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Fuel System Trouble Shooting Help

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Andrew1

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Hi Gang:

I believe that I am suffering though multiple fuel system issues with my BJ8 using HD6 SU carbs. It's driving me buggy and have already cost plenty of rookie time and money in unecesary parts replacment without a cure.

I'd like to explain my general experience and tell you what has been done to date. From this I would love to get feedback from the forum on where I should spend my efforts? Do you think this might require a minor adjustment or a full carb rebuild?

Here is the experience:

1) The positive ground SU fuel pump ticks over once every 5 sec upon the ignition key being turned on (after the regular initial rapid ticking) but does not cease.

2) At regular speed and idle, the SU pump will tick over once every 2 seconds. However, there is no fuel leaking from the overflow pipes (or anywhere under the car) as the float bowl valves were replaced with modern nylon/neoprene tiped SU valves, but I had to bend the forked float levers more than the recommended 7/16 " clearence. Where can the fuel be going?

3) The fuel consumption seems very high. One tank every 220km ish (thats approximately 130 miles).

4) The smell of the exhaust is pretty strong with fuel (reminding me of a two stroke engine, which will fill your clothes with gas smell after a 20 minute drive. As well in cold weather prety significant water like vapor is admitted and small amounts of soot will stick to the chrome bumper after 100 miles or so. There is no visible smoke although.

5) Performance seems fine, and idle is fairly stable. A slight engine burble when down shifting to deaccelerate, which I don't recall hearing before.

6) Not sure if this is related, but the trunk has a strong smell of fuel, no visual leaks, but some paint bubling on top of brand new tank installed last year with proper pipe dope at connections to tank and Su fuel pump.

Would like to get your starting point ideas.

- Andrew -
 
HI Andrew, Here are my starting point Ideas: Item #1 is ok, Item #2 is OK except that the fork must be returned to the specified distance. Item#3 fuel consumption does seem a bit high.Did you mean HD8 carbs instead of "HD6"??.Item#4 sounds like the carbs are running far too rich.Item#5 ???.Item #6 sounds like the cover for the fuel sender in the tank may be leaking a bit causing the petro smell in the boot.---Fwiw---Keoke
 
130 miles per tank is very low. My BJ8 (with HD8 carbs) gets 240 and I complain at that.
If you have a manuel they will tell you how to check the richness and reset the carbs leaner. What you do, basicly, is lift the pin under the dash pot dome on the light side of each carb (one at a time) and listed to the engine speed. Lift only about 1/8 inch (3mm). If the engine speed it is too rich. If it faulters or dies it is too lean. It should increase for a second the slow again if it is correct.
Also listen to the exhaust sounds from the rear for smoothness. Only slight sputtering is allowed.
Then we have the white pants test. Wear your best white pants (tan will do) and walk behind the exhaust pipes.
 
Hi Andrew,
You must be referring to HD8, not HD6.

I don't quite understand this statement:

"2) the float bowl valves were replaced with modern nylon/neoprene tiped SU valves, but I had to bend the forked float levers more than the recommended 7/16 " clearence."

Why did you need to bend the levers, & why not the 7/16" clearance? This is important.

A quick check - With the chambers & slides removed, you should be able to adjust the jet heights to be flush with the jet bridge. The fuel levels should be noticeably below the jet tops. Follow the directions in the reference, it's easy to get the adjusting screws confused.

When the chokes are pulled, the jets should lower noticeably & return to the flush positions when released. The jet adjustment will of course need to be reset to the normal running position of about 2 to 3 turns.

You can get a very good how to on the HD8 here;
https://www.hazelden.ca/austinhealey/index.html
Study it & follow the procedures exactly.

Lastly, the metering needles should be type UH. Make sure that the needles are correct & that the jets measure exactly .125", & no more.

I agree with Keoke on the fuel gage sender leak.

Good luck,
D
 
Check the spark plugs first. If black and sooty you are running rich, and it's a carb problem. If not then the problem is elsewhere unless there is some unusual float bowl problem causing fuel to leak out the drain tube or bowl gasket.
 
Dave, thanks so much for that link on the HD8s. I've been trying to get my carbs working properly, without success, for a while (ever since my mechanic helped by "tuning" them). I wash poking around blindly, and now have something to work with. Cold start is difficult, then idling is low, then exhaust is dirty, then backfiring for the first 10 minutes, and then post ignition run on. Of course, all was find before the "expert" helped. I can't tell you how much I appreciate the things I learn here.
 
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