djefk
Part of things
Posts: 844
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Agree - the carb on it should work perfectly fine, if it doesn't then it needs to come apart for a thorough clean and some TLC or you need to swap it for another, but the replacement might be worse than what you have already.
Personally I would buy an unknown used one for reference / spares if needed, buy a full rebuild set with all the gaskets, replacement accelerator pump diaphragm / valves etc. and get stuck in with the aid of a good manual, latex gloves, a bowl of thinners and old artist paint brushes for cleaning and a can of compressed air to blow through all the jets - it's not hard if you take your time and lots of pictures to refer back to - it can be satisfying to take something like this apart, clean all the parts out and then put it back together. Even if you still don't understand exactly how it all works once it's in pieces on your work bench, it doesn't matter if you follow the instructions closely!
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May 13, 2017 18:26:57 GMT
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Hi all,
I finally got round to going through most of the suggestions above so figured it worth updating, more for my own posterity than anything.
To re-cap the original issues,
The car is a 1988 Nissan Sunny with the E16s 4-cyl SOHC engine. Carb has an electric autochoke.
- the car doesn't warm up too quickly
- is prone to stalling for the first 10-15 minutes when I'm breaking to approach a junction and take my foot off the throttle/disengage the clutch.
- high idle is only 15-1600 rpm - Haynes spec says it should be more like 2200
- the normal idle is about 600rpm - spec says 750-850.
- spring connected to the accelerating pump lever is worse for wear and pops out of its mount hole all the time
So it was suggested that I:
- check for induction air leaks - check of all the vacuum hoses for splits and renew
- check all manifold / carb sealing surfaces by spraying WD40 / plusgas etc.
- check the thermostat is the correct one / opening when it should, as it should warm up fairly quickly regardless of any vacuum leak or other carb fault
- replace the hose from the air filter to the rocker cover
- have a look at the fuel pump
- change fuel filter
I changed all the vacuum hoses, the fuel lines, the fuel filter and the hose from the air filter to rocker cover (as previously mentioned).
I could tell you that it seems warm up slightly quicker in it's high-idle mode - I haven't timed it exactly but going on average length of songs played on the radio, it's quicker. That's a change from a couple of weeks ago as opposed to Feb vs. May, by the way. So that's good.
I also went through most checks in the haynes manual - only ones I haven't done are the autochoke (seems to work as it's warming up OK), and the dashpot.
I did check for leaks and there is one! It's down around the manifold gasket or the PTC unit between the carb and manifold. I wonder if this causes two things,
1) leans out the fuel when cold so, as mentioned, it dies almost instantly without being set into high idle mode
2) accounts for higher idle when warm as expansion of parts has sealed the leak?? perhaps?
A basic question though - should the car start instantly and then idle normally from cold? I'm not missing something like it's supposed to go into the high-idle/auto choke mode from cold?
I still need to replace that spring on the accelerator pump arm - perhaps that's responsible for the jerky response to on the accelerator pedal
I might overhaul the carb completely now I'm more comfortable with the engine although finding the service kits for the carb seems like more of a mission than simply ponying up for a Weber from the US. Foxy mentioned if I'm not bothered about high performance - I wouldn't mind seeing how well this car can run, so performance is definitely on my mind.
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Nissan N13 owner | Mechanical neonate since 2016 (Give me all the info)
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djefk
Part of things
Posts: 844
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The car should start after a few seconds from cold at most ( pressing the accelerator a little helps in most cases as you're squirting a little extra neat fuel into the intake via the accelerator pump, plus (although I don't know about your engine specifically) it mechanically triggers the choke in some cases- then idle cleanly straight away.
Fix the leak you've found, rebuild the carb according to a good workshop manual, replace the spring and it sounds like all your woes will be solved
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The car should start from cold and immediately idle fast to aid quick warm-up. You shouldn't have to do anything to get it into "high-idle mode" as you've called it.
Try getting the WARM idle and idle mixture set up first, before touching anything on the auto-choke. If the warm idle is too slow, the engine could cut out approaching junctions as you've mentioned.
I would think that the basic settings have to be right before the auto-choke can modify them to suit the cold start conditions.
When you take the air filter off the top of the carb with the engine stone cold, is the choke shut?
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Living vicariously through other people's projects!
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foxy99
Posted a lot
Posts: 1,376
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May 19, 2017 22:24:34 GMT
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Nice to hear you're still working on it. At least ppl in here are listening lol. The lack on idle on my Polo breadvan was like the 'drainage in the lower field issue' that Ted & Ralph had on Fast Show and no-one in my real life was remotely interested in it.
Thank God for the internet lol
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1974 Daimler Double-Six VDP 1965/67 Hillman Imp pick-up 1984 VW Polo breadvan 1970s Yamaha Twins (4) 1976 Honda SS50ZK1
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The car should start after a few seconds from cold at most ( pressing the accelerator a little helps in most cases as you're squirting a little extra neat fuel into the intake via the accelerator pump, plus (although I don't know about your engine specifically) it mechanically triggers the choke in some cases- then idle cleanly straight away. Fix the leak you've found, rebuild the carb according to a good workshop manual, replace the spring and it sounds like all your woes will be solved I actually feel like a bellend for not understanding this beforehand. I've been running it in warm-up mode everytime without realising that wasn't always neccessary!
