My Grandpa's 720 (musicman's 720)

[Silky_Johnson]

Actually, now it's my dad's pickup - a 1985 Nissan 720 - but it has always been in the family.  My grandpa bought it new, and I think he must have sold it to my folks sometime in the early 90's.  I'm posting this for my dad until he gets savvy to Ratsun.  My folks live two hours south, so I come down on the weekends to help with projects.

 

 

 

 

The story goes that my Grandpa bought the truck, and within a short period of time (maybe a couple of months) he was in a front end collision that nearly totaled the whole thing out.  He worked in forestry, and he bought the truck to drive around on mountain roads.  He used to take us out with him on the weekends, and we all remember being out with Grandpa on some steep gravel road spinning out the back wheels.  As a result, the back end got all rusty underneath, and below the tailgate is rusting through.

 

My family used this truck for work - mostly hauling things - and for some commuting here and there.  My dad used to drive it to work.  He even drove it back and forth to southern California a couple of times.  For a no-so-short time, my older drove it and adopted it as his own.  It was consequently in two more minor front ender crashes.  I drove it for a while in college.  I got nailed by an old lady that ran a stop sign and messed up the whole passenger side of the bed.  The accident threw me sideways over a curb and I blew out both passenger tires as well.  The rims were destroyed.  We expected the insurance company to total it out and not give us enough money to replace the truck, but it was all taken care of, much to our surprise.

 

This truck ALWAYS ran poorly - right from the get go, even when my grandpa owned it.  The carburetor was always out of adjustment, and for longer than a decade, the electric choke had a short that made the idle either race all the time, or die all the time.  I remember having to "heel-toe" it at red lights just to keep it alive.  Some years ago, my folks had the short fixed, but it still ate up gas and had the hardest time with cold starts.

 

Fast forward to a few months ago.  I bought a 510 a few years back, and my 510 taught me how to work on cars.  With my knowledge and experience, I talked my dad into installing a Weber 32/36.  My dad bought a redline kit on eBay, and we went for it.  I need to have my dad take some better pictures, but here you go for a teaser.

 

 

 

We swapped out the Weber successfully on a Saturday, and it breathed new life into this little pickup.  Fuel economy is way better, and power is also noticeably better than anyone can remember.  It is no longer the slowest car at any green light, and it always starts with one turn of the key.  I caught the Datsun bug a couple years ago, and now that we've got this running so well, my dad is now developing symptoms of the Datsun/Nissan bug too.

 

I've told my dad that he needs to come to Ratsun to learn and get ideas.  His next project was definitely Ratsun inspired.  The emergency/parking brake handle busted of when my brother was driving it.  For the better part of a dozen years, there was only half of the handle.  Now, we have this:

 

 

 

I believe that's a shift lever from an unknown American car.  Who knows?  Either way, I think my dad did some drilling, stuffed a pin in the hole, and JB welded it all together.  It works!

 

Next up was more Ratsun fix.  We decided that we like the "patina" look of our old truck.  Rather than do extensive body work, my dad used a bunch of Ospho to convert the exposed rust into something black (?) and then primer over the top.  I told him moisture will eat through the primer, so I'm not sure whether there's a clear coat or not?  It may or may not stop the cancer, but it might slow it down?

 

[Silky_Johnson]

Next up, my dad picked up a tach from an ST model.  He bought it on eBay.  We read that this is supposed to be plug-n-play, but it didn't turn out that way.

 

 

We found the resistor already installed.

 

 

 

I bought another resistor directly from Nissan before we knew there was already one in the truck.  I think Dad has tried the new resistor, but no dice.

 

We did some diagnostic tests, and all fuses are good and both coils work and are firing.  I got jolted twice by the one of the coils.  I was kind of sleepy before that happened, but not after.  I figured maybe we could have screwed up some of the wiring when we put in the Weber carb?  The engine runs great.  We did some smog delete - not everything, but we did disconnect some hoses and maybe a couple of wires.  The wiring on the dash side is pretty fool proof.  Here's what we have in the engine bay.

