more carb trouble

F

fett

Member
:cry:

so you may remember my thread:

viewtopic.php?f=5&t=10566

so been using the car a little more and was intending to use it a lot more this week, took it to get it cleaned, parked up for about 45 mins then went to drive it over to the wash area and it sounded like an areoplane and had no power, top speed was about 20 mph lol.

I think it was running on one carb only basicly, it did this once before I remember , again on the 2nd start of the day after a short rest. that time I thought the choke was sticking and fiddled around with it for a lil while to no avail and then it came good on its own and I though it was because I was off choke by then.

Anyway this time I limped to the wash area, cleaned it and then when I started it-it was still bad so I really put some effort in with no tools messing about checking all leavers rods etc and it made no differance, then again it just came good and I drove back to work. then about 2 hours later it was home time- same again running like crap so I though maybe something was stuck gave both carbs a tap all over with a small gasket hammer and it free'd off and ran good :mrgreen:

same again today, I topped up the dashposts started well ran well and went for a drive, came back and to test I left it a couple of hours and started it and after about 30 secs or a min it started "planing" again.

now its hard to pin down but I did check that the pistons were lifted the same ammount with the engine running and they were so I gave it all a tap and again (maybe due to time or chance though) it came good hmmmm

well, for those that cant remember they are a pair of newly refurbished HIF6 carbs from andrew turner and I dont really want to have to take them off or apart but I am thinking that maybe the float is a bit sticky in the passenger one and maybe that is giving me very occasional fuel bubbles out of the overlfow with engine off and also cutting off the fuel with the engine running sometimes giving me my areoplane effect.

so please please help me , these are new to me and I am way outta my depth untill I learn :(
 
so I gave it all a tap and again (maybe due to time or chance though) it came good hmmmm
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It sounds like one of the pistons is sticking in it's bore. Whip off the dashpot and give it a clean and inspect the guide pin that keeps the piston aligned for straightness and the piston groove for damage.
I had a similar issue and my carbs were dirty inside the dashpots.
 
thanks-ok, forgive my ignorance but do you mean take out the plastic top/plunger or do you mean take off the whole big chromed bit from the top of the carb?

I cant see how it would be dirty as they are new but I guess as I have the problme there must be a cause.

I am using 10w40 oil in them is that ok?
 
TAke off the big chrome (actually normally just polished aluminium) dome - secured by three screws - after first removing the damper (black screw in thingy). The piston is inside and you are looking to clean (eg with duraglit or other household metal polish) the surfaces of the piston and the insude of the dashpot that work together. This has no effect on the settings of the carb.

Chris
 
I wouldn't use any type of abrasive cleaner on the piston or the dashpot. The best thing to use is cellulose thinners.
 
empty out both dashpots of oil and refill the same and try before fully tightening the 3 screws lifting both dashpots up fully by hand and letting them drop , they should drop smoothly with a light thunk,i think this may be what is happening to the white car on the other thread,good luck rich
 
HI Harvey, I agree about not using abrasive cleaners - but didn't yo get to polish the brass with your Mum when you were little? Duraglit is wonderful stuff for carbs!

Chris
 
ok guys thanks, so when I take off that polished bit I will need to unscre the plastic bits first , will it all come off in one go? I can see it getting messy with the oil lol.

any gaskets I will need to replce in the process?

not much cop having to do that on a new carb is it , bugger!

I am guessing its the passenger on becuase of the fuel bubbles out of the over flow but is that consistant?

also I had my carb balencer on the carbs and although not perfectly balenced (sadly, just had it done too) the airflow through each one did not change during or after the problem, is that consistant with the removal of ploished bit remedy?
 
rover100rich said:
empty out both dashpots of oil and refill the same and try before fully tightening the 3 screws lifting both dashpots up fully by hand and letting them drop , they should drop smoothly with a light thunk,i think this may be what is happening to the white car on the other thread,good luck rich
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Just read this thread, you must be talking about my car :wink: . The problem seems very similar to mine. I think I will try the same thing and clean out the dashpots. :)
 
I agree with MIkeP, Fett. Have a look at what I've written over on his thread.

You can spend a very long time dodging from one thing to another, so best to take the fault finding methodically one step at a time, always leaving a known good situation behind at each stage. Very few garages understand how to do this nowadays - they are far too used to plugging a lap top into the dash and doing what it tells them!

