car's behavin great now just seems a bit low on revs. Havn't checked the nipples though, yet. The Idle OverRun Control Valve is getting 12V. The TTV, however, is getting nothing at all. I used the test bulb and it doesn't even light up at all. If I connect it to a AA battery it is a little dim, so the TTV isn't even getting that amount.
so it seems the problem is mainly happening from dead cold. Would not getting 12v at TTV cause these problems? What does it do and when?
Here's a little "what's going on normally" thing for you: The red pipe from top of carb to the TTV (11) allows air at approx. atmospheric pressure to one nipple of the TTV. If the internals of the TTV are cold (below 15C approx.) the air passage through it is open so this 'spoils' the vacuum being generated at the carb end of the pink pipes, and gives no vacuum at the lower port of the 3-point unit. The TTV has a little electrical heater inside it, that should get 12V as soon as the ignition is on. As this heater does its thing, it closes the valve and stops this 'spoiling' of the vac to the 3-point unit. Depending on outside temperature, this takes a shorter or longer time. If outside temp is warmish (>15) it will be closed from the start, and the electrical heating won't be needed. Engine bay heatsoak can sometimes make up for lack of electrical heating, but not reliably. This might be why you have an intermittent problem when running at different speeds etc. Without vacuum on the diaphragm of the 3PU, it can't retract, so the throttle is held in the 'start' position. If you have CE1 electrics, I think the feed to the TTV (and part-throttle-channel heater) are fused, so have a look for a popped 15A fuse. Check that the wiring to the part-throttle-channel heater low down on front of carb isn't shorting to anything before replacement though.
check for 12v at the carb heater wire, this gets 12v from the same feed as the TTV. if you follow this wire back, make sure therte are no brakes or shorts to earth. might be an idea to peel the rubber boot back on the plug, to check for damage there. As EZ says its fed from fuse 15, pin D/7 on a pre-90. I think this may expain your issue, intermittant connection on this wire, and eventually heat soak brings the 3/4 back under control
Explains why it was fine when I went back and drove it with no problems half an hour or so later. After it was still warm inside! I'll have a mess and hopefully post later but maybe sat sun.
Okay didnt get round to a mess about last night. Went to work this monrin, same thing, moody carb high revs. after 4 hours at work..... Checked all fuses and location 18 was 15A blown.... put a new one in and started up fine. Revs seems fine from cold but do seem a bit low. Can't even tell the engine is on! Drove home and seems fine, no probs with revving throught gears, just a bit jerky on the gearchange but I guess that's just the slightly low revs. No power loss and I think it actually sounds beefier, could it be that its fuelling/mixing better? Will check the TTV voltage, overall workiness, etc after, coz just got the battery for the multimeter fitted.
I've just had a glance at CE1 wiring diags in Haynes, and fuse 18 is the one for TTV and part-throttle-channel heater. Looks like you may have fixed it. Interestingly...the same fuse covers the electrically heated windscreen washer jets... If you have a rev counter, or another way of measuring the fully-warmed-up idle speed, tweak it up to about 900-950 with the 13mm nut labelled "13" in the vac-pipe piccies.
okay, got it right up to temp. The Idle OverRun Control Valve is getting 12V. The TTv is too. The Auto-choke is getting 0.14v However, the revs are still low and the battery light flickers slightly, but this maybe the voltage regulator on the alternator, which i'll check once got the revs sorted! The 13mm nut is wound all the way in. Unwound it and the engine statred to stall and cut out. Wound it back in and it was okay but too low. Will the mixture screw need adjusting now because it has been over conpensating due the the 13mm idle nut being wound fully in?
When are you measuring the autochoke electrical heater voltage ('cos above 35C coolant temperature the thermoswitch switches it off, so can only be measured on really cold engine) and where are you putting the negative probe? If you are doing it cold, but putting the positive probe on the feed wire, and the negative probe on the metal water housing, try it again with the negative probe on battery neg. instead. This will tell you whether the problem is the feed or the load. If the feed then looks OK, switch to resistance measurement (ignition off) and check with one probe on battery negative (or camcover stud) and the other probe first on the metal water-housing - should read close to zero Ohms - and then with the other probe onto the tail of wire coming out of the heater element; this reading should be around 12-13 Ohms. For the low-revs: How clean is the top of the carb? If it's grubby, treat it to some carb cleaner. Blocked air jets, particularly the slot in the mixture-screw tube, will alter things in a bad way. You can't really see this slot when the tube's in-situ unfortunately as it's near the bottom, facing the primary barrel. If cleaning makes no difference, you could try winding the mixture screw a turn or two one way or t'other; do write down how much you've changed it, and in which direction though. It's dead easy to lose track of where you were to start with. It may be that the screw that bears against the 3-point unit's plunger has been adjusted at some point in the carb's history, or the bracket that it goes through has got bent open a bit from its original 90 angle. If the mixture isn't miles out, and you have no vacuum leaks that could be spoiling the manifold vacuum, that's about the only reason I can think of that you'd have run out of adjustment on the 13mm.
forgot it switched off when warmer! Does seem quite clean all over really. Regularly gets plenty of redex (about half a big bottle to 20 litres, usually!) I'll try and see how adjusting it goes, and also see how clean the mixture pipe is. If the mixture does seem okay I'll just adjust the small screw in the lever to increase the revs a bit!
