78 L20b #1,#2 cylinder dead at idle

[banzai510(hainz)]

vacuum secondary has a leak???????

 

Im thinking if you say the car runs fine in the upper rpms and you let off the gas then gas it hard and no stutter i would think the accel pump is fine.

I seen the accel pump linkage stick in the IN mode once and was hard to start haveing no accell pump(no gas squirting in)

 

I hate those later smogged up L20s.

Thats why I like the L16 intake. simple and no extra ports,air injection ect.....

[Sar_moby]

In all honesty I think the car is fairly close or has one or two underlying problems that cause the driveability issues.

 

I have to keep in mind that cold start driveability and heat-up transition is why people went to F/I in the first place.

 

I can adjust the car to run great hot (lean= good throttle response), pretty good with the choke on( rich) and only have the problem during the transition from cold to hot (unless quite rich).

 

My in-experience with Hitachi carbs is some of the problem. This being my first Datsun, I have been learning what they like and don't like as compraed to my Toyota experience.

 

I can turn this vehicle in and get paid for it - but it will get crushed( not good in my opinion, a vehicle that runs pretty clean as compred to a SUV)

 

Vacuum secondary looked okay, held vacuum.

I will adjust the choke colder and work on the accelrator pump to see what can be changed (more fuel/less fuel). I am wondering if the accelrator pump linkage somehow got bent as the shot doesn't seem real powerful...... hummm

 

Scott

[banzai510(hainz)]

I adjust my stock 521 carb once. was a 72 with eleltric choke.

I couldnt get it just right between cold and hot.

 

I found the orginal box on ebay from Hitachi .packed it up with foam peanuts then dumped it in the river where i was arrested for littering!!!!!!!!!!!!!

 

 

If you lived closer I have a L20b carb from a truck to swap in (but you live to far away)

[datzenmike]

Ah yes, someone modified mine before I got it. The A.I.R. is gone, hole plugged... looked factory.

[Sar_moby]

mixture set rich, motor cold, pump pedal and starts right up.

after 40 sec. the engine is real rich with the choke on, rev the motor to open the choke, choke clears and we are back to the 2 cylinder motor. increase mixture again, increse idle speed, rev a few times and it will hold idle on all cylinders.

 

on accleration, sometimes it bogs at tip in real bad. You can slowly keep opening the throttle and continue the bog ( motor sounds like it is starving).

 

i can't see the float level with the air cleaner on but could fuel supply cause this? anything else?

Possibly the accelerator pump is bad( already?) or the pump is not refilling with fuel?

 

It seems that the 2 cylinder problem is air/fuel ratio related( WOT is great) and that for some reason those two cylinders need more fuel to fire. At the same time the extra fuel makes the rear two cylinders too rich and they bog( theory). Makes me think intake gasket is bad.

 

Well as time permits I will keep investigating.

 

Anyone local wants to take a look- I'd be thankful

 

Thanks for the help

 

Scott

[banzai510(hainz)]

I worked on Tanas 521.

I cked the ignition and seem fine. I drive it around and ran ok. The accel pump looked fine but a little on the weak side.'

Later she said it died on her. I didnt believe it. Gave her 2 black eyes!!

 

next day I showed up again to drive it and it died on me.

I said I dont know Buy a weber DGV. She got one for 150 almost new w/adapter. Installed it and has been fine.

 

if you think your motor is fine mechainically and eleltrrically(which I think it is) then must be a carb thing. I block passage or soemthing.

 

Im only guessing that its the carb. Maybe NAPA has a cheap rebuild and try that.

Im out of awnsers

[Sar_moby]

thanks for the help Hainz-

 

I think it maybe mixture into cyl 1,2 and will see if the accel pump/fuel pump etc. are doing there job and look at changes to see how it runs.

 

Thanks all

Scott

[Sar_moby]

Well, I took out some accelerator pump shot and re- adjusted mixture and idle speed and most of the bog on tip-in is gone. It still revs better if I run it lean(er) when hot but it is getting closer. When cold it still mis-behaves some and gets better as it heats up- leaking intake or exhaust manifold (It sounds like exhaust manifold as of late, probably #1 or #2 as those are the ones that need the mixture rich to run)

When this thing is hot, it runs like a rocket. The 4 speed makes freeway driving kinda loud though.

 

Thanks for the help- will get back to you IF I tear into this motor.

 

Regards-

 

Scott