Jump to content
Lachlan

Lachlan's 1972 Datsun 1200 Sedan

Recommended Posts

I think you already know.. it's the carb. 🙂

 

The hardest part will be just finding a kit to rebuild it. After that, just take your time and be organized. Take pics along the way so you know how it goes back together.

  • Sad 1

Share this post


Link to post

You can always go with a Weber. I am running one in my a14. It’s fantastic!

  • Like 1

Share this post


Link to post

i just started it then to see how it would run today.

 

It took a little longer to start (5 seconds), but still started up fine. There was a little bit of white / light grey smoke coming out the tailpipe, but no black smoke. It ran for about 60 seconds and then died. I didn't try to start it again as I didn't want to hammer the battery (again).

 

I realise now I should have grabbed another video, but I think @Draker and @slowlearner are both on the money regarding the carb. The research begins!

Share this post


Link to post
On 9/7/2020 at 5:47 AM, Lachlan said:

Sadly, I think you've nailed it. I've never rebuilt a carb, so this is scary new territory. In fact, there are very few car things I have actually done, so this car is a steep (but fun) learning curve.

 

I despise rebuilding carburetors, but you are definitely starting with the easiest one there is. In fact, the first one I ever did was a 1200 and it was a piece of cake. 

 

 

  • Like 2

Share this post


Link to post
On 9/8/2020 at 3:23 AM, Draker said:

You can always go with a Weber. I am running one in my a14. It’s fantastic!

 

This is definitely the easiest path, but on A12 engines it's barely worth it. They work great on A14/A15 engines, but it's tough to get them jetted down enough for a smaller engine like the A12. 

 

In fact, the A12 carb is so simple/reliable, most of the time it's what I use for an "upgrade" on B210s and 210s. All you need to do is swap the A14 jets into the A12 carb and you're good to go. 

 

Side note, the best bang for the buck is SUs, but those are getting pretty spendy/hard to find. 

 

large.20181023_190944.jpg.8b600394f129f5

Edited by datsunfreak
  • Like 2

Share this post


Link to post
On 9/7/2020 at 3:55 AM, Lachlan said:

Thanks again to your help, and that of @slowlearner, Doris (as the car is now known as) moved under her own power for the first time in many years.

 

I finally pulled my thumb out and tested whether there was adequate fuel pressure at the carb. I don't know why I didn't do this earlier. Here are the results.

 

 

 

The car will start without any help, will run for a while especially with the manual choke pulled out, but once it returns to a normal idle it cuts out. I can't figure it out ... yet.

 

This went on all afternoon without resolution. I did manage to get the car to move up our driveway, but she soon conked out and I had to roll it back down. No pedal brake, just the handbrake. Sketchy as.

 

The adventure continues.

 

Running with the choke on requires a lot of gas so if it runs, then it's getting lots of fuel. When the choke is on the engine will run very rich and there is a fast idle cam to speed the warm up, so when it's off it has to run on the warm idle setting. If it quits when warmed up you may have...

 

1/ The idle mixture is not set properly. Too rich or too lean. Or may be blocked with dirt. Remove the screw, counting the turns, spray carb cleaner or WD-40 in hole to flush. Put screw back in.

2/ The idle speed is set too slow. It may be as simple as turning the screw in.

3/ Small vacuum leak. Too much air getting in making the idle mix too lean to run

 

 

  • Thanks 1

Share this post


Link to post
6 hours ago, datzenmike said:

The idle mixture is not set properly. Too rich or too lean. Or may be blocked with dirt. 

 

This. There's dirt in those jets somewhere. 

  • Thanks 1

Share this post


Link to post

I'm unimpressed by the flow from that fuel pump from the video.  I'd want to check it for flow and pressure against the manual, or at least T in a pressure gauge and see that it maintains a few PSI.

Could be a flat lobe on the cam, could be leaky return springs, or it could be just fine.  Easy thing to do is put an electric fuel pump in the line as a test.  If it runs better or the same, you know something about the state of your fuel system.  Also worth checking the fuel level thru the window in the side of your Hitachi carb.

 

That said, I'm sure servicing your carburetor would be worthwhile, particularity if the car sat for a while as the accelerator pump cups tend to dry out and get loose.  Be aware the linkage for the accelerator pump has to be set just so to get the timing right, so if you wind up with flat spots in your acceleration that's not a bad place to look.

Edited by pdp8
  • Like 1

Share this post


Link to post

IMG-20200927-WA0001%20-%20Copy.jpeg?dl=1

 

What ... have ... I ... done? 😶

 

The carb internals are surprisingly clean. I can see through all the jets except the primary & secondary slow jets (they aren't a straight through design). The throttle pump looked a little corroded, but again nothing that was indicate a clear fault. The needle seems to function fine, but I've got another on order as I notice there was never any fuel in the bowl when I managed to get the car running. Other than that, I'm guessing vacuum leaks might be part of the problem? @pdp8 you're probably on the money regarding fuel pressure. I have no idea why it wouldn't be at full power after installing a new fuel pump that is identical to the factory part. Maybe there's more detritus in the tank?

 

I've got this kit inbound: https://www.ebay.com.au/itm/HITACHI-2-BARREL-DCG306-CARBURETOR-KIT-FITS-1970-1981-NISSAN-HONDA-MAZDA/401792402236?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

 

I've been recording short clips as I remove parts, so I'll try and compile this into a long form video for future carb rebuilds. Stay tuned.

  • Like 1

Share this post


Link to post

Good luck! Hope you find the issue.

  • Like 1

Share this post


Link to post

How is your throttle-body?  When these get worn the shaft gets sloppy in the bore and it's hard to get a really good steady idle out of it.

Last I checked these folks had them at really great prices: https://www.oem-surplus.com/nwp/1200.htm

 

Setting the timing of the accelerator pump is a little fussy to get just right on these carbs, pay special attention to the linkage and the pre-travel above the plunger.  You'll know it when you get it right since it won't bog on rapid acceleration.

 

Oh, and of course remember to make note of which jet goes where, yada-yada.

 

  • Thanks 1

Share this post


Link to post

Watch out for aftermarket fuel pumps.  I had a 1200 Coupe where I replaced the fuel pump with a generic unit.  The generic pump was putting out about three times the pressure of the stock unit, and would flood the carb once the motor was turned off, making it very hard to start when warm. 

 

Turned out a the fuel line from the tank to the engine was clogged, so I put the original pump back on after that was remedied.  I drove the car daily to work for about three years and never had a problem.

 

 

  • Thanks 2

Share this post


Link to post
2 hours ago, graveltrapp said:

Is there Gas in the Tank?

 


worth checking, we’ve all done it. Lol

 

”it ran just fine yesterday!!!”  Lol

Share this post


Link to post

I have never run a Datsun out of gas.  And I DEFINITELY have never done it to the same 720 at least 6 times....

  • Haha 2

Share this post


Link to post

Typical case I’ve seen and done.. diagnosing while on jack stands for long periods of time. 

Share this post


Link to post

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.