Some Diagnosis.

[Motu]

Yeah,when the customer says ''don't worry about the ''*****'' that's been fully rebuilt'' - that's the first thing we look at,I'll bet my life on it!

I'm no auto electrician,far from it,I'm just a dumb mechanic.Like most mechanics we have ignored the electrical side of the game - we have mates in the trade who deal with that stuff.I have a problem with electronics and maths....maybe a left/right brain thing,as I'm left handed.I don't have an anylitical mind...I think I work in pictures and patterns.

As a little fulla in school we were learning subtraction - I had no idea what was going on,I hadn't understood a word the teacher said.We were given a line of sums to do and I just sat there looking at them...totaly clueless.I figured the next best thing to do was cheat,so checked out the girl next to me,and watched how she was doing it - ah,no worries,I got the idea pretty quick,I picked out the pattern straight away,something like 1,1,2,1,1,2,1,1,2,3 - so I raced through all the sums with that pattern,and got most wrong.More talking and more sums...so I applied the correct method,and got them all wrong! I checked the girl beside me again and picked up the new pattern - wrong again! In the 4th form maths was an optional subject,and I dropped it real quick! - phew!


By the early 90s cars were a whole new game,we bought $25,000 tune scopes,went on training courses and tried to force our fuddled brains to take on the new concepts...but it didn't work - the normal reaction from a mechanic to some electronic failure is to panic and try and pick the most complicated thing wrong...just throw parts at the car and hope you fix it.By the late 90s I was getting annoyed as I did as much on a car then sent if off to the experts,only to have them send it back with a list of ''possible'' faults I had already eliminated.Time to up my game.

With the new found internet as my university I applied myself to learning how these systems worked,making it make sense to my poorly educated brain.I got my Fluke 98,then later the Vantage,having dome my homework on what I needed - and they opened up a whole new world to me - electronics in pictures,and patterns.I don't have to know how a Hall Effect generator works or what it does,I just have to know it's place in the scheme of things,and know what sort of reading I should see on my scope.I just walk up to a car and plug into as many wires as I can get at,look at what I see and build up my mental library of waveforms,good and bad.I don't have to know the intracies of how the system works,just what each thing does and what it should look like - I keep my mind clear and just think about what effects what.

There are new systems out there now,I need to step up to the plate again - but I don't think I will,time for new challenges,not old ones revisited.

[Brian d marge]

Yup that was a good bit of mechanicing there Motu!
I was thinking about this thread last nite , and the funny thing is , Computer of no computer. 1901 clackhammer ..or 2007 F1 missile, It came down to spark/fuel/compression ..Same as its ever been . ( except you have that vantage , I am envious there !!!!)

just reading you last post , I found myself thinking nope I am opposite ...but for the same reasons. I also think in pictures, and in order to learn I need to see and do...Its no use untill I do both it just doesnt stick.

Maths ...Maths was black stocking and a young relief teacher ...I failed on both accounts ..It just didnt make sence.

But Electricity, for some reason its easy ...I just get a feeling and can see through the process ...... and because no one else knows about it they leave me alone ... I think it was when my tutor explained electrics as the same as a lazy student ..then I twigged

its a funny ole game, thanks for that bit of sharing , it was a good read and a good bit of Mechanicing

Did ya charge ...( bet you didnt !!!) ????


Stephen

[WINJA]

full credit , i love this sorta stuff

[2_SL0]

Christ I dont need to read this, its like a day at work. I do enjoy solving problems, especially when other people have looked and couldnt.

Nice write up Motu.
Fluke meter, one of my favs.

Went down a similar track, did all the courses etc, got all the software etc, but at the end of the day I spent a good number of hours, days working with the technology and understanding what did what and how it all intereacts. The laptop/pda is great. But they dont solve the problem I find I take the information they present and use it to track the real cause down. That might sound strange to someone who hasnt experienced Engine management programs, but those who have will understand. Often the software gives you a code of what is faulty, but you need to track down what has caused that item to become fautly or give the impression it is faulty.

[Motu]

So many mechanics are looking,hoping for the black box they plug into the computer and it tells them what's wrong and how to fix it - it doesn't exist,and is not needed,all that's necessary is an understanding of the systems and a basic scope or GDMM.I have a scanner,the Snap On brick is old and basic these days,and I just use it for a guide on what to look at.

Although I used it today to diagnose a stalling complaint on a Nissan Sunny,throttle body injection.It told me it had an air flow meter problem 2 key starts ago - I didn't even bother to check,I know it's right,because I knew it would say that....5 min diagnosis.

How to charge? that's always a hard one....I've wasted hours I never charged for not being able to find problems,I've spent hours training myself,paying for it...just the 3 meters I can hold altogether in one hand cost me $20,000...who pays for that????

Man,I get angry about people who bleat about how much mechanic's charge!!!

