1984 720 4x4 manual tran 2.4 motor

[mattthruwalkin]

first off HELLO ALL!!!!! new guy here and so glad to have found yall i am matt from florida

ok here is the problem , again 84 nissan 720 4x4 runs great on the road then i get on the dirt road headed home and it shuts off like it ran outa gas i have replaced the fuel pump , fuel filter , fuel relay "black box under the dash on the passanger side"
and still it will run great till you hit the dirt roads then after hitting a bump act like it runs out of gas and need towed home then it mite start back up in 30 minutes or 3 days ?????? after many hours and days of google searches i found one reply stating that a worn needle in the carb can block off the fuel and cause this problem ????? any ideas ???????


also second issue is temp gauge is not working and not sure why had a shop get rid of all vac lines that i didn't need and got it back with the temp gauge not working

problem 3 only 1 coil is working replaced the coil not working and still not firing so i ran some wires from the top of the working coil "negative and pos post under the rubber coil cover to the dead coil and unhooked the factory wires" both coils are now working , was wondering if this will screw anything up or not been running for 3-4 months fine with coils bridged

soo if it is needing a new carb anyone found any webers cheap yet or is 250-260 about the best price i will find threw weber direct for the kit

also i have a 5speed and was wondering if 5th gear is always loud as in hearing the gears rattle or grind

[fastboatman29212]

I would think that the "cuts off when on the dirt road" is an electrical problem. It does not sound like a carb problem to me.

My 5th gear is noisy and it's because it has a tooth out in 5th. Other 4 gears are fine. I'd avoid using 5th gear if I were you. You will probably still get pretty decent MPG with only 4 gears.

Temp gauge. Hmmmm. Not sure about that either, but sounds like something electrical. I have a 1984 factory service manual and we can troubleshoot this later if you want.

Coils are mysterious and scary. I have no idea.

Keep the thread going and we'll get it sorted out, (probably).

Oh, and WELCOME to NICO 720 trucks.

[mattthruwalkin]

ty for the fast reply , if its electrical were would you start ? i did inspect the distributor all wires seemed fine none loose or broken inside the cap @ the base when it goes in to the block it's self
next time it stops running i think i'll turn it in to a boat anchor .......... one other thought does the fuel pump need to mount tightly to create a ground to work properly the new pump was a universal and has a little play in the housing like you can slide the pump back and forth but come to think of it the whole reason i replaced the old pump was the truck would shut off on the dirt roads can't deal with it much more i need it to be dependable again so my wife can drive it back and forth to work , the good or bad news is an auto shop here told me 65$ an hour to fix it and nooooooo clue how long it would take same with the carb if i bought a weber he wouldn't even give me an estament on how long it would take


so wait to buy a carb as it is more then likely an electric problem?

[fastboatman29212]

It sounds like maybe the fuel pump might be shutting off, possibly due to a bad ground? That would cause the motor to cut off.

[N-Dually]

Welcome!

I agree, I think your shutting off issue is probably electrical. I have been knee deep in my harness. Make sure all your grounds are good. I used a continuity checker/setting on my DVM and made sure all my connections are good. Wiggle the wire, while you are testing it. Look for frayed and exposed wires. Fix them now of else. Else? Like what? Oh, IDK a fire in the cab like I had.... (NOT MY DOING)!!!!

Now, having said that... How clean is your tank? Check to see if the fuel is clean going to your pump. - Just to be sure.

Check the end connector on your temp sensor. They are sometimes very loose. I had to tighten mine up when I replaced the sensor. I just pinched it a little with pliers.

Speaking from experience, I would forgo the carb rebuild. Save your money and get a Weber.

Good luck!

[breadbox]

yeah the temp gauge runs off a single spade clip connector, I forgot to reconnect mine at first, just look for a spade clip hanging off the intake and make sure there is something plugged into it.

I would just go over the rear wiring and see if anything got hacked up. I'd start looking at all rear light wiring then move to the fuel tank(might want to clean it)and check the wiring there.

[mattthruwalkin]

hey guys found the problem with the temp gauge there was a yellow wire just floating around in there that when to no where after some browsing threw some of your guy's pic and doing a search i found that wire goes to the sensor just above the thermostat LOL so hooking it up now and that will prolly make it work , still have no idea what makes the truck shut off , but the last time it did i pulled a coil wire off and sat it next to the fender and turned the key and had a spark so thinking its not getting fuel ???
i did run a wire from the positive wire on my fuel pump and to the positive post on my battery a couple of times it started back up and other times it would not all times u can hear and feal the fuel pump working , next time i will see if i can see gas in the window on the carb , and keep a can of gas to dump some in the carb to see if it will start back up when it shuts down.

also i will drain the tank today and check for trash and change fuel filter again , you guys know of any way to blow out the fuel lines or purge them ??? also anything i can run threw the carb to clean it better then a can of carb cleaner ???

also do you really think that bad shocks could be tripping my inertia switch "fuel relay black box under dash brand new "
if checking wires would you start at the fuel pump wires first ??? or where and do i cut open the tape on the wire harness or just look for worn or broken spots and check there ??? ty again guys

[fastboatman29212]

My bet is that the fuel pump is not properly grounded. The fuel pump should have a wire grounding it to the frame. If the ground is interupted, then the fuel pump shuts off, carb runs outa fuel, truck don't go no more.

