I don't believe in coincidence but....

codekiddie

codekiddie

Active Member
The car has been running fine recently, except that she has exhibited the dreaded vapour lock symptoms of not wanting to run as sweetly when re-started after stopping for a while. She has never really had any issues like this before, has an electric pump fitted with all pipes and hoses wrapped in some heat resistant tape.

The other evening she was really bad after stopping for 20 minutes or so, and I only just made it home again. being rather late I only took a cursory glance under the bonnet at all the usual things, points, rotor arm coil etc... and it was whilst I was looking over the coil that the LT wire from the dizzy pulled off its connector. AHA! I thought. Found the culprit.

The next day I decided to completely replace the wire from the dizzy to the coil, both ends soldered and crimped, and a quick start of the engine to confirm I had a good connection. She started as she always has:- on the button. Before taking her for a drive, the new fuel filter I had ordered arrived, so I decided to fit that as well.

Unfortunately after fitting the filter and starting her, she was like a bucket of bolts and could hardly hold her own just ticking over :(

So, in a bid to find out the problem I reversed my steps, and I re-fitted the old fuel filter but with no change :x

By coincidence has something else gone wrong whilst I was doing a fairly simply job on her??? Surely not!!!

So, in a bid to find out what is going on I removed the throttle linkage between the two carbs, and the left, (offside), carb is fine if you increase the throttle, but the other side sounded asthmatic, and really didn't like it.

I cleaned all of the plugs, which although were very sooty, made no change to things.

Since only one half of the cylinders seems affected, I assumed that the dizzy, coil, and anything else common to all cylinders surely cannot be at fault. I removed the carb from the poorly side, and one of the gaskets showed traces of fuel having been leaking, so I made a new gasket, and re-fitted the carb, thinking that I MUST have found the issue, but no :( :( :(

There is no mention in the WM of any priming of the fuel required after changing the filter, and I guess the fuel pump and the float chambers should take care of that. Just very odd that this has started since I changed the filter:- very infuriating.

I have AUD623's carbs fitted. Out of interest, where is the mixture control on the carbs, since I had such sooty plugs, I thought it may need adjusting. I will not be changing anything yet, as I don't want to introduce more variables, but a job for another day.

I am meant to be going to the Enfield Pageant on Sunday, so any help gratefully accepted, as at the moment she is going nowhere :shock:
 
Hi Phil,

Whereabouts in your electric fuel pump fitted, within the engine bay or underneath at the rear? How old is the fuel within your fuel tank, and what was the ambient temperature during these periods of poor running?

The mixture control is a screw located on the front side of each carburettor. When they leave the factory after the mixture has been set, a plug is fitted to prevent people tampering with the mixture. If you can't see the screws, then you'll need to remove the plugs.

The screws adjust the idle mixture whereas the taper of the needle sets the mixture off idle. Float height, jet wear and the specific needle will all influence how rich the mixture is. Do you know what needles have been fitted?

Ron.
 
Hi Phil . I'm not up on part numbers , And your car could well have HS or HIF carbs fitted , I'm guessing HIF's by your discription but can you confirm before we get too involved :D
 
SydneyRoverP6B said:
Hi Phil,

Whereabouts in your electric fuel pump fitted, within the engine bay or underneath at the rear? How old is the fuel within your fuel tank, and what was the ambient temperature during these periods of poor running?

The mixture control is a screw located on the front side of each carburettor. When they leave the factory after the mixture has been set, a plug is fitted to prevent people tampering with the mixture. If you can't see the screws, then you'll need to remove the plugs.

The screws adjust the idle mixture whereas the taper of the needle sets the mixture off idle. Float height, jet wear and the specific needle will all influence how rich the mixture is. Do you know what needles have been fitted?

