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A Mechanic's Life - Tales From Under the Hood

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  • xwesxxwesx Fairbanks, AlaskaPosts: 8,267
    I'm certainly interested in knowing what the issue was with the Lincoln and how you went about hunting it down. I've had a couple of vehicles with electrical gremlins that created hard or no start situations in the past. Neither were correctly diagnosed by multiple shops (nothing's more frustrating than spending money on having other people say, essentially, "I don't know"), though both were ultimately fixed. One was fixed as the result of another failure (or further failure of same part... I'll never know...), and the other was fixed by a flipper who had dealt with the same issue on many other of the same model vehicle.

    In both cases, the vehicles were not getting fuel as the result of a circuit called the "automatic shutdown." The problem was determining why that circuit was open when it should have been closed. And no, neither online searches, literature, nor certified mechanics could get it fully right (or agree). :sick:

    In the first case, a '96 Outback, the car's knock sensor failed eventually, with a code in the system also indicating intermittent faults on the cam sensor, so I replaced the knock, cam and crank sensors together (it had somewhere around 175K on it at that point). After that, no more no-starting issues for the rest of the car's life. The problem is that I'd had trouble with the no-starts since I bought it at 83K! :sick:

    In the second case, a '98 Dodge Grand Caravan, the issue was a ground fault. The problem for me was that it was momentary, so I never found anything to be out of spec with the limited testing equipment I have, yet it was enough to set open the ASD relay when the car was turned on once in a while.
  • thecardoc3thecardoc3 Posts: 1,521
    Well, if it’s not trying to fire at all, my guess would be no spark or fuel.

    Excellent, and you would be correct.


    If you have both of those, then it should least try to do something.


    Most of the time, and that of course is one of the keys that require techs to not only have the high tech tools, but that learned seat of the pants feel when it comes to doing diagnostics. That's why it takes decades to learn to be good at it.

    So I would first check to see if I have spark, then see if I’m getting fuel to the fuel rails (weak fuel pump?).

    "Hint....The car starts sometime after the fuel pressure rises".
  • thecardoc3thecardoc3 Posts: 1,521
    edited November 2012
    Neither were correctly diagnosed by multiple shops (nothing's more frustrating than spending money on having other people say, essentially, "I don't know"),

    I can think of something far more frustrating. Imagine spending a lot of time to correctly and succesfully analyze either of those issues, and not get paid for it. It happened to me so often in the past that the only solution was to quit working for other people who didn't understand nor respect what it genuinely takes to diagnose some problems. In a way, I'm taking that very same problem to task with this part of this thread.

    though both were ultimately fixed. One was fixed as the result of another failure (or further failure of same part... I'll never know...), and the other was fixed by a flipper who had dealt with the same issue on many other of the same model vehicle

    What's a flipper?

    Today it's common to have to troubleshoot issues that we have never seen before and may never see a second time in our careers. That's one of the biggest failures with the idea of google diagnostics. Sure there are pattern failures, but relying on them is a trap that inexperienced techs often fall into. Just because there is a known issue or TSB for a given symptom you're doomed to fail eventually if you don't know how to test and prove that the failure is related to the one described in a given TSB.

    In both cases, the vehicles were not getting fuel as the result of a circuit called the "automatic shutdown."

    When I am teaching diagnostics I stress that it is important to understand a circuits operation in order to effectively troubleshoot a problem. When it comes to intermittent failures, you have to pre-plan a lot of your testing.
    The ASD or "Auto Shutdown Relay" is Chryslers way of shutting down the fuel pump and a few other systems when the engine isn't running. It's convenient for them to interrupt not only the fuel pump but a number of opther circuits to reduce the load on the battery when the engine isn't running. Needless to say if you lose the command for the ASD, or the output from it the engine is going to stall because you just lost your fuel pump power, power to the ignition system and the injectors to name a few. The PCM only needs to see the crankshaft position sensor signal to command the ASD on. The PCM at key on will turn the ASD on to run the fuel pump for two seconds as well as perform a circuit check on the igniton coil circuits and the injectors etc.

    Armed with that information testing needs to be done to prove if the reason you are losing the ASD output is because the PCM stops providing the ground control for it, or if the command circuit fails open. Plus testing needs to be done to prove if the supply power to the controlled side is lost when the circuit fails.

    There is a little more to it, but this is the short version for how it would be approached. Then it's a waiting game to get it to act up. Each time it is then driven I would also be monitoring a scan tool so that I could watch and see if the PCM is recieving the crank sensor signal, as well as see if the PCM is commanding the ASD to be on or not.

    In the first case, a '96 Outback, the car's knock sensor failed eventually, with a code in the system also indicating intermittent faults on the cam sensor, so I replaced the knock, cam and crank sensors together (it had somewhere around 175K on it at that point). After that, no more no-starting issues for the rest of the car's life. The problem is that I'd had trouble with the no-starts since I bought it at 83K!

