Fingerlickin_B Posted May 14, 2016 Report Share Posted May 14, 2016 Hi people, Have a 32/36 on my 4K that for the most part works okay...BUT.... It will idle fine, but after driving for a few minutes idles fast then eventually stalls. I have figured out that this is due to fuel dribbling out of the venturi at idle...but only after it has been driven. It only happens after a few minutes of driving. If you start the car & let it idle (hot or cold), it will do so forever, with no venturi dribbling unless you then take it for a spin. Tried both Repco low pressure electronic fuel pump & brand new standard spec Nikki mechanical fuel pump. New fuel lines. New fuel filter. NEW CARBY! Checked needle & seat, looking good. Removed & checked jets/tubes, no cleaning required, just like new also. Checked float level & adjusted for 1mm variation from spec. Put a restrictor inline with the hose from pump to carby with a bloody tiny hole in it...no difference. Pro Fuel pressure regulator also yields no result, except the the bowl runs dry when you give it to the car up a very long & very steep hill. Checked for vaccum leaks, none found. I'm now thinking EGR valve. Since the vacuum line to the valve isn't connect to a vacuum source, I expect it to be doing absolutely nothing all day long. However, does anyone think it possible that maybe it opens up/leaks when exposed to the higher temperatures of loaded engine operation but may otherwise stay sealed if only seeing idle temp exhaust gasses? Other than this possibility, I can't for the life of me figure out why the carb is doing this & it's driving me insane! Please help... Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted May 15, 2016 Report Share Posted May 15, 2016 Wouldn't the EGR just add dirty air to the inlet and not affect the fuel system?? I have figured out that this is due to fuel dribbling out of the venturi at idle.. Have you seen this happening? That's pretty definitive if you have. In theory the good ol' mechanical pump keeps a constant pressure going as it is rpm related, so low flow at idle and lots at high rpm. That leaves the float and needle to control the rest, and both of them you have sorted out. One other is the heat from the motor expanding the fuel in the lines, the problem that causes vapour-lock and used to push the fuel out of the fuel filter on one of my KE70s. Only if the motor has more heat being given off after being driven than just idling, which is most likely. That would put more pressure in the system after the fuel pump, so up the line and through the needle & seat. A long shot as the pump shouldn't pump against the increased pressure in the line anyway. Go for a run, let it idle at home and make sure it dies. Go for the same run, let it idle with the bonnet open and a wet rag on the fuel line/pump and see if it still dies. Best answer always.. "put a 4AGE in it!" Ah, no, my 4AGE does the same and its injected. Idles higher and higher from 1000-1300, then goes slower and slower until it dies. Doesn't do it when cold, only when hot. I think I might have it sorted now. Quote Link to comment Share on other sites More sharing options...
Clapped out Posted May 15, 2016 Report Share Posted May 15, 2016 (edited) Probable cause -Crap leading up to your carby and resting on the needle and seat, in which causing your needle and seat not to seal properly, put in a fine fuel filter, not those re-useable redline jobs, -And even though its new, replace your needle (needle and seat), and check your float to see if fuel is filling up inside, may have to replace, this should fix your problem, Your needle and seat is where your problem is, partially staying open and causing your bowl to fill up with fuel and creating your "dribbling" problem through your venturi, hope this helps, cheers! Edited May 15, 2016 by Clapped out Quote Link to comment Share on other sites More sharing options...
Fingerlickin_B Posted May 15, 2016 Author Report Share Posted May 15, 2016 Thanks for the replies :) The ProFuel branded regulator ended up having a broken diaphragm, so it wasn't actually doing anything. However I'm still at a loss as to why the inline restrictor didn't help. Either way, installed a new regulator today & she's behaving quite a bit better! After a few pure idling & driving then sessions today, the throttle plates are dry at idle :D Bit of idle speed variation however...heat as suggested by altezzaclub perhaps? Pretty happy now, but the drive to & from work tomorrow will be the decider! Quote Link to comment Share on other sites More sharing options...
rebuilder86 Posted May 15, 2016 Report Share Posted May 15, 2016 can you explain, did you mean fuel was dripping out the vent into the venturi, or dripping out the main jet while at idle? Quote Link to comment Share on other sites More sharing options...
