Automotive Question: Could the fuel pump be the problem?

I am responsible for a 2007 Kia Rondo that has very, very few miles on it. It is in many ways a great little car, but I tend to forget it exists for weeks at a time so occasionally it has only been started or driven about once a month (or even less). Some time ago it became hard to start with lots of cranking to get it started. Once you got the thing started it ran fine and was easy to start the next day or later the same day, but difficult after more time had passed. That situation has now devolved to where it will crank, and crank but not start - - - unless you spray some starter fluid into the air intake.

A weak or failing fuel pump has been the suspected problem for quite some time, but now I have my doubts. Once it fires up, it will run for hours, or idle in the drive for thirty or forty minutes. The petal is very responsive whether driving or sitting, and once it is running there is NO evidence of any fuel problems. In addition, fuel pumps are expensive and fairly hard to replace for this vehicle.

So my factual questions are:

  1. Would the car run so well (once started) if the fuel pump was the problem? (Does the engine ‘draw in’ gasoline once it is running without need of the fuel pump—working like a siphon?)
  2. If the fuel pump isn’t the culprit, why won’t it start on its own?

Thank you in advance for any and all help and suggestions.

I doubt it’s the fuel pump. If that were the problem, the engine would have power problems when under high demand, such as when climbing a hill or running at high speed for any length of time.

Does your car have fuel injection? If so, it could be a problem with the computer, which is supposed to inject more fuel when the engine is cold. The problem could also be with a temperature sensor. If your car has a carburetor, it could be the choke.

If it reliably starts when starter fluid is added, but not until then, it is a fuel delivery problem. It sounds like it does not maintain residual fuel pressure when shut off, which indicates a faulty fuel pump assembly.

To your question, it’s just the nature of electric in-tank fuel pumps. Starting an engine without residual pressure is a different challenge from keeping an engine running. There is no “drawing in” of fuel – the gas must be delivered, at pressure, by the pump.

While the fuel pump is pricey, I wonder why you say it’s fairly hard to replace. My repair info indicates it can be done without removing the fuel tank, which puts it on the easier side for modern vehicles.

No car available in the U.S. has had a carburetor for over 20 years.

Agree that it’s a fuel delivery problem. However, the pump might be fine and it could simply be the fuel lines being old and/or cracked and not sealing and holding the vacuum pressure — when the engine is shut off, the fuel can be falling back into the tank instead of staying at the injectors.

To the OP: after your car has been running a while, when you shut off the engine, open the trunk and sniff near the top of the engine, do you smell gasoline? If so then it might be the fuel lines, which would be easier and cheaper to fix than the fuel pump.

Jeff Lichtman
Yes, this is dilemma! I haven’t tried to take it up long grades—it is pretty flat around here. But I have driven it for over an hour twice after starting it using starter fluid because it failed to start without it, and both times it accelerated easily, went up and down short hills, and maintained highway speeds for at least a dozen or so minutes at a time. Makes me think it CAN’T be the fuel pump. Thank you for the other suggestions.

** Gary T**
I thank you for the response, but I didn’t understand it completely. Your second paragraph seems to suggest that the fuel pump does not deliver the pressure to start the car, but then it requires pressure to operate the vehicle. You state it is a faulty fuel pump assembly; is that different from the fuel pump itself? (You have to explain this stuff to me like I am a five year old.) The way I read your post, the fuel pump doesn’t work when it is off (yes, and neither does anything else), but it does deliver fuel at pressure once the vehicle is started. (Again, please explain it like I am a five year old- but a gifted five year old.)

The reason I say it is fairly hard to replace, is that this particular vehicle has a big plastic shelf where the third row of seats seems to be in all the videos I have watched. That whole thing (as far as I can tell) would need to be removed before the fuel pump can be accessed, and the whole thing is a finished surface which I have a knack for damaging while working on them. Also, they never seem to go back together completely snug, and then it makes a jiggle noise while driving. Also, the thing has to be accessed through the rear doors and that position is painful on my back. A lot of this boils down to I am old and cranky and not as nimble as I once was—but it is also influenced by the fact that if I spend a day (or even half a day) in the sun being miserable, that damn well better solve the problem. The very idea of going to the trouble and expense and not solving the problem for good makes these old bones ache.

Bullitt
This makes the most sense to me, it explains both circumstances. Aside from the sniff test (which I will try soon, but not when my kid is around- I just pulled the old get him to stick his head right into the engine compartment then hit the horn trick and he is looking for payback!), is there a way to tell definitively if this is the problem. If it is the problem, is it the kind of thing a very novice mechanic should attempt? I have a knack for making mechanical projects worse, then needing help with the original problem plus what I messed up trying to fix it in the first place. Are we talking a short rubber piece here and there, or are we talking replacing metal tubes that need to thread over, under, and through a complex series of structural members and exhaust pipes and spare tires under the vehicle?

