ColtonMelson Posted January 19, 2013 Report Share Posted January 19, 2013 Hello, I have an 83' datsun 720, nap-z24s 2 wheel drive single cab. I have put a rebuild kit on the carb, changed the fuel filter, plugs, cap, rotor,oil, oil filter, and some other small things im sure. The truck sat for around 10 years when i got it for FREE. I drained the tank and all other fluids and had it running the next day. After a set of tires, tags and a seat cover, i was on the road After the truck running great for about a month and getting 30mpg, something happend. it died one day on me. llong story short it just never did run the same. After putting some money into it, checking spark, making sure i had fuel up to the carb, (still have not checked the fuel pressure), and hooking my dist vac line back up i have my truck running good enough to take it down to the store for beer. Now, when i start it, it starts great. no problem. When i take off down the road, it drives great. after getting about 2 or 3 miles down the road and my engine starts to heat up, i start to notice the changes. The throttle hits a really big flat stop at low RPM, in any gear. I come to a stop sign and when i take off i have to feather the throttle to get it to a high(im guessing lean) RPM. Then i take off and every gear i go through hits this flat spot or stumble untill i get to a high rpm. Please elp im new to datsun but not engines or forums Quote Link to comment
.sunlover Posted January 19, 2013 Report Share Posted January 19, 2013 Have you pulled the valve cover and checked your valve lash? I'm sure you know that if the trucks happy at high rpm, fuel pressures probably not a problem. Cheap as hell to get a fuel pressure gauge though. Quote Link to comment
ColtonMelson Posted January 19, 2013 Author Report Share Posted January 19, 2013 I am embarrassed to say no i have not checked my valve lash..... tomorrow i will buy a fuel pressure gauge.. What should the pressure be on a good fuel pump? Also What should i look at after this. i have read a small passage on this site about a common problem of an over rich override that will not let the truck run and have to "limp home". i have done this. please help. I have not replaced the plug wires. could this be a problem? should i just spend 300$ on a weber 38 2 barrel? Would this handle my problem. My thought is that there is some type of failure in the carb but i have been wrong many many times in my life :-) Quote Link to comment
ggzilla Posted January 19, 2013 Report Share Posted January 19, 2013 This problem is not caused by valve lash. Either the coil has gone bad, or the carburetor has a blocked passageway. Quote Link to comment
ColtonMelson Posted January 19, 2013 Author Report Share Posted January 19, 2013 I would think if my coil is bad it would not start... But! i do have 2 coils... SO i will check both of them tomorrow with a plug test (thx guy i didnt think of that). But like i said my concern has been that there is still something wrong with the carb (even after a small clean and gasket kit). SO anyone else wanna pipe in with some ideas. Im about ready to just order the damn carb cuz i Love driving the truck and i cant drive it. it frustrates me that it runs great for about 3 miles then runs like shit. Its like a teaser.... So any input will be taken in to acct. if a brand new weber is the answer, please let me know. But it would be crushing to spend 300$ and the truck still not run.... Thanks to all who read and reply!!!! Quote Link to comment
Rays74 Posted January 19, 2013 Report Share Posted January 19, 2013 Vacuum leak OR partially blocked primary jet OR the accelerator pump has quit working. The "huge flat spot" that has come about all of a sudden reminds me of when the carb on my '74 started acting up.....one quick look into the throat as you jazz the throttle will tell you if the accelerator pump is squirting fuel or not. --Ray Quote Link to comment
ColtonMelson Posted January 19, 2013 Author Report Share Posted January 19, 2013 unfortunately i did put a new accelerator pump on the carb when i put the gasket kit on it. i could not get even one jet out of the carb. EVERY jet in that carb would strip before it would break loose.... take this into consideration. I did drowned it in carb clean and blow it out with air and try to bloe the jets out the best i could... Quote Link to comment
ggzilla Posted January 19, 2013 Report Share Posted January 19, 2013 Scrap that carburetor. Quote Link to comment
ColtonMelson Posted January 19, 2013 Author Report Share Posted January 19, 2013 WHoo HOo. Now were talking!! Quote Link to comment
