Should my mother's mechanic have caught a failing fuel pump earlier?
March 21, 2012 11:56 AM   Subscribe

Should my mother's mechanic have caught a failing fuel pump when he repaired a closely related relay?

My mom has a 2002 Ford Focus wagon with 106xxx miles, which has recently had a few fuel pump issues.

Earlier this week, her car died on the road and refused to start again. After some troubleshooting on the side of the road, we got it towed to my mechanic, who passed it along to his "electrical guy". That guy dropped out the fuel tank and checked the fuel pump- he says it tested good. He then did some troubleshooting on the associated wiring and repaired bad wiring and a relay- the work order says "NO START REPAIRED WIRING, R/R CCDM RELAY".

Fast forward about four days. The car dies again, won't start again, in the same way. We have it towed to the same place, where the diagnosis comes back: fuel pump is dead. The quote for part and labor is just north of $500, which jives with an over-the-phone quote from another local shop.

Should the mechanic have caught the failing fuel pump when he investigated the first issue, since he dropped the fuel tank out and said he tested the pump? The referring mechanic, when asked, said "that sucks, it sounds like you had bad luck but that sort of stuff happens, and you don't want to just go replacing good parts". This sounds fishy to me, but I don't know how quickly this part fails or how common this problem is. (Should the pump have been replaced as a matter of course when he went in the first time?)

I trust the original mechanic - he came to us with great recommendations. And I don't have a reason to distrust the "electrical guy" - he gave my mom a few pages of troubleshooting flowchart from Alldata and explained things well, it sounds like. But I'm suspicious anyway. Any insight?
posted by aaronbeekay to Travel & Transportation (10 answers total)
This sounds perfectly possible to me. There were two independent faults - the wiring and the relay. There is no way to tell which caused the other but it is possible that the pump tested fine at this stage.

Once everything was repaired, suddenly the pump is getting a different supply voltage or current (or had just been disturbed in some way) and may have been damaged (although not necessarily in a testable way) by the longer term relay/wire damage and the change was enough to set it into a failure.

Basically, if you are taking a faulty system apart and find two failures, you don't assume a third unless there is proof - assuming the pump was tested, this is perfectly fine. This is bad luck but not at all any sign of poor workmanship.
posted by Brockles at 12:10 PM on March 21, 2012 [2 favorites]

My experience with mechanics is that they have become aware of the stereotype of the shady corner mechanic who will take you for a ride and as such are more conservative with their recommendations than we sometimes expect as customers.

If he had fixed the wiring and said, "Well, it could be the fuel pump, and for another $300, I can replace that, too," would your mom have done it? I probably wouldn't have.
posted by Snarl Furillo at 12:24 PM on March 21, 2012

I think the presumption is that the mechanic tested the relay (very easy to do) and found it had failed. I can totally imagine an intermittent fuel pump fault that would result in a cooked relay. As well, relays can fail intermittently, and replacing it fixed the problem... until it didn't. Or they might have been completely and totally unrelated. I read this situation as an annoying and unfortunate coincidence.
posted by TheNewWazoo at 12:38 PM on March 21, 2012

If the fuel pump were even kinda showing a sign, the mechanic would have wanted to repair it the first time - everyone hates dropping tanks, especially more than once. And as people have said before, changing it "while i'm in there" would have thrown all kindsa red flags. So he replaced the things that were broken, and put everything else back together.
posted by notsnot at 12:39 PM on March 21, 2012 [1 favorite]

Fuel pumps are not cheap and you don't go and replace one if you think it is working.

You guy took it out, tested it and it passed. He's a mechanic, he's not opening up your fuel pump to see how it looks inside. You cannot open them up. He has training or a manual and it says "do this to figure out if it is broken." That's what he did. He even took time out of his day to show your mom this, time that he gets paid $80 per hour for.

What are you suspicious of? How is he making money off this "let's not replace broken parts" scam?
posted by bdc34 at 12:43 PM on March 21, 2012 [4 favorites]

The mechanic's course of action sounds completely reasonable to me. Fuel pumps can fail intermittently and be very difficult to diagnose when they do so. A good mechanic at a high end shop can put a questionable pump on an oscilloscope and see if the power it draws is normal or not, even when it appears to be working fine. Failing this test tells you it's a bad pump, but a pump can be bad and still pass. Things are much simpler when they fail completely.
posted by LowellLarson at 12:48 PM on March 21, 2012

As mentioned above, electronic fuel pumps are finicky beasts. They'll usually fail gradually: they can deliver low fuel flow rates fine, but when you step on it going up a hill they can't keep up and the car will stutter and chug. Or they'll run fine when cold, but you'll get somewhere, turn off the car to run in for a minute-long errand, and when you come out the car won't start because the fuel pump is nice and hot now.

So given your description of the problem (a sudden failure with no warning) and that testing the pump cold in the shop won't always reveal all potentially-bad pumps, I can understand why the mechanics looked elsewhere. A failing fuel pump relay sticks out like a sore thumb. They usually fail hard (not intermittently), so if you believe the shop then you can believe that the mechanic pulled the relay, it wouldn't close when energized (or closed but had a high/infinite resistance), so he replaced it and closed the case. Why look elsewhere and waste your money and his time once you found the problem?

I wouldn't suspect the mechanic unless you have other data. Yeah, maybe a more careful examination of the pump would've found it, but he was likely playing the odds of most likely failures. It's all educated guess-work.
posted by introp at 1:20 PM on March 21, 2012 [1 favorite]

I had the exact same problem on a different kind of car, and I was the mechanic. EVERY. DAMN. TIME I pulled the fuel pump, it would test good. I'd check that off the troubleshooting list and work my way down the list, it would work for a while and then die again. Even the first time I replaced the pump, that part was bad out of the box, confounding my confidence that I'd made the right diagnosis. The second pump eventually fixed it.
posted by gjc at 4:36 PM on March 21, 2012

Actually, to follow gjc's point, this could easily have gone another way. I replaced a pump in a car of mine because the thing would start but not run. Over, and over again: *Crank*, VROoooom.......phut. I checked everything, cleaned out the fuel system, changed the filter and the thing kept doing it. $200 pump later and it STILL did it. I was spitting fire at this point (I have no hair to speak of to pull out).

I found out that the brand new filter I'd just fitted had been manufactured badly and only had a really small hole to let the fuel through - it'd get enough volume to make fuel pressure to start it, but then couldn't flow the fuel fast enough to retain pressure once it started. The car would essentially 'run out of fuel' right after each start. So a shitty $20 filter cost me a $200 pump for nothing.

It's not always an exact science, fixing cars, and a faulty diagnosis can cost you more or less than you were expecting. It's unfortunate in your instance that you have to pay for the tank to come out twice, but honestly I'd not have looked at the pump if I'd already found two supporting potential faults, especially if it had tested ok. Bad luck only.
posted by Brockles at 5:23 PM on March 21, 2012

Hey, that's just what I needed to know. Brockles' answer actually sounds very similar to something the original mechanic told me, about the possibility that the replaced relay delivered higher voltage/current and that finished off the pump. It sounds like pumps don't fail in obvious ways and that the mechanic certainly did due diligence- we'll get it fixed there and keep coming back.

Thanks, everybody!
posted by aaronbeekay at 7:48 AM on March 22, 2012

« Older Lose weight fast!   |   how do normal people enter the freeway? Newer »
This thread is closed to new comments.