carburetor problems

[pwrcat4000]

Hey ,

Thatks to all of you I have had months and months of cheap worry free driving. I keep running out of gas because I am not thinking about gas very often no big deal usually I just carry a 1 gal can with me pour it in and go to the station (the gas gauge works I am just ingnorant)

Ran out of gas monday did the usual and poured in my 1 gal spare the truck made it about 100 feet and died would not restart no matter what. pushed it home and parked it it seemed to be flooded.

Wed I went out to see what gives, still would not start would run when I poured gas dierctly in the carb figured lost prime or some thing replaced ratty fuel line to the fuel pump still nothing from the pump.

Repalced pump (off of my blown up 1.6L) finally got fuel stared truck made it about 1 block pushed it back home thank god this truck does not weigh much.

popped the hood and took a look at the carb there is bubbling gas comming out of the ?Air horns? and floodiing the carb.  I am not a mechanic but I am very mechanical however carburetor's might as well be the space shuttle

This is the carb off of the 1.6 liter I have not stripped all the crap off of the l20B carb yet it is still on the intake from the swap

I don't have any idea what could be wrong but I would be willing to bet someone here knows exactly what is wrong.

 

[DanielC]

Letting any vehicle run out of gas is not good.  There is usually some crap in the gas tank, and if you use the "last drop" of gas, you suck that crap into the fuel filter, possibly the pump, and even into the carb.  Dirt in the carb commonly causes the needle and seat to quit sealing.  this causes the float bowl to fill too full, and flood gas out where ever it can.   If you disconnect the fuel line, and run the carb bowl empty, sometimes the needle and seat open far enough to flush the dirt away, and the float, needle and seat will act normally again.

 

But the dirt in the carb can also get into small passages, and clog them.

 

Your truck is 45 years old.  it would not hurt it to clean and flush the gas tank.

[bananahamuck]

^^^  Try doing that up there first ,, but if that don't work

 

 

Take the front plate/cover off carefully and remove float  (there is a tiny metal hoop spacer thing at the end of shaft you can very easily lose)  pull out needle and blow into hose that goes into carb and see if anything falls out ,,,, like dirt,, that might be holding needle off the seat... You can do all of this without ever removing carb from truck.

 

And ,, do i see RED RTV on the fuel window,,, cuz that is not good ,, buy a carb kit...  That front cover gasket comes in every one. (  doesn't have to be exact year),,  as some parts counter guys may bullshit you into.

[pwrcat4000]

Ok I am convinced the truck is maintained by gremlins

Went out to do as  bananahamuck Sugessted looked at the float and the fuel in the chamber looked "normal" figured wtf se if it starts at worst i could move it in to the shade before it floods out again.  It started it did not die drove it aound the block still no problem drove it to the gas station filled it up started as normal I guess it was dirt or somethiong and it worked its way out of the seat???

Any way thanks for your suggestions guys I promise not to feed it after midnight or get it wet. LOL

[pwrcat4000]

Ok having what I belive to be carburator problems again.

This time with the idle I cant seem to get the truck to idle smoothly at low rpm.

I have turned What I belive to be the the air fuel screw every wich way but loose cleaned it out with carb cleaner it will die when I remove it so I think that means the passage is open.

I have played with the manual choke and have it on just a little bit to keep it form stalling.  I have adjusted the throttle screw I have played with timing (turned it counter clock wise which i think is retarding timing. then set it back to the previous mark as it seemed to have no effect.

I know that most people gop with a new webber but I really want to stick with the stock carb unless there is no other option.
It may be that I am runnign my 1.6 liter carb on my 2.0 liter motor.

 

Ohter recent changes

1. #4 intake rocker came off I put it back on and adjusted it to .008 I think it may have been off for a while but I amnot sure

2. #2 Exaust rocker was off the truck would not run and was backfireing though the carb noting in the carb seems bent or damaged

3. I just adjusted all the valves some were very loose like .016

4. new plugs and wires al the plugs have even burn

5. Seafoam in one tank ran it empty and refiled with fresh gas.

 

It is still rough at low rpm and dies if the nose of the truck dips on braking or if idel and park nose down.

