Signs of fuel pump problem? - Toyota Nation Forum : Toyota Car and Truck Forums

haux · 12-06-2009, 11:27 PM

Yesterday something odd happened that reminded me of other odd occurrences a few months ago. My gas tank was close to empty, so I filled up with ten gallons of gas. When I started the car, the car shuddered for a moment, the rpms were very low, then they shot up as normal to about 1,200 and then dropped down to a steady 800 or whatever it's usually at. The shuddering reminded me of a choking or misfiring engine, if you know what I mean.

A few months ago, I'd say this happened about three times: I'd be filling up with the car still running. My friend is inside the vehicle, so she told me what happened. I didn't hear anything odd from the outside. During the fillup, the car's rpms go up and begin to jump up and down, and it revs erratically. One of those three times when this happened, the car stalled during the fillup.

Is this a sign of something going bad? Maybe the fuel pump? Maybe a sensor?

chronoti · 12-07-2009, 08:09 AM

maybe the fuel system need the fuel cap on for emissions systems?

i have an extra fuel pump from my v6, i'll sell it to ya for a deal

haux · 12-07-2009, 01:16 PM

Quote:

Originally Posted by chronoti

maybe the fuel system need the fuel cap on for emissions systems?

I'm not sure what you mean by that. ...fuel cap on?

hill8570 · 12-07-2009, 01:19 PM

Are you getting any of the "classic" signs of low fuel pressure, such as cutting out at high speeds?

My first thought was that you might have a lot of crap in the fuel tank, and when you fill up when you're running on fumes it gets stirred up and sucked into the fuel system. Generally, 'tho, that causes a permanent problem (clogged fuel filter or injectors). Maybe you're lucky / unlucky enough to have "finer" sludge?

What it really sounds like is air getting into fuel system. I could sort of see that happening if you're filling up when the rig is running, but, offhand, I can't see how it would happen when the rig isn't running when you fill up.

Sorry I don't have a good diagnosis...

haux · 12-07-2009, 01:41 PM

Quote:

Originally Posted by hill8570

Are you getting any of the "classic" signs of low fuel pressure, such as cutting out at high speeds?

Nothing whatsoever. I don't even consider THIS to be a problem, yet. More like, symptoms of a problem to come.

Quote:

Originally Posted by hill8570

Generally, 'tho, that causes a permanent problem (clogged fuel filter or injectors).

I'm currently using a Fram filter that I put in last year. At that point, the car was still using it's original filter. I have a new OEM filter that I may be putting on this week. I've read bad things about aftermarket fuel filters. I'm unsure if the Fram filter could be the cause of this.

Quote:

Originally Posted by hill8570

What it really sounds like is air getting into fuel system. I could sort of see that happening if you're filling up when the rig is running, but, offhand, I can't see how it would happen when the rig isn't running when you fill up.

I would say maybe the stuff that happened a few months ago could have been caused by the car running... and I should just turn it off when I'm pumping in gas. But prior to that, I had done the same on numerous occasions, without the weird RPMs or the stall. And yes, this last time, the car wasn't even running, and the shuddering occurred on startup, which made me concerned.

Any idea how difficult it is to take down the gas tank?

Hajoca · 12-07-2009, 02:09 PM

First thing is Fram fuel filter should not be causing any issue.... the filter is too simple of a component to foul up. Filter life though may be shorter than the OEM, but I do not think that to be an issue.

The engine when running will activate the charcoal canister VSV to purge the fuel vapour using your engine vacuum at the intake manifold.

You basically experienced low vacuum (leak out the gas filler).

haux · 12-07-2009, 02:48 PM

Quote:

Originally Posted by Hajoca

You basically experienced low vacuum (leak out the gas filler).

So you think the filler tube is faulty?

haux · 12-08-2009, 02:24 PM

Any more ideas?

carsrus · 12-08-2009, 07:21 PM

Its probally not the filler neck.

Easiest solution: Dont fill up with the car on lol.

EEngineer · 12-08-2009, 07:42 PM

^ yea seriously? isn't it common knowledge on safety to never have the car running when you fill up?

haux · 12-08-2009, 09:11 PM

Quote:

Originally Posted by carsrus

Easiest solution: Dont fill up with the car on lol.

That doesn't explain or help me with the recent oddity of the shuddering on startup AFTER the fill-up.

If that was indeed due to low vacuum, how would I confirm that?

haux · 12-08-2009, 09:18 PM

Quote:

Originally Posted by EEngineer

^ yea seriously? isn't it common knowledge on safety to never have the car running when you fill up?

I can't think of anything that could go wrong by pumping gas with the engine running. Not that I smoke, but same thing with smoking and pumping gas. I mean, yes, flame + gas vapor is a nono... but I guarantee you will have a difficult time to get gasoline to light with a cigarette even if you seriously tried.

Nevertheless, that wasn't part of my question, and it isn't an every day occurrence. That fact is that I have done it in the past, and I have done it not long ago, and only those last few times did the RPMs jump like they did... plus the stall.

I'd rather fix this now, not later when something completely fails at the worst possible time/place.