Hesitation upon accelerating from a stop

[jboulukos]

Tried a compression test.

-Took cool wire out of coil.

-took out all spark plugs

-Attached compression gauge spark plug hole 1

I then cranked the engine and the gauge moved up to approx. 60 but only when turning the key. Also sparks flying from coil.

I then tried cylinders 2 and 3 but same effect. The pressure was there only when cranking.

Am I missing something? Is it possible to have zero compression?

[jboulukos]

Adjusted the carb as per the service manual.  Very difficult to adjust, not fun.  Did my best to follow the directions.  After finding 650 rpm with the idle speed screw, little to no difference was made by turning the idle mixture screw.  Turning it slowly, quickly, or large amounts of turning hardly creates a change in rpms.  The hesitation upon acceleration decreased slightly although the car runs a bit more rough or feels as though there's less power and the exhaust smells a bit more gassy.  I think the car runs smoother at 700 rpm.  I'll revisit this of course.

[jboulukos]

Na, did you check the ignition timing....timing gun....loosen dist nut...so on n so on.

 

For the head I was not concerned about warpage, as you stated it ususlly is not a problem...it was the condition of the valves n valve seats I spoke of.

Checked timing, it's right on the money.  New distributor cap, rotor, wires, plugs.

[datzenmike]

The compression gauge has a one way valve and stores the reading. There should be a small push valve to release it to zero so you can move to the next cylinder. Maybe your compression tester isn't any good.

[jboulukos]

The compression gauge has a one way valve and stores the reading. There should be a small push valve to release it to zero so you can move to the next cylinder. Maybe your compression tester isn't any good.

Yeah, I thought the gauge or hose may have been faulty.  Its 40 years old and today was the first time it was used.  I'll rent one from AutoZone.

[jboulukos]

What's the difference in the manual version and the automatic version of this carb.  I'm pretty sure the extra ones I have are manual since I got them from a guy with a manual B210.  I took apart one yesterday and learned a ton.  

Also, is there any preferred carb store/website that people have had good outcomes with buying carbs?

[datzenmike]

The differences are subtle. What they are exactly I don't know. Automatics idle in gear under a slight load where standards do not. Automatics usually have a dash pot, although my 710- is a standard and it had one. The dash pot prevents the carb from closing quickly if you should step on the gas and then for some reason decide not to accelerate. The sudden closing of the carb plus the load of being in gear can cause the engine to stall. On a standard you would simply depress the clutch.

[jboulukos]

The vintage compression gauge I have has an attachable pressure release screw that I had not attached yesterday. Used an autozone compression gauge and successfully completed the dry and wet compression.

Results:

 

Compression in psi (dry/wet)

Cylinder

1 (124/152)

2 (127/154)

3 (126/152)

4 (124/148)

 

Looks like all is well with compression as to my knowledge...expected increase in wet test, no significant decline in numbers dry or wet.

Are the actual numbers for compression good?

 

Adjusted the carb again after this test. I have yet to adjust choke and to my understanding should be completed on a stone cold engine. As far as choke adjustment goes, does anyone have any thoughts on how it should be adjusted?

[jboulukos]

Test drive after today's carb adjustment helped decrease if not eliminate the initial acceleration hesitation.  It currently feels less smooth overall after my adjustments.  Going to continue to look into this.

 

[datzenmike]

Buck fifty isn't so bad.

 

Engine dead cold, hold the gas pedal down and turn the choke housing counter clockwise as viewed from the back. If marked, turn towards RICH. Turn until the choke plate is fully closed. Next fall when it gets colder you probably will need top turn it even richer.

 

If working properly, depress the pedal once or twice if colder. This will pump raw gas in and both set the choke and the fast idle cam in place. It should start and have a fast idle to speed warm up. Choke should turn off in under 8 min.

[jboulukos]

I read over some of the past threads of the trials and tribulations of the Hitachi carb.

Here's a few more questions.

1. How can you know if the carb is original Hitachi and not a remanufactured or knock off carb?

2. What's a good carb body cleaning solution for soaking the parts in?

3. How long to soak the parts? I understand the middle portion with the circular float window shouldn't be soaked "too long" due to rubber being a component of the window and is a recommended warning on the carb rebuild kit I have.

4. To clean the jets, should they be accessed from the inside, unscrew the top ceiling screws and removed/cleaned? Do those top screws to access the jets have a certain position/depth or are they screwed in to the lowest position?

5. Should gasket sealer be used on carb to carb gaskets and/or carb to manifold gasket?

6. I currently do not have a clamp on the lower end of the Manifold heat riser white tube that leads to the neck of the air cleaner assembly. Would this cause vacuum loss?

7. When removing the carb from the car, how can the metal cable coming from the firewall be detached to free the carb?

 

Thanks!

[jboulukos]

8. Where do I obtain a filter piece like this?

 

9. Should this line in my hand be capped?  The service manual says it goes from the distributor to the 3 part thermal vacuum valve.  How many lines go to the distributor? The line over the top of the valve cover attaches to the distributor currently.

[Cosmonaut]

Any suto parts store...you have to just ask for the air filter box side piece...I always buy the cheapest one...then cut it to fit....

[Cosmonaut]

PO bypassed Nissans timing "retard system". If you wish to hook it back up, make sure you have all of the original pieces, including the part in the hose. I personally have never had that particular system fail...well not including rotten rubber hoses.

[jboulukos]

10. Should choke be open on a stone cold engine?

[jboulukos]

PO bypassed Nissans timing "retard system". If you wish to hook it back up, make sure you have all of the original pieces, including the part in the hose. I personally have never had that particular system fail...well not including rotten rubber hoses.

