Any Carburetted - Crisco on the Carburettor - A sequel to FOTR

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Fri 16 Aug 2019 02:13
Any Carburetted - Crisco on the Carburettor - A sequel to FOTR - edlithgow

Crisco on the Carburettor - A sequel to Fuel On The Roof.

So, having (probably) eliminated the fuel supply as a source of the kangaroo-ing,(see Fuel On The Roof topic) other possible causes I can think of include 1.untracable vacuum leak,2. temporary/part time blockage in carburettor, 3.ignition fault, 4. temporary/part time blockage in exhaust

Vacuum leak is probably favorite

I can't find a vacuum leak by blowing butane over the pipework and inlet manifold. Most of the complex system of vacuum hoses (which I don't understand) was disconnected and blanked off as a response to running problems a couple of years ago.

Over the past couple of months I’ve painted sunflower oil over the carburettor and inlet manifold in the hope it’d seal off any leaks. My main concern was that this would cause the throttle to stick, but short test drives have been OK

Time to go for inspection. since I’ve already got a late fine and more penalties loom (Told myself its only 20 quid but these days its 27. You people are costing me money)

What else could possibly go wrong?

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Fri 16 Aug 2019 08:56
Any Carburetted - Crisco on the Carburettor - A sequel to FOTR - Bolt

Crisco on the Carburettor - A sequel to Fuel On The Roof.

So, having (probably) eliminated the fuel supply as a source of the kangaroo-ing,(see Fuel On The Roof topic) other possible causes I can think of include 1.untracable vacuum leak,2. temporary/part time blockage in carburettor, 3.ignition fault, 4. temporary/part time blockage in exhaust

Vacuum leak is probably favorite

I can't find a vacuum leak by blowing butane over the pipework and inlet manifold. Most of the complex system of vacuum hoses (which I don't understand) was disconnected and blanked off as a response to running problems a couple of years ago.

Over the past couple of months I’ve painted sunflower oil over the carburettor and inlet manifold in the hope it’d seal off any leaks. My main concern was that this would cause the throttle to stick, but short test drives have been OK

Time to go for inspection. since I’ve already got a late fine and more penalties loom (Told myself its only 20 quid but these days its 27. You people are costing me money)

What else could possibly go wrong?

Is their any play in the butterfly valves centre spindles as this can cause your problem, common fault on old carbs due to wear on spindle, the valve tends to drift in its mounting so air flow fluctuates ?

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Fri 16 Aug 2019 09:52
Any Carburetted - Crisco on the Carburettor - A sequel to FOTR - edlithgow

Thanks. Havn't noticed any but I'll have a look.

I believe that was a particular problem on the small Subaru (Justy?) because I was thinking of buying one here , but by the time I'd researched it it'd sold ,

(That's why I only run awful cars. Too slow to catch the good ones. .Women...well...)

The fault is vey unpredictable, though, and MAY be associated with it getting hot, since its OK initially. (Women..well..)

I supposed that could fit a loose spindle getting looser with thermal expansion.

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Sat 17 Aug 2019 02:25
Any Carburetted - Crisco on the Carburettor - A sequel to FOTR - edlithgow

Car performed impeccably on the 20k ish drive into the city centre testing station (well, there's a rythmic pulsing through the steering that wasn't there before but the engine response was fine.)

Looking like that sunflower oil soaking might have done the trick.

The "What could possibly go wrong" question was answered by a big cloud of steam in the testing bay. Apparently the fan wasn't working and the static revving for the emissions test popped the cork.

Still passed (Huzzah!), in fact they might have skipped a bit to get rid of it, but limping it back home,stopping to dribble ditch water over the radiator a few times, was a bit fraught and tedious.

(No free parking in the city any more. Taiwan's anarchic charm is fading fast and soon it'll be a bigger PITA than...well...The Yook)

Can you guess yet?

Edited by edlithgow on 17/08/2019 at 02:47

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Sat 17 Aug 2019 13:11
Any Carburetted - Crisco on the Carburettor - A sequel to FOTR - edlithgow

Carb butterfly spindle seems OK.

When I wrote “Can you guess yet” I was convinced A RAT had chewed on the wire from the temperature sensor, which in hindsight seemed a predictable downside of soaking it in sunflower oil, though I hadn’t predicted it.

(CORATERAL damage? works with a cod Japanese accent. )

Now I’ve had a better look I’m not so sure. Some insulation is missing but the wire seems intact. Shorting it to earth (which I THINK should activate the fan), doesn’t

Fan is OK from jumpering it direct to the battery with half an old power cord, though I got my feet quite badly bitten by aggressive little red ants (probably Fire Ants, an invasive pest here) getting some field sand to rub the contacts with. Still hurts.

What I guessed was the fan relay seems to work when 12V is applied to the low resistance (about 100 ohms) contacts, and jumpering the ports in the connector block corresponding to the switched contacts together with a bit of wire makes the fan run.

This SEEMS to indicate a break between the temp sensor and the relay, inside the wiring loom, which would be a pain to trace. I could maybe bypass it with an extra wire though.

I used sunflower oil because I thought its special characteristics gave it a chance of working, and maybe it did. Hard to tell with an intermittant fault but that’s the longest roo-free run I’ve had since this started.

Are there any commercial products for this sort of vacuum leak-stopping?