Ron.
Click to expand...
Hi Ron

Pump in the front of the engine bay, just below and to the right of the fuel filter, fuel 2 days old and done approximately 15 miles since fill up, not sure of the temperature but felt quite warm, maybe 17 or 18C. Think I know the control you are talking about for mixture. Had the carb off earlier and it is a BBV needle fitted.

stina said:
Hi Phil . I'm not up on part numbers , And your car could well have HS or HIF carbs fitted , I'm guessing HIF's by your discription but can you confirm before we get too involved :D
Click to expand...
Hi Stina.

HIF carbs fitted.
 
Hif Phil ( see what i did there :roll: )
A couple of years back i experenced similar symptoms . After a good week of head scratching , measuring , removing and refitting the carbs , bodging it to run out of a can , thus bypassing the fuel tank , reserve etc , and every other trick you could think of it turned out to be the elbow had come loose/dropped from the bottom of the jet in one of the carbs rendering any adjustment void ( without me knowing :? ) Ethonal in the fuel ? who knows , a debate for another thread ! The guy at Burlin services said it could well be . I bought a couple of kits and rebuilt both carbs . :?

Ps . if you have BBV needles fitted they are standard . You don't mention any recent upgrades , or wilfull carb fettling ???
I would totally rule out vaperisation in good old Blighty at the present time of year , unless you have other overheating issues , then i'm sure you'd know any way :D
 
Inside the cold start thing (mixture enrichment device...) are a couple of O rings that when they are old and fail can create all sorts of running problems, like you have.
If the condition of the carbs is unknown, it is worth to take them apart and change a few consumable rubbers and seals.
 
It certainly sounds like I have just been unlucky with the carb developing a fault at the same time :( I have done no work on the carbs at all since I took ownership.

Typical that these things happen over a bank holiday, to make getting stuff through the post an extra day to wait, plus the frustration of missing Enfield :x
 
I did post a reply the other night but it obviously didn't take! Being on my way home from someone's leaving do was most likely totally unrelated ;)

You say you changed the fuel filter, my money would be in having dislodged some crap and you now have partially blocked carb. Pull plug leads to determine which carb is affected, then pull the carb, clean and refit.
 
Quagmire said:
I did post a reply the other night but it obviously didn't take! Being on my way home from someone's leaving do was most likely totally unrelated ;)

You say you changed the fuel filter, my money would be in having dislodged some crap and you now have partially blocked carb. Pull plug leads to determine which carb is affected, then pull the carb, clean and refit.
Click to expand...
Now that is a coincidence :shock: :shock:

Last night a friend of mine came around to borrow something, and I was telling them about the problem. He immediately said, "you've got some crap in the carb after changing your filter. I can tell you how to clear that?".

He then proceeded to tell me a 'trick' which is involves giving it some revs, and then blocking off the air intake to the carb and then supposedly all of the crap will get sucked out from the float chamber!!!

I never did try it, as this morning I simply gave it a bit more welly than I dared to yesterday, and after a while it seemed to do the same thing, and she sounded much better :)

I did take her out for a long run, and although she would go, (and I had her up to 80 odd but don't tell anyone), she didn't particularly like it until she got past 2500 RPM :? anything under that you could tell she was missing some beats.

I did notice, when I had the carb piston and needle out, that the needle did look and feel a little rough from about halfway up to about three quarters up from the tip. Time to change them?

Any more suggestions guys, and has anyone else heard of the 'trick' to get crap from a carby???
 
An update on this problem.

Just a quick recap:-

The car is running very rough until she gets over 2500RPM. Separating the carbs showed me that the offside one was quite happy to respond to throttle changes, but the nearside was not.

Today I spent a few hours removing, dismantling, cleaning, rebuilding with a new jet, needle, float, and all associated gaskets and seals etc..., and finally re-installing the carb that will not run sweetly, only for it to not make one jot of difference :cry:

Please can anybody shed some more light as to why one carb seems to be OK but the other not. Am I right in thinking that one carb does two cylinders each side, and the other does the other two each side?

