1980 720 2WD (AZJones' Build Thread)

[bananahamuck]

Whistling noise is probably coming from belt,, is it new?? Is it tight? 

 

Are your valves gapped correctly??  Is there a miss at idle??

 

If you have stock Hitachi,, take air cleaner housing off,,  grab top of carb and using a twisting motion,,,  Does it have any movement at all compared to the intake manifold??  

 

 

 

(disclaimer) I have no idea if your alternator is causing any of your problems ,,,,,,,,,,, but

You have internally regulated alternator,, you can switch it out for a newer higher amp one probably just as cheap as getting a new one.  FAT510 put a 93 pathfinder alternator on his 79 A10 ,, only had to change plug ( avaliable at your nearest PnP for the price of admission.

[Lockleaf]

Have you checked charging voltage at the battery when the charge light is on? Then check output at the alternator? If they match, then the problem is alternator related directly. Whether that's belt slip or regulator or what have you, at least you know to pick a fight exclusively with the alternator

[arizonajones]

Hi guys, Thanks for the suggestions.

I've checked into some, but not all:

 

Belt is tight,Valve lash is proper, no miss at idle, checked for tightness of the carb and It's tight.

 

I haven't done your electronics check yet Lockleaf, but I will for sure.

 

I also checked for proper function of vacuum advance on the distro with a vacuum pump/gauge and it checks out.

 

It's still getting me around town, thankfully, just runs weird at times.

 

I'll focus in on the alternator next. Also got a couple of plugged vacuum/emissions lines to fix and unplug. As soon as I get closer to figuring it out I got a Rock Auto gift certificate burning a hole in my pocket, so hopefully I can pinpoint and replace whatever's wrong.

 

ALSO! I just got a phone that takes good pictures... so naturally, I took a couple Ratsun glamour shots on my lunch break. ;)

 

 

[arizonajones]

Swapped for new plugs plugs today. Running rough and weak. These are the old ones - very carbon-fouled.

TIming is good, but I leaned the mixture a bit and raised idle speed a bit. Runs a bit better.

 

I also checked compression - all four around 160.

[arizonajones]

I think I'll grab an alternator at half price pick n pull this weekend

[Charlie69]

Love the roadrunner!  The plugs look to me that your truck is running real rich.  Are you running stock carb?  If so I believe there is an altitude thing-a-ma-bob that can cause rich mixture if not working properly.  I always change to a Weber.  Much simpler carbs.

 

Datzenmike Is real good with stock carbs.  Maybe PM him.

[arizonajones]

Love the roadrunner!  

Thanks! It reminds me of my desert roots (and it distracts the eye from my unfinished bodywork ;) )

 

The plugs look to me that your truck is running real rich.  Are you running stock carb?  If so I believe there is an altitude thing-a-ma-bob that can cause rich mixture if not working properly.  I always change to a Weber.  Much simpler carbs.

I am running a stock carb. I have been having some trouble with it lately - runs real rough at first start in the morning. I'll investigate the altitude thingy. Does your Weber have to pass smog?

 

I'm pretty sure I've got a problem with the alternator's voltage regulator or a diode or something in the alternator. My battery light comes on at idle. Battery isn't draining, but if I have any load on the system, the light comes on, there is a little buzz from the fuse box and slight whistle from the alternator - and it lowers idle speed slightly. Gonna look for a replacement at the yard this weekend.

 

I've been wondering about weak spark as a problem, but I don't know if that's a direct connection to what I just described.

[Rhino13]

You can get the Weber to pass smog, I did it on an 81 I had. I just had to leave, adjust it, then go back through. If you fail you don't have to pay, and there's no limit on how many times you go through in a day. I think it took me 4 tries to get it on my 81. I live down in Eugene now but I have a 32/36 I could part with so I can upgrade mine. It's been run for 4-6 months now and was new when I got it, pm me if you'd be interested.

[Charlie69]

Yes I have to pass smog here in Phoenix AZ.

 

If your charge light comes on at idle change out your alternator.  This may be all your problem is.  Try to find a shop that can rebuild your alternator or do it your self.

 

I purchase all my Webers and parts from Pierce Manifolds.  Been dealing with them over 30 Years.  They know Datsuns!

 

http://www.piercemanifolds.com/

[arizonajones]

Alright Ratsuners, I got a new alt, did some testing, and I have updates and questions (and pictures)...

 

 

The original alt: (will probably keep and rebuild eventually)

 

I got an alt off of a 92 Subaru Loyale (its a reman, but pretty damn new) It wires up directly, but does require a longer belt and some extra length on the arm.

