Hesitation upon accelerating from a stop

[jboulukos]

Great weather in Chicagoland + newly rebuilt alternator = a bunch of cruising around in my blue B.  Since the day I purchased this car in 2009 in Kent, WA, it has required the driver to do a particular "feathering" of the gas pedal to accelerate from a stop.  I remember the previous owner teaching me prior to me taking her home to Bremerton.  To this day, the gas pedal requires a partial and quick 'tap tap' prior to a continued depression of the pedal to start moving.  If the feathering is not done, and the driver begins a gradual depression of the gas pedal, the car hesitates a second or two and may die at times. 

 

Back in '09 and '10 I had a few mechanics look into it.  They always focused on the carb (original).  Although vacuum leaks and carb-to-manifold gaskets were attended to, nobody could figure out the initial acceleration issue.  I have a working anti-dieseling solenoid.  I recently changed the fuel filter and new spark plugs and there's no change.  I am thinking it may be an inner carb issue.  The fuel pump is original Kyosan Denki.  I have read that simply disassembling the fuel pump, cleaning off the diaphragm and adding a new gasket is enough to service it.  I have not done the recommended fuel line pressure tests yet.  I'm trying to narrow it down a bit prior to purchasing more diagnostic equipment.  

 

Another symptom, although not certain is related, occurs while maintaining a steady speed say 45mph.  The car's power will slightly go in and out.  Not quite hesitating, just not smooth, and consistent.  

 

Maybe a fuel line pressure issue?  Carb needing cleaning?  

 

Anybody experience the same issues?

 

    

  

[flatcat19]

Think fuel; fix ignition.

 

 

 

Don't rule out your distributor.

[Cosmonaut]

Not so much the feathering, but the at speed sounds like a valve job may b needed. It could also conceivably cause your feather problem.

 

Have they tan a compression check? Wet n Dry?

 

I have found on a few B's that an accurate valve adjustment n timing make a world of difference....which also brings to mind, what kind of shape is your distributer n vacuum advance..

 

I am not a genious but I always look at the vacuum, timing, compression and fuel flow before I think of a carb.

[Cosmonaut]

Cat beat me to the dist while typing...He is one fast cat.

[jboulukos]

Think fuel; fix ignition.

 

 

 

Don't rule out your distributor.

 

Not so much the feathering, but the at speed sounds like a valve job may b needed. It could also conceivably cause your feather problem.

 

Have they tan a compression check? Wet n Dry?

 

I have found on a few B's that an accurate valve adjustment n timing make a world of difference....which also brings to mind, what kind of shape is your distributer n vacuum advance..

 

I am not a genious but I always look at the vacuum, timing, compression and fuel flow before I think of a carb.

 

Last month I took it into a shop, had a leak down test, compression test and pressure test of the cooling system.  Got charged $240 and was told to drive it home slowly and not to ever drive it.  The mechanic didn't want to fix the head gasket without completely rebuilding the lower engine and quoted me $4500.  I was never given an exact measurement on the compression and leak down tests.

 

Since then, I've studied this forum and the service manual.  With the help from Ratsun, I became inspired and motivated so I changed the head gasket, and adjusted the valve clearance in the process.  

 

The last full tune-up I have had was in 2009.  This feathering problem was present before and after that tune-up.  I plan on giving the car a tune in the upcoming weeks.  

 

Not certain how to check a distributer.  I don't know where the vacuum advance i located.  Definitely starting from the drawing board but I gotta start somewhere.   

[flatcat19]

Rent a compression tester from the parts house.

 

Plenty of videos on YouTube on how to perform this test.

[datzenmike]

My 710 has always done that until recently.

 

I always thought that there was an idle mixture screw, a primary and a secondary barrel and an accelerator pump and that was it. From idle to primary operation there was an accelerator pump to help transition. Turns out that there is also a slow  system for just off idle

 

There is an idle mixture screw. Just above this is a thin vertical slit cut into the carb throat (known as the primary by pass hole) with the throttle plate closed at idle just at or below it. When you step very lightly on the throttle that throttle plate rises up this slit applying vacuum and sucking out extra fuel. This is known as the slow system. 

 

The slow system draws fuel through a slow jet and there is an emulsion tube. There is also a primary slow air bleed. The idle cut solenoid shuts off fuel through the slow circuit which also contains the idle mixture screw.

 

Any one of these jets or air bleeds could be obstructed.

 

 

I couldn't cure mine and swapped another carb on and it immediately works much better!!!!! Rolling along at aide clutch out you step slowly into the gas and it ... just picks up and goes.

 

 

Here's something to try.

 

 

Remove the idle cut solenoid.

 

Get a can of carb cleaner that has a straw. Poke it in the idle cut solenoid hole and spray. This will force cleaner back through the air bleeds and jet. Wear goggles that stuff stings! No guarantees.