 

 

 

 

 

 

Does anyone know how to do a test to find out if the tach itself is bad?  If the tach's good, how do we find the gap in the circuit?

 

Anyway, the most recent upgrade was a major upgrade.  I don't have any true before pictures, but I have some during.

 

Seat out:

 

 

Under seat area cleaned:

 

 

 

And newly upholstered seat installed!

 

 

 

 

 

 

 

 

I believe my dad took the seat to a guy by the name of Bautista (?) in Springfield, Oregon.  He completely redid the seat foam and sewed new material to somewhat mimic the stock look.  It looks like he did excellent work!  The padding is better than new stock, and he put fabric sections in the seat to help keep temperatures comfortable.  I remember wearing shorts and hoping in this truck in the summer time.  Bad idea.  The stock vinyl always felt like it was burning you in the summer and freezing in the winter.

[Silky_Johnson]

I know this was mentioned, but does anyone have any ideas on the tach?  We're pretty stoked to get it figured out.

 

I'm a little concerned about the disconnected brown wire at the bottom of this picture:

 

[Silky_Johnson]

Another project my dad's in the middle of has to do with the license plate lights.  One of them is shorting out.

 

 

 

 

The good one:

 

 

The bad one:

 

 

I think my dad said he was trying to fix the short, but was unsuccessful.  He might just end up buying a new housing.  Evidently, my grandpa installed some other light in the same circuit around the trailer hitch?  I'm not sure what for exactly.

 

EDIT:  my dad was talking about the trailer hitch wiring on the bumper...

[vanmansam]

I love the seat. Need to have mine done up like that.

[MicroMachinery]

Awesome. I love father/son projects. That upholstery job is incredible. You should get that guys info for me.

 

As for your tach, check out 720world.com. I guarantee someone there can steer you in the right direction, and then some.

[musicman]

I'm pleased how the bench seat turned out in my 720.  The refurbished seat height is about an inch or so higher than the old broken down foam and torn up covering.  My son and I also installed new front ball joints, and new front shocks.  That fix and the addition of the rebuilt seat, transformed the ride to as 'good as new' --or better.

[Dirttrack510]

That seat looks great :) nice job!

[datzenmike]

The tach resistor has a White/Blue stripe wire coming from the intake coil. The other wire, Black/Blue stripe goes to the tach in the dash. You're sure the tach is plugged in OK?

[Silky_Johnson]

I'm pleased how the bench seat turned out in my 720.  The refurbished seat height is about an inch or so higher than the old broken down foam and torn up covering.  My son and I also installed new front ball joints, and new front shocks.  That fix and the addition of the rebuilt seat, transformed the ride to as 'good as new' --or better.

We also did tie rods at the same time. I suspect the steering box still has a little play in it, but it's not too bad. The good thing is you can drive in a straight line again, and you can drive over speed bumps without hearing the front suspension clunk around.

 

How did you get that guy's info for the upholstery? I think some Ratsun guys may be interested in talking to him? And before anyone gets too excited, the bench seat was not a cheap job by any stretch of the imagination, but it is conceivably a better job than Nissan did.

[Silky_Johnson]

The tach resistor has a White/Blue stripe wire coming from the intake coil. The other wire, Black/Blue stripe goes to the tach in the dash. You're sure the tach is plugged in OK?

Thanks Mike. I'll verify the wiring the next time I visit, or maybe musicman will get up the courage to cut up some of the harness himself? I wasn't around for the tach install, but as I understand it, it was pretty obvious where the the tach was supposed to plug into. Perhaps not? We'll see.

[JoeCool]

Good looking truck. And that seat looks great. How much did it cost if you don't mind me asking? Mine needs a redo bad.

[musicman]

I got the name of the upholsterer from Econosales on main street in Springfield, Oregon.  The store carries bolts of material for do-it-yourself upholstery/carpet projects.

 

Paco Bautista did the work for me--very impressed with his work, I did not negotiate the cost downward: it was pricey at $500 including everything.  Work was finished within one week.  Message me and I will send his phone contact to you.

