Tomakze Posted March 8, 2010 Report Share Posted March 8, 2010 the other day, i decided to take the little roadster out to pick up some ink from wally world. It has been running wonderfully for the last few months, so i have been driving it a lot. :) well, it was warmed up, started instantly, and went down the road willingly. after i drove a few blocks, it suddenly started to occasionally miss. this is unusual for the car, so i immediately became suspicious. as i pulled up to the stoplight, i put the clutch in, and it died immediately. i coasted as far as i could and pulled over. after waiting a short time i decided to try to start it. i turned the key, and it immediately sputtered happily to life! of course, it ran only a few seconds, and died again. i can always start it, and it starts willingly, but it wont stay running. if i hold it at the right throttle, the rpms will slowly increase, (running horribly the whole time...) and after it gets over 3k rpm, it runs well. i nursed it home in this way. anything under about 3k rpm, and it spits and sputters. over 3k, it has plenty of power and runs beautifully. I know i have fuel getting into the bowls, because i can see clean fuel flowing between both carbs, and no bubbles. it actually starts even easier right now than usual, but wont stay running. upon first starting it, it runs for about 4 minutes with no issues, but after that, it starts acting up. help? i miss my toy, and the weather keeps mocking me with sunny days. thanks in advance! Quote Link to comment
MicroMachinery Posted March 8, 2010 Report Share Posted March 8, 2010 Sounds to me like it could be over-fueling. When it runs at the higher RPM, it can handle the amount of gas, but at low RPMs, it drowns. I'm not incredibly familiar with the roadsters, but they run the SU carbs, correct? Again, I haven't familiarized myself with those style carbs yet, but it sounds like something is causing an over fueling condition. Wrong? I could be, but that's just what it sounds like off the top of my head.. assuming it IS in fact, the carbs... On that note, are you sure it's your fuel system, and not the ignition? What do your points look like? Condenser? When was the last time you went through all the usual tune-up stuff? Cap, rotor, wires, plugs, etc.. Quote Link to comment
Tomakze Posted March 8, 2010 Author Report Share Posted March 8, 2010 It does use SU carbs. i dont think the ignition system would cause these symptoms, so i haven't really looked into that much, but it has a new cap, wires and plugs. someone on another forum said to check the floats and see if one has sunk, but i thought the overflow tube would prevent that from affecting the engine... but i agree, it does seem to be getting too much fuel. now if only i can figure out why! thanks, and if anyone else has any ideas, keep 'em coming! with any luck, ill get this little turd running today, and then i can start preparing my turbo 300zx to hit the street again. Quote Link to comment
datzenmike Posted March 8, 2010 Report Share Posted March 8, 2010 Take the air filters off and reach into the carbs with your finger and gently lift the slide up and let drop. It should lift smoothly and easily with no binding or tightness and should drop smoothly and seat with an audible 'click'. Quote Link to comment
Tomakze Posted March 8, 2010 Author Report Share Posted March 8, 2010 well, the floats are fine. the front carb was puking fuel out of the overflow tube, but when i disassembled the float chamber, the float had no fuel in it. it dry as a bone. after starring at it for a while with a befuddled look on my face, i put it back together and started her up. it ran great, and no fuel came out of the line. we took it for a spin to autozone to buy a fuel filter (i followed the lines, and it didn't have one at all!!!!) i installed the filter, and i cant get it to reproduce the stalling issue. it ran great, we went all over town. im just confused because i didn't fix anything!?! i will have to try the slide trick, but judging by how well its running right now, im not sure thats it. i suppose it could have been before though... im going to bet it will do it again, so please keep the ideas coming!!! this is frustrating! Quote Link to comment
Skib Posted March 8, 2010 Report Share Posted March 8, 2010 well, the floats are fine. the front carb was puking fuel out of the overflow tube, but when i disassembled the float chamber, the float had no fuel in it. it dry as a bone. after starring at it for a while with a befuddled look on my face, i put it back together and started her up. it ran great, and no fuel came out of the line. we took it for a spin to autozone to buy a fuel filter (i followed the lines, and it didn't have one at all!!!!) i installed the filter, and i cant get it to reproduce the stalling issue. it ran great, we went all over town. im just confused because i didn't fix anything!?! i will have to try the slide trick, but judging by how well its running right now, im not sure thats it. i suppose it could have been before though... im going to bet it will do it again, so please keep the ideas coming!!! this is frustrating! your using the bowls with the brass floats right? Quote Link to comment
