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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
Posted to sci.electronics.repair
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I really don't know the subject, but this is on topic
This regurgitated to the top of my mind today, and started an
argument, because I was interrupted, which derailed my train of thought. This has to do with quite a while ago when I did alot more car work. Generally I did not change brakes and stuff like that, I was more of a diagnostician. Well now I work on bigscreens, and only troubleshoot cars when it is really bad, when all other avenues have been exhausted. One guy, even Mr Goodwrench told him to change the engine. I found the problem, and it was not the whole engine. Anyway, after gong through the hoops the pickup comes to me for diagnostic. Nissan, in the 80s, four cylinder. Now this guy is my ex lawyer. I mean he was MY ex lawyer, so he had money. He was very pleased with the truck and wanted to keep it. It had been around and noboby found the cause of the problem. I and my cohorts did. Now we all know how fun it is to follow work after someone else in electronics, but read on and picture this. The light argument at my house tonight was about me getting interrupted, because my mechanic was here and I wanted him to hear this. So bear with me, I intend to be complete and precise. The symptom is, every once in a while, at almost random intervals the thing would start running very bad, to where you can't drive. This happened on the freeway, anywhere. There was no correlation expressed to me about temperature or miles driven, in fact IIRC they told me that it was almost independent of those factors. I was not talking to dummies, they know things. But they ran out of ideas and I am sure I am at least the fifth or sixth person to try to tackle this. This was years ago. But it came up, so I thought I would bring it up. We had to drive it around a little bit to get it to act up. Sputterin and spitzen on two cylinders. Now I have been in the game for a long time, but I tried initially eliminate possible electrical causes. Spark, fuel delivery all that, I basically rechecked, but alot of people know that drill. My buddy was running the job. We were baffled at first but just, as usual found out all the things it is NOT. He had the logical mind, but this even befuddled him. I think he was getting close, but he called me. He knew I know the guy, and just, it was time. After making sure the engine had everything it needed to run, the focus becomes the engine. But what kind of mechanical problem could be intermittent ? OK, a stuck valve or something, but that would only affect one cylinder. For a time we were thinking some kind of anti- pollution device. But this thing still did it with any of them disabled. Illegal to drive ? Screw that, we needed to, to find the problem. Well it took a few beers, but it happened. We were sitting there bull****ting and started talking about it, my buddy said "Why does it sound to me like it is out of time ? Everything else is there, my gut says it is out of time" (that is not verbatim). I said "More than that, it sounds to me just like when someone gets the distributor off 180 degrees after they reassemble an engine, like a headgasket job, we have all had it happen, there is a 50 50 chance". He and I got to the point where we were thinking that the cam timing was off, and since it had a computer, it compensated, so it was only when certain parameters existed, that the computer couldn't compensate, thus the problem. Having nowhere else to go we physically checked the cam timing. It was about 10 degrees off. AHA ! we thought. But the timing belt had just been changed several months or possibly a year ago. He looks, sees no damage, pretty much a perfect installation, or so we thought. At first of course to check this you tap the starter until it is real close, and a norrmally strong Man can turn it a bit to line everything up. Well the starter went a little bit past the datum place, so it is time to turn it back a hair. I don't know the exact sequence of events, because there were a few of us brainstorming this. But what happened to cause the revelation was that this is a stickshift. When the wrench went on the crank, you would need someone to put it in neutral, or hold down the clutch pedal. Otherwise the truck moves. He said it didn't feel right, that damper was really hard to get off the shaft. We found out the reason. This may be a theory, but it is damn solid, in fact I would stake my reputation on it. Remember the timing belt was replaced ? They lost the original METRIC key that goes on the crank to align the gear. They replaced it with a readily available ENGLISH key, that was a few thousandths of an inch smaller. I wish I had pictures. Now understand, the bottom timing pulley is an integral part of the damper. That means that for those months, every time a cylinder fired in that engine, it was moving. It dug an egress sort of from the keyway, in one direction of course, and then sheared, but not nicely. Once sheared, the metal fragments smooshed between the shaft and bore were solid enough to run for awhile. They held good for many many cross state runs, all kinds of driving. But it would do this, and it got more frequent. Go figure. That mis-sized key pounded that crank pretty bad. My Dad was involved, I called him in once we figured this out. He recommended that we rent the proper stuff and regrind the crank, put the right size key in it and just retime it accordingly. I know it can be done, but it is a big PITA, and this truck really is no