I do not think you need a new carb. But if you decide to get one anyway, probably should think about a Weber.

If it runs fine on paved roads and only cuts off on bumpy roads, I'd say your fuel pump is not properly grounded.

[N-Dually]

Ok, just because you hear and feel the pump running isn't enough. You have to make sure that it is primed. I had this happen to me both times a ran out of gas. (need to replace the sending unit) Anyways, what I did was to undo the hose from the tank to the pump (THE TANK SIDE!!!). Pour gas in to the hose and top it off. Quickly reconnect the hose to the tank. Unhook the fuel line going in to the carb. Turn the key just enough to engage the pump. DO NOT TURN IT OVER. When you see the fuel come out of the hose by the carb, stop and reconnect the hose. You should be good to go now.

Having a fuel pressure gauge helps to determine whether or not you have any pressure.

Good luck!

[synack7350]

as far as the coils based on your description you are just running them both in parallel of off one coil. well the problem with that is timing. one is the exhaust coil one is the ignition coil. you're either firing both your plugs for ignition (which wouldn't necessarily be a bad thing but its not to design) or you are firing both your coils on exhaust which would be a bad thing but I doubt the truck would run in that case. You prolly have a bad module in your dizzy maybe it half way burned out. or you don't have continuity on your other set of wires.

A coil is just a transformer it steps up your voltage from 12 volts to I dunno 40,000 volts or so (your mileage will vary).

The fuel pump I have to agree with all others. It sounds electrical but it doesn't have to be the ground that is pooping out. could be the hot too. You just have to hook up a meter to it (or a 12vdc test light) and start jiggling s***. when the light goes off or the meter goes to 0vdc you've found your problem. lol I've never heard of any inertia switch that black box is just a cut off relay.

[rocky1234]

float bowl goes low....ck my thread dtd oct 18....i'm determined to find the problem

[mattthruwalkin]

ok update time , the fuel issues still stalls from time to time but i keep my trusty 1/2 inch drive ratchet under the seat to smack mt bish up " wack the carb on the passengers side just above the fuel window and the truck starts rite back up ..... neat trick just beat it , now new problem is just recently it started missing and getting about 10 miles per gallon and the whole motor shimmies poked a test lite in to the top of the wires where they plug in to the top of the distributor and i have a few plugs not firing or a few bad wires looked like 3 outa the 8 wires were getting fire or "were lighting up the test light " , sooo i was thinking time for plugs n wires ? tested both coils and both will start the truck and run the same with either one un plugged or plugged in , " took one main coil wire off the 1 coil and started it took same wire and ran to second coil starts fine just same lope or shimmie in the motor " , leaks oil , oil pan gasket is shot and steering box leaks power steering fluid , drivers side cv boot is now missing and its rusting appart as we speak , also on a good dark night i can pop the hood and start it up and see and hear the lovely lightning bolt show near the spark plugs ........ so any chance that 50-80$ plugs n wires would fix the misses and the shimmy or think i burnt a valve due to the exaust leak where the pipe connects to the manifold .

drove the truck from carrabelle fl near apalachacola fl all the way home to lake county 300-400 miles and took 120$ in gas but still made it home so now i got ol betsy parked for a tune up and repair , just wondering if yall know if plugs n wires would fix it ty i also have 180k miles on it and it don't run hot or take water and does not have water milk in the oil

[dreadsiren]

I've owned and rebuilt 4 of these fun little trucks plugs & wires can cause alot of problems!! also a good idea to test your ignition relay, (under hood, passenger side, 4 blade, usually blue) I had one going out that was hard to id and it caused me sooo much grief! easy to test esp if you have a good spare (its the same as your heater relay above the fuse box) or 12.00 - 34.00 on ebay if its bad (oem#2523089977). but get plug wires fast as this same problem caused my icm in the dizzy to fail (wire shorted out against exhaust manifold and I didnt catch it soon enough) I've gotten 320k with out a rebuild on a z24, very hard to kill motor, body usually rusts out before the engine quits good to test all ignition components, or if you happen to have a parts store that will test things for free (autozone) then ask them to test both coils, your distributor (ICM), and the relay... save time and money!!

p.s. if it does turn out to be the ICM let me know as I have all the info you will be needing as far as interchange, oem and parts numbers. this JUST happened to me, lol.

[Malia123]

We have a 84 Datsun 720 King Cab 4X4. There is an issue with the truck cutting out over 55mph. The more you give it gas the worse it gets. It runs fine below 55MPH. We have replaced, carb (weber), fuel filter, plugs & wires, distributor & rotor. anyone have any ideas

[Malia123]

We have a 84 Datsun 720 King Cab 4X4. There is an issue with the truck cutting out over 55mph. The more you give it gas the worse it gets. It runs fine below 55MPH. We have replaced, carb (weber), fuel filter, plugs & wires, distributor & rotor. anyone have any ideas