Just bought 84' nissan 720

[84720FourWheel]

Also, get a timing light and check your timing before throwing parts at it.

[hellcatfa]

Well I pulled the plugs just now and they were shot.

 

Five of the insulators were loose. They just kind of float around the electrode. A few had chipping as well. Four of them the ground was touching the electrode completely shorted. It seemed as though they had melted.

 

Im going to get some plugs later and see what happens. I guess that road took out the plugs.

[84720FourWheel]

Overly lean mixtures cause excessive heat. Do you still have the OEM carb?

[hellcatfa]

Okay the plugs fixed the main problems studder, backfire, and miss. Now it purrs like a kitten.  B)

Never seen plugs quite this bad. Slightly melted, insulators loose.

 

Now the problem is the cutting out like its starving for fuel.

 

I drove it about 4 miles then hit the highway. I get to about 55 cruisin hell yeah the truck is fixed. Then cuts out phhh phhhh but wait then takes off as I floor it.

Back to the back roads fluttering the pedal in first and 2nd to keep it running sometimes accelerating without flaw. I pulled over to check the fuel pump, pump jumper, and sightglass.

Pump is pumping, jumper in place. Sightglass is just past halfway. Thats strange. Coils sparking. Limped it home like this. Partway home it cured itself then back to cutting out.

The truck never actually died, it just completely cuts out during acceleration then jumps back.

 

This one has me stumped.

[hellcatfa]

Just had another look around the engine bay. Both in the light and dark.

 

No visible arcing wires. Fuel in float bowl. Both coils sparking.

 

Carb sucks fuel visibly when throttling up, but doesnt seem to burn it up right away.

I can watch it suck in fuel for about 3- secs before it thinks about raising rpms then takes off.

 

Sprayed carb cleaner around intake and carb base while running. No apparent vacuum leaks.

 

My plug wires and rotor should be here tomorrow. I dont think they will help.

 

If its not one thing its another.

[hellcatfa]

Well went to start the truck this morning. Started right up then dies. Ok normal.

Start the truck again it stays running kind of out of the ordinary. Still experiencing the problem I had last night like its out of gas.

 

I go look in the carb got fuel, both coils sparking. I throttle it and it stumbles. I do this a few times. Now I try it with the secondary.

I lift the butterfly it sucks in fuel stumbles then clears up. After doing that a few times. It seems cleared out and running good. I go drive it around and no problems.

[84720FourWheel]

So your secondary throttle plate was stuck?

[hellcatfa]

No I dont think it was stuck . Although I think its a bit stiff, and would like to see it open easier.

 

The fuel lines have begun to degrade. All the fumbling around caused some dingleberries to make their way into the carb.

It was pulling fuel but not enough for hills and stuff. Also it was running fine untill I try to tackle a hill and the main jet cloggs.

 

Pulled out some bits of rubber, and a small cedar berry from the float bowl.

 

Its not real fun to make 7 unexpected stops to have to backwash the jet with carb cleaner. :ninja:

 

Stock carb question. Are there any alternative air cleaner options? The stock one seems to rattle too much. I dont care how its bolted or how tight.

[hellcatfa]

I just realized something from your avitar four wheel. I think my headlight relay is bad. When my brights are on only the two middle lights light up. Sometime when switching they all turn off.

[84720FourWheel]

Actually my high beams shouldn't have been lit up, I put h4 headlights in, and it messed with the grounding so all the lights would be on.

 

Check your headlight fuses, I blew one when I wired up my fog lights, and I got 3 headlights. Maybe both fuses are blown?

 

It could be the switch that is bad though. Could be dirty or something.

[hellcatfa]

Am I suppose to have this crazy gasket under my carb?

 

 

 

http://www.autozone.com/fuel-delivery/carburetor-mounting-base-gasket/victor-reinz-carburetor-mounting-base-gasket/138334/?_requestid=11479586

[Charlie69]

Yes if you are running stock carb.

[hellcatfa]

Dang.. My truck hasnt had one of these since I have had it. It has a stock carb.

 

It seems to run okay for not having it. I suppose thats why my idle is always kind of funky.