If it is any clue at all, she makes a sound like a tractor on the dodgy side :shock: :shock: :shock:

This is driving me nuts, and it also means that tonight another local meet will be attended without the car again :(
 
codekiddie said:
Separating the carbs showed me that the offside one was quite happy to respond to throttle changes, but the nearside was not.
Click to expand...

The nearside carb feeds 1,4,6,7 so whip those plugs out and compare them to a plug from one of the other cylinders. The normal cause of that is that the seat that holds the needle into the piston drops, making it run really weak. The plugs would tend to confirm that if they're really white. If they're black, so over rich, then it could be the seals on the choke barrel failed, which will give similar symptoms.
 
harveyp6 said:
codekiddie said:
Separating the carbs showed me that the offside one was quite happy to respond to throttle changes, but the nearside was not.
Click to expand...

The nearside carb feeds 1,4,6,7 so whip those plugs out and compare them to a plug from one of the other cylinders. The normal cause of that is that the seat that holds the needle into the piston drops, making it run really weak. The plugs would tend to confirm that if they're really white. If they're black, so over rich, then it could be the seals on the choke barrel failed, which will give similar symptoms.
Click to expand...
Thanks Harvey.

Prior to overhauling the carb today, all 8 plugs looked like they were running rich, (and they have always looked a bit on the rich side to be honest). All seals were replaced today during the overhaul, and the needle is rock solid where it should be. I have the elbows off at the moment, and if you look down at the piston and needle assembly it looks as though it hardly lifts out of the jet when you open the throttle, although it does lift correctly by hand so is not sticking :?

I will check the plugs later, to see if there is any marked difference between sides.
 
codekiddie said:
if you look down at the piston and needle assembly it looks as though it hardly lifts out of the jet when you open the throttle, although it does lift correctly by hand so is not sticking :?
Click to expand...

Firstly I'd rev that carb, and if the piston doesn't rise and the engine won't rev as you say, then try again while simultaneously lifting the piston with a screwdriver. That should get it to rev better and if that's the case I'd say you're not getting a vacuum above the piston, so that needs investigating. Look down the carb while you're doing it to make sure you can see the mist of fuel coming out of the jet.
 
harveyp6 said:
codekiddie said:
if you look down at the piston and needle assembly it looks as though it hardly lifts out of the jet when you open the throttle, although it does lift correctly by hand so is not sticking :?
Click to expand...

Firstly I'd rev that carb, and if the piston doesn't rise and the engine won't rev as you say, then try again while simultaneously lifting the piston with a screwdriver. That should get it to rev better and if that's the case I'd say you're not getting a vacuum above the piston, so that needs investigating. Look down the carb while you're doing it to make sure you can see the mist of fuel coming out of the jet.
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Hi Harvey.

That makes perfect sense to me for a test. Unfortunately I wont be able to do any more this evening :( but will let you know what I find tomorrow :)
 
harveyp6 said:
Firstly I'd rev that carb, and if the piston doesn't rise and the engine won't rev as you say, then try again while simultaneously lifting the piston with a screwdriver. That should get it to rev better and if that's the case I'd say you're not getting a vacuum above the piston, so that needs investigating. Look down the carb while you're doing it to make sure you can see the mist of fuel coming out of the jet.
Click to expand...
Well Harvey I did as you suggested and there was clearly no fuel to be seen, so off came the carb again :?

I took of the bottom cover to see if there was any fuel in there, and not a hint of the stuff :shock: I re-read the carb assembly instructions and it turns out I didn't adjust the float properly, so the needle valve was letting none in:- DOH!!! The fact that I had exactly the same symptoms before I did the carb rebuild, and when I opened it before it DID have fuel in it, I'm guessing that the old jet must have been to blame. Float adjusted properly, cover back on, carb back on the car, and fired up first time. So nice to hear that burble of the V8 once again instead of the V4 I was listening to :LOL:

Did a quick tune up, and she has been out for a couple of hours now and behaved very well :p

Thanks again to you Harvey, you are a star Sir.

Now just to check over everything else before Tuesdays MOT :LOL: :LOL: :LOL:
 
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