DONT CLICK THE ABOVE THUMBNAILS!!

I'm getting dodgy malware-infected links popping up when I do.

Might be OK with full-sized images, otherwise I'll have to stop using that site. Pity cos otherwise it works OK and is simple to use.

Used to use Flickr but lost patience with the DaVinchi Code-inspired user interface

If I recall your the guy who posted a question about a Gunsons glass spark plug a while back.

If you resolved the connection issues try putting it in the engine and checking the colour.

Never did resolve those connection issues, though I now have a reason to.

Re-sealing the various plugged ports seemed to get it running OK, though with a high idle and probably rich. Passed inspection OK apart from an advisory on the tyres, so I left it at that.

Until now. After a rather long stand while I fixed the exhaust, cleaned up the brakes a bit and did an oil change, its back to misbehaving, only worse.

Ran fine initially, long enough to get it to an especially inconvenient spot on the coast, then deteriorated rapidly. This time there were some 'ting!" ringing sounds when trying to get it moving that I havn't heard before and which I'd think might be detonation and/or pre-ignition. Re-sealing had no apparent effect (apart from wrecking my knees carrying my tools a very long way). Abandoned for a few days, but eventually with a lot of clutch slipping, avoidance of flyovers, and a very p***ed-off GF scooter escort, I limped it back home.

Should probably do a compression check in case I've bust something in the cylinders with that :ting!" thing.

Then I'm thinking a distilled water decoke as a first step, so i'll have to distill some water.

I don't have a borescope but it may be possible to photograph the top of the pistons through the plug hole with a white LED, Tried it with a little incandescent but the light was too red

Then check the timing and try and work out what's happening with the vacuum advance.

And resolve those Colortune blues.

Edited by edlithgow on 06/04/2019 at 04:24

Difficult to do completely consistent compression checks with the push-in rubber cone (tester was supplied with the wrong adapter. Correct one not available separately) but they all seem to be about 170 psi (plus or minus 10) dry, all plugs out, so 4WIW no evidence of damage,

Occurs to me that if I decoke with steam I wont need to distill first, so I'll look into that.

from what you said I would go for vacuum leaks maybe if not from pipes possibly inlet manifold then sort out your advance/retard which will make a difference to its power, only my opinion

A couple of years ago, here

https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/4398000/re-coke-can-for-brake-drums#Post4398000

I wrote

"Re flame spraying, I had an exhaust manifold-downpipe gasket failure recently and took the opportunity to shove some rolled beer can into the pipe. .......................................................................................................My theory is that this will flame spray the inside. I put about a teaspoon of portland cement in too for extra acid buffering.

Of course if the can had rolled itself up and caused a blockage I'd have looked pretty silly, but so far, so-so."

I've probably done it a couple of times since, and did just recently

Perhaps Sod's Law has caught up with me.

I think this last time I may have included the can top. which is quite a lot thicker. That was probably unwise(r). A loose "flap" causing an intermittent partial blockage might explain these symptoms, and might be quite hard to both diagnose and deal with.

I'll have to see if I can find something to rod the exhaust, though if the obstruction is loose that might not help.

Perhaps I could hose it out?

Of course if the can had rolled itself up and caused a blockage I'd have looked pretty silly, but so far, so-so."

are you sure the top end hasn't softened in the heat and given a valve effect ie as it expands it constricts the exhaust so it suffocates the bores

just a thought?

Well, I'm not sure of anything at the moment, except that a repeat of the carb-cleaner hose down didn't give any indication of a vacuum leak, and a drive around campus didn't produce any extreme misbehaviour. Probably have to take it further and faster, but then I risk getting stranded far from base.

There was an odd sort of whistling on first startup which went away after about 5 minutes or so of idling. I suppose that could have been an obstructed exhaust but I couldn't locate it. Next time I'll try and have a bit of tube on hand for stethescoping.

An explanation in terms of thermal expansion of a bit of can sounds a bit too subtle though.

I know aluminium and steel have different expansion rates but the dimensional changes are going to be fairly small, and I'd think it more likely that, IF there is a variable obstruction, its being displaced by exhaust gases. If it was close to the engine end it would probably burn off, but if its been blown into the rear section it wont get very hot, and I can't get that section off without access to a pit or lift either.

Might have been an tdea to sandwich a chicken wire screen between the front and back exhaust sections. I doubt anything that goes through chicken wire is likely to cause an obstruction.

Sure you haven't a leak through the brake servo they can be hard to detect sometimes as they can leak for a short time then seal for a while, some of the old datsuns used to suffer that problem, I bought one once that had a vacuum leak intermittently, replaced the servo and cured it.

funny though that was the only car I ever had that never needed choke to start and was really economical, someone had taken the choke assy off for some reason?