[musicman]

The tach resistor has a White/Blue stripe wire coming from the intake coil. The other wire, Black/Blue stripe goes to the tach in the dash. You're sure the tach is plugged in OK?

 

Thanks datzenmike,

 

Here are views of the tach resistor with White/Blue wire coming from the intake coil. The next photos show the tach plugged in to back of cluster with Black/Blue wire, etc.

New resistor attached to harness plug

 

 

White/Blue wire on negative terminal of intake coil

 

 

Back of cluster view of factory harness with tach plug: Black/Blue.  I wrestled the plug several times to be sure it seated--there is no "snap" or "click" when attaching plug.  The leads should have 3/16th inch of contact surface between plug and pins on back of tach. (good connection)

 

 

 

looking inside the dash.  speedo connection is out of view behind the harness.

 

 

I'm leaving the cluster here overnight... 

 

 

Attaching the multi plugs to cluster is straight forward.  What shall I try next?  I removed tach a week earlier and plugged it in directly without mounting it into the cluster: ran the engine--but no life in tach.  With battery reattached everything else electrical has worked except for license plate lights.

 

 

[musicman]

I'm still trouble-shooting ST tach that hasn't moved yet in my base model 720.

 

I ran 12 volt test light into the connection at resistor White/Blue and got plenty of light signal flashing (turning engine over without coils connected).  I put the test light probe on the other wire out of the resistor (into the line to tach), Black/Blue, and had no light when turning over the engine.

 

I'm a newbie... how do I test the Black/Blue line from resistor to tach?  I suspect there is a ground issue.  Is the break in the circuit at resistor?  I've tested both the original resistor and the new resistor... they both behave the same.  I need to learn how to check all of the harness; I've pulled back enough tape to see where the Black/Blue wire runs.

 

I am an old guy trying to learn, and having fun! 

[Sick720]

Well just got a tach, it worked for about 5you seconds then quit. I changed the resistor for and same thing. So i pulled the tach out of the housing and hooked it back up. Still didn't work. So i looked real close at all the solder points, and some had broke loose. So i soldered them back. And it worked! For about a minute. So i left it hooked up again and wiggled the little green wire and that was a problem so i replaced the wire and soldered it back in place. And it hasn't given me a problem yet! I would try it on yours, 'cause a bad connection can really give problems.

[Sick720]

Damn auto correct! >_<

[musicman]

Hey Sick720, thanks for the loose connection tip.  I gave it a try tonight.

 

the tach is still life-less... it has not run for even a second. but I'm getting very good at taking cluster out of dash--and everything but tach runs very well.

 

Is there a missing part on my tachometer?  check pictures 3, 4, 5, 6 below.

 

With the tach out of the cluster one more time...

I ran a continuity test from intake coil to resistor, through firewall and up to the connector for the tach.  I have continuity signal all that way.  I checked the tach below, by itself, at the three prongs and got a number like .738  (?) I'm a novice at this!

 

 

 

 

 

Here's the front side of PCB where the three tach prongs connect to the harness.  The wiring harness is pristine through engine and dash areas--it doesn't look like it has been messed with.  We've had the truck from the beginning in 1985 and it has been kept in original condition.

 

 

Question: Is this tach missing an adjuster or another part in the bare metal screw type socket stamped "503?"

 

 

you can see where there is place for something to screw into the gauge.  I recently bought this as a "complete" unit.  Hmmm.

 

 

I've carefully checked each solder connection, including the green and white wires that attach to the springs on the working side of tach.  They seem fine--test signal runs through the various elements.  

 

 

I cleaned up some nearly 38 year old flux from the PCB with a bit of alcohol and q-tip.

 

 

Another backside view of the opening for a missing piece?  I plugged the tach in without the rest of the cluster, ran the engine, and I had all kinds of points that indicated continuity of circuit.  But still no needle movement.  Black/Blue wire runs cleanly from resistor to the tach connector and is solidly grounded.  What is a next step to get this puppy running?

