Quick question would closed exhaust valve cause tight spot?

if the cam is not trying to open it then there would be no tightness. the head of the valve embedded in the piston is a different matter. get a borescope in and have a look.

But it is a wonderfully inventive use of an inappropriate tool.

Now I know what to do with all those current clamps that the power companies keep sending me.

Thanks, the broken rocker was someone else's suggestion (they reckon it's not uncommon on this engine) and I was sidetracked by thinking a stuck open valve would cause a low current spike on the offending cylinder due to low compression. I didn't consider a stuck valve causing the load on the cam - funny how it's painfully obvious when someone else says it :) Wouldn't have fallen for that if I could have got a compression gauge on it but it's pig awkward to do anything on this engine due it it being cranked over in the van but at least the injectors are accessible so that should provide a place to look ;)

I seem to remember this is an engine that bend rods somehow, try and google it.

How is it inappropriate?

A "bore" scope is for looking down plug holes at engine "bores".

Need a 7-8mm one for modern 12mm plug holes.

oh, I thought he meant the oscilloscope was inappropriate. which in a way it is, a mark one ear would do.

Since he mentioned current clamps that's what I thought too, although I understood current sensing was the "usual" way to do basic compression tests these days?

it can only really give a comparison, but it is a quick way to narrow things down a bit.

Especially when the glow plugs are virtually inaccessible under the bulkhead and nobody appears makes a dummy injector for it :(

I see. That would be the object of a previous paragraph of an earlier posting and not the last object mentioned by the last poster.

I failed my English "O" level 4 times. Didn't do it a 5th time until I was 24 and then I changed exam board from JMB to AEB to get a B.

An oscilloscope been a standard part of MV tech equipment for well over

25 years (and maybe 50 but I was 5). It was there slap bang in the middle of the ubiquitous SUN tester, on a big red cart. By the late 1980's even colleges had to have one to teach MV technicians at Nat Dip 3 level. It was just about up to the use the OP used it for and ignition trace analysis for electronic ignition. It wasn't up to the frequencies found inside a late 80's 6305 based 8 bit ECU running at 1MHz.

I have both. 100MHz analogue storage scope in use.

What you find with a boroscope after the 5000 mile new pattern inlet gasket fails between number 1 and the thermostat housing. (saving on OEM gasket set £100, £425 + £50 p&p for new engine)

Nothing wrong with my posting format. I meant the 'scope. I will admit to being behind the times in automotive diagnostic methods though. I'll shut up now....

experience and a keen ear are still the best diagnostics there are, too many people get bogged down in tech. stuff when, for instance the car has run out of petrol, or the battery is flat.

I know a couple of mechanics for who this is undoubtedly true but even they have been known to be tripped up on occasion when the ECU does something unexpected in response to a fault.

And I have come across rather too many 'technicians' that go straight for the codes, rather then checking the basic stuff first. Not that some of theses seem to understand why they codes are being generated, most of the time, just that their computer says 'change part y' :(

I was using the 'scope function of a Modis Ultra. Nice bit of kit for the garage I guess, but I prefer my 100Mhz digital 'scope for when things get complicated -mainly because I find it easier to use :)

I also have a multimeter with an 8Mhz 'scope, one of the Uni-T ones, bit basic but it's great for quick sanity voltage/waveform checks.

There are times when it's difficult to beat the analogue 'scope sat on my bench - but those times are getting fewer for the old beast :)

Lee

Years ago I had a company Astra. Having had it's engine rebuilt after shedding its cambelt at 36,000 miles, it didn't run right. It was fine normally, but once in a while you'd put your foot down to overtake and it'd refuse to gain any speed.

I drove around for 10 days with a data logger plugged in. The garage analysed the data and diagnosed a faulty EGR valve. It was replaced, but the problem remained.

They then sent the data to some technical department at Vauxhall, who diagnosed a faulty engine bay wiring harness, which was going to cost £1200 to replace.

One morning the garage collected it from work, an hour and a half later, it was back. An old style mechanic had ignored the diagnosis and decided to change the ignition leads - problem solved!

SteveW

Bit thick, are you?