New owner Q's

[turtle720]

I just bought a 1980 2wd 720 AT for $200 yesterday and read though some of the posts but have some questions and problems.

1st. I left the lights on like a dumbass for a few hours yesterday. Thinking I drained the battery I tried to jump it but it sounded like a fuse or relay blew when I tried to start it(pretty loud). I read through my Haynes manual but can't seam to find where the issue is. Is there a starter relay? What would have caused it?

2nd when driving it home on the highway it felt like there was no overdrive. Where should I start to trouble shoot this?

3rd When I first started it up and drove it I had to put it in N to brake otherwise it stalls. Any suggestions?

Thanks for the help and let me know what other info you need to help.

[Aven]

Turtle, I can't help with the first two, but the third sounds like a vac line issue. Either cracked, missing or in the wrong place.

[turtle720]

Do I need all the Vac lines?

[Aven]

Depends. Do you have to worry about passing emissions testing? If not, then no. If you do, yup, you will need each and every one of them.

[Charlie69]

#2 Why would you think there is an overdrive?

If the trans shifts 2 times are you take off from a dead stop it is working right.

If in third gear at I believe 45 to 50 miles an hour and you mash the throttle to the floor the trans should downshift to second gear like a passing gear.

You should have an L20B engine & a 3N71B transmission with 3.889 gears in the rear differential.

If you plan on keeping the truck you should hit up ebay for a 1980 Datsun Pickup Factory Service Manual.

[turtle720]

Thanks it just seemed to rev so high doing 60.

I still can't figure out what happened when I tried to jump it. I will put the battery on a trickle charge and see what happens. But nothing happens now when I try to turn it over.

[turtle720]

Well I got it started after I charged the battery. I drove it around for a while. Tried to start it later, got it going and then it died. So I am guessing something with the battery is a miss. I will try swapping it out to see what happens. Any suggestions I may not be thinking of?

Also it is not shifting into 3rd gear. Other than having a transmission shop look at it what can I do to trouble shoot? It seems to pull good through 1st and 2nd but just stays there.

[captainzeros]

Factory manual to the rescue!
It should shift from 2nd to 3rd between 62-68mph at zero intake manifold pressure on the vac hose, and between 36-42mph at 13.3 kPa manifold vacuum.
Edit: ie, if your vacuum lines are messed up, it wouldn't be shifting up until speeds you haven't mentioned yet.

Some raw data if anybody wants it:

[turtle720]

Sweet I have not taken it that high/fast so I have no idea if it will shift. I am going to redo the lines anyway so I am not too woried about it.

I also need to replace the valve cover gasket. Any tricks I should know before I start?

Thanks for all the great help!

[Charlie69]

On the valve cover gasket i do not use any sealers. I assemble dry.

On trans make sure your vacuum line is connected and no leaks. on driver side

On the passenger side of the truck there is 4 wires 2 for the inhibitor switch (same as neutral safety switch on manual trans) and 2 wires for the reverse lights.

The inhibitor switch when working correctly will let the truck start only in Park & Neutral Positions on the shifter. If trucks starts in any other position of the shifter the switch is bad.

These little motors run forever if general maintenance and same with the auto trans. I had my 3N71B auto trans rebuilt at 178,000 miles only because I rebuilt the motor also.

[turtle720]

I'll say that the switch is good because I can only start it in P and N. But the lights are another issue. I think one reverse is blown but my turn and brake lights are all messed up. Front pass turn stays solid while the back does not work. Back pass brake does not work & driver side tail does not work. I have not had time to check all the blubs yet but I will get there. I did read some other post about grounding issues causing problems. I hope it is something simple. I hate electrical work. Anyone else have issues like this?

I also tried to have my battery tested but the shop could not verify. It said that it wanted to charge again and I could not wait. I may just suck it up and buy a new one. The thing that gets me is It was fine before I left the lights on and now its done. I even put it on the trickle charge a second time and nothing. I am no battery expert but WTF?

Also on the valve cover can someoen give me the specs on the bolts, torque and order if any?

Thanks!

[Aven]

Not sure if this applies to an '80, but some of my vac lines had restrictors in them. They are just a small piece of brass with a hole. They are about the size of a pea. Feel for them when you take the hose off.

[turtle720]

Are they right at the end of the lines?
Also I have read a few posts here and some say that the truck runs as good or better with just the dist. vacuum line and everything else capped off. I have always been the guy to do it as stock but less work seems alright with me. Is one way really better than the other.

I have no emission tests.

[PEZi]

it will run better with all the lines off... but it will also get worse gas mileage

[captainzeros]

sounds like the guts of the battery may have shorted, that would make a pretty impressive noise as well. If that's the case, it would be new battery time.

[turtle720]

Yeah it is. I will suck it up and get a new one. I connected both positive and negitive when I jumped it. Not the negitive to ground as recommended.I threw my car's battery in to move it back into the driveway and it fired right up.

