Hard learned lessons

Chris from Commack Diagnostician Posted   Latest  
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We all get our butt handed to ourselves from time to time. For some of us, like me, it happens more than we like to admit. This isn't always a bad thing. We can use these horrible, horrible experiences as a learning opportunity. Most times, these failures can be our greatest teachers.

Early in my diagnostic career, I was working on a crank/no start on a Wrangler. I took the vehicle over from my fellow tech who got in over his head. I questioned him on what he did and where he was in the diagnosis. He said he checked powers, grounds, fuses, and a visual on the wiring. This was a long time ago and I do not remember all the specifics. I do however remember that the pcm was not turning on the coil. 

I determined that this truck needed a new pcm. I called the dealer, bought one and had it bench programmed. Installed the computer, and nothing. Same symptom. I got that horrible feeling in my stomach when a misdiagnosis happens. 

I decided to start from scratch. One of the first things I learned as a mechanic, was to check EVERY fuse when there was an issue. I pulled out my handy-dandy test light and got started. I immediately found a blown fuse. I replaced it and the truck fired right up!! I went over to the tech and said "I thought you told me you checked the fuses!!". He replied, "umm, sorry?"

I learned an expensive lesson at that point: Treat every vehicle as a new vehicle. Always start with the basics. I kept that pcm on the shelf where I could see it as a reminder. 

How about you? Which lessons did you learn the hard way? I'm looking forward to your stories.

+13

Bob from East Longmeadow

 

Diagnostician
 

Nope, don't know what you're talking about. Never happened to me.....................

OK, just kidding, I've had my ass handed to me more than I would like to admit also. It's usually something really stupid simple that I missed because I was rushed and tried to shortcut things. 

One that I will always remember from years ago was a door diagnoses. It wouldn't open from the inside so I figured it must have some kind of handle or linkage problem. It was only after removing the door panel that I realized the child safety lock was engaged. Felt pretty stupid that day. 

+2

Martin from Burnaby

 

Instructor
 

Don't feel too bad Bob. One day at the dealership some years ago, I was asked to fix the non-functioning DRL lamps on a white Chevy Impala parked out in the service driveway.

So, I hopped in, drove it into the shop and started checking the lights, but found nothing wrong.

That was about the same time the service writer arrived to tell me I'd got the wrong car. Another SA had moved the car I was supposed to work on and another identical Impala had arrived and taken its place!

+1

Chris from Commack

 

Diagnostician
 

That’s the best way to learn all about child locks!

+1

Martin from Burnaby

   

Instructor
   

Okay Chris. I'll "bite" and "play".

I'd like to say that "In the past 50 years I've never screwed up." Yeah, I'd like to say it, but that would be total BS. If there are any technicians out there claiming to never having had a FUBAR, either in a repair procedure or a diagnosis, then then haven't done anything!

I'll start off with a couple of mine from the 1970s. It's funny how we can recall (or maybe its just me?) where we were, when it was and exactly what the vehicle was, right down to the colour, when stuff didn't go quite according to plan and we got our butts handed to us!

# 1. In 1975 I worked in an independently owned Esso station at 25th and Kingsway ("St. Catharines Esso"), for an owner who also operated the used car lot next door, "Small Car Specialists".

Anyway, I was in the process of reassembling a Datsun 1200 engine from a blue 2 door coupe from the car lot. All was going well and the block was sitting on a low work bench. I had positioned the head gasket on the block to ensure that I had the orientation correct and then set it down on the bench while I went out to pump some gas.

When I returned, I put the head gasket back on the block, installed the head, adjusted the valves, put the "lid" back on it and installed the engine back into the car. A self-induced problem soon made itself evident, just after I started putting coolant into the radiator. The next thing I saw, was green coolant pouring out at the head to block interface. I'd installed the gasket upside down!

#2. This one is from 1979. I worked in a Gulf Station/Service facility and was working on a Toyota 4M engine for one of my neighbours, who was a customer. This was another engine rebuild in process. So, late on the Friday afternoon I'd got the re-bored 6 cylinder block on the bench with crank and bearings all in place, with piston and rods assembled, ready to be installed. These were correctly oriented on the bench top. Since it was my neighbour's car, I'd agreed to work on the Saturday to finish the build and installation, as she needed the car for work on Monday morning.

