Unable to restart Daily Driven '79 620 l20b

[Mitchell]

Hey Guys,

 

Need another set of eyes and thoughts about this...

I have a '79 620 l20b with factory matchbox and a genuine weber 32/36 dgev (electric choke) that I've daily driven for more than 30 years and have an issue I can't figure out. Initially I started the truck right up cold (but warm outside temp here in Florida) as normal but after about 20 seconds it shut down by sputtering and not able to build revs before stalling out. It wouldn't restart. I tried the following:

I checked the spark plugs and they were wet with fuel.

I checked the float chamber inside the weber no dirt or rust particles whatsoever, blew on the inlet of the carb to check the float to see if the needle would shut the gas flow and it does. The float is the black plastic type and doesn't appear to have leakage.

I double checked the static timing at 0 and is pointing at number 1 in the distributor and looks good.

I've owned this truck for many years and have many spares...

I have spark to the plugs. The Cap Rotor Wires NGK / NGK plugs are in excellent condition. 1,3,4,2 verified.

I added an additional ground to the distributor which has a spade terminal, no difference. I've swapped Distributors, no difference.

The carb is about 15 years old, considering getting a new one as previously the carb sometimes floods when hot starting causing extended cranking, but always starts... Possibly some tube is clogged or accelerator pump rubber is age cracked...

The color of the spark might not be as bluish as I remember so I've tried several coils including a .6 ohm igniter II, several matchboxes OEM E12-80's as well as new aftermarket

Valves were adjusted about a year + ago. Truck isn't driven hard.

I appreciate anyone's thoughts.

 

Thank you!

 

[datzenmike]

 Fix the fast idle or what ever is causing it to not kick in. Choke forces an over rich mixture, what it needs is the fast idle set, to hold the throttle open slightly and it will rev up. (1,800-2,200 RPMS) This will keep it revved up and running and it speeds the warm up time. 

 

I should imagine the 32/36 has something like the original Hitachi carburetor had... 

 

 

 

The fast idle cam has steps the set screw stops against. At the choke warms and opens the cam moves and the steps lower the idle.

 

[Mitchell]

Thanks Mike,

 

I was able to pull the throttle cable to progressively open the lower set of throttle plates and tried starting with a remote starter to see while cranking but no change. I could see both barrels there with the 'throats' opening as they should but no result. I'm going to do a compression check next since the motor has a total of 525k miles, twice rebuilt, 55k miles since most recent rebuild. I appreciate your response. I'll post the compression results.

[banzai510(hainz)]

it runs for 20sec!!!!!!!!!!!!!!!!! no need to ck timing ect.

 

  maybe the needle valve sticky and bowl goes driy

 

DO THIS!!!!!!!!

right when it dies go to carb and cycle the carb and see if gas squirts in there!!!!!!!!!!! maybe the needle valve sticky and bowl goes dry.

also right when it dies do the spark ck. feel the coil. I assume you havent changed anything and been fine for years.

 

you said your getting spark.

 

one could make sure the carb and intake bolts tight. and if really motivated recheck the valve lash but it runs for 20secs so I dont think its it.

 

Ialwasy look under the dist cap for moisture or something odd. . check the vacuum advance plate is not wiggle around.

[Mitchell]

Hey Hainz,

 

Thanks for your reply. Actually it ran for 20 seconds once and sputtered like out of fuel or flooded out, not suddenly stopped running, that's the very last time but no longer will run at all now, just wet plugs and has spark. I did open up the weber to check the bowl fuel level and looks good at about halfway full not overflowing. The needle for the float appears to work, when I blew into the fuel intake banjo while raising and lowering the float the needle valve closes. I'm thinking my compression is down so will be checking that in the morning.

 

Thanks again

[datzenmike]

Put as brick on the gas pedal to avoid even more flooding by the accelerator pump. With the primary barrel now open, try removing the plugs and spinning the engine with starter to dry out the cylinders. Use a propane torch to heat up the plug tips to dry and clean them. Don't forget to remove brick... try starting. 

[Mitchell]

Thanks Mike, I'll give that a try and report back...

[banzai510(hainz)]

I recently had a moisture issue with mine. as it sits for a long time and high humidty soemtimes. I hairdryed the dist cap and down inside dist. then was fine.

 

I usually well really never open up a carb. its more likely something more simple.

[banzai510(hainz)]

29 minutes ago, Mitchell said:

about halfway full not overflowing.

this is good and really didnt need to be open carb. if anything should run out of gas if needle was bad. Since it not OVERflowing.

 

choke not stuck ON? 