    While the base strategy is similar, Subaru uses a PCM relay and a circuit opening relay (fuel pump). The knock sensor failure would easily be a known failure that could be googled, or diagnosed with following the regular trouble tree in service information. It had nothing to do with the engine stalling. From there you simply "got lucky with the crank/cam sensor replacements. A DSO (digital storage oscilloscope) would have been a valuable asset towards proving what the failure was.

    The problem with getting lucky is that you don't have any proof that you made a difference other than it simply hasn't acted up yet. If the car quits for any reason after that even if you did in fact fix it, as far as the customer is concerned it's still doing the same thing, you didn't know what you were doing and you failed to "fix" it.

    In the second case, a '98 Dodge Grand Caravan, the issue was a ground fault. The problem for me was that it was momentary, so I never found anything to be out of spec with the limited testing equipment I have, yet it was enough to set open the ASD relay when the car was turned on once in a while.

    By planning and presetting your test points and having the right equipment at your disposal this would be a very easy diagnosis, the first time that you experience one of these or the tenth time.
  • xwesxxwesx Fairbanks, AlaskaPosts: 8,267
    edited November 2012
    That's a heck of a response, Doc!

    Let me see if I can hit the pertinent areas for mine.

    Okay, so first, "flipper." That's someone who buys a car cheap, fixes it, and sells it for profit.

    I stress that it is important to understand a circuits operation in order to effectively troubleshoot a problem.
    And, therein was (and is) the root of my limitations when hunting down electrical gremlins. Without a circuit schematic and the training to understand it, one cannot possibly test thoroughly. Mine are pretty simple: This should be getting power, with this voltage, or that resistance across these points... is it? Yes. Okay. No, okay... what does that mean... ?

    I can entirely understand your frustration of not getting paid for diagnosing something correctly. personally, I would have much rather taken that $350-400 I spent on nothing when my Outback first started acting up and put that toward a higher-in-the-end bill that resulted in a fully working car than having spent that money in vain.

    With the Subaru, the problem I was fixing was more immediate: The car was running like crap due to no feedback (or bad feedback?) from the knock sensor. So, replacing the sensors was to get it to run well again. The no-start situation wasn't even on my mind, as I had learned to live with that long before. It wasn't until a month or two later, when I had yet to be stranded by the car while running errands, that I even started thinking, "wow, could it be that the August repair fixed this problem, too?!" I had the car to 220,000 miles (another 2+ years after that), and not once did I have a no-start after that. Before that, it would act up at least weekly, more often daily (or even more frequent).

    With the van, I was dealing with multiple issues but didn't know it initially. The first problem was a fuel pump. I pinpointed that and replaced it, then the van was perfect again. The problem is, it stranded my wife (and our children) in a very awkward place, and she is not quick to forgive such things. So, after I fixed the fuel pump, she reluctantly took ownership of the van again (willing to give it a second chance). Then, two weeks later, this no-start thing begins. She says, "that's it, I'm done. I want a new car." *sigh*

    She got her new car, which meant I then had no use for the van. I half-heartedly attempted to sort out the problem, but finally decided it wasn't worth my time and sold it to the flipper for a grand, who fixed the ground fault and sold it for $2,200 the next weekend. We both made out fine on that one, and I still see it tooling around town 2.5 years later! That's pretty good, considering it had 214,000 miles on it when I sold it.

    ----

    I'd love to send my son to your shop for an apprenticeship just to watch you work. I bet he'd find the whole process fascinating.
  • Stever@EdmundsStever@Edmunds YooperlandPosts: 38,919
    Doc needs to hook up a live cam in his shop with a good mic so we can tune in anytime during working hours and admire his handiwork.
  • explorerx4explorerx4 Central CTPosts: 9,444
    At first I was thinking leaky fuel injectors, but you didn't mention an expensive fix, so that's out.
    How about a clogged fuel filter?
  • thecardoc3thecardoc3 Posts: 1,521
    Honest, hard work doesn't make a good reality show. On the other hand, train wrecks do. You won't find what we do as being able to garner much interest.
  • thecardoc3thecardoc3 Posts: 1,521
    At first I was thinking leaky fuel injectors, but you didn't mention an expensive fix, so that's out.

    With the fuel pressure dropping after the pump turns off, that would be possible, but its easy to prove/disprove. The engine would be flooded (too rich) and holding your foot to the floor would interrupt injection command and that would allow the fuel mixture to lean out until the engine manages to start. It would be labored and missfiring at first and then clear up with a few throttle snaps. This car is not doing that.

    How about a clogged fuel filter?

