pleadingbark Posted October 31, 2011 Share Posted October 31, 2011 What are the signs the carbs are clogging up? Last night I was driving the car and it seemed like it lost almost all power and was running on 3 cylinders. The car had no power, could hardly rev and was constantly back firing. Pulled the plugs and the front 3 are half brown/half black and the back 3 are brown but were soaking wet. Would that indicate that the rear carb was stuck open? If you shut the car off it would be fine until you got on it while driving then it would suddenly run like total crap again. Any thoughts? Its got a pertronix on it now with a new coil, but it was running like a top all day then just suddenly started running like crap. Does it sound like the back carb's clogging up? Its done this before when it gets low on gas and the fuel filter gets clogged up, but I stuffed a new one on. Did have to drive w/o one for about 2 miles though as the car pooped its pants on the side of the road. Quote Link to comment Share on other sites More sharing options...
at-jefft Posted October 31, 2011 Share Posted October 31, 2011 (edited) Check to see if the choke is binding and a jet is stuck in the down position. Edited October 31, 2011 by at-jefft Quote Link to comment Share on other sites More sharing options...
pleadingbark Posted October 31, 2011 Author Share Posted October 31, 2011 I noticed the front was stuck open, but it would still do it with it pushed up and closed. Should I just pull the choke out and shoot some cleaned up tehre? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 31, 2011 Share Posted October 31, 2011 Isn't there a little filter right on the carb body itself? I seem to remember my brother-in-law getting stranded a couple times before he cleaned and coated his gas tank, and we pulled the little screen filter and it was full of rust. Quote Link to comment Share on other sites More sharing options...
at-jefft Posted October 31, 2011 Share Posted October 31, 2011 Have you double checked your float levels? remember that the front and rear is different for 72 roundtops. Float level was the solution to my low power this last summer. Isn't there a little filter right on the carb body itself? I seem to remember my brother-in-law getting stranded a couple times before he cleaned and coated his gas tank, and we pulled the little screen filter and it was full of rust. yup there are brass filters on the banjo bolts. Check those. Quote Link to comment Share on other sites More sharing options...
pleadingbark Posted October 31, 2011 Author Share Posted October 31, 2011 Isn't there a little filter right on the carb body itself? I seem to remember my brother-in-law getting stranded a couple times before he cleaned and coated his gas tank, and we pulled the little screen filter and it was full of rust. Will do that right when I get home. Gracias. Quote Link to comment Share on other sites More sharing options...
gogriz91 Posted November 1, 2011 Share Posted November 1, 2011 Will do that right when I get home. Gracias. There are some videos on youtube for troubleshooting SUs that might be helpful. http://www.youtube.com/user/MossMotorsCom?blend=8&ob=5#p/search/2/wLRFnTJ28oQ Quote Link to comment Share on other sites More sharing options...
pleadingbark Posted November 2, 2011 Author Share Posted November 2, 2011 Have you double checked your float levels? remember that the front and rear is different for 72 roundtops. Float level was the solution to my low power this last summer. yup there are brass filters on the banjo bolts. Check those. Those little filters were 100% it, they were both almost totally clogged. Cleaned them out and stuck inline glass fuel filters on them until I can get the fuel tank dropped and boiled out. Quote Link to comment Share on other sites More sharing options...
2_4680Z Posted November 23, 2011 Share Posted November 23, 2011 (edited) Glad you solved your problem. I read about those screens but how can the rust make it through the first fuel filter, through the pump, then get stuck right before the carb? Maybe I am misunderstanding something. Do you have the FSM in hard copy or online? It helped me a lot to do a baseline balance of the carbs and there are some thorough diagrams of the SUs. My plugs were just as wet and black as you described since I bought it. I bought the Z Car "240z Tune-Up" dvd and did a half-way "tear down" of the carbs then balanced them. It took about 2-3 hours. After I balanced them with the meter, somehow (not sure if it was while driving it 50 miles in a week or during the tuning?) my front three champion plugs were completely dead and had me running on three cylinders. After putting NGK plugs in and gapping them, it runs so much better. Edited November 23, 2011 by 2_4680Z Quote Link to comment Share on other sites More sharing options...
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