Issues Running (Carb Clean/Rebuild?)

[klam07]

Hi all, sorry for long post.

 

I've got an issue with my 79 kingcab that started last summer'ish. When I got the truck last spring it ran pretty well, started up almost everytime. But after parking it for a couple weeks while I was out of town it seemingly developed some issues starting/staying running - first it'd sputter on start, then it idled strange, then eventually wouldn't start. Now it just cranks til the battery dies.

I suspect its carb related as when I put some gas down the carb directly it'd run off that for a few seconds, and tapping (hitting) the bowl seemed to temporarily solve the issue once or twice in the past.

From what I've been reading over the winter, it sounds like something in the carb is just clogged and keeping gas from getting into the bowl..?

 

My questions are then:

• Should I find the suspected jet/part and just clean it, throw the carb back on, and see if it'll get gas n run again,

or

• should I (with little knowledge of carbs but experienced with cars in general) attempt to rebuild the carb using the supplied kit?

 

Ultimately I'll be doing a KA swap because I better understand EFI and the weather in my city can go from dry hot to snowy in the same week...

but until I can get the rest of my parts from the US, I'd like to have this running and driveable for the summer at least.

 

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Heres a quick summary of notable things if anyones interested:

 

• Carb was supposedly rebuilt prior to me buying the truck (early last year). Likely just cleaned I suspect, since the truck came with a carb rebuild kit thats still sealed in box

• OEM Hitachi carb on l20b engine

• Verified fuel pump works by cranking into a bottle

• Don't think fuel made it into the bowl that I could see

• Engine would run off of fuel being directly supplied into carb

• Hitting the carb/bowl seemed to temporarily fix it once or twice early on

 

Fast forward to now (roughly 7 months of winter later)

 

• Haven't started truck since last fall

• The tent/car shelter smells decently of gas

• Just removed the carb off the truck (major PITA, how do you guys do it so easily)

• Carb looks good inside and out, no apparent leaks or anything but carb was bone dry inside

• I took out the primary and secondary main jets and they were not clogged - could see straight through

• Carb bowl and float look clean since I opened it up last summer

• Have not dissassembled or removed any other parts as of yet

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As always, thanks for any and all help!

Heres some picture tax (Heres an album link for more photos and higher resolution)

 

 

 (from carb rebuild kit)

 

[datzenmike]

Direct the fuel line into a container and bump the engine over with the starter. Does gas spurt out? Sometimes it takes a while to pull from the gas tank. But if no gas find out why.

 

 Is the choke closed? If it isn't, it should be for starting. If it is, it might have flooded and caused that gas smell. Only way is to put on and start it. The choke can be adjusted by loosening the 3  screws around the black thing at the back and turning it. It may be fixed in place by the factory on a '78 to prevent the owner doing just that.

[banzai510(hainz)]

if it ran above idle thse jets are clear

If not idle the idle jet is plugged

 

smelling gas  lots of it could mean nnedle valve not closing so it floods 

 

I always ck the fuel filter and cut it open to see if lots of rust or dirt.

trucks need the change filters more often as tank is exposed to the elements and water

[klam07]

I had some pictures embedded, think they got removed. They're still visible in the album though.

 

@datzenmike -- I did verify the pump was working last summer, still got a water bottle with some tinted gas.

Choke started off closed/cold position yes, but after cranking for a bit n pumping the pedal it eventually opened. Under regular pumping of accelerator pedal it'll open and close when the engines cold. This means the auto choke is working as it should yes? I haven't tried adjusting it yet.

 

@banzai510(hainz) -- Last time I started it, it wouldn't idle unless I poured gas in the carb. Sounds like the idle jets then..? Needle valve seems easy enough to get to, I can change that out, looks like its in my kit.

I didn't look into the old fuel filter.. but the gas is a bit rust tinted and I did change fuel filter for a see-through cheapy for now. Ill see if theres any rust particulates in it.

 

So, takeaway for now is, potentially flooding carb and potentially clogged idle jets or stuck needle valve.

