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Engine Barely Running - Need Help

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Gary Pope

Jedi Trainee
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I got my new SU HS-6's all shiney and looking great. Couldn't get the car started after an hour of trying. Eventually after turning the jets way down almost to the point of unscrewed off the jet holder and chokes full on it fired up. Sounding terrible all flappy and won't rev up, sounds like it is running very lean. I have good sparks but cylinders 1 & 6 seam to be bone dry. The middle four are wet and sooty. After reading Shawn Bens post I am starting to wonder if I have piston ring problems. I don't have anything to test them with. I am not sure how this has happened because the car was running great a couple of months ago, I changed out the old Volvo HS-6's for 3 sets of other carbs. Now after buying a new set of HS6's which incidently are the ones used on the 2500 Saloon (Alec) so they should work in theory.
I feel at a total loss now, not sure what to do next.
Help needed .. Thanks.
 
First thing that comes to mind.....did you also get the interior parts all nice and shiny too? I have heard that if that is the case, they won't operate correctly, apparently cleaning and polishing internal parts is a major no-no.

If not, then I would suspect adjustment. I would not think that you have piston ring problems. If all was fine when it last ran, have you considered sticking valves?

Just a few ideas, I do not profess to be an expert mechanic.
grin.gif
 
Check float levels.

Look for vacuum leaks....spray WD-40 around manifold gaskets and related areas, when engine is running.....if it runs worse (because it's sucking in the WD-40), you've found your vacuum leak.

Also, jets centered? Fuel filter clean? Good fuel pump pressure?

[ 04-14-2003: Message edited by: aeronca65t ]</p>
 
Sorry to hear of the problems. Double check (1) float heights, (2) proper needle designation, (3) dashpot fill. Good luck.
 
I checked tonight .. all plugs are bone dry.
The jets are fully lowered and even with chokes on .. no gas gets to the plugs.
I stuck finger inside carb over jet hole and is plenty of gas there.

How can this be .. ? is the gas going into the sump ?

Not sure what to try next ..
 
Gary
As suggested earlier, I'd first check the float levels and needle and seats. Are the throttle linkages operating evenly?
While pulling the plugs, are you sure the wires are back in the correct firing order and actually getting spark. I know this is elementary, but often assumed.
If you don't have a compression gauge, pull one plug and spin the engine, it should blow your finger off the plug hole, as I can't imagine all the valves sticking, or a broken timing gear from sitting.
I'd bet it's floats or spark if it won't even try to run.
Good luck.
Dave T
 
If the problem is in the carbs, procede as follows. Remove the dashpot& piston assy, look at the fuel level in the main jet, it should be appx 60 to 80 thou below deck level. this is set by propper adj of the floats. Then look at the needles, are the shoulders below level with the piston botom? start flush as a baseline.Or raise it 20 thou if it was flush.
Put the pots back on and double check the jet centering, they MUST slide up and down freely, without a hint of binding.
Next put your hands over the carb throat and have your assistant turn it over How is the vaccum?? Both should pull several lbs and it should be even.
Try starting off at 3 or 4 flats of the last jet setting. If it is still rough check to see if one carb seems to be doing all the work, leaving no srtong vaccumm in the others throat. This is fuel starvation from a bat gross jet.
Good luck
MD(mad dog)
 
I get good spark and plug leads are definately on correct order.

The needles I have are "BBQ" and are not fixed, they are on a spring and can wobble about from left to right and up and down. Shoulder is flush with piston edge.

Since my jets are way down maybe 8-10mm below bridge, then the gas has a long way up to travel up towards the carb throat. Is it possible that the engine vacuum can only suck the gas out of the bottom of the jet only as far as the carb and not through the manifold and combustion chamber.?
 
Gary
It really sounds like the float levels are set way too low, lowering the jets dosen't change change the fuel level in the carb, only the opening between the jet and the needle.
I haven't played with SUs for a while and am not sure of the float level spec for your carbs, but MDCanaday's suggestion sounds like a good start.
In my Spitfire book, it calls for 1/8 in. gap between the inverted top of the float bowl and the float. It seems that this was std. for all the SU carbs but I may be wrong for your model.

I don't know if you have used Ask.com but going there and typing SU Carbs gave lots of helpful links.

Hope you get it running soon, as driving is more fun than fixen.

Dave T bluspit@attbi.com
 
Gary--It's been my experience that the more correct needle for the HS6 SU's on the TR6 is "BAX", not "BBQ". Perhaps that's contributing to your problem. Also, your jet should be 0.100, not 0.090 as was common for HS4's which may be what you have installed.
 
Rick,

Thanks for the info .. the bbx is much richer needle than bbq which is apparently the direction I need to go in.

I am using 100th jets.

BAX 990 958 926 896 861 814 774 742 718 694 673 652 630 610 590 570

BBQ 990 950 930 908 877 852 813 795 777 760 744 720 695 670 647 623

[ 04-15-2003: Message edited by: Gary Pope ]</p>
 
I now fear the worst.
On examination of the oil from the dip stick .. it just runs off like thin liquid.
The oil is a dark grey color .. no sign of white foam, just liquidy .. like gasoline has mixed with the oil.

What a bummer.
 
If you've got fuel leaking into your sump, you probably have a bad fuel pump (assuming you've got a mechanical fuel pump...not electric fuel pump conversion). This would also cause low fuel pressure which would explain the poor performance.

With most mechanical pumps, the diaphragm will fail and allow fuel to enter the crankcase.

Be careful! I saw an air cooled VeeDub explode because of this problem (a Molatov Triumph?).

Of course, this could be super rich condition...but I'd think it would take a stuck float to richen mixture to that level.

[ 04-15-2003: Message edited by: aeronca65t ]</p>
 
Oh man you took the words right out of my mouth.. a torn fuel pump diaphram sounds like the culprit
yesnod.gif
 
The fuel pump is only 1 year old brand new .. however it could be broke I suppose.
The thing is, it still pumps gas to the carbs, the float chambers have gas in them yet the gas doesn't wet the plugs even with chokes full on.

I will check out the diaphram tonight.
 
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