 

[Sick720]

Hook it up out of the cluster, start your truck and just slightly wiggle stuff around. Thats how i found my problem. And the three prong connectors were loose on mine so i just heated the solder back up and they were good. And you said you had another resistor for it? If so try it! It might be bad, ya never know.

[Silky_Johnson]

I think "503" is an adjustment pot.  Check out this link: http://720world.com/forum/topics/incorrect-tach?commentId=2016119%3AComment%3A81557

 

Some guys find their tachs aren't running at the right rpm, and the adjustment pot is the culprit?  Perhaps yours is set too low to read anything?  Maybe plug it back in, get the engine started, and turn the pot up and down to see if you get a signal.  If that's the case and you do get a signal, you'll have to borrow or buy a digital timing light to set the RPMs right on the tach.

[musicman]

I believe the link above may answer my question about why my tach doesn't run, and give me one more thing to try.  Tomorrow, Friday, is potentiometer "tach-pot" day.  It is sunny and warm... It's going to work!

[musicman]

today I continued to pursue starting and running 720 ST tach in our base model 720. No life.

 

I drove the rig to an auto electric company in Springfield today.  (with cluster out!) They did simple 12 volt test on the white/blue wire connect of resistor near the left front of the engine area.  They got strong blinking signal, as did I.  Next, they did the same test inside the dash area on the tach connector plug at end of harness; they only got a continuous power signal (yellow/red) on middle prong with 12 volt light test.  But no 12 volt "light" on upper (black) and no (12 volt light tool) reading on lower Black/Blue.  The auto electric shop seldom (never) deals with small tach electronics.  They concluded that the coil signal is not getting to the tach.  that part they can check.   But I wonder if they know about resistor that steps down the signal that is sent to tach... is my train of thought close to correct?

 

Would a 12 volt circuit tester be the tool to determine if the line is carrying the live signal to the tach?  Is the voltage too low after the resistor to measure with 12 volt probe light?  what kind of signal would indicate a good signal is making it to the tach?  my ohm meter gave me a digital read-out... the 12 volt tester said, "no dice."

 

I wiggled the two skinny wires, one white, and one green, on tach with truck running.  I heated up some of the solder connections, and I rotated the pot around.  

 

I am persistently wanting to get the victory with this tach puzzle--more than one thing could be wrong...  

 

The auto electric people seemed to discount datsun/nissan 720 harness capability to plug-and-play a tach from and ST into base 720...

I'm doubtful about their shotgun response from everything I've read on Ratsun.

 

What is next?

[Sick720]

All the wiring harnesses are the same, they just didn't know what to do. I still think it's a bad connection somewhere. Just take you're time and look closely. You'll be able to notice if something ain't right.

[musicman]

Waiting on some tach install details, here are more 720 oiks...  

Ospho was used to cover rust, then rattle-cans of Rustoleum Primer (Gray), and "sand" color coat.  The patina on this rig is campy, but it all comes together for me.  Check out the new upholstered bench again.

 

 

More patina, lol...

 

Reasonably straight, except for front bumper...

 

I finally got a top coat over the Ospho and Rustoleum primer.  I treated and painted the inside of body panels due to logging 'road' rocks that were thrown up and under the bed.  This is a minimal budget fix... for now.  Back bumper was treated inside as well.  Oh yea, the windshield has a bit of patina :)

The cancer hole is what it is for now.  I treated it on both sides. The bumper is flat black Rustoleum.

 

The sand color spray can was fine all over the surface rust and scrapes...

 

Nearly all of our 720 is orignal stock, and an old friend to me.  We are replacing worn elements one by one and enjoying it!

 

 

The bed was in need of surface rust removal around the wheel wells... OK, there are about four or five colors of 'sand' here and there, some old, some new.  

Some tach work to be done in a few more days...

 

The end, so to speak

 

 

 

[Draker]

Hey, I'm pretty local to you. Do you know for sure the tach is good? or the resistor? Feel free come test whatever you need.. I've got a tach in my truck.