Since it has been over 110 degrees several days here over the last two months, the idea of rubber cracking and becoming inflexible and loose makes great sense. If this was a literary contest, so far your answer would certainly win the * Sherlock Holmes and the Case of the Noncombustible Carriage* twist solution.

Thank you all. Do I have to climb the Rye Creek hill to test the fuel pump? Or do we all agree it is something else? (Either the fuel lines, or a sensor of some sort.)

The fuel pump module includes the pump itself, the fuel pressure regulator, and the sending unit for the fuel gauge. Part of the pressure regulator’s function is to maintain pressure in the lines after the engine is shut off and the pump is no longer pumping. A common problem is the pressure regulator failing to do this, requiring the pump to do a lot of pumping to restore sufficient pressure to start. I’ve seen many cases where this results in extended cranking (long start times) but does not affect performance once the engine is running. My guess is that this is because during cranking the pump gets less voltage than when the engine is running.

While it may be possible to replace only the pump (for some cars but not all) for less money but more work, the common repair is to replace the whole assembly (pump module).

It’s possible that there are leaks in the fuel lines, but in that case there is almost always a detectable gasoline smell. It’s also possible that the lines are losing pressure because the injectors are leaking, which usually also causes a drop in gas mileage. I suggested that the pump module is the culprit because it’s a far more common problem than leaking lines or injectors. However, to be certain about that it’s necessary to test the fuel pressure with a suitable testing gauge, remove and inspect the injectors for leakage, and inspect the fuel lines for leakage. The procedure isn’t terribly challenging but if you want to verify that the system is losing residual pressure the gauge is necessary, and it’s not a tool that most laymen have. I don’t know if one can be rented from an auto parts store.

It’s also possible that the cause is a faulty engine temperature sensor, which again is less common but is fairly easy to test with an ohmmeter or scan tool.

In sum, if you want to be certain of the problem’s cause, it will be necessary to do some testing.

I assumed that access to the pump was simply a matter of removing a seat cushion, but now I see that in this vehicle it’s more of a pain in the neck.

Gary, does the fuel system need to maintain residual pressure or just keep the lines full of fuel until the engine is cranked and restores pressure through the fuel pump. Would turning on the key for a couple seconds allow the fuel system to reprime itself? I am wondering if lower voltage from sitting might be slowing the cranking and reducing voltage to the pump and electrical system. Starter fluid will fire easier than gas under these conditions.

Normally it will maintain pressure. The official instructions say “After engine stops, the gage reading should hold for about 5 minutes.” I wouldn’t expect it to keep that pressure indefinitely, but I didn’t see any specs on how low it can go and how long it should take to get there.

If the pump runs for a few seconds simply from turning to the “on” position (not to start), it may be possible to prime it by doing that several times.

It occurs to me that possibly there’s no power to the pump while cranking (there should be). That should be tested before replacing the pump.

Running with the fuel pressure thing, I’d suggest turning the key to on, waiting a few seconds, turning it off and waiting a few seconds and repeating that a handful of times before starting it. If there is a bad check valve or the fuel regulator is allowing the pressure to drop, cycling the pump a few times may prime the lines well enough that it fires right away.

Might be unrelated, but I had problems with a 2001 Chevy Cavalier. A lot of advice focused on the fuel pump, and I wound up ripping out a lot of things trying to find the malfunction. Replaced virtually the entire electrical system and then some until finally I found a malfunctioning ignition coil. Make sure the ignition coils are working properly. It’s a cheap and easy item to just check off the list before you go doing anything major. It may not be handling the voltage well on startup.

If it was a bad coil, starter fluid wouldn’t get it going.
Since starter fluid does something, the problem is likely to be lack of fuel making it to the engine.

Hey I’ll take any prize I can get.

I’m not an expert but I do believe replacing the fuel lines is generally straightforward and easy. Check first that your fuel system is not under higher (or any) pressure. I don’t think that’s the case but check it. And I’m not familiar with your particular engine, be it the 4 or the 6, but I’ve generally found that the guys at auto parts stores are helpful if asked something like, “Hey, I’ve never replaced fuel lines on my 2007 whatchamacallit. Any suggestions or tips?” You might have to ask a few of the folks, maybe at different stores. But it should be straightforward. (Key word there, “should”)

Also I’ve found that buying a basic fix-it book on your particular car will readily pay for itself when doing your own repairs or maintenance. This might be one of those situations. And the good thing is, as you go along you get to collect some cool tools for the jobs you do.

Signed,
Sherlock Homies :smiley:

If the fuel line is broke, the OP would almost certainly smell it, or at least see it dripping on the ground.
If they need to be replaced, you have to check to see what type of pressure they’re under. On two of my trucks (GMs), the working pressure of the lines is 62psi. Those lines need to be steel. However, replacing a section of it is pretty easy.

IMO, the first thing that needs to be done is to go rent a fuel pressure tester and see what’s actually going on. That will eliminate a lot of the guessing. You can rent them for free at most autoparts store. I’m not sure if the Kia has a test port, if not, it’s going to mean splicing one into the fuel line (the kit will come with the parts to do that and youtube will show you how).