So, with the engine re-assembled and back in the vehicle and primed, it was time to fire it up. The engine started and ran smoothly, but with a clicking noise in the top end at idle. I was a bit puzzled at the noise since I'd thought that I'd been very careful about orientation of the components the night before and the reassembly process. So, off came the cylinder head to expose all 6 pistons installed backwards! The result had been a very slight contact in the valve relief on the pistons. Off came the pan, rod caps removed and the crank rotated to allow each rod to rotate 180 degrees in the bore. When re-assembled and re-fired, all was fine. She drove that vehicle for many more years without incident.

Discussing this with my boss on the Monday morning, he alluded to the fact that the "clean up kid" had moved everything from the bench top when he was cleaning and put it back afterwards. It turned out that he'd put the piston and rod assemblies back on the bench the wrong way around!

Now, from both of these situations, I learned never to trust others around my work and to always double check during disassembly and re-assembly.

Ultimately I owned and was fully responsible for both of the mistakes above. There was nobody to blame but myself for not double-checking.

It almost goes without saying that many of us have been supplied with incorrect components that at a glance had appeared to be correct, but that after the fact didn't fit properly or function correctly. Subsequent investigation revealed a wrong component installation! How can that be???? Sure, the parts department will get you the correct part, but who is responsible for the lost time and any resulting damage? We, the installing technicians, who should have more closely inspected the component before installation! Sometimes the hardest learned lessons are the most valuable ones!

So, there are sometimes circumstances where we own the FUBAR, but also times when it resulted from a sublet repair and the issue was not readily visible. In this instance, I was in the process of replacing a blown head gasket on a Toyota 2M engine in a 1969 Crown and had sent the cylinder out to a local machine shop for repair. When I reassembled the engine, it had a light knocking noise at the front end of the block.

Subsequent removal of the cylinder head revealed light piston contact at cylinder # 1. Since there had been no noise prior to the sublet repair, the head was sent back out for inspection. The result was that the machinist had created a 0.065" taper on the head! "No, I will not double gasket the engine", was my response when the machine shop manager tried to weasel out of their error!

Now, I've been very fortunate to have not had any major FUBARS over the years. Perhaps, as a result of mistakes I had made early on, I became extremely detail oriented. I learn from any mistakes such as a diagnosis that didn't go well, by reviewing the path that I'd taken and consider how I would approach the same diagnosis the next time.

In classes, if my students mess up, they own it and get to fix it. However, if they can recover from their FUBAR and learn from that experience, they may have actually learned more from having made a mistake than the original repair or diagnosis! Now, if I could only get my hands on the tech who used 0.64 probes when testing Nano 50 terminals last week! ........Grrr.

+3

John from Morgantown

 

Technician
 

I had a 2008 Chevy express van land in my bay last week from a fellow tech in my shop. Complaint was a crank no start, and a fuel pump relay control DTC. Tech before me replaced the fuel pump as he had no fuel pressure. So I go through checked the fuse for the pump, key on it had 3v. Okay that’s strange. The fuse is after the relay in the circuit. So I pull the relay out, still 3v at the fuse. I scratched my head, rechecked the fuse about 20 more times thinking, “What the hell is going on here?”. During cranking the fuse would have battery voltage, but just key on it would have a constant 3v. So I went to the fuel pumps ground (was trying to avoid dropping the tank) and there was 3v on the ground side. Okay now it’s coming together, checked another ground about 2 feet up the frame, 3v again. So I started checking every ground looking for crustys and I finally found it. Turns out a bad engine ground was backfeeding 3V through the entire ground circuit. Took me almost a whole day to finally find the issue. Definitely one I won’t forget.

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Andrew from De Motte

 

Technician
 

Had a G-van that would run on the rack but not on all 4 wheels because of this one time... took me a while to figure it out. Ground from engine to frame was bad, somehow it would pull just enough when on the rack and start. I have noticed this on many others since.

