
Hi all,

What are the symptoms of a failing fuel pump?

For the past several months, the SVX has been misbehaving, with the occasional stalling at idle, as well as what I would describe as the engine "skipping a beat", where when cruising the rev would all of a sudden drop a few hundred revs, followed by a feeling of "slam" where the engine re-engages.

Over the past several days, it's gotten progressively worse, with a frequent erratic idle, frequent stalling, frequent slight hesitation when accelerating (a go-pause-go-pause-go feeling), and the occasional severe hesitation (pedal down half way, car won't go). The car is starting to feel like my friend's Colt, when the distributor went south on him, except there's no distributor in the SVX. When the severe hesitation happens, it almost feels like I've run out of gas, but eventually the car does pick up and go.

There's no tranny slippage of any sort (revs would not rise without a matching speed), I've recently cleaned the throttle body, the TPS, the MAF, and new spark plugs (NGK Iridiums) were installed today. Fuel filter was replaced after the initial symptoms appeared, but did not help in the situation.

I'm scratching my head over this. Any ideas?

Thx.

VK

Could be the crankshaft sensor. Does the rev counter continue to show rpm when it happends, or does it drop from lack of signal. If it dosen't then it's something else. If it does the sensor is faulty. No sensor signal, no ignition, no fuel injection, no rev counter.
Hope it's cheap.
Harvey.

[vkykam]

I can see rev's throughout the whole, um, "experience".

From what I gather from your suggestion, Sensor Signal Faulty -> No Signal -> No Ignition -> No Fuel -> No Rev Counter. So I *think* I can rule the crankshaft sensor out?

As for cheap, nothing on THIS car is cheap (ATF filter excepted). But we all love it to death still anyways.

VK

Originally posted by oab_au


Could be the crankshaft sensor. Does the rev counter continue to show rpm when it happends, or does it drop from lack of signal. If it dosen't then it's something else. If it does the sensor is faulty. No sensor signal, no ignition, no fuel injection, no rev counter.
Hope it's cheap.
Harvey.

If it was a sensor, coil or most things electronic, I would think you would get an fault code. As you are not getting one (?) I would look to things not monitored by the ECU.

[vkykam]

Nope, no fault codes at all. No codes are stored in memory, and I've been driving it in diagnostic mode for at least a week now, with no codes showing up even as the car starts to act up.

VK

[DavieGravy]

It doesn't work anymore.