SU Carb, no power on acceleration.

T

TV8

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Deb took Brian her Commer for an MOT yesterday which he passed. Problem is he isnt running right at all. Since having the SU fitted he has seemed a little flat on acceleration but now he is struggling to pull away at all without spitting and back firing. He starts and ticks over fine but is virtually undrivable. I know he has got the needle that gets fitted for a 1725 but Brian has a 1600 engine fitted. Ive checked the dashpot oil level and thats fine. Gonna take a look at the carb settings tonight but as Im getting stick from Deb for convincing her to have the SU mod done I just wondered if anyone could give me any pointers, I do have a needle for a 1600 Sherpa which I might try. The exhaust is also virtually straight through as its a single TR8 box so back pressure will be minimal.
Cheers Dave
 
Some vans are fine straight out of the box with the SU but I found Bonnie needed the needle tweaking due to a big dead spit on acceleration. I tried various needles but couldn'the find the perfect match so l ended up filing a tiny flat on the shank right at the top which cured it. Runs great now. Remember you screw the middle ture screw in to rItchen it up on the HIF carb.
 
Thanks for the replies guys, had a look at him tonight and he's running really rich which adjusting the mixture screw doesent seem to reduce. Tried the Sherpa 1600 needle and it was no better so after a lot of messing about (that mixture screw is a right ba""ard" to get at) I fitted the needle that came with the carb which I presume was from a 1275 mini and it seems a lot better co2 is now down from 12+ to 2.5 and he picks up ok whilst revving him. Road test tomorrow night but I have my doubts as the mini needle would surely be wrong for a 1600. As a matter of interest the mixture screw does only move 180 degrees is that right? To be honest the needles all look the same to me
 
I had this on mine and turned out the SU had been built with the float chamber valve in upside down! Not saying it's that but popping and backfiring could be to do with float levels set incorrectly as may cause similar symptoms. Other than that Sounds like an air leak in the vac advance or the advance not working correctly.
Not sure where you're based but there's a genius SU guy in Dinnington, he tuned on a rolling road, customised the needle to my spec etc etc etc all for £91 the difference was amazing
 
Well Ive been messing around with the SU and it's still not running right. I've replaced the points and condenser with an Accuspark unit and he starts and runs fine for about two miles irrespective of which needle is in the carb and then he starts spluttering and dies. Leave him a few minutes and he will start and run for about another two miles. So he picks up on acceleration ok now but then falters after two miles, I think it's fuel related but I am at a loss now as to what to do next.
 
Take the fuel cap off and try again, could be a blocked or kinked breather pipe.
 
Tried that Panky and it made no difference, thanks for the advice though. I'm thinking carb now as I can't get more than a couple of turns on the mixture screw and I'm wondering if there's an issue with the float. Big bonfire is looking favourite at the moment.
 
Worth an ask. To answer your earlier question the mixture screw should turn a lot more than 180 degrees, probably three or four turns. You probably already know but the screw raises and lowers the jet - it could be that the mechanism is jammed.
 
Thanks Panky, gonna try stripping the carb tomorrow. Was hoping to use him for the TR international at Malvern next weekend but Debs has got no confidence in his reliability now so it looks like we will be camping. Newark Auto jumble tomorrow so might keep my eye out for a spare carb.
 
Well I've now replaced the SUcarb with a another SU which has improved things a little but he still starts to splutter and loose power after about 3 miles and won't accelerate above 30mph once he's done the 3 miles. As the ignition is electronic and the coil is a quality replacement I'm now thinking fuel starvation, blockage in the fuel line/tank or fuel pump. Going to remove the alloy fuel tank this weekend as the fuel sender hasent worked since it was fitted so I need to fix that and I'm going to give it a good clean out. I've also ordered a fuel pump just in case so will replace that as well.
Spoken to the guy at Dinnington but he can't fit the van in until after the weekend at Martins and we couldn't get the van to him at the moment anyway.
If I can't fix him this weekend we will not be able to make it to Martins which would be a shame.
 
Yeah, sounds like fuel as well. I had a similar problem where the float bowl would fill up under a trickle and cough and fart after a few kms. Turned out to be the fuel line.

Do you have an electronic fuel pump? Pretty easy to test those with a bucket of fuel and a short line.
 
dmulally said:
Yeah, sounds like fuel as well. I had a similar problem where the float bowl would fill up under a trickle and cough and fart after a few kms. Turned out to be the fuel line.

Do you have an electronic fuel pump? Pretty easy to test those with a bucket of fuel and a short line.
Click to expand...

No unfortunately it's a mechanical one with glass top. It's always full when starting the test runs. I'm going to check the fuel line and if it's in good condition I will blow it out with an airline. Got to remove the fuel sender from the tank so will give the tank a good flush out at the same time. Thanks for the advise.
 
Hi Dave I had a very simular problem with jim after we woke him up from his winters hibernation, could not get him to run once he had warmed up, messed about stripping and cleaning the SU even swopped the one from Gladys but stil no luck. Endded up changing the manafold gasket and he runs perfact now.We did a 660 mile trip at the end of June with out a hitch.
 
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