Here is the beginning shot of my extendo-arm:

 

Finished welding, grinding, and threw some paint on it:

 

So I got it installed (used a belt from a NapZ motor) and while I was messing with it, I cleaned and re-attached all my grounds.

 

Soooooooo........ here's the thing.... It fired up fine. No more whistley bearing sound, Battery reads 14.5V pole to pole when its running... but... It still ain't running right.

On to the next post...

[arizonajones]

So it starts real rough and lope- y for about a minute or two. Then it starts idling faster and smoother, but the tach needle is still jumping around all over. When I rev it the tach jumps up and basically bounces up into the red. Right after that it'll backfire a little. I drove it around the block a couple times and it will drive okay for a bit, then it will feel gutless and misfire. All of this time the tach needle never really settles down.

 

I have the carb set 2 turns out and yet it smells super rich, but if I lean it anymore it barley runs.

 

I checked the timing and everything checks out 12 deg btdc.

 

So I kept the diagnostic party going:

 

-Battery voltage when engine is off: 12.67V

-Matchbox connector positive lead to ground on block: 12.25V

-Coil resistance- pos to neg w/ engine off: 0.9 ohms

-Pickup coil wires connected to matchbox resistance; 355 ohms

-Voltage of negative side of coil w/ ignition on: 12.25v

-Pickup coil resistance with matchbox removed: 356 ohms

 

So I looked into the distro for physical issues, there is a little side to side play (maybe 1/32" ?) and the pickup coil felt a little loose in there. I'm not sure if any of that means anything, but I'm looking for clues.

 

 

Also, the coil, the cap, the rotor, and the plugs wires are less than a year old. The plugs are basically brand new.

 

So one question I have is the pickup coil resistance - Chilton  says it should be around 400 ohms or its bad. Does 355 ohms sound close enough, or could this be the problem?

[arizonajones]

Doing some more reading on the pickup coil. It says the resistance should not be 'substantially' higher or lower than 400 ohms.

 

Anybody know what 'substantially' is supposed to mean? Anybody got the FSM?

[wayno]

Is your distributor cap completely dry inside?

Check the Tee connection that plugs onto the matchbox, make sure the connections on both posts are tight, as if they are loose when the engine moves from side to side like when you give it the pedal and then let off the pedal, it will freak out and make the tach jump all over the place when it loses the connection and then connects again, although this is usually associated with the engine cutting out also and then backfiring when it hits again.

You still using that carb you rebuilt a long time ago?

Maybe it is time for a Weber?

[arizonajones]

Is your distributor cap completely dry inside?

 

It looked pretty dry to me, but I did take a pic of it right after I tested it, just for reference:

 

Check the Tee connection that plugs onto the matchbox, make sure the connections on both posts are tight, as if they are loose when the engine moves from side to side like when you give it the pedal and then let off the pedal, it will freak out and make the tach jump all over the place when it loses the connection and then connects again, although this is usually associated with the engine cutting out also and then backfiring when it hits again.

You still using that carb you rebuilt a long time ago?

Maybe it is time for a Weber?

I'll check all those wires and make sure they're secure. It occurs to me I haven't looked at the wires going to the carb in a while. It is the same carb I rebuilt a long time ago. I think you might be right about the Weber. As soon as I can cross off electrical stuff from the list, I might buy Rhino's 6 month old Weber. Hopefully I'll have a solid answer on electrical very soon. I guess I keep thinking its electrical, because of crazy tach bounces without actual RPM change, but maybe it is more a carb problem than I'm thinking?

[Buzzbomb]

Doing some more reading on the pickup coil. It says the resistance should not be 'substantially' higher or lower than 400 ohms.

 

Anybody know what 'substantially' is supposed to mean? Anybody got the FSM?

 

http://datsun510.com/manuals/

 

There's an 1980 FSM up on the site..Along with others! And if the person who owns or posted those books on that site read this site, THANKS so much for giving all Datsun enthusiasts access to it. What an incredible resource  :ninja:

[Charlie69]

I bought mine on ebay.  Have not had time to copy and pdf it.

[arizonajones]

http://datsun510.com/manuals/

 

There's an 1980 FSM up on the site..Along with others! And if the person who owns or posted those books on that site read this site, THANKS so much for giving all Datsun enthusiasts access to it. What an incredible resource  :ninja:

wow thanks for the link! I can't believe I've never seen this before! what a great site  :thumbup:

[xsdg]

Can you pull a plug and see if it looks super carbon-fouled again?