[jboulukos]

Great.  I just read more about this part of the carb system.  Thanks.  

Is the idle cut solenoid different than anti-dieseling solenoid or are these two terms interchangeable/same?

[datzenmike]

Same thing different name.

 

My carb had been off before and at least partly apart, maybe rebuilt? The hollow screw in the bottom that allows vacuum up to the power valve was mixed with a solid screw. I fixed that and now has more mid range and up grunt. It still stumbled off idle. Did the carb spray, no change. Did not know about the air bleed in the top section of the Hitachi so one day I'll take it apart. Maybe a jet was swapped too. Damn previous owners.

 

My FSM says, under hesitation.... 

 

(first three)

Main jet or slow jet clogged

By pass hole, idle passage clogged

Emulsion tube clogged

 

 

This was a '76 L20B and I swapped a '79 L20B carb on and away I went!!! Pulls away from a stop with idle and clutch, adding gas and it just drives away like it should. Before I had to rev it and slip the clutch to get rolling.

[jboulukos]

I will start with the cleaner spray and then go from there.  I have 3 extra A14 carbs picked up from a car being parted out.  I am tempted to open one up and do a test run for learning purpose.  

[jboulukos]

Rent a compression tester from the parts house.

 

Plenty of videos on YouTube on how to perform this test.

I'll also do a compression test and give a report.

[jboulukos]

Besides going out to buy a manual oil pump, are there household items I can use to add oil to the cylinder for the wet test?

[Lockleaf]

A funnel a and a spoonful of oil should do the trick

[datzenmike]

This hesitation is not caused by your compression, so why test it?

 

 

Take one apart, clean and assemble it. Throw it on. Rebuild the original and save it. If the other carb runs well leave it on. Enjoy.

[flatcat19]

I think the compression test is more for peace of mind. Last tech told him not to drive it and wouldnt give pressure specs.

[datzenmike]

this.

[B2Fresh]

I'm having the same issues on my B210 as well. I'm glad I came across this post to learn as we go also.

I was talking to a mechanic and he mentioned that it might be the float valve in the carb that's causing the problem and suggested that I rebuild the carb to fix the problem. But to rebuild the original carb. So I'm giving it to him to rebuild it and see what happens.

Hopefully the problem will be fix and my car will run better and better performance as well as gas mileage.

Will soon see.

[Cosmonaut]

Last month I took it into a shop, had a leak down test, compression test and pressure test of the cooling system. Got charged $240 and was told to drive it home slowly and not to ever drive it. The mechanic didn't want to fix the head gasket without completely rebuilding the lower engine and quoted me $4500. I was never given an exact measurement on the compression and leak down tests.

 

Since then, I've studied this forum and the service manual. With the help from Ratsun, I became inspired and motivated so I changed the head gasket, and adjusted the valve clearance in the process.

 

The last full tune-up I have had was in 2009. This feathering problem was present before and after that tune-up. I plan on giving the car a tune in the upcoming weeks.

 

Not certain how to check a distributer. I don't know where the vacuum advance i located. Definitely starting from the drawing board but I gotta start somewhere.

 

After the work, did you put the "B" into time?

[Cosmonaut]

Also, when you changed the head gasket, did you have the head checked by a machine shop?

[jboulukos]

After the work, did you put the "B" into time?

No way.  Idle time is death to a car and the human body.  I turned to Ratsun and got dirty.  Immediately started learning so I could change the cylinder head gasket out.

 

Also, when you changed the head gasket, did you have the head checked by a machine shop?

I did a lay person examination with a straight edge and feeler gauge.  No pressure test was performed.  I have read that in many cases the head is fine and not warped.  I winged it a little by not getting it checked.  Success on the head gasket change was achieved to my understanding...no overheating, no loss of coolant from radiator, no white coolant smelling smoke out the tailpipe, normal color oil and oil consistency.    

[Cosmonaut]

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.

[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.

 

I'm very new to all of this.  I haven't looked at timing or the distributor yet because I frankly don't know how.  I certainly will do that but will have questions and I'll need to study in order to understand what to do.

[jboulukos]

Update

I sprayed carb cleaner into the anti-dieseling solenoid hole and on the inside pin of the solenoid itself.  This resulted in a slight decline in hesitation at initial acceleration that returned to no effect after a few stop-and-go's.  The solenoid wire seems so fragile and I feel those 3 wires get completely baked between the valve cover and the carb.  Does anyone put a sleeve on the wires or protect them in anyway?

 

poor little wires

[jboulukos]

Here's the 3 extra carbs I grabbed from a part-out.  They look pretty crispy.  Is it worth choosing the cleanest one and rebuilding it?  The one on the right seems clean.

Thinking about putting some Pink Floyd on the turntable and getting at it.  I have a carb rebuild kit as well.  Any suggestions? things to avoid?  things to be careful of?  

 

[LenRobertson]

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