SamNewey28 Posted July 10, 2015 Report Share Posted July 10, 2015 Hi all. We are trying to revive a TR4A with twin HS6 carbs. We managed to get the engine to run, but only on 2 cylinders. The carbs were the culprit, and the jets had seized in the (sorry I don't know the actual part name) tube that feeds them to the carb. So we ordered some new jets and have installed them, as well as giving the carbs a thorough cleaning. The problem now is the engine will not start, and we suspect that the fuel either isn't atomising correctly, or being delivered at all. When replacing the jets is it necessary to also replace the needles? They seem to seat alright in the jets and we have centralised the jets also to ensure the needle/piston returns correctly. If anyone has any ideas on how to further test the fault or what could possibly be causing the problems please feel free to snowball a few suggestions. Thanks, Sam. Quote Link to post Share on other sites
peejay4A Posted July 10, 2015 Report Share Posted July 10, 2015 I'll pitch in. Are the float chambers filling with fuel? Did you set the jet height after installing them? P Quote Link to post Share on other sites
SamNewey28 Posted July 10, 2015 Author Report Share Posted July 10, 2015 Hi again. I have just found that there are 2 different jet assemblies for 2 different carbs. The ones I purchased are for AUD284 carbs and the ID tag on my carbs are AUD209. I suspect that is the problem so I will go check if I can return the parts in exchange for the other ones. For my own interest, what exactly is the difference between the jets on the AUD284 and the AUD209 carbs? Thanks. Quote Link to post Share on other sites
RogerH Posted July 10, 2015 Report Share Posted July 10, 2015 Hi Sam, are you using 'NEW' fuel. Old fuel goes off pretty quick. When you rebuilt the carbs did you have a manual to work from. TRy a squirt of one of the sprays to get started Roger Quote Link to post Share on other sites
SamNewey28 Posted July 10, 2015 Author Report Share Posted July 10, 2015 I'll pitch in. Are the float chambers filling with fuel? Did you set the jet height after installing them? P Hi peejay, The float chambers are filling with fuel and we have set the jet height also. The jet height also adjusts with the choke so it is currently moving up and down as we play with the choke hoping to get a bit more variation in conditions. Just for confirmation, by 'setting the jet height' you mean adjusting the sprung nut on the underside of the carb that pushes against the jet base? Sam Quote Link to post Share on other sites
SamNewey28 Posted July 10, 2015 Author Report Share Posted July 10, 2015 Hi Sam, are you using 'NEW' fuel. Old fuel goes off pretty quick. When you rebuilt the carbs did you have a manual to work from. TRy a squirt of one of the sprays to get started Roger Hi Roger, when I built the carbs I followed between both an SU guide online and the TR Workshop Manual, which I also followed when setting the jets etc. We put brand new fuel into the tank and flushed the lines a bit and also filled the float chambers with brand new fuel to begin with. Sam Quote Link to post Share on other sites
Lebro Posted July 10, 2015 Report Share Posted July 10, 2015 After cranking at bit, pull out a spark plug (or 2) if they are wet, then fuel is getting through, so start looking at ingnition problems. Bob. Quote Link to post Share on other sites
SamNewey28 Posted July 10, 2015 Author Report Share Posted July 10, 2015 After cranking at bit, pull out a spark plug (or 2) if they are wet, then fuel is getting through, so start looking at ingnition problems. Bob. Hi Bob, I did as you said and they were dry. This confirms the suspicion that the problem is with the carbs, good check to do though! Now what... Thanks, Sam. Quote Link to post Share on other sites
RogerH Posted July 11, 2015 Report Share Posted July 11, 2015 Hi Sam, you say there is fuel in the float chambers - is there enough. Is it being replenished. Remove the fuel feed pipe from the front carb and spin the engine - is there fuel pumping out? Roger Quote Link to post Share on other sites
peejay4A Posted July 11, 2015 Report Share Posted July 11, 2015 On the HS6 the usual advice is to set the jets level with the jet bridge then lower them 12 flats to get the engine going. Tune from there. Quote Link to post Share on other sites
