Just bought 84' nissan 720

[JoeCool]

32mpg. Thats pretty impressive in a truck.

 

Mine is getting right at 25mpg on the highway with bursts up to 90mph.

I feel like this can be improved upon by removing the tail gate, and using skinnier tires.

 

The gasket paper is still has the carb sealed.

 

Does anyone here use any other than the recommended fuel filter?

I believe that it is somewhat restrictive. I cut the old one open and there was less filter media than you will find on an aircooled vw.

 

 

Does NOBODY watch Mythbusters here? They determined that myth to be just that, a MYTH. Removing or lowering a truck's tailgate does absolutely nothing for fuel economy or power. Trucks are designed and wind tested with the tailgates on.

[ggzilla]

I watched both episodes

 

The found tailgate DOWN was bad. Tailgate off didn't help

 

Tailgate off and net across was the most fuel efficient http://mythbustersresults.com/episode64/

[Robert]

Driving back from Atlanta to Charlotte last night, my engine went way lean under boost.

 

As soon as it started creating boost it shot to 16:1 A/F.....a while later, its was even idleing lean and the ECU couldnt compensate.

 

Stopped at Auto zone and bought a new filter...didnt help. Checked fuel pressure and it was ok. Removed the pressure regulator and cleaned it...didnt work.

 

Drove down the road about 50 more miles and it went past 16:1 normal driving and I had to pull off again.

 

 

Finally I hooked a fuel hose to the supply line from the gas tank and blew backwards through it.....I could barely get air through it. I went to a gas station, pulled off the gas cap and used the tires pump to force air through the line. It cleared it and it ran fine. 11.5:1 at 15lbs.

 

I do get alot of rust that looks like black sand in the filter. I guess my tank is pretty bad inside.

 

Anyone know if there is a pick up filter inside the tank?

Anyone know where to get a new tank?

 

Not trying to highjack.

[Robert]

 

32mpg. Thats pretty impressive in a truck.

 

Mine is getting right at 25mpg on the highway with bursts up to 90mph.

I feel like this can be improved upon by removing the tail gate, and using skinnier tires.

 

The gasket paper is still has the carb sealed.

 

Does anyone here use any other than the recomended fuel filter?

I believe that it is somewhat restrictive. I cut the old one open and there was less filter media than you will find on an aircooled vw.

 

 

With the stock tires, 3.7:1 gears I was getting 34mpg consistantly (highway only) and about 22 city.

 

Of course I swapped in fuel injection. My carb was getting 24mpg tops.

 

 

With 10" wide drag radials, 4.11:1 gears, and 248 cams, I get 25mpg.

[hellcatfa]

Tailgate = wind resistance

 

Dont trust the television for scientific information.

 

I wonder why in the show fuel enconomy with the net the was better.

Because even a net creates drag.

Ill bet the net manufacurer was a sponsor for the show.

 

 

Robert your truck sounds like a bad mofo. I am quite envious.

Any photos of the swap?

[hellcatfa]

Today I adjusted my valves because I have been experiencing some backfiring . A few intake valves were a bit tight.

 

I'm backfiring if the truck is under load and the accelerator is fully pressed. Only seems to be doing it when the secondary tries to open.

 

The secondary does not appear to be opening, but I cant hold the throttle open long enought to see because it shoots flames back at me.

I have tried retarding the ignition but doesn't make it any better.

[xsdg]

Compression test

[ggzilla]

^^ this

 

Compression test will tell you if there is a mechanical problem (as opposed to electrical or fuel problem)

 

If low compression in one cylinder then get a vacuum gauge reading to further pinpoint it.

[ruckycharms]

Awesome truck man. Good luck with this one.

[hellcatfa]

Is it possible to change out a main bearing without pulling the crankshaft?

 

Will the ka24 out of a 1st gen altima bolt into my truck?

[hellcatfa]

Also whats the best way to go about lowering the rear of the truck?

 

Are there any other options than lowering blocks?

Air shocks?

[hellcatfa]

All my problems have been solved.

 

Backfiring, poor fuel economy, lack of power, dieseling, and a glowing manifold .

