1984 GL Hitachi carb Duty solenoids chattering.

[oczuk32]

Got the wagon running after being parked for 13 years. Who knows why the duty solenoids are chattering. Who could explain the reason it's why the solenoids are doing that.

 

Edited yesterday at 05:50 AM by oczuk32

[el_freddo]

I’ve never seen those devices before. Californian unit? We certainly didn’t get them in Australia! They almost sound like air pumps. 

Cheers 

Bennie

[bushytails]

That's normal operation.  The duty solenoids allow extra air to mix into the fuel in the emulsion tubes, leaning the mixture.  Off all the time, mixture is too rich and you get black smoke from the exhaust.  On all the time, mixture is too lean, you knock and can't go up hills.  The ECU varies the on/off duty cycle (hence the name) to adjust the fuel mixture in the middle of this range, until the oxygen sensor is happy, cycling just above and below stoichiometric.

 

 

[oczuk32]

2 hours ago, bushytails said:

That's normal operation.  The duty solenoids allow extra air to mix into the fuel in the emulsion tubes, leaning the mixture.  Off all the time, mixture is too rich and you get black smoke from the exhaust.  On all the time, mixture is too lean, you knock and can't go up hills.  The ECU varies the on/off duty cycle (hence the name) to adjust the fuel mixture in the middle of this range, until the oxygen sensor is happy, cycling just above and below stoichiometric.

 

 

I learn something new every time from you guys in this forum—really appreciate the insights. The solenoids are a bit noisy, and I initially assumed the ECU was causing the chatter or there was a bad connection. Interestingly, when I unplug them, the engine runs noticeably smoother. But when they’re connected, it feels like the engine is starving. I’m planning to clean the carb a bit more and take a closer look at the O₂ sensor. According to the manual, the solenoids operate based on readings from the O₂ sensor.

[oczuk32]

9 hours ago, el_freddo said:

I’ve never seen those devices before. Californian unit? We certainly didn’t get them in Australia! They almost sound like air pumps. 

Cheers 

Bennie

Yeah, it's all California emissions junk. I'm pretty sure it's robbing some horsepower. Honestly, it'd be way easier to slap on a Weber carb and call it a day. But I must comply with laws.

[bushytails]

It should run best with the solenoids plugged in.  Make sure the green test connector under the dash is not plugged together, then get your 'scope on the o2 sensor line.  Keep in mind it's an unheated sensor, and you may need to rev it a little to get it to come to life.  It should be switching between around ..2v and .7v every couple seconds.  Check at idle, at a constant no-load slight rev, and during gentle driving.  It'll always be rich at full throttle, by design.

If the o2 sensor is switching at idle, but you have more power with them unplugged, check to make sure the power valve isn't stuck closed.  On the topic of power valves, make sure not to damage the gasket around the tiny passage in the middle of the carb when taking the top half off.  It's easy to tear, and will smoke and run like total spoob if you do tear it.  Also check secondary is opening correctly - it's semi-vacuum-operated and can be sticky.  And, of course, clean every single passage and jet in the carb...

Also check timing.  Rich mixture can hide overly advanced timing.  Check timing with vacuum advance unplugged and idle set correctly.

[bushytails]

8 hours ago, oczuk32 said:

Yeah, it's all California emissions junk. I'm pretty sure it's robbing some horsepower. Honestly, it'd be way easier to slap on a Weber carb and call it a day. But I must comply with laws.

The California Hitachi actually flows pretty well.  It gets you several horsepower over the 49-state Carter version.  There's also a 49-state Hitachi, but I've never seen one here in California.  Unless you pair it with other upgrades, I don't think a carb swap will give noticeable power gains.  It is, however, more complicated to work on.

[moosens]

Just a little info at this time. The rest of the country pretty much all has the 49 states Hitachi and the Carter single barrel is much less common to the point that those folks now can’t find diddly for their carbs. 
 

Carry on. 

[moosens]

And great info, thanks bushy. Kind of glad I’m sticking with my 70s cars. 
 

Good luck. 

[oczuk32]

Cold idle startup is solid. Ambient temperature was 89°F. After revving the engine to transition out of warm-up, the idle RPMs drop very low. I adjusted the carburetor idle screw to raise the RPMs above 700 and set the timing to just over 8 degrees BTDC. It's improving little by little. I'm currently running a cheap Amazon fuel pump until the correct one arrives from RockAuto (shipping from New York). I can still smell remnants of the old fuel coming from the exhaust. Once the new pump arrives, I plan to add fresh gas to the tank and see if there's any improvement.

 

 

Edited 3 hours ago by oczuk32