 

edit: But if it did flood, wouldnt there still be gas in the carb somewhere even now 7 months later? The float bowl and everything else is dry, I tipped the carb right after removing and nothing came out. Come to think of it, I dont recall gas squirting into the carb after pumping the accel pedal..

Edited April 22, 2020 by klam07

[datzenmike]

There's a round glass window in the front of the carburetor. After trying to start it have a look . Fuel level should be near the dot on the glass.This will tell you if empry or over filled and flooding. If near to the middle it's fine.

 

When cold choke should be closed. As the engine warms up it slowly opens. If closed don't pump the gas or you'll flood it. If you think it's flooded, hold pedal all the way to the floor, this opens the choke. Hold it open and crank the starter till the flooding clears and it starts.

[klam07]

Yeah, but to be honest I cant remember if the glass showed low or high last summer. It was hard to see.. Ill be sure to get a good look this time around.

 

When/If I pump the gas a couple times while the trucks off, should I be able to see gas actually squirt into the carb? Because I couldnt before.

 

While the carb is off then, I'll go ahead and look at cleaning/replacing the needle valve and idle jets. But, looking at my FSM can someone point out which are the idle jets? (25. coasting jet, or 30. primary slow jet maybe?)

 

Thanks all, I'll see if I can have the carb on and report back by the end of the week hopefully

 

Higher resolution link

 

 

[datzenmike]

If these is gas showing in the window then yes it should squirt when the gas pedal is pumped.

 

There is no idle jet, but there is an idle mixture adjustment screw. This merely makes the idle mixture richer or leaner to improve the idle but should only be adjusted when the engine is warm and the choke fully off.

[klam07]

Guess I've got an order of operation and things to look for when I get the carb back on then.

Thanks for the clarification mike

 

Also, couple notes on reinstalling the carb:

•  is there an easy way or trick to get the carb on or off? The 4 nuts were a pain to get at with a regular combo wrench. I had to remove more things than was probably necessary.. lol.

•  Theres a ~1/8th red plastic spacer on the bottom of my carb, and there was a metal tray between carb & intake. Is this normal?

 

Side note, the images I'm embedding from google photos show up when I post, but then disappear a while later.. are they being removed or am I tripping?

 

Edited April 23, 2020 by klam07

[banzai510(hainz)]

the later L20 seem like a lot of emissions stuff in the way its like down deep in there.

Key is finding the right wrenches then small ect to get enuff movement out of them.

[datzenmike]

 

I use an old 14mm and cut the box end off. Otherwise too long and can't swing without hitting stuff

[klam07]

@datzenmike -- Funny, I made a 10mm version of that years ago to keep on my daily key set. Has come in handy more times than I can count working on Japanese cars lol.

Luckily I had some dollar store key chain wrenches that are basically ~13ga steel punched out in the profile of your wrench that worked much better!

 

Got the truck running today!

I ended up replacing only the needle valve/body, n made sure gas was getting from the inlet to the bowl through the valve. Previous one looked a bit old n oxidized. Also adjusted the float level quite a bit - adjusted it to spec and it runs, but from what I can barely see the gas level looks low on the sight glass.

Should I re-adjust the float even if it means putting it out of what the carb kit and FSM says for spec? Or leave it as long as it runs well.

 

Other than that, reinstalled decently easily, put the blue hat back on and it started pretty easily. Sputtered out the first time but second start it caught with a bit of pedal play. Idled super high til the engine warmed but eventually dropped to regular low idle.

 

Sounds like everythings working as it should! Ill run it daily n report back I encounter any problems

 

 

[banzai510(hainz)]

I say changed the filters and call it good

maybe do a turn test where you drive around the corner giving it gas and hop it don't cut out. Maybe a steep hill also incase it drops out that way.

[klam07]

Thanks banzai. The filter is fresh, fuel and filter actually look clean - and Ive got a couple more if need be.

 

Truck is currently on lockdown in a tent lol. But Ill leave it as is until I can get it out and do the tests you mentioned!