 

All this was caused by a worn PCV valve.

[hellcatfa]

Truck has been a great daily driver all this time. Until yesterday.

 

I drove it high speed down a bumpy dirt road for about a half mile. When I got back on the pavement something was wrong.

 

Sluggish sputtery acceleration, backfiring on acceleration. If i give it gas it spudders and backfires. It was running just fine before my high speed jaunt. 

Idle quality is poor didn't seem to change much. Maybe a bit of a miss now.

 

Fuel filter changed. Vacuum lines in check, no leaks. Carb seems to be operating properly. Coils both sparking. No blown fuses. Fuel pump pumping.

Blew some air back into the fuel tank. Spark plug wires seem to be sparking without grounding to anything.

 

Im thinking distributor cap,or rotor.... Cap seems pretty worn. Any ideas?

 

This is my only transport aside from my motorcycle, and its cold out. Need to get it up and running.

Any help is greatly appreciated.,

[hellcatfa]

Jumpered fuel pump relay the problem still persists.

 

After fumbling with the coils and getting zapped a few too many times I realized something. I can dissconnect the one closest to the cab and has no effect. if i dissconnect the farthest forward coil it runs like crap.

 

Weak or dying coil causing the problems? They both seem to pack a pretty good wallop.

 

I haven't changed the cap yet. Probably buy one tomorrow.

 

This one has me stumped.

[Charlie69]

Check timing.

[wayno]

You said you did a high speed run, check your plugs,  clean them, check the gap, it's free to do this except for your time.

Also you said it was bumpy, maybe all that vibration loosened some dirt and it got in something in the carb jet if yours has one.

[hellcatfa]

Distributor is in the same spot it was. Tried advance/retard didn't change the situation.

Distributor has a good ground.

 

I didn't make the run at an high rpm, just driving fast. Will probobly check 1/2 the plugs tomorrow.

Last I checked my carb was spotless inside. It burned pleanty of fuel tinkering in the driveway.

 

Im almost positive it's ignition/spark related. Just dont know where to look.

 

On one test drive it ran pretty good through the rpms  in 1st and 2nd, then randomly studder/spuddering through the gears.

A second its fine then a few seconds of spuddering.

 

It almost sounds like its firing more than one plug or all of them at once. Seems to backfire out both ends near simultaneously.

[hellcatfa]

Distributor cap was a no go. It changed nothing.

 

Pulling valve cover to see if something came loose

 

[hellcatfa]

I believe that the problem has been isolated.

[wayno]

So, what was the issue?

I believe that the problem has been isolated.

[hellcatfa]

The problem was never solved.

 

I switched cars but now im back in the 720.

 

Was almost left on the side of the road earlier. Random backfire through the carb at low rpms. Random miss. Ran through high rpms ok.

Now the same but it starts sputter then nothing like its out of gas then over again.

 

I'm starting to think the fuel pump is on its way out.

 

Cleaned out the carb today.

Coils sparking, wires dont seem to be arcing to one another.

Jumpered fuel pump.

 

Have plug wires and a rotor on the way.

 

This problem just doesn't seem to go away.

[84720FourWheel]

Wrong thread.

[Charlie69]

Check your timing sounds like worn timing chain set.

[hellcatfa]

I dont doubt it Ive been worried about that forever.

 

Yesterday I reoriented the plug boots at the distributor. made it run a bit better. Also removed the fuel filter, and jumpered the relay.

 

Drove it about 16 miles this morning constant random stumbling in the low rpms and while cruising. Seems to accelerate without stumbling. Also cruised a bit better.

 

Was going up a very big hill and it dies out like no fuel. I suspect the fuel pump going bad, or an in tank filter clog.

 

Does this truck have an in tank filter????   Could there be a stuck check valve in the fuel purge system? This problem was caused by excessive vibration I know that.

[84720FourWheel]

There might be a screen on the pickup. Fuel filter is next to the fuel pump on the frame.

Get a large mason jar, unhook a fuel supply line after the pump, put it in the jar and have someone turn the key to on. If the pump fills it in roughly 30 seconds it's probably fine.

 

There's better ways to test it, but they require expensive tools.