 

I dont think I could cut that one out of gasket paper. If I bought one what problems might it fix?

[Charlie69]

Idle

[hellcatfa]

This gasket is the answer. Im going to order one soon as I can.  Cant find one for less than 13 dollars, but I guess thats cheap for what it is.

 

I discovered my truck doesnt get enough fuel unless the fuel line dangles about 2-4 inches below the tank.

[hellcatfa]

What do yall think of this. I think its calling my name.

 

http://austin.craigslist.org/cto/4898821478.html

[84720FourWheel]

I wouldn't pay 1200 for a truck with a bad head gasket. Other than that, it's in pretty good shape. The dash isn't even cracked.

 

I would probably offer around 900 bucks.

[hellcatfa]

Im with you about the price. Its a bit high. I may go check it out in a day or 2 if I get my truck running right.

 

I think the fuel pump may be getting weak.

 

From what I understand is these trucks have a non restrictive fuel return line. This hasn't caused me problems in the past other than worry.

Now that the pump is getting older it isn't supplying sufficient pressure to the carb because of the recirculation.

Something must be done.

 

The pump is pumping good just not as much fuel as I would like is making it into the carb. :(

 

Has anyone dealt with this problem before? I was thinking of slightly restricting the return flow.

[84720FourWheel]

Try replacing the supply lines. The return line isn't the issue. Fuel only goes into the tank after the fuel bowl is full.

 

Carburetors need fuel volume more than pressure. Only 2-3 psi is necessary. I would bet that you have an old fuel supply line that is internally collapsed and restricting flow.

 

Do the mason jar test that I described on a previous post, and see if you are getting adequate fuel volume.

[Charlie69]

Offer $500 tell him if it was 2 wd the offer would be $300.  You get it home and find out there is more than a head gasket needed.  Cover your ass!  Hell it ain't even a King Cab!

 

I just turned down a 85 720 4x4 minus engine and trans for $200.  It has no title so I will only pay $50 for it.  Scrap value.

[hellcatfa]

Thats spot on price matching. I feel exactly the same way. Id go 700 if it was real nice,and with a/c and stuff.

 

 I found a post from a while back about an lb20 fuel return that is practically a pin hole.

 

Iast night I restricted the return with a brass collet off a harbor freight dremel tool. It was the one for the small bit thats like 2mm.

I have not had any problems since. Even accelerated up a pretty big hill from 55 to 70 without stumbling.

 

As for fuel hose I had some bad luck with advance auto fuel line I replaced the hose from the tank to the pump. Well yesterday morning I was fumbling with it and noticed it had a small rip.

Brand new fuel hose degraded slightly, and broke in 3 days time. I bought the hose I think 4 days ago.

 

I think my truck was designed to run in the 80s. There was more unburnt fuel in the atmosphere therefore making it perform better then than now. :rofl:

[hellcatfa]

Fuel pump crapped out. It still sounds great. Just no volume or pressure. It might pump 3 gal/hr. Fuel siphons through it just fine.

 

Gets just enough fuel to accelerate and cruise at about 50 then the shuttering begins.

 

New one is on the way.

[hellcatfa]

Got my new pump installed and the trucks running great.

 

Now I have what I call a flat spot when trying to accelerate. I believe it was starting this before the new pump. I can floor it through all the gears just fine and cruises fine at any speed. However while cruising in 4th or 5th if I floor it I have what I would call a flat spot. No shutter or stumbling. Just light acceleration.

If I ease the throttle on it accelerates better than trying to floor it. Kind of an annoying problem.

 

Pump primer is ok

Timing ok

 

Any Ideas?

[harlow426@mail.com]

What do yall think of this. I think its calling my name.

 

http://austin.craigslist.org/cto/4898821478.html

 

I have never pay'd more than $300 4 a 720. I just wait 4 the right one! Have had enuf of them I know what to look/listen/feel for.

[hellcatfa]

I think the timing chain jumped, or lost a piston. It blew about a mile from home. Still managed to limp it home somehow. Not really sure how I made it home.

 

I was just cruising and it let loose inside.       It started running like this  ------>   :frantics:

 

 

Might not sell if I can find a nice v8 to swap.