 

Also, might be useful to test the spark.  There are a bunch of ways.

1) The cheapest is just to use an old plug, hold it near the block (or another grounded surface), and see how far the spark jumps and how strong it looks.  Don't pull a plug from the motor, or if you do, plug the hole with another one so fuel doesn't escape :o)

2) You can do the same test with a test light straight to the plug wire.  Watch demo by ScannerDanner here (relevant bit starts at 32 minutes in):

3) You can use something like this, which basically does the same thing, but correlates distance with spark voltage: http://www.handsontools.com/Thexton-404-Adjustable-Ignition-Spark-Tester_p_6828.html

4) You can use something like this, which has the benefit of still firing the plug, so you don't kill the cylinder while running the test: http://www.harborfreight.com/inline-ignition-spark-checker-69014.html

 

Also, if you're seeing issues with those, you can do the exact same tests straight off the ignition coil while cranking the engine with the starter.  That's an easy way to figure out whether the dizzy is part of the problem or not.  If the dizzy is getting a weak spark, then you know you've gotta look upstream.

 

That said, the tach signal comes from the coil.  That would seem to signal either a ground problem or some problem upstream of the coil itself.  This part is just a guess, though.

[arizonajones]

Hi Guys,

 

I appreciate everybody's advice. I haven't gotten to run these detailed diagonostics yet, but I will. In the meantime, I was able to run out and get photos of my plugs (and my oil - for good measure) during my lunchbreak today.

So, here they are:

 

Plug #1:

 

Plug #2:

 

Plug #3:

 

Plug #4:

 

Oil on dipstick:

 

 

Soooooooo....

Plug number 2 is wicked carbon fouled. the other 3 are not as bad (although plug #3 is almost as bad as #2). I cleaned them up and re-installed. BTW these plugs probably only have about 300mi on them.

Also, the oil has about 500 miles on it.

 

Another thing is that it has been real smokey at startup anytime is sits for a couple of hours. The smoke is sort of dirty off-white. No coolant is missing and its not burning up oil like crazy. It also has decent and even compression. Is it possible this has to do with the over-rich condition?

 

Also, the fact that plug #2 is way worse than the rest makes me curious - if it were a carburetion or ignition coil problem, wouldn't the carbon fouling be about equal? Does that point a finger at the distro?

 

Obviously I'm not going to go replace stuff till I can get into more detail, but, do you guys get any clues from this that I'm not seeing?

[Charlie69]

Valve stems seals need replaced will clear up the smoking issue.

[Charlie69]

Replace your valve stem seals to solve the smoking issue.  This can be done without pulling the head.

 

I run the standard  NGK plugs in my trucks easier to gap and cheaper.

[arizonajones]

Replace your valve stem seals to solve the smoking issue.  This can be done without pulling the head.

 

I run the standard  NGK plugs in my trucks easier to gap and cheaper.

Do you think the carbon-fouled plugs are just too gapped and that's why the middle 2 are more fouled?

[Charlie69]

It could be.  I always gap my plugs before I install them just to be sure they are correct.  As you get older it is hard to see those needle like spark plugs.  LOL

[wayno]

I also run NGK plugs, they last me a long time.

[arizonajones]

Hi Guys,

Thanks for all the helpful input!

I finally got some answers, but I had help! I ended up taking it in to Altered Motives, in Tualitin, to have Nelson look at it. It's the first time I've ever taken it into a shop since I've owned it. Those guys are the absolute best. They know Datsuns inside and out, they have complete integrity in their work, and their prices are pretty damn good.

 

So... what they found was:

 

-intake & exhaust leak at the manifold gasket (I think it was a small enough intake leak that as it heated up it mostly closed up, so it still held a vacuum, but it still ran like total crap)

-a short in the wiring to the fuel cut solenoid and the choke that made the fuel-cut fire on and off intermittently

-a couple of bad valve stem seals (like you said Charlie)

-some loose carb bolts (starting to vibrate loose) making it run a bit extra lean

 

So, the gasket is replaced and it runs awesome now. There is still a little exhaust leak click because apparently there is a little warping on the head where one of the exhaust ports is (#4). But the intake is good now, so hopefully I don't have to mess with it for a long time.

Carb is all tuned up, wiring no longer shorting, and timing is reset.

 

It still needs the valve stem seals done, but i'm putting them of for a bit because its not too bad yet.

 

Its so much more fun to drive now. Like it used to be! I'm still considering a Weber, though... we'll see.