Chris
 
hi , just had a look on mikep's thread (I think its the right one)and am sure its a carb problem due to the noise, its literlally like a rotory areo engine on one set of 4 and a normal running sound on the other 4 .

if the carb pistons are the same height on both carbs when its doing it , does it not indicate the problem is one carbs has no fuel? mind you then it wouldnt sound like it does probably- oh bugger I dont know.

btw the igntion is perfect and all new lumention with magnecores leads and genuine cap and rotor and so I am ruing that out atm
 
OK, so you've effectively already done the first stage of the checks on Mike P's thread. Only extra thing I'd recommend is to take the opportunity to have a look under the bonnet with engine running at night, just to check there isn't any spark tracking anywhere.

So, on to the fuel system. First off, as a matter of course (it ought to be part of maintenance) change the ruel filter. Then try and assess whether you have a decent flow of petrol. Are there LOTS of bubbles appearing in the fuel filter, and or it stays completely empty? if in any douby, have a pipe off the filter and crank the engine on the starter motor with the ignition lead off the coil so that the engine doesn't fire. Plenty of petrol coming through? If not, try it in both main tank and reserve tank positions. If one is OK and the other not, change the O ring on the changeover valve and make sure that the cable opertes it correctly. None at alll, start by blowing through the lines back to the tank with an air line (fuel filler open - you don't want to balloon the tamk!). Then put a service kit onto the fuel pump (you're still on mechanical?). That should get you a decent flow. About the only other thing that could go wrong is if the fuel pump isn't getting the correct amount of poking from the camshaft for some reason. Final stop now is to the carbs, Have the float chambers off and renew the needle valve and float that control the amount of petrol that can enter. (But note that a needle valve stuck shut is very unlikely - they normally fail to close!)

Now a bit of theory behinnd the suggestion above. What you've described sounds like the passenger side bank running normally and the drivers side bank starved of fuel. That is very unllkely to be carb trouble if both pistons are raising to the same extent. Far more likely to be fuel supply. The passenger side carb receives fuel first and then any spare goes to the drivers side carb. It sounds more as if there is only enough fuel coming through to keep the passenge side carb satisfied. Even if this doesn't turn out to be the problem, you now have a fuel supply in which you are confident to move on to other problems.

Hope that helps to start with.

Chris
 
Hi - does the o ring and reserve stuff still apply to a range rover or is it set up differently?

Rich.
 
thanks gents , yes nor reserve supply on mine.

its on a facet style elctric fuel pump mounted by the back wheel , the fuel fileter and the pump are both brand new.

just to throw a spanner in your suggestions I feel its the passenger carbs that running badly and that getes the fuel first.

reason I think that is that its the carb that had the bubbles from the overflow whith the engine off.

the needles jets and everything else are brand new as these were newly refurbished carbs by andrew turner, if I could get hold of him I am sure he would know but this is really a pain :(
 
Ah, right, Range Rover, sorry!

OK, so if you have a facet fitted and you are seeing fuel bubble from the passenger side overflow, have you got a fuel pressure regulator fitted? Facets are known to be able to force fuel past the needle valve in the float chamber, as most people fit unsuitable high pressure ones. There's absolutely no point trying to tune the carbs or look for other defects until you can be sure that the fuel level in the float chambers is correct. Any hint of too much fuel (ie overflow traces) in either carb implies either that the needle valves are not shutting off or that fuel is being forced past them by excessive pressure.

Chris
 
ok so I took the old ones apart today for a practice.

I see all the bits inside th dashpot your talking about now , just not sure which bits to clean on the real one as they are new but will give a try.

also its the most bog standard facet pump ever so hopefully no over pressure as it ran fine on it for weeks then all of sudden trouble startes then gets worse. although it is still pretty low on the milage front!
 
it's the bog standard facet pumps that are the problem! You have to go to a fair bit of trouble to buy one that is suitable for use with SU's. Facet's started as pumps designed for circuit racing. Thus they had a high pressure on the assumption they were dealing with 40DCOE's or Dellorto's and very high flow cos racers tend to drive on full throttle. Then people spotted they were cheap and started using them on everything! I much prefer to see a HUCO or similar rotary pump, where you have some control over what you are buying.

http://www.gowerlee.dircon.co.uk/HUCO.html

Chris
 
Hi Gents, at andrew turners recommendation I spent quite a while taking the "bubbling" carb off today thinking that would also be a good place to start with the intermittant bad running problem too.

after checking the piston which seemed to slide ok I then took the bottom off and tried the float.

about 10% of the time under test it stuck in the top most position so I am guessing that is the fault, do we agree gents?

I am planning to sent it back to be fixed when I get hold of Mr turner, which it seems can be quite difficult!
 
We definitely 100% agree that that is the fault!

But why not fix it yourself? It is very easy to do - in fact you've already done the difficult bit! Simply order up a new needle valve from:

http://www.sucarb.co.uk/

After all this is exactly what Mr Turner will do and I suspect he will want you to pay the postage to send the carb to him!

Chris
 
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