 

As Always i really apricate this forum and the great help I have recived keeping this truck on the road.

[datzenmike]

When idling look at front of carb for the fuel level indicator.  Could be a glass front or a round window. Where's the gas at?

 

Carb mounting bolts snug?

 

Valve lash not set*

Firing order 1342 counter clockwise.*

Timing at 12 degrees BTDC* Disconnect the vacuum advance temporarily.

 

*These three very important for strong intake vacuum

 

 

 

Idle mixture screw won't do much if

 

The idle cut solenoid not working. If idle cut not working there will be no way for gas to get to the idle circuit. Turn ignition on off on off on off. You should hear a light click sound from rear of carb.

 

The idle is too high. Too high will be above the idle position, and no adjustment possible. It will also mess with the vacuum and mechanical advance. Get the idle as low as possible, under 800 at least, before adjusting.

 

 

 

Do you have an intake with an EGR valve on it? Remove and wire brush the valve clean of deposits. Make sure it closes completely or exhaust air will leak in. EGRs are supposed to be OFF at idle.

[banzai510(hainz)]

what year is the 521 if its not a elelcic choke model then most likely you dont have a eletric idle cut off selinoid on the carb.

 

To me your idle jet is plgged and your putting the choke on to get gas running threw the main jet

 

or loose carb or loose intake manifold or cracked.

 

I bet it runs ok whith manual choke pulled on

 

once a rocker arm falls off you should be able to KNOW this immedialtey!!!!!!!!NO power running on 3 cylinders

 

 

if your old fuel filter is full of rust then highly like its plugged the ilde jet as its so small. then when you rev up it goes to the main jet

[pwrcat4000]

I will try some of the suggestions to day and post back.

[pwrcat4000]

When idling look at front of carb for the fuel level indicator.  Could be a glass front or a round window. Where's the gas at?

 

alittle over half way up

 

Carb mounting bolts snug?

 

They are

 

Valve lash not set*

 

Set it the other day it was way loose .008 on intakes and .010 on exhaust cold

 

Firing order 1342 counter clockwise.*

 

Firing order was 1243 counter clockwise the idle is way way smoother now.

I am not sure if the wires are on the distributor are right  is there a #1 on the distributor and how do you tell when i replaced the 1.6 motor with the 1979 2.0  i did not remove them from the distributor

It fires through the carb occationally with this firing order (under load at  low rpm) especially in 3rd gear maybe one of my rockers is off again?

The idle is way way smoother so something is wrong I have not chected the timing

 

Timing at 12 degrees BTDC* Disconnect the vacuum advance temporarily.

 

Need to borrow an timing light

 

*These three very important for strong intake vacuum

 

 

 

Idle mixture screw won't do much if

Agrreed

 

The idle cut solenoid not working. If idle cut not working there will be no way for gas to get to the idle circuit. Turn ignition on off on off on off. You should hear a light click sound from rear of carb.

There are 2 electical hook ups on the carb a can shaped one on the drivers side and a semi rectangular on on the back of the arb neither make any noise with the key

 

The idle is too high. Too high will be above the idle position, and no adjustment possible. It will also mess with the vacuum and mechanical advance. Get the idle as low as possible, under 800 at least, before adjusting.

Adjusting idel by ear I get it as slow as i can without it dying

 

 

 

Do you have an intake with an EGR valve on it? Remove and wire brush the valve clean of deposits. Make sure it closes completely or exhaust air will leak in. EGRs are supposed to be OFF at idle.

 

there is a fitting at the very bottom of the intake that has a 1"  hose connected to it from the side of the block

 

 

 

 

banzai510(hainz)

 

what year is the 521 if its not a elelcic choke model then most likely you dont have a eletric idle cut off selinoid on the carb.

1971 carb and intake from my 1.6L on my 1979 L20B

There are 2 electical hook ups on the carb a can shaped one on the drivers side and a semi rectangular on on the back of the arb neither make any noise with the key.