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Tue 20 Aug 2019 10:00
Any Carburetted - Crisco on the Carburettor - A sequel to FOTR - edlithgow

Running the engine for a while with a multimeter (in 200 ohm continuity test mode) connected between the sensor and negative battery terminal, resistance stays at infinity until I switch off.

On switching off it goes to about 30 ohms and the buzzer soiunds.

I assume this is normal and that the temperature around the sensor rises when the coolant stops circulating, though I've never noticed if the fan starts running under these circumstances.

Does this sound plausible?

If it does, it suggests the sensor is OK and I just need to run a bypass wire from sensor to fan relay connector block, though getting the right terminals to achieve good contact might be tricky.

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Tue 20 Aug 2019 10:17
Any Carburetted - Crisco on the Carburettor - A sequel to FOTR - bathtub tom

Running the engine for a while with a multimeter (in 200 ohm continuity test mode) connected between the sensor and negative battery terminal, resistance stays at infinity until I switch off.

I'd check for voltages around first. In continuity mode you don't know what effect external voltages could have on any reading. Also, magnetic pulses from HT can play havoc with an LCD multimeter.

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Tue 20 Aug 2019 11:05
Any Carburetted - Crisco on the Carburettor - A sequel to FOTR - edlithgow

Thanks. I suppose if I let it go cold and my model is correct, the resistance should go to infinity with the engine off, which should eliminate the artefacts you mention.

Means a lot of hanging about though.

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Wed 21 Aug 2019 02:42
Any Carburetted - Crisco on the Carburettor - A sequel to FOTR - edlithgow

Engine off, coldish, ignition off, resistance infinite

Engine off, coldish, ignition on, resistance about 50 ohms

I dunno how to interpret that.

I think I'll take it off and bench test it if I can (not that I actually have a bench).

Tried and failed earlier with an open-ended spanner, and probably rounded it some.

Hoping it might yield to the correct size of brake spanner.

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Wed 21 Aug 2019 06:51
Any Carburetted - Crisco on the Carburettor - A sequel to FOTR - edlithgow

Camr off OK with a 12mm brake spanner.

Seems to have PTFE thread tape on it/

Normally I like to see that, and use it a lot myself in places for which it is not intended. like the caliper pins

BUT here doesnt it have to make lectrical connection through the threads in order to work?

Unlikely to be the cause of the current problem, though, so I suppose I.ll put some more on when I re-install it

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Wed 21 Aug 2019 08:06
Any Carburetted - Crisco on the Carburettor - A sequel to FOTR - edlithgow

Well, that was F for FIDDLY.

Trying to get consistent multimeter probe contact with a wee cylindrical metal thing in near boiling water, I said MANY words which would exercise the Mary Whitehouse Module, and a few that it/she probably wouldn't know.

But seems the thing works.

Painfully hot water, about 80 ohms

Cold water: INFINITE

I don't have the specs, but that seems to be doing the right thing in qualitative terms at least.

If it had been broken I might have just rigged the fan always-on, which is still an option, but nice to avoid if possible.

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Sat 24 Aug 2019 09:27
Any Carburetted - Crisco on the Carburettor - A sequel to FOTR - edlithgow

t A direct wire from the sensor terminal to the back of the negative coil port in the relay connector restores apparently normal fan operation.

The wire is attached by a ball-point pen spring (slightly unwound) and is just twisted and pushed in at the connector block, so it could be more secure. I was going to use more pen-bits (plastic sleeve for sensor connecton, and nib as bullet connector, but I parked them in the roof gutter and they blew away. Probably have somethiing else suitable though.

Temperature guage (which uses a different sensor) isn't working either but access to the guage back is likely to be a pain and I may not bother.

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Sun 25 Aug 2019 04:46
Any Carburetted - Crisco on the Carburettor - A sequel to FOTR - edlithgow

Temperature guage (which uses a different sensor) isn't working either but access to the guage back is likely to be a pain and I may not bother.

Well, that was a bit of a clue, and I finally checked the fuzes. Sho nuf, 15 amp one blown.

How embarrassing.

Quite like to know WHY though.

I had a (stuck"?) cooling fan apparently burn out the wiring loom on a relatively new and shiny Renault 5. ultimately causing it to be scrapped, and, from a look in scrap yards for replacement looms, it seemed to be a common problem.

Since this car sees low use in very high humidity, seems quite likely the fan could be a bit sticky.

Edited by edlithgow on 25/08/2019 at 04:57

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Sun 25 Aug 2019 07:26
Any Carburetted - Crisco on the Carburettor - A sequel to FOTR - edlithgow

Since this car sees low use in very high humidity, seems quite likely the fan could be a bit sticky.

Not likely to be the cause of the present problem, though, because its the control ciircuit rather than power, which was faulty.

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Wed 21 Aug 2019 06:57
Any Carburetted - Crisco on the Carburettor - A sequel to FOTR - edlithgow

Sorry, other way around.

Ign off 53.6 ohms

ign on INFINITE

BUT I still dunno how to interpret it.

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Wed 21 Aug 2019 08:13
Any Carburetted - Crisco on the Carburettor - A sequel to FOTR - edlithgow

No leakage when I removed the sensor, which suggests the head is empty.

Not a surprise since I had air pockets that took a while to clear when I renewed the coolant last time, but of some concern since these wee 3-cyl engines are said to pop head gaskets without too much provocation.

I might try a sink unblocking syringe when I refill. I did know where I could...er...borrow one, but its gone, so I might have to buy.

Failing that maybe a cheap Chinese venturi pump.

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