Redex will keep fuel passageways clean, but do nothing for air paths, and I've always thought petrol was quite good at keeping fuel passageways clear. May be easier to bend the bracket a tad than adjust the screw. Hold/wedge the throttle wide open on the nearside of the carb so the 3-point isn't pushing against the screw, then give the bracket a little 'tweak' to close the angle up a bit. I have a feeling that this bracket is thinner on some carbs I've seen than others, so if yours looks chunky, go for the screw adjustment instead.
AHOY THERE! Got engine up to temp. Everything seems to have correct voltage now! 13mm nut on 3-4PU fully wound in = stalled when unwound 3 times. so put back fully wound in as that gave best idle and does produce a plunger of 14mm engine off and 8mm on. Unscrewed mixture screw = finally made engine stall. Couldn't really get a mutual agreement between the two. Took out the mixture screw and there wasn't even half of the rubber washer left (so binned the rest). Gave the mixture hole a dousing of the old unleaded 95. Started up and obviously stalled - did this a few times for a clean. Refitted the mixture screw (3-4PU nut still wound all in) Managed to get a similar idle, but lumpy. With all electrics switched on full beam etc, alternator belt would squeel on giving it go-pedal. Went for a drive, this setup gave a TERRIBLE jerky gearchange and terrible throttle response (so bad it was like the CV joints were going). Screwed in mixture screw a bit more and this gave lower revs and even lumpier so brought it back out a bit. At this point I had the best idle of the night and that was till awful. Decided to try the small screw on the lever (everyone should know what this bit is by now ).....because the lever seemed about 3mm thick... ...Screwed it in towards the plunger, so it brought the lever away from the 3-4PU 1 - 2mm or so..... .....this resulted in increased revs, much better idle, instant throttle response, much less lumpy and no alternator squeel on full electrics. Also checked the go-pedal to floor/butterfly full throttle position and that's spot on. It does even seem throatier and like more power is coming from it. Guess the real test will be in the morning when it's stone cold!
From stone cold (1'C inside the carb) this morning. Was absolutely fine started after a few turnovers. Revs came up abit and died off after a few seconds to an acceptable, smooth idle, when I guess the 3-4PU kicked in. Drove perfect from go, and could give full throttle. After about 5 mins of easy driving (still in the warning up period, about a third up the tepm gauge) came to junction and it tried to stall with battery light on and off, gave it go pedal and was okay. Could possibly be carb icing, not too sure but the in carb temp was 20'C. Got off the motorway after 10 mins and it was fine. Similar thing coming back from work, but it was uuuuber foggy and misty. Am in the process of getting some clocks from a gti to plug in so I get the idle spot on at least, then i'll get to a garage for a co2 readout.
does sound like carby icing to me also, exactly the time period when I would get it on my daily drive to work when the warm air feed pipe/shroud was missing and/or vac pipe to airbox fell off
Get the warm-idle and mixture set up nicely, then if you're still having occasional trouble, maybe have a go at restoring the hedgehog relay and bringing the little spiky fella back into play. Could also be worth looking at the wiring/connections on the back of the fusebox that goes in and out of the hedgehog relay, on the CE2 f/b these connections are in a prime position for suffering from the Mk2 water-leak-onto-fusebox problem, dunno where it goes on CE1. If the wiring/connections look OK, but you don't fancy getting in amongst the relay's guts, post it to me and I'll have a go for you.
Cool. I'll get it set up best as I can. I did spring a tiny leak a few months back when travlelling on the motorway, but I'm sure it was blocked drains from under the scuttle as I took it to bits, cleared it, fitted my GTI hard scuttle and have had no problems even in the mega rain on the motorway. Will have a look at all the guts back o the F/B. I've had em out before coz I was going to get my KR lump into it before I moved house in Dec.
One more thing... Might actually be more relevant to idling/icing problems than the hedgehog. In the first post of RJ's FAQ, this little fella (part throttle channel heater) seems to escape a mention: Have you checked this one out? Test the feed wire for 12V whenever ignition is on, and measure resistance of the thing (in situ) from its wire-tail connector to a good engine earth. Should be around 5-10 Ohms I believe, when cold. The surface that butts up against the carb is the ground connection as well as the bit that gets hot, and I've known a couple of these to have corrosion bad enough to give no electrical connection. Easily fixed with fine wet-n-dry on the mating faces of heater and carb. Also, check the wire insulation where it goes past the metal mounting bracket, it's often in bad condition, asking to short itself out.