 

Edited April 20 by banzai510(hainz)

[Mitchell]

Thanks Hainz, the cap looks very clean with practically no wear rotor also looks good, but I'll go through everything to make sure they're completely dried out... Prior to all this, it has always started best from cold. I'm not sure how to disengage the electric choke, just unplug the lead?

Edited April 20 by Mitchell

[banzai510(hainz)]

Im not a Matchbox expert. I run Pertronix. But if you get spark from center coil t ground I saw that pretty muck good. and was running for 20sec means out to the plugs was good also.

I myself never had a carb flood out in all my years of owning at one time 4 datsuns.

 

needle valve stuck closed and accell pumps tearing for me and idle jets being plugged. no idle would not run.

 

ok good luck got to go

Edited April 20 by banzai510(hainz)

[Mitchell]

Good Afternoon,

 

Here's today's results...

I tried cranking with the 'brick' on the gas pedal to open the carb up and it barely fired once on the first attempt with a single cylinder or how it felt and then nothing changed after that.

An addition symptom is cranking a bit slower than normal even though it has been on a charger for over a week and reads at full charge.

Next, Performed a compression check with 1@165, 2@120, 3@130, 4@120 

Could it be that the timing chain jumped even though distributor points correctly to 1? Should I check the bright link location and do a lash adjustment?

 

Thanks Guys

[datzenmike]

Clean the plugs first?

 

I don't think there is enough slack in the timing chain for it to slip over a tooth on the sprocket. Never heard of it happening.

[Mitchell]

Hey Mike, thanks so much for responding. I didn’t clean them up but they looked dried up from yesterday, in the photo 1 is on the bottom and is the only plug that looks good…

I’m glad to hear it’s unlikely that the chain jumped.

Edited April 21 by Mitchell
Wrong photo

[banzai510(hainz)]

weird how #1 is 165.

 

#1 looks cleaner hope it isnt sucking any water.

 

I air out the plugs. Pull the valve cover off and turn so cam lobes are up and make sure the rockers wiggle.

 

you sure you gotr spark?

Gas squirting in the carb?

Choke not stuck open

idle jet clean?

Edited April 21 by banzai510(hainz)

[Mitchell]

it is strange, but it matches with the best burn colored plug so might be that my gauge read the 1st cylinder on the high side from not being used in a while

[banzai510(hainz)]

one time I went to a guys place and just put new plugs in and it started

[Mitchell]

I wish that would happen here, but I noticed the gap was a little too wide on these plugs and will try them with the smaller gap as well as another new set tomorrow...

[Mitchell]

Here's the latest, after rechecking compression on cylinder 1 it measured 165 again and then rechecked cylinder 2 at 130, but all numbers were measured cold. Then using clean dry and re-gapped plugs, I attempted to start up with the throttle floored. The truck fired and backfired a few times with some small flame bursts out of the carb. I did have to use the 100amp start boost setting on the charger to get it to crank a bit faster which made a difference. I guess it's time to adjust valve lash? 

 

Thanks again

 

[datzenmike]

 

Try with brick off the pedal and choke closed. Give a pump and try starting

[Mitchell]

Hey Mike, Thanks for your reply. That's how I normally start the truck, one pump and then crank. So I tried again now and pumped once using the cable linkage, boost mode on the charger and used my hand to completely choke it while using a remote starter trigger to crank it, no change wouldn't fire. Do you think I should get a new carb?  

[datzenmike]

I would get 4 or 5 friends and push it down the street in second gear, turn ignition on and let the clutch out once moving. 

[Mitchell]

Thanks I thought about that, a little tough to do here on the farm because my gravel driveway is over a half mile, but worth a try. Might be able to get pulled by tractor. I'll let you know...

[banzai510(hainz)]

On 4/22/2026 at 12:04 PM, Mitchell said:

Do you think I should get a new carb?  

NO 

pour gas in the carb(or starter fluid). this is bypassing the jets and everything. See if fires again.

 

But I did ask ?????????? you see gas squirting in the carb from the accell pump.??????????? This is same as pouring it in there there just smaller amount

 

DONT PULL/push START IT UNLESS YOU WAS ON A HILL AREADY.

if it would start it would have already.

 

I figured you check the rockers already

 

 

 

 

I never FLOORed the pedal in last 35years. Thats just to blow the gas out I gas. I guess.

Edited April 23 by banzai510(hainz)

[banzai510(hainz)]

On 4/21/2026 at 12:17 PM, banzai510(hainz) said:

Pull the valve cover off and turn so cam lobes are up and make sure the rockers wiggle.

 

you sure you gotr spark?

Gas squirting in the carb?

Choke not stuck open

idle jet clean?

did you do any of this?