    A clogged fuel filter is detectable by first watching fuel trims under heavy throttle load until you get such a throttle load that the computer commands an open loop acceleration, and then you simply need to watch the O2 sensors. If the O2 sensor voltages stay high, you're getting enough fuel. A clogged filter will cause a starvation for fuel when the engine is demanding the greatest amount of fuel per second. It is common to see fuel trims having to add a lot of fuel in both the long and short term corrections when the engine is under a load. When the engine is not under a load and fuel demand is light, the fuel trims don't need to correct as much. Watching that change in the trims makes the diagnosis easy.

    This is neither a clogged filter nor leaking injectors. Leaking injectors would cause fuel trims to need to subtract fuel at low load conditon such as at idle in park/neutral, and the fuel trims would be closer to normal the higher the engine load becomes.
  • thecardoc3thecardoc3 Posts: 1,521
    I'd love to send my son to your shop for an apprenticeship just to watch you work. I bet he'd find the whole process fascinating.

    Thanks. When I step in front of a group of techs as an instructor, I try to "bring them into the shop" to learn the routines that help me get through the day. Trying to watch me work though wouldn't be as interesting. To try and show what I am doing, while I work, leaves me splitting my concentration and has proven at times to be a very significant challenge. When I write a class I normally am collecting scope and scan data on one of my laptops, then I have to go back and take the photographs as a re-enactment of the process after the diagnosis has been completed.

    The lady with the Durango that I diagnosed is supposed to pay for the diagnostics and tow the truck out. She doesn't have the 2K that it would take to repair it. That being said, where is she coming up with the 30K to replace it?
  • xwesxxwesx Fairbanks, AlaskaPosts: 8,267
    She doesn't have the 2K that it would take to repair it. That being said, where is she coming up with the 30K to replace it?

    That doesn't seem to be an uncommon mindset, unfortunately. It's no big deal to go out and get a loan to buy a car, but $2,000 out of pocket? No can do.

    Twice in the past I have "loaned" family members funds for an emergency auto repair, complete with generous repayment schedules, etc., and neither time did I ever see a penny from it. While I haven't held it against either of them, neither have they asked me for anything since then. At $1,200 each, maybe I won on those deals after all? :shades:
  • xwesxxwesx Fairbanks, AlaskaPosts: 8,267
    So, getting back to the Fusion, I think you said that the problem your customer had was not related to the P2111 code she was convinced was the problem, but instead due to her vehicle running off battery and draining down, correct? You also mentioned that the system was charging correctly after you charged the battery.

    So, why did it drain in the first place? Was it somehow related to the 8-mile commute, since you did mention that? Or, the - nevermind. My wife is interrupting me and destroying my concentration. :mad:
  • thecardoc3thecardoc3 Posts: 1,521
    edited November 2012
    At $1,200 each, maybe I won on those deals after all?

    I have only ever sold one "used" car and that one I never really owned, or at least used. I got it because of a random stalling issue that the owner simply didn't want to deal with and once I got to figure it out and fix it a friend needed a car and asked for it. He paid for the repair and enjoyed the car for a year. Then passed it onto his son-in-law who had it for another year, who gave it to a friend who crashed it.

    Other than that one, I have given away every other car that I no longer had use for. There was never anything wrong with them as you can figure they get maintained to the max. I have a neice who will be getting her license in another year. I already know what car I will be giving her.
  • thecardoc3thecardoc3 Posts: 1,521
    So, why did it drain in the first place? Was it somehow related to the 8-mile commute, since you did mention that?

    Yes.

    So, getting back to the Fusion, I think you said that the problem your customer had was not related to the P2111 code she was convinced was the problem

    The stalling was not related to the P2111, however she does in fact have an issue with the throttle body. Keep in mind the car is not repaired unless all of the issues are dealt with.

    Now I'll give you one that will be really tough to swallow. The P2111 is basically caused by oil changes that used products that even though they were 5W20, don't actually meet the demands of the engin, or Fords specification.
  • in the past I have "loaned" family members funds

    Ah... otherwise known as a "gift".. ;)

    Moderator - Prices Paid, Lease Questions, SUVs

  • roadburnerroadburner Posts: 6,011
    edited November 2012
    That doesn't seem to be an uncommon mindset, unfortunately. It's no big deal to go out and get a loan to buy a car, but $2,000 out of pocket? No can do.

    I hear that all the time; "I need a new car because__________"
    Fill in the blank:
    "I need a car that gets better gas mileage"
    "my car is old and things will start breaking"
    "I can't afford to keep my old one running"

    I once calculated that if I bought a car for $10,000(cash, no loan) plus my trade and the new car returned 16 more mpg than my old car it would take 7.5 years to break even- and that was assuming I drove 20,000 miles per year with a gas cost of $5.00 per gallon. Less annual mileage and cheaper fuel would move the break even point even further down the road...