gem. So my buddy decides, after we obtained the really correct size pin, to braze it in. This was discussed. With other option. which included removing the crank for remachining, or anything like that, the value of the vehicle did not warrant it. So we brazed the key in. Timing marks were as per original (and stayed that way now), but the problem is that this seriously complicates changing the front oil seal. After figuring this out, we decided that an old, working seal that is a bit work hardened would be better able to take the heat. After thinking about it I agree. New rubbery ones could make a mess where old leathery ones would just be fine. We figured if we ever had to do the front seal, we would just burn that bridge when we came to it. But it was good, nothing leaked. He said something like "I got real acetylene here". And that's what it took. But two things come to mind. In his thing (dunno what to call it) all he has to do it make a piece of metal that fills in the gaps, he doesn't really need a bond. Just a filler. As long as it doesn't move. That is all that is required. Actually the key was off about three degrees from line bore, I told them to just force it on. Future work would requires a puller. It has been fine ever since. I think it must have ½ million miles on it by now. So basically, if you are as ecstatic as I am about folliwing someone else into something, at least you know it hppens in other fields as well. In spades. JURB |
#2
Posted to sci.electronics.repair
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I really don't know the subject, but this is on topic
wrote in message oups.com... This regurgitated to the top of my mind today, and started an argument, because I was interrupted, which derailed my train of thought. This has to do with quite a while ago when I did alot more car work. Generally I did not change brakes and stuff like that, I was more of a diagnostician. Well now I work on bigscreens, and only troubleshoot cars when it is really bad, when all other avenues have been exhausted. One guy, even Mr Goodwrench told him to change the engine. I found the problem, and it was not the whole engine. Anyway, after gong through the hoops the pickup comes to me for diagnostic. Nissan, in the 80s, four cylinder. Now this guy is my ex lawyer. I mean he was MY ex lawyer, so he had money. He was very pleased with the truck and wanted to keep it. It had been around and noboby found the cause of the problem. I and my cohorts did. Now we all know how fun it is to follow work after someone else in electronics, but read on and picture this. The light argument at my house tonight was about me getting interrupted, because my mechanic was here and I wanted him to hear this. So bear with me, I intend to be complete and precise. The symptom is, every once in a while, at almost random intervals the thing would start running very bad, to where you can't drive. This happened on the freeway, anywhere. There was no correlation expressed to me about temperature or miles driven, in fact IIRC they told me that it was almost independent of those factors. I was not talking to dummies, they know things. But they ran out of ideas and I am sure I am at least the fifth or sixth person to try to tackle this. This was years ago. But it came up, so I thought I would bring it up. We had to drive it around a little bit to get it to act up. Sputterin and spitzen on two cylinders. Now I have been in the game for a long time, but I tried initially eliminate possible electrical causes. Spark, fuel delivery all that, I basically rechecked, but alot of people know that drill. My buddy was running the job. We were baffled at first but just, as usual found out all the things it is NOT. He had the logical mind, but this even befuddled him. I think he was getting close, but he called me. He knew I know the guy, and just, it was time. After making sure the engine had everything it needed to run, the focus becomes the engine. But what kind of mechanical problem could be intermittent ? OK, a stuck valve or something, but that would only affect one cylinder. For a time we were thinking some kind of anti- pollution device. But this thing still did it with any of them disabled. Illegal to drive ? Screw that, we needed to, to find the problem. Well it took a few beers, but it happened. We were sitting there bull****ting and started talking about it, my buddy said "Why does it sound to me like it is out of time ? Everything else is there, my gut says it is out of time" (that is not verbatim). I said "More than that, it sounds to me just like when someone gets the distributor off 180 degrees after they reassemble an engine, like a headgasket job, we have all had it happen, there is a 50 50 chance". He and I got to the point where we were thinking that the cam timing was off, and since it had a computer, it compensated, so it was only when certain parameters existed, that the computer couldn't compensate, thus the problem. Having nowhere else to go we physically checked the cam timing. It was about 10 degrees off. AHA ! we thought. But the timing belt had just been changed several months or possibly a year ago. He looks, sees no damage, pretty much a perfect installation, or so we thought. At first of course to check this you tap the starter until it is real close, and a norrmally strong Man can turn it a bit to line everything up. Well the starter went a little bit past the datum place, so it is time to turn it back a hair. I don't know the exact sequence of events, because there were a few of us brainstorming this. But what happened to cause the revelation was that this is a stickshift. When