720newbie Posted February 16, 2014 Report Share Posted February 16, 2014 Hey guys im new to this forum and new to owning a carburated nissan 720 4x4 truck...It has a weber 32/36 ( pretty sure but not positive ) and all the emissions stuff has been eliminated. I just bought this pickup due to the fresh rebuild and rebuilt tranny and how clean and straight the body is. I have driven it 50 miles exactly and then refilled the tank and it was almost 5 gallons of gas (4.995 gallons)... Would the carberator needing rebuilt cause my truck to get such shitty mpg i figure this truck should at least get 18 mpg with a fresh rebuild. It does have a small vacuum leak by the throttle plate.,. Any input on this would be helpful im kinda lost Quote Link to comment
MicroMachinery Posted February 16, 2014 Report Share Posted February 16, 2014 Who rebuilt the motor? Quote Link to comment
smoke Posted February 16, 2014 Report Share Posted February 16, 2014 That is really low. Might want to make sure your tank was the same amount full as it was the first time, this can throw u off sometimes. Quote Link to comment
datzenmike Posted February 16, 2014 Report Share Posted February 16, 2014 18 would be on a good day, 15 is more likely. 10 is very possible if short trips to work and home where the choke never shuts off. Poor milage... Driving too fast and too close to the guy ahead of you. Every time you use the brakes you just threw away the gas used to get you to that speed. Avoid braking by spacing yourself and anticipate slowing in advance. As soon as you see a red light ahead release the gas and coast up to it. Does it really make any sense maintaining your speed only to put the brakes on at the last second to wait at idle?? Cam timed wrong but usually the performance is very bad also. Fuel leak at tank or lines. Carb jetted wrong (too rick) Choke stuck on or not shutting off. Carb flooding. Float stuck or adjusted wrong or needle valve dirty and not closing. Ignition timing wrong. (retarded) Possibly T V V stuck not allowing vacuum advance when motor has warmed up, as it should. Vacuum advance on distributor stuck or vacuum advance leak in hose or hose removed by a well meaning owner. Brake(s) dragging. Wrong thermostat (too cold) or thermostat stuck open. Motor never reaches propper efficient working temperature. Too thick of an engine/trans/trans case or differential oil Could be any one or several of the above. Quote Link to comment
Cpl620 Posted February 16, 2014 Report Share Posted February 16, 2014 WOO, that thing must be like 800HP! Quote Link to comment
Zeusimo Posted February 16, 2014 Report Share Posted February 16, 2014 When I Rebuilt My Motor The Mileage Was Halved I Bought A Wideband And It Turns Out I Was Running SUPER Lean!! Quote Link to comment
720newbie Posted February 17, 2014 Author Report Share Posted February 17, 2014 Motor was rebuilt by Southworth machine shop here in eugene Oregon and they do awesome work I've used them many times ... I guess I'm gonna just wait a few hundred miles and see if anything changes cause the motor is still tight and not even close to being broken in . Thx datzenmike I'll check on some of those things and CPL620 800 horses....ha I wish that would make one bad ass wheeler Quote Link to comment
Draker Posted February 17, 2014 Report Share Posted February 17, 2014 I checked the mileage on mine on the last fillup.. 14.5 mpg. But lots of driving in 4x4 and snow. Maybe 16-17 normally. I'd wait and check it again later. Welcome to the forum.. lots of us in the Eugene area. 2 Quote Link to comment
datzenmike Posted February 17, 2014 Report Share Posted February 17, 2014 Yes, add a tight rebuilt motor to my list. You'll find as it breaks in the idle will increase. Quote Link to comment
Huntin720 Posted February 19, 2014 Report Share Posted February 19, 2014 I average 17 in mine. When I got it i was getting 14-15. I replaced torn fuel filler hose, opened an unnecessarily blocked breather for the gas tank, and replaced a clogged fuel filter and now 17 is the magic number. I have the stock hitachi carb though so you should probably expect less mpg and more hp than mine. 1 Quote Link to comment
720newbie Posted February 25, 2014 Author Report Share Posted February 25, 2014 I think I need to let this motor loosen up plus I'm gonna completely rebuild the weber carb Quote Link to comment
720newbie Posted March 11, 2014 Author Report Share Posted March 11, 2014 Ok so today after talking with Weber about a diaphram on the opposite side of my accelerator pump I found out that I have a very rare Weber double pumper carb. They don't make these anymore and haven't for a while and they only get a call about once a year for one of these new diaphragms($24)... Damn kinda spendy but I'm thinking I am due to buy a new 32/36 that's up to date lol... can't do 10 mpg for too long Quote Link to comment
ronnny Posted March 11, 2014 Report Share Posted March 11, 2014 my tranny is bad still so don't use 5th gear and I still get 16-18 and have a 32/36 that could use a rebuild Quote Link to comment
ggzilla Posted March 12, 2014 Report Share Posted March 12, 2014 Yes buy a $350 new carb instead of $24 to fix the rare performance version of the 32/36. 3 Quote Link to comment
datzenmike Posted March 12, 2014 Report Share Posted March 12, 2014 At a tank full per week saved with a new carb, say 10 gallons US at $4 a gallon that's just under 3 months. Sell that junker on E bay. 1 Quote Link to comment
720newbie Posted March 12, 2014 Author Report Share Posted March 12, 2014 I was thinking of doing some research and possibly re jetting it and using it strictly for off road... It takes 3 minutes to swap it out and the acceleration is crazy with these carbs it almost instant with no bogging but it sucks fuel down...I have definitely put in the time tuning the damn thing though Quote Link to comment
tr8er Posted March 12, 2014 Report Share Posted March 12, 2014 Re jet it. Why not. Get a new one too. And I'm not sure if it is a problem on 720's but is the fuel pump regulated to webers desired pressure? My weber ran for a long while sucking down those hydrocarbons way faster than needed. Anyone want to comment on the stock 720 fuel pump pressure? Quote Link to comment
ggzilla Posted March 12, 2014 Report Share Posted March 12, 2014 Stock 720 fuel pump pressure is 3.8 psi, perfect for Weber carbs. If you have determined the accelerator pump diaphragm is leaking, you know what to do next. Quote Link to comment
720newbie Posted March 12, 2014 Author Report Share Posted March 12, 2014 I love the fact that this forum is so helpful to people who seek help. Definitely beats having to take it go a shop to diagnose a problem really liking this forum. You guys rock Quote Link to comment
datzenmike Posted March 12, 2014 Report Share Posted March 12, 2014 You should be getting a minimum of 50% better mileage. If leaking fix it. If jetted and leaking fix them both. If double pumper for a six cylinder Capri or w/e get the correct carb for your application. You don't need it Quote Link to comment
720newbie Posted March 12, 2014 Author Report Share Posted March 12, 2014 Ya that's definitely the first on the list of new things for my truck Quote Link to comment
datzenmike Posted March 12, 2014 Report Share Posted March 12, 2014 If you are indeed getting 10MPG then this isn't good for the rebuild. The unburnt gas is going to wash the lubricating oil off the cylinders and rings and dilute your oil. Plugs, combustion chambers and rings will carbon up. Rings will stick in place and can score the cylinders. 1 Quote Link to comment
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