Mike8199 Posted January 12, 2017 Report Share Posted January 12, 2017 On my 83 720, (z24) what controls the second throttle valve? Linkage, vacuum? (The one not under the choke) Quote Link to comment
datsunaholic Posted January 12, 2017 Report Share Posted January 12, 2017 Both linkage and vacuum. The linkage allows it to open, the vacuum does the actual opening. That way it can't open when the main barrel is closed (low throttle but high vacuum) or when the engine is bogged down at low RPM, but heavy throttle. Quote Link to comment
Mike8199 Posted January 12, 2017 Author Report Share Posted January 12, 2017 Both linkage and vacuum. The linkage allows it to open, the vacuum does the actual opening. That way it can't open when the main barrel is closed (low throttle but high vacuum) or when the engine is bogged down at low RPM, but heavy throttle. ok, i ask because my truck has been sitting inoperable for 17 years and i recently rebuilt the motor and tranny, (manual) but i havnt touched the carb. but when im driving her around i notice she doesnt like to go above 3k under load keeping me around 55mph max speed, and hills, forget about it like 35 max). so im thinking the secondary in the carb was stuck, i unstuck it with some carb cleaner and a screw driver but i havnt been able to test the truck because my starter just died last night... lol. any other ideas on what else it could be besides the secondary valve not opening?? Quote Link to comment
datsunaholic Posted January 12, 2017 Report Share Posted January 12, 2017 Plugged up jets. The jets on these are at the very bottom, so that's where all the sediment is. But one thing at a time. Fix starter, then test since you freed up the secondary. If that didn't work then take the carb off for a good internal cleaning with carb cleaner AND compressed air- and I mean more than what you'd get with canned air (don't have to take it apart, but you need to get the jet plugs off to access them for cleaning). Quote Link to comment
Mike8199 Posted January 12, 2017 Author Report Share Posted January 12, 2017 Plugged up jets. The jets on these are at the very bottom, so that's where all the sediment is. But one thing at a time. Fix starter, then test since you freed up the secondary. If that didn't work then take the carb off for a good internal cleaning with carb cleaner AND compressed air- and I mean more than what you'd get with canned air (don't have to take it apart, but you need to get the jet plugs off to access them for cleaning). Will definitely try that once i get the starter on. (should b here today, but its raining so might install it tomorrow) will report back the results, thanks for ur help!! Quote Link to comment
Mike8199 Posted January 13, 2017 Author Report Share Posted January 13, 2017 Ok so starter is fixed, and second butterfly moves, but i dont know when its supposed to open. Sitting there revving it I don't see it moving, but when it is running it is harder to open it manually via the linkage. So vacuum is workin i guess. But when i do open is manually, i dont see any fuel being sprayed. Thoughts? Quote Link to comment
Mike8199 Posted January 13, 2017 Author Report Share Posted January 13, 2017 Update the truck drives better at high rpm, but now when i step on the throttle a little but it sputters a bit, but if i go past half throttle it smooths out. Is this a pluggef jet characteristic? And can i pull off the carb without any gasket on hand? Quote Link to comment
datsunaholic Posted January 14, 2017 Report Share Posted January 14, 2017 Sounds more like the accelerator pump isn't working. Could be plugged up, or the plunger is cracked from drying out. Can check that without pulling the carb, it's on top. 2 screws, has the rubber bellows on it. Can try spraying carb cleaner down it with the plunger out to clean it out. You can pull the carb without a gasket in hand, but putting it back on will be the problem... If you're really handy with a razor scraper you can clean the spacer off and make your own gaskets. They sell rolls at the parts stores. Pair of scissors and a hole punch, or an x-acto knife. I make gaskets all the time. Hard to find them for what I rebuild. Quote Link to comment
Mike8199 Posted January 16, 2017 Author Report Share Posted January 16, 2017 Took it off, opened the bowl sprayed the main jets, with cleaner and air, now the truck runs great at idle, but if i blip the throttle it sputters way worse than before. I then took out the accelerator pump thing, cleaned it, no change. Quote Link to comment
datsunaholic Posted January 17, 2017 Report Share Posted January 17, 2017 OK, you opened the bowl, but did you take the jet plugs out? Because if you didn't, all you did was push all the crap in the bottom of the bowl into the jet chambers. You gotta take the jet caps off. Now you'll probably need to take the JETS out, to clean them, as something is probably lodged in one of them. Now imagine doing this on the side of the road. I have done this. Quote Link to comment
Mike8199 Posted January 18, 2017 Author Report Share Posted January 18, 2017 Rebuilt her and sputtering is gone, thanks all Quote Link to comment
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