the wrench went on the crank, you would need someone to put it in neutral, or hold down the clutch pedal. Otherwise the truck moves. He said it didn't feel right, that damper was really hard to get off the shaft. We found out the reason. This may be a theory, but it is damn solid, in fact I would stake my reputation on it. Remember the timing belt was replaced ? They lost the original METRIC key that goes on the crank to align the gear. They replaced it with a readily available ENGLISH key, that was a few thousandths of an inch smaller. I wish I had pictures. Now understand, the bottom timing pulley is an integral part of the damper. That means that for those months, every time a cylinder fired in that engine, it was moving. It dug an egress sort of from the keyway, in one direction of course, and then sheared, but not nicely. Once sheared, the metal fragments smooshed between the shaft and bore were solid enough to run for awhile. They held good for many many cross state runs, all kinds of driving. But it would do this, and it got more frequent. Go figure. That mis-sized key pounded that crank pretty bad. My Dad was involved, I called him in once we figured this out. He recommended that we rent the proper stuff and regrind the crank, put the right size key in it and just retime it accordingly. I know it can be done, but it is a big PITA, and this truck really is no gem. So my buddy decides, after we obtained the really correct size pin, to braze it in. This was discussed. With other option. which included removing the crank for remachining, or anything like that, the value of the vehicle did not warrant it. So we brazed the key in. Timing marks were as per original (and stayed that way now), but the problem is that this seriously complicates changing the front oil seal. After figuring this out, we decided that an old, working seal that is a bit work hardened would be better able to take the heat. After thinking about it I agree. New rubbery ones could make a mess where old leathery ones would just be fine. We figured if we ever had to do the front seal, we would just burn that bridge when we came to it. But it was good, nothing leaked. He said something like "I got real acetylene here". And that's what it took. But two things come to mind. In his thing (dunno what to call it) all he has to do it make a piece of metal that fills in the gaps, he doesn't really need a bond. Just a filler. As long as it doesn't move. That is all that is required. Actually the key was off about three degrees from line bore, I told them to just force it on. Future work would requires a puller. It has been fine ever since. I think it must have ½ million miles on it by now. So basically, if you are as ecstatic as I am about folliwing someone else into something, at least you know it hppens in other fields as well. In spades. JURB You're right. I hate working on stuff that someone else has butchered before me. I used to treat it as a real pride thing, and get to the bottom of the problem no matter what. A few years ago I made the concious decision that when you work for yourself, and need to put bread on the table, sometimes it just isn't worth the time wasted for the financial return, and the 5 boring laser replacement jobs that could have been done in the same time, are a better proposition. On cars for a moment, it's amazing how sometimes the real obvious can be missed. I had a problem with mine that went on for several months, and it went back to the shop 4 or 5 times in that period, until they relieved me of money for work to date, and gave up on it - imagine a customer's reaction if we tried that in the electronics game, but it seems to be the norm in the garage trade, at least here in the UK. It's only a little Ford Fiesta - not rocket science. It developed an idle problem, worse when warm. As you pulled up at a junction or whatever, it would drop back to correct 900 RPM idle, after a fashion, most times. But after 15 seconds exactly, the revs would drop right down, then pick back up leaving a very rough idle, but with the rev counter steady (!!) Occasionally, it would cut out when you dipped the clutch at an almost-stop to change down to do a rolling pull-out on a junction. Very dangerous. I explained it all carefully to the garage, and told them that it felt like something really simple like an air leak or something, that the ECU was doing its level best to compensate for. I knew I was on a loser when the guy smiled indulgently at me, and gave me that ' Yes sir, of course it is, now you just leave it to us ...' look. They read fault codes from the ECU ( so they said ), they replaced all sorts of expensive stuff like the MAF and IACV and IAT sensor - all stuff that can't be put back in the box and returned once it's used. It remained the same. Eventually, an amateur mechanic friend of mine volunteered to take a look. Within a few minutes, he found a half inch split in the underside of a hose in the PCV system. Admittedly, it wasn't an obvious spot, being located under the branches of the intake manifold, but it was the fact that from above, the hose looked hard and partially collapsed, that lead my friend to it. A replacement cured it in one. So just goes to show, that in any game, sometimes you can get overcomplicated with fault diagnosis, and miss the obvious stuff. Arfa |
#3
Posted to sci.electronics.repair
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I really don't know the subject, but this is on topic
Now that is interesting!
Whatever happened to that Pontiac you were troubleshooting? Did it ever get fixed? William |
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