littlejim Posted July 11, 2015 Report Share Posted July 11, 2015 there are heaps of other potential problems. Spark? timing? air leaks in manifolds? Whiskers on plugs? Plug lead problems. Etc. Welcome to the club. Quote Link to post Share on other sites
SamNewey28 Posted July 11, 2015 Author Report Share Posted July 11, 2015 On the HS6 the usual advice is to set the jets level with the jet bridge then lower them 12 flats to get the engine going. Tune from there. Thanks Pete, this will be of help to set up. Hi Sam, you say there is fuel in the float chambers - is there enough. Is it being replenished. Remove the fuel feed pipe from the front carb and spin the engine - is there fuel pumping out? Roger Roger, As you said I removed the fuel feed, and fuel is indeed coming through to the floats. As one of the more experienced members on this topic I was wondering if you could shed any light on my previous response asking if there is a difference in the jets for the AUD209 or AUD284? there are heaps of other potential problems. Spark? timing? air leaks in manifolds? Whiskers on plugs? Plug lead problems. Etc. Welcome to the club. I am fairly certain the problem is with the carb. We have had the engine running with the original 4° static timing etc. and we haven't changed anything since then. The only thing that has changed is the carb set up. Thanks all, Sam. Quote Link to post Share on other sites
Peter Cobbold Posted July 11, 2015 Report Share Posted July 11, 2015 4 deg static? is that correct? I'd expect nearer 10-12BTDC for 9.5:1 compression. Peter Quote Link to post Share on other sites
stuart Posted July 11, 2015 Report Share Posted July 11, 2015 Your numbers refer to whole carb units both as fitted to TR4a I cant remember if one type is N. American version, There is a difference in jet but it certainly wont be enough of a difference to stop it running. http://www.oldengine.org/members/diesel/SUCarburettors/AUD284.htm http://www.oldengine.org/members/diesel/SUCarburettors/AUD209.htm 4 degrees BTDC is correct for 4 cylinder Peter. Stuart. Quote Link to post Share on other sites
RobH Posted July 11, 2015 Report Share Posted July 11, 2015 Are you sure the choke linkage is allowing full choke ? That has been the problem with poor starting in previous similar posts. You should be able to pull the choke knob out about two inches. Rob Quote Link to post Share on other sites
SamNewey28 Posted July 11, 2015 Author Report Share Posted July 11, 2015 Your numbers refer to whole carb units both as fitted to TR4a I cant remember if one type is N. American version, There is a difference in jet but it certainly wont be enough of a difference to stop it running. http://www.oldengine.org/members/diesel/SUCarburettors/AUD284.htm http://www.oldengine.org/members/diesel/SUCarburettors/AUD209.htm 4 degrees BTDC is correct for 4 cylinder Peter. Stuart. I have driven to David Manners and they were very kind to exchange the jets for the correct part number. The only visible difference was a slight ring cut near the top of the jet. The carbs are AUD209 so the jets now fit the carb as they should. And I agree with 4 ° BTDC for static timing. Thanks, Sam. Quote Link to post Share on other sites
SamNewey28 Posted July 11, 2015 Author Report Share Posted July 11, 2015 Are you sure the choke linkage is allowing full choke ? That has been the problem with poor starting in previous similar posts. You should be able to pull the choke knob out about two inches. Rob Hi Rob, For the purposes of starting I am manually controlling the choke from the engine bay so I can see the jets are both able to go fully down and fully up. I will then tune the choke appropriately when the car is running nicely. Sam. Quote Link to post Share on other sites
SamNewey28 Posted July 11, 2015 Author Report Share Posted July 11, 2015 Right! It appears the problem must have been the jets! I swapped them straight out, sucked some fuel through with a few cranks and it started first time! For an engine that old that has been locked in a barn for years I was shocked at how well it ran! I will now start tuning using the advice from you guys. Thanks, Sam. Quote Link to post Share on other sites
peejay4A Posted July 11, 2015 Report Share Posted July 11, 2015 Excellent. I wonder if the duff jets were 0.09" instead of the correct 0.1". That wouldn't help. Quote Link to post Share on other sites
RogerH Posted July 11, 2015 Report Share Posted July 11, 2015 Keep going Sam. You are doing very well. Roger Quote Link to post Share on other sites
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