I think I will just shove a screw in it then.

[Cosmonaut]

Depends, have you gone into the car n hit the peddle to set the choke?

[Cosmonaut]

I am impressed by your learning curve and your dedication to doing it right.

[jboulukos]

Depends, have you gone into the car n hit the peddle to set the choke?

 

no pedal touched, popped the hood to check it and the metal flap was open.

 

I am impressed by your learning curve and your dedication to doing it right.

 

Thank you.  I'm trying my best and enjoy the hobby of it.  I got hooked after changing out a blown head gasket.  I review the service manual but mostly rely heavily on Ratsun to build my understanding of how stuff works.  

[Cosmonaut]

Ya, the clutch needs to be set after it has been driven. Go ahead n give it a quick depression and look at the choke plate again.

[jboulukos]

Ya, the clutch needs to be set after it has been driven. Go ahead n give it a quick depression and look at the choke plate again.

No clutch, It's an automatic trans.  

 

I read over some of the past threads of the trials and tribulations of the Hitachi carb.

Here's a few more questions.

1. How can you know if the carb is original Hitachi and not a remanufactured or knock off carb?

2. What's a good carb body cleaning solution for soaking the parts in?

3. How long to soak the parts? I understand the middle portion with the circular float window shouldn't be soaked "too long" due to rubber being a component of the window and is a recommended warning on the carb rebuild kit I have.

4. To clean the jets, should they be accessed from the inside, unscrew the top ceiling screws and removed/cleaned? Do those top screws to access the jets have a certain position/depth or are they screwed in to the lowest position?

5. Should gasket sealer be used on carb to carb gaskets and/or carb to manifold gasket?

6. I currently do not have a clamp on the lower end of the Manifold heat riser white tube that leads to the neck of the air cleaner assembly. Would this cause vacuum loss?

7. When removing the carb from the car, how can the metal cable coming from the firewall be detached to free the carb?

 

Thanks!

 

 

Any input here is much appreciated.

[Cosmonaut]

It was the choke that needs to be set...mind farted while typing...in this case clutch = choke

 

 

When driving the choke opens due to it being at operating tempature. It remains at that setting (after you have turned off the vehicle) untill you give the accelerator pedal a quick depression (once) to reset the choke (closed) for starting a cold engine.

[Cosmonaut]

Sorry for the earlier confusion

[jboulukos]

One thing to be aware of when you tear down a Hitachi - there are a couple of tiny check balls inside that are easy to lose if you aren't watching for them. Take a close look at the sheet that came with with your carb kit and see if you can locate them. I'm looking a the sheet for a DCG-306 Hitachi and it shows two balls.- one for the "Pump intake check" and one for the "Secondary fuel Valve".

 

If I had to choose between several Hitachis to rebuild, the first thing I would look for is one without the California spec small venturis. If you look down the primary (need to open the choke butterfly) and secondary carb throats you will see a small round ring held in place by a hanger bar. In the Cali carbs this bar goes clear across the carb throat. It is held in place by a set screw through the side of the carb body. I've had two Hitachis where the set screw didn't hold and the venturi/cross bar came loose. The non-Cali venturi has a hanger that comes from just one side and the hanger is held to the carb body by one or two screws (two for the bigger 340 Hitachis, but maybe just one screw for the smaller carbs). Maybe datzenmike or someone has pics of the two venturi types which will make more sense than my rambling description. Anyway, I would go with the version with the hanger from just one side as I think they are more secure.

 

datzenmike mentioned the hollow screw that comes up through the carb base. These screws can get switched around during previous rebuilds, so the hole the screw is in may or may not be correct. You can figure out which hole it should be in by looking up into the carb body for a through passage.

 

No reason not to put a plastic sleeve or something over the carb wires to protect them. The wire to the idle cut solenoid is known to sometimes break off, so anything to support and protect the wire is a good idea.

 

Len

I read over some of the past threads of the trials and tribulations of the Hitachi carb.  

Here's a few more questions.

1. How can you know if the carb is original Hitachi and not a remanufactured or knock off carb? 

2. What's a good carb body cleaning solution for soaking the parts in? 

3. How long to soak the parts? I understand the middle portion with the circular float window shouldn't be soaked "too long" due to rubber being a component of the window and is a recommended warning on the carb rebuild kit I have. 

4. To clean the jets, should they be accessed from the inside, unscrew the top ceiling screws and removed/cleaned? Do those top screws to access the jets have a certain position/depth or are they screwed in to the lowest position? 

5. Should gasket sealer be used on carb to carb gaskets and/or carb to manifold gasket? 

6. I currently do not have a clamp on the lower end of the Manifold heat riser white tube that leads to the neck of the air cleaner assembly. Would this cause vacuum loss? 

7. When removing the carb from the car, how can the metal cable coming from the firewall be detached to free the carb? 

 

Thanks!

[banzai510(hainz)]

looks like a stock carb to me. rebult? who knows after all these years.

 

You got a automatic since the shiftening is related to vacuume soemwhwere.  That's all about I know about automatics.

 

 

cold motor the choke should be closed. Maybe someone took the wire off the heater coil on side of carb or some one took the choke and loosen the screws and turn it till it was open on a cold motor. Look at the carb and the choke has a round thing. it will have screws its just a coil that heats up and unwinds or vise versa when elelctricity goes thru it.   But really once warm this has nothing to do with your issue. Just a intial warm up issue.. I could never adjust tehm right myself after I fucked with them as choke stayed on too long or not enough so I just fucking open them up and pump the gas when cold untill warm or get a manula choke.