Does it have a condenser in the distributor? Many moons ago my TR7 was misfiring for no apparent reason and a new condenser cured it.

Maybe worth replacing anyway, likewise the points.

I've got a Maplins (now defunct) transistorised-assist kit, but I've been putting off fitting since my soldering is poor and I won't be able to replace it if I bust it.

Any tips on diagnosing a brake servo leak? Maybe my usual spray-it-with-carb-cleaner would be contra-indicated.

You could try removing the brake servo hose and plugging it to see if that changes the way it runs. However you will be driving without brake assistance!

Engine was still kangaroo-ing (with squeeks that MIGHT have been clutch slip) after that, so not fixed, but as I drove around to dry the exhaust it seemed to settle down.

More likely alternator belt slip, but will probably settle down as you said, it wont happen straight away, give it time to get used to normal mixture

Worse yesterday, so I doubt its fixed. Good point re alternator belt slip, should have thought of that.

I noticed yesterday my aircon drive belt has gone awol but don't know exactly when that happened.

Exhaust could still be obstructed but rodding isn't practical due to angles and baffles on the rear section. Only other trick I can think of apart from replacement (if available) or cutting up the exhaust (difficult to get clamps here but I suppose hose clips might work) would be explosives :)

Taiwan (an automotive desert for all things non-bling) scores for once, since firecrackers should be available all year round.

I'll try rodding (and perhaps flushing) the front section (didn't have time before, since the manifold gasket is fairly inaccessible) but that is much less likely to be a problem.

Brake servo plugging didn't seem to make any difference to engine operation.

Steam decoke was an ineffective hassle and I'm lucky I didn't scald myself badly. Surprisingly difficult to get steam to go where you want with improvised gear. It IS (Stevensons) Rocket Science. However, its been pelting down for a couple of days so I could just use rain water in a hand sprayer.

Havn't done anything with the ignition system or its timing yet. .

Maybe it would be an idea to fix one thing at a time so you know what's effective and what isn't.....just a thought ;>

Surprising how much debris it still in rain off a roof on the third day of rain. I'd have thought it'd be pretty thoroughly flushed clean by then, but no.

Was going to filter it but managed to scrounge a couple of litres of "distilled water" off someone in the Biotech Teaching Lab (its in quotes because the apparatus didn't look much like a still. Didn't have time to work out what it was doing but it had "Millipore" written on various bits of it which implies filtration. Hopefully deionised as well)

Anyway, hand mister spraying that into the idling engine took over an hour, made my trigger finger ache, and a lot of the mist didn't go down the carb throat .

AFAICT with a little 12V bulb inside cylinder number 1 (no success with "white" LED's so far) is has cleaned off the piston top quite a lot, but some patches of carbon remain, mostly around the piston edge.

Was still faltering when revved though, so it apparently hasnt fixed the problem, but was still worth doing. Might give it another go after I've fiddled with timing and vacuum advance.

Well, I am, more or less but this isn't a science project. If I don't get it running reasonably reliably for inspection it'll have to be scrapped, and time is limited.

I wasn't suggesting it was, only that jumping from one possible fault to another possible fault without making sure one is right, is not the best way to do it as it normally is more time consuming and often takes longer.

whether you have time or not

I have over the years had many deadlines to get cars on the road but rushing always seems to get you nowhere fast....funny as it seems

I spaced out the the flanges with crumpled aluminium foil smeared with potters clay from the art department dump, setting a short length of aluminium arrow shaft in it to provide a tap for exhaust gases, and wrapping the bolt threads in PTFE tape to keep the clay out of them.

Seems to have done the job, though it wasn't the best way to do it.

Since it doesn't have to last, and I'm not planning to have it in place when emissions are tested, gaskets cut from closed-cell foam, plywood, or cardboard would have been a lot easier and more reliable. I should also have used a longer arrowshaft section to reduce heat transfer to the hose.

For a longer-lasting installation, crumpled foil sandwiched between a couple of aluminium plates would perhaps be favorite.

Doesn't show any pressure at idle or revving up to about 4000 rpm, apart from a brief needle swing on liftoff.

So no evidence of exhaust restriction

Could still be an intermittent/mobile obstruction not manifested in this static test. I'll see if I can extend the hose to allow monitoring during a test drive.

Could also be a blockage in the front exhaust section, but I think thats much less likely.

Back flushed the rear section of the exhaust again. A long shot, but fairly easy to do.

This time I put a washing up bowl under the outflow for diagnostic fragment trapping.

Some bits of aluminium, some rust fragments, and a very few bits of clay, but nearly all about rice grain size and not much of it.

I suppose there COULD be something bigger in there that won't wash out, but its probably more likely to be a carb fault.

I rebuilt that a couple of years ago so I'm not very enthusiastic or optimistic about doing it again.