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Acceleration Probelms 710


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Please post links to other places in this forum that might shed light on this.

 

I am the owner of two 1977 710 wagons. One is a parts car that was my first datsun, a rusty mechanic owned and duck taped beauty. It ran before I started using it for parts for a perfectly kept garaged wagon I found about a year later.

 

Me and my second wagon had a wonderful time for the first two years. Until gas was leaking profusely out of the base of the carburator. I fixed a gasket, but it was still running bad, turned out the carb needed work too. I decided to get the carb rebuilt rather than buy a new carburator, as a new carb would mean many modifications (origional carb no longer available).

 

The carb was rebuilt, but the car was now having trouble accelerating. It never had this problem before. I am told that the newly cleaned carb can effect everything else. It struggled all the way to 60km (35m), stubornly stayed at 60km (35m), and than it seemed to shift and it accelerated fine after that, although it did not sound as good as I remember. Every time I slowed down this process happened all over again.

 

I took it to a mechanic to adjust the timing and choke in case me and my helper did it wrong. He said it was still running ruff, and I gave him the go ahead to replace the points and condenser and to adjust the valves.

 

The car still has the same problem it did before the timing and choke was adjusted by the mechanic, it does not want to accelerate, until it is able to pass 60km (35m) and than it accelerates fine. The one thing that did change after taking it to the mechanic, is once it passes 60km (35m), it accelerates at a rate like I never knew a 40 year old car could. I am attributing this to the valve adjustment.

 

oh yeah and there is black smoke sometimes. again a post carb problem.

 

So this is where I am at now, my manual spans many models and years and I am having difficulty identifying where the parts are that I need to check. Info on the interenet is inconclusive. I have learned that I need to check for a vacuum leak and the fuel pressure. I am choosing to assume at this point that the EGR and relays are working fine until I eliminate the more common causes. I do not think my car has a throttle position switch (?).

 

I don't know where the Throttle Body is, do 710's have one? I am not a mechanic and this is my first car ever worked on. Without 77 specific manual I am never sure if the parts even exist on my car. If someone could explain where the intake and throttle body are in relation to parts that I know (carb, alternator, rad, motor) that would be great. I am an artist, so as a visual person pictures and videos would really, really help. If you are going to post a close up of parts, please also take a zoomed out photo.

 

I am going to check out a Chilton's Manual at the Library on Monday. I am also going to order to order a datsun service manual on line. Would appreciate the help in the mean time.

 

The engine is a L20B.

 

Thanks, I love driving this car. I can't imagine driving anything other than a datsun.

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I will assume it has the stock carb still on it?

You mentioned black smoke.........that would indicate an overly rich condition. When you rebuilt your carb did you replace the float valve? Adjusted it correctly?? I know you said you have no manual to look at, that may be a problem for a first time troubleshooter like yourself :)

As 'Zilla said above, you are gonna have to go back into your carb.

 

Your 710 is not equipped with a "throttle body", that's a Fuel injection term. Your fuel system is much more basic than that, thankfully.

--Ray

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Poor acceleration and then it takes off .... Likely the big increase is the secondary coming in. The problem then is poor performance on the primary. Overly lean or rich could do this.

 

It's very possible that you have swapped the primary and secondary jets. It's easy to do. The jets have small numbers on them and the primary number will always be smaller than the secondary. This would cause an over rich condition. The primary jet is the one closest to the valve cover.

 

When warmed up is the choke completely open?

Looks like this... open

carb720shouldlooklikethisLarge.jpg

 

Not like this... closed

carb720notlikethisLarge.jpg

Closed will cause a rich condition

 

It's also possible that not all the dirt was removed or something came loose and is partially blocking the primary jet causing it to run lean.

 

 

When idling check the sight glass in the front of the carb. Is the fuel level at the little dot on the glass. If not the carb may overfill and flood when running causing an over rich condition.

 

Whatever, you will have to take the carb off to get at this

 

 

 

 

 

I am the owner of two 1977 710 wagons.

 

Thanks, I love driving this car. I can't imagine driving anything other than a datsun.

 

I like this guy already.

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Logically it would seem that if the problems all happened after putting in the carb, than the problem is the carb.

 

Thank you guys, that is what I thought but not what I was hearing/reading. I was also on the wrong forum. No wonder I was confused.

 

The carb is stock, rebuilt.

 

I actually didn't rebuild the carb myself, I should have, I thought as a beginner it might not be the best thing to mess with. I also don't have a super clean shop to work on it. But at this point who cares, its not working anyway and now it is clean so I could even do it in my house? If I mess that up I can get a fancy one, I just don't use my car for racing, I use it to move art supplies around and travel.

 

Should I order a whole new rebuild kit? Any reccomendations on literature to help me through it?

 

I did cut one gasket myself. I thought it was perfect but maybie not. Should I start there first?

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I will check the jets carefully when I do it myself this time.

 

The choke is the only part that can't be replaced, but I do not think it is the choke, It was open when warm, and I even wired it open and drove it and it helped nothing.

 

If the carb is overfilling does that mean the carb needs readjusting? or that it was rebuilt inproperly?

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You don't need another rebuild kit. The gaskets are still good from the other.

 

 

The choke is the only part that can't be replaced
Sure it can be replaced, it is the most common size.

 

 

If the carb is overfilling does that mean the carb needs readjusting?
Yes, adjusting. You can look at the sight glass to tell, no need to take the carburetor off or take it apart. Where is the fuel level in the sight glass? Go and compare it to the diagram from the rebuild kit.
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All you need is a kitchen table covered with newspaper for an operating theater and a couple of hours.. A digital camera helps as you take it apart. The Hitachi has dozens of small parts so keep them separate and in order.