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Nissan N13 owner | Mechanical neonate since 2016 (Give me all the info)
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Nice to hear you're still working on it. At least ppl in here are listening lol. The lack on idle on my Polo breadvan was like the 'drainage in the lower field issue' that Ted & Ralph had on Fast Show and no-one in my real life was remotely interested in it. Thank God for the internet lol Yeah, living and learning! Imagine trying to discuss this with non-gearhead friends or my GF even. Eyes glaze over in under 5 seconds.
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Nissan N13 owner | Mechanical neonate since 2016 (Give me all the info)
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The car should start from cold and immediately idle fast to aid quick warm-up. You shouldn't have to do anything to get it into "high-idle mode" as you've called it. Try getting the WARM idle and idle mixture set up first, before touching anything on the auto-choke. If the warm idle is too slow, the engine could cut out approaching junctions as you've mentioned. I would think that the basic settings have to be right before the auto-choke can modify them to suit the cold start conditions. When you take the air filter off the top of the carb with the engine stone cold, is the choke shut? The choke isn't entirely closed when cold. For lack of finding the service kit for thr carb (or not being 100% on having the right one on the screen in front of me), I opted for using some gasket sealant to try and seal the leak. Seemed to do the trick as it idled higher afterwards, so I dialed that down. Idles a bit rough - maybe it all needs setting up again?
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Nissan N13 owner | Mechanical neonate since 2016 (Give me all the info)
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djefk
Part of things
Posts: 844
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Speak to these guys about rebuilding the carb - I have a pair of fairly obscure carbs on my BMW and straight away when I phoned for advice the guy knew exactly what type I had and also had all the kits in stock Carburettor hospital Also when you say I've been running it in warm-up mode everytime without realising that wasn't always neccessary! - do you mean you've been manually triggering / selecting this? If so how, I thought your car has an autochoke?
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Last Edit: Jun 7, 2017 18:26:51 GMT by djefk
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Jun 22, 2017 21:23:30 GMT
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Also when you say I've been running it in warm-up mode everytime without realising that wasn't always neccessary! - do you mean you've been manually triggering / selecting this? If so how, I thought your car has an autochoke? See now I'm confused. I think I need to find someone with a working carb to know what it should do but basically here's the operation for the warm up, 1. When cold, the chokeplate is slightly open. 2. Pump accelerator - I assume this closes the choke. If I do the same and pull pull the throttle lever on the carb when the engine is cold, the chokeplate opens fully and on releasing the throttle lever, the chokeplate snaps shut 3. Turn the ignition - engine starts and instantly into high idle mode at about 1500 rpm. 4. After a minute or two, the high idle gradually drops down to about 1000rpm - I assume this is the autochoke doing it's job 5. Pump the accelerator again and the revs die down to 750ish and off I go. I swear, I'm going to grill so many heads at the RR gathering about this
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Nissan N13 owner | Mechanical neonate since 2016 (Give me all the info)
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foxy99
Posted a lot
Posts: 1,376
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I could be wrong bit I don't think pumping the accelerator has that much bearing on the position of the choke-flap. I think on some cars slowly pressing the accelerator sets the auto-choke system.
If the car has manual choke it's obviously a cable from dash that pulls/pushes on lever which opens and closes the choke flap.
If car has auto choke it's combination or heat/vacuum operated devices that do this for you. Most basic one is a spring which if cold enough contracts to close the flap. as temp increases spring expands and flap opens. Some carbs also have water-heated element to open the choke-flap.
I think all carbs have system where vacuum collapses and opens choke-flap if throttle plate suddenly opened wide.
Section 3/4/5 in your post sound fine (like car is running fine but without re-reading the thread I can't remember what your problem was exactly) but 2 I'm not following...
What do you mean by 'pull the throttle lever on the carb...'?
Do you mean you pump the accelerator (thereby closing the choke flap) but not start engine then get out car, go to engine bay, actuate throttle lever which opens the choke-flap then let go of it and the choke-flap closes again?
If so this is probably some sort of device on the carb which mechanically cancels out the choke-flap if throttle-plate wide open then allows it to close again at smaller throttle openings.
It's all to do with the designers trying to make sure the choke works until the engine is at normal operating temp except when you're 'flooring it' lol
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1974 Daimler Double-Six VDP 1965/67 Hillman Imp pick-up 1984 VW Polo breadvan 1970s Yamaha Twins (4) 1976 Honda SS50ZK1
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Thanks for bearing with me, Foxy! You're doing God's work by trying to interpret my reports on this Yeah, that's it exactly. Sorry, that second sentence in point #2 should be an NB - not actually part of the process I was trying to describe. The original problem was to do with cold starts (not just cold weather) and the car spluttering out after a few seconds. It still does this - second start up, it runs fine everytime. I'd just like to figure it out so it starts up from cold first time round and stays running. Will give Carburettor Hospital a bell today and see if they can help. Cheers!
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Nissan N13 owner | Mechanical neonate since 2016 (Give me all the info)
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