There’s a good chance that the pressure is fine while running (so it’s pumping okay), but drops soon after the car is turned off.
If that’s the case, it can be a bad injector, bad regulator or bad check valve in the pump. Barring a broken line, those are the only three places the fuel can bleed off to. Again, check youtube and you’ll find videos on how to determine where the fuel is going if this is the case. It’s mostly a matter of pinching off different hoses and seeing what happens.

Okay, I was able to get the thing to start without the fluid by just cranking it half of forever. It finally sputtered and stalled, but I turned the key off, then back on for a three count and it fired right up. I was in a hurry and didn’t think to look or sniff under the hood that time. By my count it could be losing pressure in three places: 1) Regulator attached to pump in the tank, 2) A rubber fuel line someplace near the engine itself (how about at the other end, is there a short rubber hose between the pump and ridged lines?) 3) Or an injector

A buddy of mine has a tester for the fuel pump, but neither of us have any free time until the weekend at the earliest. I appreciate all the suggestions and hope to put some of this wisdom to good use on Saturday or Sunday. I am very glad I didn’t just order a fuel pump from Rock Auto; the Dope has taught me yet another lesson. Again my thanks!!

By-the-way, while the vehicle is about eleven years old, it has less than forty thousand miles on it. That is why I am suspecting some form of dry rot in the fuel line to be the culprit. Once I look at it for real, I hope to find a hose that is visibly the problem, dry and cracked—practically dust. Easily accessible, and costing no more than thirty bucks - - - but I seldom have those kind of days. You guys already saved from buying a fuel pump that would not have solved the problem. Automotive heroes, each of you!

Joey, for the most part I would agree with you but keep in mind that starter fluid fires easier than gasoline when low voltage is involved. So I would stay open minded on this one. Low fuel pressure should generate a code. I am not sure low voltage on start up would generate a code. He only has problems after the car has been sitting.

You’re right, I’m just saying that if starting fluid got it going, I’d go in the direction of fuel delivery first. Of course, as far as throwing parts at a car, throwing in a new set of plugs is pretty cheap and it’s very easy to check them for spark while you’re in there.

As for low pressure throwing a code, that may very well happen. Personally I’ve never seen it though, but I have pretty limited experience. And, my expierence with low pressure comes from working on a GM Vortec engine. The pressure on the lines in those vehicles is 62, any lower and you’ll have all kinds of issues. When the pump on my pick up ‘died’, it was still putting out 52-55psi and holding, but it was just about undriveable. No codes though. At least not with regular scanner. A thousand dollar bi-directional Snap-On may have picked up something in the live stream, but nothing to set the CEL.

Low Voltage, to the plugs, may generate a random misfire code.

TL;DR, look up what the pressure should be and see what it is. Remember to see how long it holds the pressure after you turn the key off.
IMHO, I think that’s going to be the quickest way to decide what to do next. If it gets up to pressure and holds it. Fuel is likely making it to the injectors as it should.

This being a modern high-pressure (~50 psi) fuel injection system, the fuel lines are made of steel, strong and slightly flexible plastic, and/or very tough rubber compound, all of which are quite durable. I’m sorry to say that a fuel line problem looks unlikely.

My info shows a test port on the fuel line to the injectors under the hood. If your friend’s gauge has the right fitting, the pressure test will be fairly easy to do.

This is in line with what I was thinking.

It’s probably not the ignition coil, but it costs like a few minutes to check and $15 bucks to replace if necessary. And it might be the ignition coil. One thing I’ve learned from fixing my old beater is to check the cheap stuff first. It can save you a lot of money/headaches in the long run.

Changing the fuel pump - or really, any fuel related repairs besides maybe a filter - isn’t a DIY job for most people. Doable, certainly, but not for most. And unless you’re a long-time customer of your mechanic, they’ll gleefully change it for you even if it’s brand new operating at 110%. And if that doesn’t work, hey, they get to charge you for the coil too!

This vehicle has a coil-on-plug design, meaning it doesn’t have “a” coil – there’s one for each spark plug. Somewhere between extremely unlikely and impossible that coils are the problem here.

I don’t want to beat a dead horse, because the real point I’m trying to make is to check off the easy, cheap parts before you rush into assuming some expensive part must be to blame, but the coil on plug thing is completely unrelated to the point - my 2001 has the same system, and it gave issues that weren’t exactly the same but we’re similar enough that a malfunction of the same part might explain it.

Now I already said it’s probably not the coil, but why not take a minute to go over all the possible malfunctions, sort them from super-easy to check to requires professional and work ones way through it rather than risk blowing up the bank account fixing what isn’t actually broken? People like to assume the worst has happened and every car problem will cost thousands of dollars to fix (and plenty of shady mechanics do their best to perpetuate the idea) but it’s often as not something minor and easy to repair.

All I hope that someone takes away from this is take a few minutes to make a complete list of potential issues and check what’s trivially easy to check first. Maybe save a few thousand while you’re at it.