Tomakze Posted March 9, 2010 Author Report Share Posted March 9, 2010 Yes, it still uses brass floats. Quote Link to comment
MAG58 Posted March 9, 2010 Report Share Posted March 9, 2010 Don't SU's have a little button under the slides to move them up to check that? I know mine do... Quote Link to comment
Skib Posted March 9, 2010 Report Share Posted March 9, 2010 Yes, it still uses brass floats. sometimes the brass floats can stick cock-eyed. or just be sunk. If it is your floats Id get some Z car float bowl lids with the attached "rubber" floats Quote Link to comment
FoxyRoadster Posted March 9, 2010 Report Share Posted March 9, 2010 sounds like its time to freshen up your carbs along with the new floats. The brass floats are prone to springing a leak over time and sinking. Quote Link to comment
datzenmike Posted March 10, 2010 Report Share Posted March 10, 2010 well, the floats are fine. the front carb was puking fuel out of the overflow tube, but when i disassembled the float chamber, the float had no fuel in it. it dry as a bone. after starring at it for a while with a befuddled look on my face, i put it back together and started her up. it ran great, and no fuel came out of the line. we took it for a spin to autozone to buy a fuel filter (i followed the lines, and it didn't have one at all!!!!) i installed the filter, and i cant get it to reproduce the stalling issue. it ran great, we went all over town. im just confused because i didn't fix anything!?! i will have to try the slide trick, but judging by how well its running right now, im not sure thats it. i suppose it could have been before though... im going to bet it will do it again, so please keep the ideas coming!!! this is frustrating! It may have simply stuck or perhaps a bit of dirt was caught in the needle valve preventing it from closing. Just moving things may have freed it up and got it going. Quote Link to comment
Tomakze Posted March 10, 2010 Author Report Share Posted March 10, 2010 the car is continuing to run well... but despite a perfectly fine float and a relatively new needle, the front carb is pouring fuel out the overflow like a faucet. i didn't notice anything wrong with the needles or float when i disassembled them, but i am going to take another look tomorrow. I'm beginning to suspect the lever that moves the needle may be stuck... man, i cant wait until i find enough time to drop my KA24E in... fuel injection is so nice! btw, im hoping i will find time soon to show you guys all the work that has gone into this car since i purchased it. it had sat in a field for 2 years before i got it, and had had some serious abuse before that. it has been a long road to get it to where it is today, and it has an extremely long road ahead of it yet! Quote Link to comment
zerow Posted March 10, 2010 Report Share Posted March 10, 2010 You say 'relatively new needle'. It sounds to me like you have a sticking needle condition, only because the front carb is spitting fuel. Did you check the through pin that the lever rests on? It may have some debris or a burr on it causing the lever to stick. Just a few ideas to look at before it becomes a larger (engine fire sized) problem :o Quote Link to comment
zerow Posted March 10, 2010 Report Share Posted March 10, 2010 sounds like its time to freshen up your carbs along with the new floats. The brass floats are prone to springing a leak over time and sinking. If the floats are the same between the SUs for an L-Series motor, then the P/N is 16061-K1407 for the new and improved plastic floats. If they are in the Nissan bag packaging, you will see that the material is correct. If they hand you old Nissan boxes, check before you leave. I got one plastic and one brass float. Parts Department was confused until they realized someone hand-wrote the P/N on a new label and put it on the box. Hope this Helps. Quote Link to comment
banzai510(hainz) Posted March 11, 2010 Report Share Posted March 11, 2010 buy these instead http://www.v-performance.com/products/air_fuel.html#mikuni_carbs Quote Link to comment
Tomakze Posted March 12, 2010 Author Report Share Posted March 12, 2010 well, as long as the floats aren't sunk for now, im happy. as i said before, im hoping this summer or next winter at the latest, i can begin installing the KA24E i picked up. so, im really trying to not spend money on this motor. I have almost everything i need for the swap, i just need an assortment of wires, some steel, a borrowed welder, and a fuel pump. my father has decided to let me use a garage he rents out for a while, so im good there. at this point, im really trying to get the body ready for more power... as in fix everything. i have an upper spindle that wants to fall out and only 3 brakes at the moment, lol. so for now, im focusing on that! i messed with the lever that the float pushes on to control the fuel entering the carb, and i seem to have stopped the fuel from pouring out the overflow. the car is running fantasticly. look for an updated build write up very soon!! Quote Link to comment
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