    The lady in the Durango may not be thinking that way, but 99% of the time "I NEED a new car." can be translated: "I'm bored and want something new."

    2009 328i / 2004 X3 2.5/ 1995 318ti Club Sport/ 1975 2002A/ 2007 Mazdaspeed 3/ 1999 Wrangler/ 1996 Speed Triple Challenge Cup Replica

  • Stever@EdmundsStever@Edmunds YooperlandPosts: 38,919
    neither time did I ever see a penny from it. While I haven't held it against either of them, neither have they asked me for anything since then.

    If you get paid back be very careful. That just means they are going to hit you up in a few weeks for something even bigger.
  • explorerx4explorerx4 Central CTPosts: 9,444
    Congrats, you got yourself a nice little graphic on the main Car Forums page!
  • thecardoc3thecardoc3 Posts: 1,521
    The Fusion. The main problem is all of the accessories draw some 140 amps of current, the alternator can produce 120amps as long as the engine is at or over 2000 rpm. Her communte has her "in town" for some 60% of her trip and the battery has to supplement the alternator's output when she is stopped in traffic. Over time this pulls the battery into a low state of charge because she simply doesn't drive it on the highway enough without all of the accessories on to ever allow the alternator to re-charge the battery fully, so the battery slowly sulfates and eventually dies. The car stalled because of the throttle plate sticking in the bore due to varnishes built up in it from the PCV gasses, and some reversion due to late intake valve timing under high efficiency mode. Once it stalled, the battery was simply too dead to allow it to start up and run on that morning. It had to have a new throttle body, and a software update for the PCM.

    The Lincoln. This car fired right up the moment it had fuel pressure. During cranking the first thing that I found was the battery voltage dropped to 3-4v for an instant and then the engine cranked just fine, at 7.5v. At 7.5v the voltage was too low for the PCM to be turned on and command the fuel pump to run, that could leave you crank the engine until the battery was completely dead and it would never start. Charging the battery helped but it still tested as marginal and needed replaced but that wasn't the only issue. The batteries state was aggravated by the fact that the fuel pressure would drop as soon as the car was shut off. Fuel pumps have a check valve in them to hold pressure on the fuel rail and lines and this one has to be leaking. (that or maybe the hose that connects the pump to the fuel sender is leaking) Either way the longer the car was turned off, the longer it would take to prime the fuel system and get it to deliver fuel to the engine. If your cranking it the whole time you could be cranking it for five to ten seconds. If you didn't want to do that, by cycling the key on for two seconds, off, then on for two seconds would cycle the pump and the engine would fire up normally. The shop that sent the car over is going to service the fuel pump.

    The check engine light on the Lincoln was an evaporative emissions leak and testing showed that the hoses and fittings that connect the cannisters at the rear of the car need replaced.
  • thecardoc3thecardoc3 Posts: 1,521
    That's pretty neat. It might get busier here now.
  • xwesxxwesx Fairbanks, AlaskaPosts: 8,267
    edited December 2012
    Dang. That's an impressively complicated set of conditions for both cars, but especially so for the Lincoln! The leak aside, it seems almost counter-intuitive that the battery would be weak given its ability to crank the engine for extended periods trying to get the thing to start.

    I'm a little bummed that I didn't get a chance to respond on the Fusion's issue. I was thinking along the lines of the over-draw, but did not at all connect the throttle body issue to the no-start. I was thinking it was the charge issue that was causing the stall, which was throwing me off since you said the system was charging properly. I'm curious why the throttle body required replacement vs. cleaning if it was a varnish issue. And, what was it in the oil that would be out of spec to cause such varnish in the first place?

    Finally, how does one determine what the overall amperage load on a vehicle is? I'm having an issue with my 2010 Subaru Forester right now (over the last year) in that it doesn't fully charge it's battery. Over the course of a few months, it gets to the point where I have to hook a charger up to the battery to fully charge it in order for the vehicle to reliably start for a few more months. While running, the voltage at the terminals is 14.4-14.6. The same symptoms persist regardless of the battery in the vehicle... batteries that work fine in other rigs, including my plow truck (which demands some major current and is used infrequently, at low speeds, and for short periods of time).

    I was thinking it must be something to do with the charging system, but I cannot catch it behaving out of spec. The dealership was no help when I took it there last winter, as they simply told me the problem was due to my not having a heater on the battery for winter use. I explained to them that I don't use battery heaters on any vehicle, and have no problem with any of them (for years and years, including several other Subarus), but my request to actually investigate my concern fell on deaf ears.

    Dealerships love battery heaters here, but my experience is that they only do a great job of nursing weak batteries so when you have to start the vehicle without the luxury of electrical access nearby, you end up stranded. :sick:
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