+1

Martin from Burnaby

 

Instructor
 

Speaking of the rack making a difference Andrew. I was doing NVH course with the PicoScope with my class using an '07 Silverado two years ago and again last year, All was fine for the first 7 pairs of students in both classes doing the run ups and when the 8th pair of students ran the truck up to the worst vibration amplitude, the PRNDL and VSS dropped out.

They did all sorts of diagnostics by the book that pointed to a TCM issue. I told the last pair of students not to chase the ghost and sure enough, when the tires touched the ground and the vehicle was started and driven out of the bay, the PRNDL and speedo returned. Go figure.

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Pj from Pleasant Hills

 

Technician
 

I had this exact thing happen to me, on this exact vehicle. I seen about 6 volts at the fuse, so I thought I was losing 6 volts from corrosion. What I didn't realize was there was 6 volts running through the body of the vehicle (where I had my multi meter grounded) and 12 volts at the fuse. But with how multi meters work, it was displaying 6 volts.

I for sure learned about testing my grounds first

+1

Andrew from De Motte

 

Technician
 

Early 2000's Saturn L300. Had the 3.0 motor in it. Came in for a t-belt. I somehow forgot to lock the tensioner and took it on a nice long test drive. On my way back to shop it jumped time. Bent every valve. Send heads out have it repaired, then I learn about head gaskets. They are different side to side, somehow I flipped them around. Car ran for about 45 seconds then.... I break the cam shafts. That car ate my lunch I was about 3-4 years into my career at that point. I got really lucky the owner of the shop was really cool and let me keep my job. I learned after this one the importance of proper tools and double and triple checking yourself. I was so close to walking away from auto repair after that. My ego was bruised, I had a few guys in the shop give me hell for years.

+1

Andrew from Commack

 

Technician
 

I had a similar experience - I was working on a very old Land Rover and the customer was determined to drive it across the country to California but it had a no-start problem. I think I couldn't talk to the ECM. I checked everything twice and I couldn't find the ignition on power feed. The windshield had been resealed and water had leaked into the car.

The customer wanted to drive the thing out so he threw an ECM at it while I scratched my head. Then I found it, the 15 input in the schematics. So simple, how did I overlook it blindly time and again? But why doesn't it have power? All the fuses were good, I checked.

No, seriously, all the fuses were good. None blown, all had B+ voltage on both pins and all would light my 1/2 amp test light brightly though the test light would not light at the ECM connector.

The female terminals of the fuse box were corroded by water that leaked into the dash from the windshield seal

One simplistic oversight and one complicated one...

+1

Sean from Cincinnati

 

Technician
 

I also learned early on to treat every car as no one has looked at it, customer said they had checked all fuses all on and passenger window still inop went down now stuck, me being all gung ho rip the door panel off motor works fine. Switch inop, go to master switch to be sure notice the window lock was on. 

+1

Greg from Wilmington

 

Manager
 

As a tech for …'s Auto Care i have abandoned the test light a use a meter and halogen bulb for testing and loading circuits. We just had a 2008 Cobalt with a no crank, no security light, multiple codes in the theft deterrent module etc. 

I was bouncing back and forth while working on another car and helping a fellow tech on it. this originally had an auto start installed and was removed by the dealer which sad to say hacked the hell out of the harness. after finding a cut wire from the BCM that feeds voltage to the instrument cluster we now had a working security light. cleared the codes and they did not return, still no crank, keys were recognized and by all accounts the car should have started. found that PCM was on;y supplying 2.5 volts to the crank relay coil control side. had the tech check power and grounds and supposedly all good. this morning I had him go back out and check the transmission readings to see if it was seeing the car in park and it was but the kicker is when he went to attempt to cycle the crank relay it said car must be in park. 

I had him remove the TCM connector and probe the wire that runs to the gear position sensor and was showing open, odd because it sees it in park. after pulling on the harness I lost communication to the TCM located the ground which had about 8 grounds on 1 eyelet, typical GM! several were frayed, after repairing and separating the wires into groups of 3 the car started and all was good. 

This business can be so rewarding and frustrating in so many ways, its great to have repaired the vehicle and gain some knowledge on each individual system and in the future use that to make a quicker decision on diaging and solutions to a quick repair.

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