Hit a bump today and now my 78 620 starts, runs and dies even if I hold the pedal down.

[SlammedhappySteveO]

I hit a speed bumps today, the truck sputtered and I cruised into a gas pump (happened at a gas station) because when it sputtered I realized I was low on fuel.

 

I put a 20 in fired it up and pulled away, it sputtered, died , I screamed and yelled... then I waited for a tow truck...

 

I can get it started but it won't idle now and wont stay running even if I mash on the gas... got home, cleaned full lines, replaced fuel filter gave er a go and nothing...

12v @ coil , 12 very at batt. Got spark. Float bowl is full on the stock Hitachi carb, fuel filter is full...

 

Guess it's time to go through the carb again.. jus seems odd, bump and no go.

 

It's been a long day, and a long week and I'm just reaching out for some insight.

 

78 620

 

Stock L20B with Hitachi carb

 

I drive this truck 100 plus miles a day with zero issue til now.

 

 

Way no?

 

Datzen Mike?

 

 

Buehler, Buller, Bueller?

[flatcat19]

I hit a bump a while ago and it cracked my fuse block in half. Killed all my electrical...still drove it home...in the dark.

 

 

My guess...vacuum hose came off somewhere. Too much air to mix with gas, can't ignite.

 

Look for the obvious.

[SlammedhappySteveO]

I still have all my electrical, but alt. Is whining now... all fuses check.. I have to feather the pedal

to keep it running... I'm thinking carb has a blockage and isn't getting enough fuel but I'm grasping here

[flatcat19]

You're feathering the throttle to stay running. I.e. Adding fuel.

 

Go look for your vacuum leak.

[thisismatt]

Does it run okay with middle throttle?

[datzenmike]

Yes a simple check may show a vacuum line off. This would be the one of FOUR possible ones.

One to the air filter for the ATC (auto temp control)

One to the charcoal canister.

One to the AB (anti backfire) valve. This one connects to the rear most intake fitting that supplies vacuum to the brake booster

One to the brake booster on rear part of the intake.

 

There are the vacuum advance and the EGR hoses on the valve cover side of the carb but these are not intake vacuum and the engine would run with these pulled off.

 

 

 

Turn ignition on off on off. You should hear a light clicking sound from the carburetor. If not, check the top left fuse, has Blue/White strip wire to it.. This is the idle cut solenoid. I accidentally jumped my old 521 and it blew out a couple of fuses.

 

 

 

A jump will disturb any sediment in the fuel bowl. If running it can be sucked into the slow speed circuit unless you were WOT (wide open throttle) in which case it may be in the primary jet. But I don't think so.

 

Find and unscrew the idle mixture screw, but count the turns (probably just under 20) so it can be returned to it's old position. Above it is a hexagonal 'thing' with a Red wire to it. This is the idle cut solenoid. It shuts off fuel to the idle mix screw and the slow speed circuit so they are connected. Have a care as there is a small needle valve that will fall out, so watch for it. Now get a can of carb cleaner, the one with a plastic straw. Stick the straw into the idle cut solenoid hole and spray liberally. Now spray the idle mix hole. You hopefully will see spray coming out the other hole when you do this. If there is a small restriction or blockage this may flush it out.

[distributorguy]

Or possibly a loose/bad plug or coil wire.  Too  many times I see folks install plug wires with the boots slid too far down the wire.  Then the wire isn't fully seated in its hole, but that boot make the wire appear properly installed.  

[banzai510(hainz)]

all good awsers.

 

Idle jet wire came off or plugged.

 

if you pour gas down the carb then STARTS the eleltricall is OK.

 

Soon as one get a weber the sooner one will be glad he did it.

[bilzbobaggins]

Grab the carb. Is it loose? I hit a crater on a trip and the exact same thing happened. Pulled over, found carb loose. Lock tite added and all has been good. Truck was loaded out causing even more vibrations than normal

[SlammedhappySteveO]

Sooo, finally off for the weekend.. I pulled the carb, it was loose by hand and dunno how I made it this long. The gasket between the heat shield and intake manifold was dry, brittle and cracked. The riser plate with the gasket on either side was HARD and not pliable . Making new gaskets now and replacing any and all vacuum lines that are dry brittle and loose.

While the carb is a Hitachi, it is a certified Holley rebuilt. It has always worked phenomenally, I love the weber but don't think k I'm there yet but I do plan to do the swap soon.