 

If you installed a rebuild kit you won't need to use another one.

 

There are or should be a float drop setting described in the rebuild kit. Yes the float setting is adjustable and best of all it can be done on the car later if you find that it isn't perfect. + or - an 1/8" on the fuel level is fine, long as it's close to the dot on the sight glass. (sorry that's 3mm + or -)

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So much good advice. Thank You.

 

Right now it is raining in Alberta Canada, so the float check will have to wait. I think I should make sure it is adjusted right before I take it apart, the mechanic is good, just not used to foreign cars.

 

Maybie the choke can be ordered in the states, haven't had luck here, but my carb looks a bit different than the one pictured above.

 

I can post pics and some updates on how it went tomorrow. Thank You Everyone!!!

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Thank you for having me. I have seen others in Vancouver (where both mine were purchased) but non in as good shape as mine. Or was, need to get on that paint job, hopefully I can get this figured out soon. I want to paint it purple fading to to orange-yellow, like a sun set. Bought the air gun years ago for it. Thank you Rays74, I didn't think it had a throttle body, its all mechanical. Just to clarify: It does not have a throttle position switch either? Does it have a fuel relay? Fuel pressure regulator? Oh and datzenmike, not that it matters but I am a guyette.

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Rays74: I have a manual, but it is not 710/77 specific.

 

The fuel was touching the bottom of the dot. Going out to measure to see if I can figure out if set right though.

 

Definately burning rich, burning way too much gas too quickly.

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There were air bubbles popping up when I checked the float/gas level. I am low on gas though. There was also some vapour coming out of one of the 3 smaller lines (altitude compenator hose or BCDD?) when I turned the car off. Vapour normal? Bubbles not? Any ideas?

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Float seems to be adjusted perfectly, right at the dot second time around. No bubbles second time around. No black smoke today. Choke open when warm. Stalled a bit though. Next going to try and adjust idle speed and mixture. Have to go help rake hay, first time driving a tractor. Pics will have to wait.

 

Any advice on adjusting a carb would be appreciated, I sucked at it the first time around.

 

Oh and I guess it wasn't the choke I had trouble finding it was the release for the choke, and a new float.

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Thank you for having me. I have seen others in Vancouver (where both mine were purchased) but non in as good shape as mine. Or was, need to get on that paint job, hopefully I can get this figured out soon. I want to paint it purple fading to to orange-yellow, like a sun set. Bought the air gun years ago for it.

Thank you Rays74, I didn't think it had a throttle body, its all mechanical.

Just to clarify: It does not have a throttle position switch either?

Does it have a fuel relay?

Fuel pressure regulator?

Oh and datzenmike, not that it matters but I am a guyette.

 

Nope, No and no not if it's stock (there are some aftermarket regulators about but yours shouldn't have one by the sound of it).

Try setting the idle mixture screw at 2 turns out to begin with and run it and see what diff it might make. As was mentioned above, recheck the main fuel jets to be certain they are in their correct slots.......it is very easy to mix these up and you would experience the symptoms you have.

 

Dudette huh? Xlnt, great to see you're not afraid to get a little Datsun dirt on your clothes :)

--Ray

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Oh and datzenmike, not that it matters but I am a guyette.

 

Now we have two guyette 710 goon owners.... both are '77s too!

 

It's very possible that you have swapped the primary and secondary jets. It's easy to do. The jets have small numbers on them and the primary number will always be smaller than the secondary. This would cause an over rich condition. The primary jet is the one closest to the valve cover.

 

 

 

I like this guy already.

 

The light just went on.

 

 

On the Hitachi carb, if you stand on the pass side and look over top of the valve cover you'll see two adjustment screws with little springs under them. The one on the left closest to the throttle lever is the idle speed screw. (self explanatory) The one closer to the front is the idle mixture screw. This screw adds or removes fuel from the idle air. Too rich and the plugs may foul and idle poorly.... too lean and it will idle poorly

Turn the idle mixture screw in or out. Idle quality will either improve or get worse. If it gets better and the engine revs up keep going. If it gets worse turn the other way. The object is to get the fastest smooth idle speed. I'll assume the idle increased, so turn it down using the idle speed screw. (left side) Now turn the idle mixture screw (right side) in until idle quality drops. Turn the screw out until idle quality drops. Pick a spot about half way between these two points where it idles best. Likely the idle has increased slightly so turn the idle speed screw down. Repeat until you cannot improve the idle quality. Your idle mixture is now set.

 

This should be done after a tune up with the valve lash set and the ignition timing checked and adjusted but it's easy to do and cost nothing and may help. I still think the primary and secondary jets are swapped by accident.

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Idle Speed and Mixture Adjustment

 

NOTE: Idle speed must be adjusted with engine fully warmed, choke butterfly fully open. Take off air cleaner lid and confirm the choke is fully open before proceeding.

 

1 Adjust curb idle speed to 800 rpm

2 Mixture adjustment.

* Turn mixture screw out until engine slows down

* Turn mixture screw in (clockwise) until engine speeds up

* Reset idle speed screw to 800 rpm

* Lean the mixture down (anti-clockwise) to 775 rpm.

 

To get a 'feel' for the mixture adjustment, turn the screw by half turns clockwise and anti-clockwise until you hear the engine speed up and slow down. Then fine-turn with 1/4 turns. Do this repeatedly until you are confident of the results

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