ColtonMelson Posted January 19, 2013 Author Report Share Posted January 19, 2013 ok so i have some new info! NO! my accelerator pump is NOT working..... like i said i put a new pump in it and blew the whole thing out with crab clean and air. ALSO im getting a small vac leak at the throttle body bushing were the shaft runs into the primary barrel. SO what do i do next. ANY thing i can do to get the accel pump working??? did i do somthing wrong? i know i put the check ball, spring, plunger, and rubber gasket all in the right place. any old experiences would be nice to hear. Quote Link to comment
ggzilla Posted January 20, 2013 Report Share Posted January 20, 2013 Scrap that carburetor. Quote Link to comment
ColtonMelson Posted January 20, 2013 Author Report Share Posted January 20, 2013 Im thinking thats whats gonna happen.. 300$ and free shipping on the weber 38 2 barrel.. Now what should i do with my exhaust after that just to pull a lil more ponies out of the 2.4? Is a header really going to make much of a difference? or should i just do a better mufler and a 2" pipe out and keep the stock headers?? Any one here that has played around with is and knows? if i got headers i would only buy the pace setters for 150$ Quote Link to comment
ggzilla Posted January 20, 2013 Report Share Posted January 20, 2013 The stock cast iron header is the best performance. 1 Quote Link to comment
Rays74 Posted January 20, 2013 Report Share Posted January 20, 2013 This may be of some help........right beside the accel pump well, there is the discharge well with the check ball assy (green bit in the pic). Pull the plug from it and be sure the spring, weight (brass) and chrome ball aren't gummed up. Also check (carb spray) that the discharge tube is clear as well. The accel pump and this work together so check it out :) Edit....this all assuming you are willing to diagnose the Hitachi.......(GGzilla cracks me up :p) --Ray Quote Link to comment
Snoopy76 Posted January 22, 2013 Report Share Posted January 22, 2013 Hey there Colton, I would assume it was you I met the other day at Napa.... Either way, welcome to Ratsun!! Anyway, what caught my eye about your post here is that you are saying that it heats up when you drive it. What popped into my head is to check the timing. Seems to me that I remember that if your timing is off, this can cause the heating issue, and problems driving. It also might be good to check your coils cold and when hot.... Then again, I could be WAY off.... Quote Link to comment
Snoopy76 Posted January 22, 2013 Report Share Posted January 22, 2013 another thought is to make sure that the choke is operating properly.... Quote Link to comment
ColtonMelson Posted January 23, 2013 Author Report Share Posted January 23, 2013 Thanks Snoopy76 and yeah that was me you met at napa. haha thats cool, small world. But i have recently set timing 5* btdc, deleted the egr and vvt crap, and moved accel pump to the second hole that is on the plunger, from the rebuild kit, and it seems to be running a lot better. still have the vac leak at the throttel plate. So i will need a carb some time. but for now its getting me around Quote Link to comment
ggzilla Posted January 23, 2013 Report Share Posted January 23, 2013 > still have the vac leak at the throttel plate That is usually not the carburetor, but is usually the gasket or the adapter plate. Quote Link to comment
Suspect Posted January 23, 2013 Report Share Posted January 23, 2013 I have the same problem with my 73 620, big flat spot. I use a 69 Hitachi L16 carb with manual choke. I bought the carb re manufactured on ebay a few years back. If I pull the choke some, the dead spot goes away but then it won't idle very well. Quote Link to comment
ColtonMelson Posted January 24, 2013 Author Report Share Posted January 24, 2013 yes i have noticed when it is cold it seems to run alot better. im thinking it cuz the choke is still on. But when i was talking about the vac leak in the throttle body, im talking about were the shaft goes into the carb. the throttle cable hooks to it the it runs inside if the carb to hold the butterfly flap that opens and closes. The other barrel is obviously ran off vacuum on the stock carb Quote Link to comment
ggzilla Posted January 24, 2013 Report Share Posted January 24, 2013 Ah, the dreaded "worn throttle shaft" problem. You can drill and bush it, but it is easier to get another used carburetor. - there are still a lot of good stock carbs in the wrecking yards. Or can it and buy a weber. Quote Link to comment
Snoopy76 Posted January 25, 2013 Report Share Posted January 25, 2013 Hey Colton, check Craigslist. There was a Weber for sale on there a few days back, used, from a Mazda for $150. Might be the carb you need, then you'd need to make or source an adapter if its not correct Quote Link to comment
ColtonMelson Posted January 27, 2013 Author Report Share Posted January 27, 2013 Any one know of any companies that make performance cams for the nap-z engines? I have not been able to find any performance cams in my search. Quote Link to comment
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