[F5 Dave]

. . .& the same people complain about what dentists charge as they sit in a 10 thousand dollar set & the drill set alone is $70,000 (my father was a dentist & to put these prices in context he retired 10 years ago & was probably 10 years before when he updated).

Just to run off on a tangent, he ran two surgeries so the patient could be set up by the nurse & ready to go when he’d finished the other, or if there was a process that needed to wait for a while. Of course it required twice as much gear + new gloves every time, but it was efficient & saved everybody chargeable time.

Problem was people only saw that they were in the seat what seemed like 5 min & “How much?” People never see the cost of the latest technology required or the price of consumables & specialise services.

[Motu]

Some more this week - on sunday I drove the son in laws '89 VN Commodore up to the workshop,running on 4 cyls and shaking like mad over 80kph.

First thing I did was put my low amp probe on the DSO and current ramp the coil pack.Checking voltages tells if a signal is being sent,but not if it's being acted upon - the current draw tells us what work is being done,it's called current ramping because of the shape of the waveform and is useful for checking ign coils,fuel pumps and fuel injectors.The Commodore VN is DIS (distributorless ignition system) and uses a 3 coil pack on top of the ign module,I just clamp the loom going to the module,and get the waveform in image one.The 3 double ended coils will get one signal each,we can see two higher ramps and one little bump...one coil isn't working,but suspect it's getting triggered to give the little bump.I clamp my cordless timing light on the wires and it's obvious the top coil isn't working - 5 minutes and 90% of the diagnostic work is done

I take the coil off and check resistances,and find everything in spec - so,it's not the coil pack.While the coil is off I check the three signals coming from the module and find I have 3,but one is weak - with the coil hooked up and a load on the signal disapears - one ign module required.I did one of these on Xmas Eve too.I also check the crank angle sensor and cam sensor,the next 2 images - the crank sensor is all even,but the cam angle sensor has 3 different sized gaps between signals to tell the computer where each cyl is.

Next image is the coil ramp again,all 3 coils working,but I'm not too happy with what I see,fluctuating current draw on the coils,changing between cyls.I check secondary ign on all cyls and find those on the right bank losing burn time occasionaly,not so much missing,more ''fluffing'',and the idle is a bit rough.The next tool I pull from my weapons cabinet is one I made myself - a vacuum probe.It uses a MAP sensor from a Commodore,4xAA battery pack and a couple of pots to adjust the range - it doesn't give a vacuum reading,but shows the actual vacuum pulses in the intake manifold as a wave form.I can't get a good reading from the Commodore,but thought I'd show you anyway - I can usualy get a good waveform,can trigger from no1 cyl and have found broken valve springs with it.

The latest theory,which I am sifting through my brain and testing...is that altering ign KV spikes are caused by sticking valves - the only thing that can alter pressures in the cyl are the valves,so altering kv demand and current are influenced by the valves.I'm thinking that's what we have here.Now the cooling fan isn't coming on and I'm having difficulty sorting such a simple thing like that out...my daughter is picking it up tonight.

Also in this week is a '97 BMW 316 with no power - it's been to the experts who have plugged in a scanner,replaced the knock sensor and fixed nothing...a typical mechanic with a magic box that tells him what to do...but he forgot to use his brain.It's gutless alright,no power at all - so check the fuel filter first,BMWs are prone to blocking them...but it's fine.I see the tailpipe is white...click,click - up on the hoist and I hear a rattle in the cat converter.It's a one piece system so cut the pipe and drop the converter - while the boys smash out the matrix I blast around the block with an open exhaust - yeeehaa!!! I weld it back together,refit and we have as much power as one can expect from a 316.Just basic mechanicing on this one,no need to be scared of the high tech Euro.The customer is an eastern European who first came to me as a new immigrant...I took the time to listen to his poor English and do the best I could on the old worn out cars he drove.Actualy in his home country he was a lawyer,and now has his NZ qualifications,practising law,I've seen him on TV even.He drives across the city to bring his flash cars to me,as someone who helped him in his early days in the country he holds me as someone he can trust.

Also in today was an '87 300E Merc...with no power,oh,easy you say...you just did that! Not so - first check was the fuel filter,collapsed,the element rattling inside.This is K Jetronic,the mechanical fuel injection system...and I don't go near them.We run over the ign system,do some housework on vacuum hoses,some are not connected,some collapsed,current ramp the pump (not a good look) It will only rev to 3500rpm,and if we add fuel into the throttle body (carb clean,engine start) it revs out.With more info from the customer I find they ran it out of fuel (new to them,and on it's first trip back from Levin it ran out at 3/4 on the gauge) With the faulty fuel filter and sucking the tank dry I reckon the distributor head is blocked,and I back out of this one...but we have improved it.The customer is an old friend - 25 yrs ago I used to see her in the Farmers monthly flyer...nudge nudge,wink,wink.

Win some,lose some...it's been a week from hell.