Fingerlickin_B Posted May 15, 2016 Author Report Share Posted May 15, 2016 Of that, I couldn't be sure. It was just dripping from the inner edge of the venturi. If it does happen again today I'll look more closely. Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted May 15, 2016 Report Share Posted May 15, 2016 Put a restrictor inline with the hose from pump to carby with a bloody tiny hole in it...no difference. However I'm still at a loss as to why the inline restrictor didn't help. Don't forget that these only restrict flow, not pressure. So they will starve it at high fuel demand but not affect it at idle. Quote Link to comment Share on other sites More sharing options...
Fingerlickin_B Posted May 16, 2016 Author Report Share Posted May 16, 2016 Good point :) Quote Link to comment Share on other sites More sharing options...
Fingerlickin_B Posted May 28, 2016 Author Report Share Posted May 28, 2016 Okay, so now this is driving me mad! Same symptoms as before, idles great when warm, but drive for a while & idle is shit, plus stalling a off-idle hesitation. No fuel dribble now, no matter what setting the FPR is on, even at highest setting. Ready for this? Put the LM1 sniffer in her today & stalling is caused by a stupidly lean idle mixture, that only occurs after driving for a while. After idling badly for some time just sitting idling, the mixture gradually richens. Let her sit for a few minutes & idle is very rich. Driving & pull to a stop: Around 40/1 Idle from start: Anywhere from 12-18/1 Blocked something, but WTF & HTF?! Please help...I've never experienced anything like this before :( Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted May 29, 2016 Report Share Posted May 29, 2016 Put the LM1 sniffer in her today & stalling is caused by a stupidly lean idle mixture, Ah, at least you know whether too rich or too lean! So, as you drive something reduces the fuel level or flow so when you stop there is not enough fuel to idle. Then slowly it catches up and has excess fuel for idle so it goes rich. The mechanical pump is chugging over slowly at idle, so it might take a minute to get the fuel back up to 'rich' level, whereas if you idle it from startup you won't burn the fuel level down to 'lean'. If I were you I would bodgy in a low-pressure electric pump before the mechanical, so it supplies more fuel at idle. Haven't you got that Repco one you used? That will tell you if it can be solved by more fuel low down. The mech pump obviously supplies enough higher up. Don't be despondent, I have the same problem on the new 4AGE. It now idles wonderfully when cold and while warming up, but once up to temp and you come to an intersection, when you lift off it dies to 400rpm or stalls out. If you flip the accelerator as the revs drop, it will grab the idle before it dies and poke it back up to 1000rpm, sometimes 1300. If you push the clutch in when driving and let it idle down slowly it will hold the 1000rpm. If I open up the idle screw when it is in the dying phase, it idles at 1600rpm in the 'normal' phase. So I'll spend the next few days doing the same as you, chasing an idle. Quote Link to comment Share on other sites More sharing options...
Fingerlickin_B Posted May 29, 2016 Author Report Share Posted May 29, 2016 Your symptoms sound identical to mine! Only thing is, I'd have thought that running down in gear from high revs with the needle seated would result in a full bowl at stop, especially with the mechanical pump...but maybe not... Thanks for the idea, will try it out next weekend & deal with the hassle until then. Today I almost managed to find a decent middle ground between idle types, but not quite there & it wouldn't be actually fixed anyway. If your suggested test setup works, then all will be good. Have a Holley Red in the garage somewhere :) Quote Link to comment Share on other sites More sharing options...
Fingerlickin_B Posted May 29, 2016 Author Report Share Posted May 29, 2016 Needle eventually seated after running down gears & bowl filling...oops...not enough posts to edit... Quote Link to comment Share on other sites More sharing options...
rebuilder86 Posted May 30, 2016 Report Share Posted May 30, 2016 these symptoms all sound like a pooly callibrated hot idle compensator valve... does this carby have one of those? Quote Link to comment Share on other sites More sharing options...
Fingerlickin_B Posted May 30, 2016 Author Report Share Posted May 30, 2016 Nope... :( Quote Link to comment Share on other sites More sharing options...
Fingerlickin_B Posted June 2, 2016 Author Report Share Posted June 2, 2016 Found the Holley. What do you think? Never had this problem with sidedraught Webers...ever! Quote Link to comment Share on other sites More sharing options...
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