I swapped out some of the vac lines before dark and we will see, once I get the rest done, about shifting into third.

I also have two hoses coming out of the firewall that have, what looks like, been cut that I can not figure out. It looks like maybe the drain for the front vents? I will try to get some pics tomorrow but any suggetions?

[PEZi]

if its the ones i'm thinking of... those cut lines from the firewall are your A/C lines

[turtle720]

Looking to finish the hoses tonight if I can. I got most of them done on the vacuum side but I think I will replace everything. Anyone know what sizes I should buy? I wanted to go and stock up before I went home and I don't carry my manual with me. Or at least where to look in the manual would help. lots of them look like they have seen better days. It would be hard to get a true size from some of them.

I will try to post pics of those cut lines tonight as well.

Thanks.

[scvfd]

Not sure if this applies to an '80, but some of my vac lines had restrictors in them. They are just a small piece of brass with a hole. They are about the size of a pea. Feel for them when you take the hose off.

so if your line is no were to be found is there a place you can get these restrictors??

[turtle720]

When I swapped some of mine out yesterday I did not see or feel any. I thought I read somewhere that it was the same as removing them and capping them off but still having the lines there for visual inspection? Or something like that.

I have no idea when or if they were replaced before as I have only owned my truck for a few days but they looked really old.

[Aven]

My truck is an '84, but I doubt there will a difference. The vac lines are 4mm lines. The restrictor I found was at the end of the hose, at the carb end of it. I'm sure that there was another one, but either it went missing before I got the truck or I missed it when changing them out. If you have your lines intact, you are a head of the game. I pulled mine and just went with the one to the distributor, but the gas mileage tanked, so I put them back on, per the service manual. The manual has two of the lines reversed for the the California model. With them flipped, the truck would run fine until you put it in gear and it would die instantly.

I didn't look for the brass restrictors, but I know you can get plastic ones with brass in the middle. They look like the plastic ones you get at Autozone for joining hoses, but there is only one in the pack.

[Charlie69]

Vacuum lines are the same size.

There is a lot of difference in the 80 720 & 84 720 the 1980 is an L20B motor & the 84 is a NAPS (Nissan Anti-Pollution System) Z motor. The L motor in my opinion is much simpler to work with, less emmision hardware. Vacuum lines are routed differently.

I will look and see if I can find the diagram for the 1980 720 L20B.

Do you know if this truck has the California smog package (should be listed on a sticker under the hood if it is aCA model it will sayso on the sticker).

[Aven]

"My truck is an '84, but I doubt there will a difference."

That should have read, ".... I doubt there will be a difference with the vac lines."

[turtle720]

Well I have not had much time to mess with it the past few days. I will look to see if it is but I doubt it since I am in VA. But you never know. I thought of deleting all the lines and caping them since I have no emission tests but I prefer to have it back to stock. I hope that it will shift into 3rd after all is said and done. And my question about the line size was not just the vacuum system but more of all hoses because the last owner did not really take are of it.

I hope to dedicate this weekend to getting some of the issues fixed like swapping out the lines and fixing the lighting problems and valve cover gasket. On the gasket issue the previous owner let it go to s*** and oil is all over the place. I want to degrease it with a cleaner but it is close to the alt and starter. Any issue trying to clean it out so close to those parts with a cleaning spray can?

Thanks for all the great help. And I will get those pics up this weekend.

[captainzeros]

huge potentially helpful images inbound:

[turtle720]

Sweet.
Also when I think of it I have nothing coming off of my hot air duct. Where is that routed? Just to the bottom of the engine bay?

[captainzeros]

on my 81 truck (different engine) it routes to a shield on the exhaust manifold which is open the the air right next to the manifold. The air cleaner is off in this picture, but the shield on the exhaust manifold with the hole where the hot air tube fits into is visible at the bottom:

It's really not a piece you need to care about having other than for emissions testing, or if you live in a Siberian climate that requires every scrap of heat you can muster to make the engine start up and run decent. I assume the 1980 truck has something not too different, just follow the tube down to the bottom and see where it goes (unless it's been removed by some previous owner, mine is)

[turtle720]

So today i have replaced all vacuum lines but still have the issue when I brake of it almost stalling. It also now diesels everytime when I turn it off.
It still will not shift into 3rd. I am going to add more transmission fluid as it is low but I don't expect that to help.

Any ideas?
Also tried to tackle some elecrical issues but I will wait to post that. Just want to get it running good first.

[Aven]

When you replaced the lines were you just replacing them as you found them or did you use a vac diagram and verify you had them run correctly?

[turtle720]

Yes I have checked and rechecked the manual. They are in as shown in both of my manuals. I am starting to get discouraged. It seems to be idling high too. Anyone else have problems like this?

Oh and I also replaced the air filter if that makes any difference. But I doubt it.