I thas a manual choke that I must use to start it regardless of the weather.

 

To me your idle jet is plgged and your putting the choke on to get gas running threw the main jet

 

or loose carb or loose intake manifold or cracked.

I have sprayed strting fluid around the carb and no change in idle

 

I bet it runs ok whith manual choke pulled on

Yes it does so that would be a sure thing not a bet LOL

 

once a rocker arm falls off you should be able to KNOW this immedialtey!!!!!!!!NO power running on 3 cylinders

In my defense I had swiched form my 1.6 liter to this L20B so i had no baseline it will now go 80 MPH with the rockers on and adjusted the #4 plug now looks like the others this would probably be due to the intake valve functining now.

 

if your old fuel filter is full of rust then highly like its plugged the ilde jet as its so small. then when you rev up it goes to the main jet

Fuel filter is nearly new

 

 

 

 

I hope that my information can help you help me I can not thank this group enough. I love this truck like an ugly old dog!

[pwrcat4000]

datzenmike, banzai510,

 

Thank you for all your assistance gentelmen but after tring all you suggestions with little to no improvement 

I detimined it has to be a vaume leak somewhere (as you both suggested) since all the adjustments only slightly improved the idle

so I pulled off the pcv hose and put my finger over the pcv and viola it ideled smooth Repalced the PCV  ($4.00) and now it is ideling so smooth I cant belive it !!! I am going to go drive her around for a while make sure it is "fixed"

 

Firing order has to be 1243 counter clockwise on this truck the other order was firing though the carb and fouling plugs

It is not the 1.6Ll it is a 2.0L L20B out of a 1979 620.

[datzenmike]

Negative. Firing order is 1342 counter clockwise. All Datsun straight 4 cylinder engines are this way.

 

Set to TDC compression stroke on #1 cylinder and take the distributor cap off. The rotor (no matter where it is pointing) will be near/under the #1 plug wire. Counter clockwise the others are 342.

 

Set the timing to 12 degrees BTDC #1.

 

Only Subaru, Yamaha cycles and some British Kent or Riley engines fire other than 1342. 

[pwrcat4000]

Negative. Firing order is 1342 counter clockwise. All Datsun straight 4 cylinder engines are this way.

 

Set to TDC compression stroke on #1 cylinder and take the distributor cap off. The rotor (no matter where it is pointing) will be near/under the #1 plug wire. Counter clockwise the others are 342.

 

Set the timing to 12 degrees BTDC #1.

 

Only Subaru, Yamaha cycles and some British Kent or Riley engines fire other than 1342. 

Ok I am a just a dumb shit.  I can't get my brain to work in counter clock wise that is what the firing order is set at 1342 COUNTER CLOCKWISE.

I was just going clockwise wich would be 1243 even though I would bet the rotor turns counter clock wise.

Anyway the dam truck is it is idleing so smooth and slow I cant hear the motor at stop lights keep thinking it stalled it never dies just sets there at low rpm idle. I feel so awesome I want to call people and tell them how awesome the truck idles. I even have called some people (BTW they don't give a shit, at all!)

Thanks Datzenmike

It is running so smooth what benifits will I get by verifieing rotor position and seting the timing?

[datzenmike]

All engines are different but it takes a finite time for the gas/air mix to burn and build up pressure once lit. During this time the piston is nearing TDC top dead center. If the timing is too advanced the pressure will push down on the rising piston and this would be counter productive. Likewise if at TDC the piston/rod and crank are vertical and no motion can be transmitted to it. The best place for maximum cylinder pressure to push down on the piston is when the crankshaft is about 15-18 degrees after TDC. Again, if too late the expanding gasses are chasing a rapidly descending piston in a rapidly expanding cylinder volume.

 

For example, on an L20B at idle, if the fuel/air is lit at 12 degrees before TDC. This gives the needed time for the pressure to build to maximum and the piston to rise and begin falling to that 'sweet spot' at about 15-18 degrees. This will give the maximum strong idle because the maximum energy in the gas is being converted to rotary motion. The L16 may have a different timing than the L20B.