If anyone has input feel free to share, but I belive that is the largest part of my dismay... I've driven this thing Dailey for months before this bologna, but Whada you expect for not turning a wrench when it was bought? DATLYF, LOL

[datzenmike]

Bet your air filter is not bolted to the intake at the front. No worries, as no one ever puts the bolts back on after removing them. This support would help hold up the air filter on a jump and likely why the carb was loose on it's base.

[SlammedhappySteveO]

The air filter assy. Was secure Mike, but only because I was in there once before.. replacing rotted lines, pcv, and inspecting intake, gaskets and mounting hardware.. if you mean something else lemme know while she's apart so I can address the issue! I see a lot of stuff I would like to eliminate but have to wait atm and just get her back to the cruising status she has been at since I got her...

 

Need some Flippin floor pan cut ins, do they still make em anywhere or is it fab city for me?

[datzenmike]

 

 

 

At the bottom of the picture, see that little brace? It bolts to the intake. No one ever puts it back on once off. It helps support the air filter on top of the carb.

[SlammedhappySteveO]

Datzenmike, I towed the p.o. before for carb issues over the last couple years, she was told the rebuilt it and re gasketed everything but the crappie I pulled out was dry, brittle and litterally fell apart upon disassemly... not typical of a job done in the last year, 6 months of which was parked... the base of the carb was seemingly sprayed with a "sealer" much like spray glue which I assume was an attempt to stop or slow the obvious vacuum leak.. shit was everywhere, my kid n I liked it to a 3m upholstery adhesive... bitch to clean... sly shop quick fix... the shop p.o. went to specializes in all German makes and Datsuns... but they are all cambodian... weird niche

[flatcat19]

Soooooo....you found your vacuum leak.

 

 

 

Running yet?

[datzenmike]

When I hear people state what was done or what was new I always take with a grain of salt. Sometimes they are just repeating what they were told. If a mechanic was paid to do something I totally get suspicious. Best results are if you do your own work then you know it was done right, or done.... right? 

 

 

In my work I sometimes am told by homeowner: 'just get it close enough' and I say "It costs the same to be balls on or totally off."

[bilzbobaggins]

Nailed it. They are vibrating/buzzy motors and it's a truck so it should be a stiffer ride than a car. Add some loctite to it this time. Check them again after you do some high speed/high rpm cruzing. This is a 78 with conjoined manis? Good luck with fixing it up

[SlammedhappySteveO]

I'm the same datzenmike, I get all kinds.. as do we all.. but I can say after 20 years I'm still amazed at what I see and what I let go because it worked... now revamp n move on I'm sure that's where air was suckin

[datzenmike]

Nailed it. They are vibrating/buzzy motors and it's a truck so it should be a stiffer ride than a car. Add some loctite to it this time. Check them again after you do some high speed/high rpm cruzing. This is a 78 with conjoined manis? Good luck with fixing it up

 

Unless the engine was swapped, only the '75-'77 L20Bs had the co-joined manifolds.

[SlammedhappySteveO]

I forgot how much fun it is to handmake gaskets... tomorrow we roll.. right as rain, hell or high-water

[datzenmike]

Not sure how you mean this. I find enjoyment in it. Hole punch and scissors and you can make a water pump gasket in a few minutes. In fact my water pump gasket on my 710 right now is made from a Cheerios cereal box, so are the two fuel pump gaskets and the thermostat gasket. The thermostat housing gasket is from boughten gasket material as is the exhaust flange gasket, but all hand made for pennies.

[racerx]

The main thing is you found out what was wrong w ur truck. Lesson learned, that is all.

[SlammedhappySteveO]

I just meant i hadnt had to do it in a while and its fun, i enjoy it! I havent put it together yet... got stuck running around but am omw home to see if that cures it

[SlammedhappySteveO]

Houston, we have lift off! Wholly wow! She is back on the road and that's what it was, suckin air and neglected....

Thank you all for your input and support.. soon as I finger out pic n video posts I'll do that!

[SlammedhappySteveO]

Alrighty then!!! Rebuilt the Hitachi and was running great til the other day.... Sooo I bought a New Weber 32/36  and have begun cleaning thinning out under the hood to prepare for the transplant.

 

until now this truck was bone stock un touched aside from maintenance..  Is there a comprehensive write up somewhere that covers all the deletes and eliminations under the hood for install???

 

I've been searching but haven't found one, and I want this to be right so any help would be appreciated..

 

Haven't done one in a while

 

 

on another note, I see my profile pic is gone.... can someone remind me again how to upload pics so ya can see what we got going on here???

 

Thanks!