LUVTruck.com

Try this. It's a cheap, maybe free, possibility. Take off the EGR Valve on the bottom back of the intake manifold. Next take off the big adapter on the bottom of the manifold to which the EGR Valve mounted. Then make and mount a cover plate to cover the hole in the bottom of the manifold. Be sure to make a gasket. I just used a piece of sheet metal I had laying around. If the EGR Valve is carboned up, it can cause a vacuum leak cuz the little shutttle valve in it won't close or regulate properly.

Also, if you haven't tried it, with the truck running spray some carb cleaner around the carb. Try to cover areas that a vacuum leak could be present. If the engine starts idleing up you've got a vacuum leak at that point. I found a vacuum leak this way on my 76, turned out to be the gasket between the intake and carb.

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Resident lurker

Also, cap off the vacuum port from the intake manifold to the power brake booster if you have such.

hey narc,
you want me to send you a copy of the complete vacuum diagram ?

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1980 luv sport 4x4 Just a memory now
Frame rusted from the inside. Truck stripped and now looking for a new donor in southern ohio

I've replaced the idle solenoid with a different one. Didn't help.

I'll pick up some carb cleaner tonight.

When I take off the adapter plate, what will I do with the exhaust gas tube that comes out of the manifold?

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Richard Barnes Salt Lake, Utah
1980 Luv Mikado 4X4
http://geocities.com/luvtruck2004/

OOPS! Forgot about that wrap around tube. Leave the adapter on and just make sheet metal cover using the EGR Valve as a template for a cover and gasket.

I tried to track down the vacuum leak and I gotta say that's discouraging, cause everywhere I sprayed the RPMs went up so I had to keep hittin' specific spots and try and find where it went up the most. RPMs didn't climb at all anywhere near the egr, but they did climb all the way around the base and really bad near the throttle shaft. So I'm taking the base off my old carb, I'm gonna try to pack some oil into the throttle shaft to condition the rings a little cause I can't take the butterfly off, (screws are stripped). Throw in a couple new gaskets and hope for the best, hopefully I'll be done by tomorrow afternoon, tomorrow night at the latest, I'll let you know if it works, cause if it doesn't I'll be lookin' for a weber, and trying to find a smog shop that can bend the rules a little. . . I'll tell you, this shit drains you. . .

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Richard Barnes Salt Lake, Utah
1980 Luv Mikado 4X4
http://geocities.com/luvtruck2004/

Handiest thing to have when you're working with carbs is a couple, three 8"X10" sheets of gasket material. Different thickness's. Since you got engine speed up around the base, don't buys the gaskets. Make them out of a thicker gasket material. About the thickness of the back of a writing tablet. They're easy to cut out with a pointed Exacto knife. See how vacuum leaks can screw up a running engine? I had a PCV Valve do much the same on my old Ford 250. Drove me nuts for two years until I compared it on a counter top to a new one. The spring in it was weak and wouldn't close it properly.

Alright. . .I did everything that everyone told me to do and it hasn't helped one little bit. I'm tired of this crap. It's really startin' to get to me. Anyone within driving distance of salt lake utah got an isuzu p'up with a 2.3 engine? or a Vortec set-up for 4x4? A new carb is gonna cost me a couple hundred bucks so I might as well see if I can get some more power. . .Unless anyone knows something they haven't told me. I just can't figure the damned thing out and I can't afford to pay someone.

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Richard Barnes Salt Lake, Utah
1980 Luv Mikado 4X4
http://geocities.com/luvtruck2004/

P.S. My avatar? That's exactly how it looks, sittin' there in that same spot not moving. It hasn't sat still this long since I bought it. I tore the head off and repaired three plug holes and replaced all the engine gaskets and still had it together in less time than this is taking.

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Richard Barnes Salt Lake, Utah
1980 Luv Mikado 4X4
http://geocities.com/luvtruck2004/

whoah!!! don't tear your hair out yet.

first, the problem isn't that bad.....it's only a carb......with a bad leak.

the weber i picked up had 3 extra vacuum ports in it that were plugged by the factory and the room for a idle cut off. worst off you could spring for one and a rebuild kit on e- bay and it wouldn't be a financial issue.It is a DGAV 33B1with an electric choke unit added on,and it was a breeze to rebuild so with a little patience and knowledge you might be able to get it to smog.......maybe...how often do you need to smog your truck out in salt lake city?

if you realy can't afford that route i'll send you a working carb, it ran four days ago and it's still primed even.it's for california ,but i can isolate the stuff you don't need if your truck has federal smog. you could bolt it right on and hook it up and be done with the whole problem.....

you've said before that you're not rich so you pay me back for shipping at your convience.

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If it will get it runnin' again I would like too, I can't stand having to bum rides to and from work. Not my style. I know beggers can't be choosers, but does it work right? It's not the reason you bought a weber is it?

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Richard Barnes Salt Lake, Utah
1980 Luv Mikado 4X4
http://geocities.com/luvtruck2004/

Is there anything else besides to two gaskets and the plastic half inch spacer that comes in the rebuild kit that I should put between the carb and manifold to keep it from leaking there?

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Richard Barnes Salt Lake, Utah
1980 Luv Mikado 4X4
http://geocities.com/luvtruck2004/

there is a gasket between the metal base plate of the carb and the upper aluminum part of the carb that could be leaking. my old hitachi had a bad habit of loosening the bolts that hold that base plate on. every once in a while i'd notice it running bad and i'd check and the screws would be loose. mine also had alot of slack on the shaft for the butterflys. i had my uncle who is a machinist, put a bushing on the shaft. i actully didn't notice a difference in the way it ran.

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1980 chevy luv 4x4 1.8 liter
1979 luv long bed parts truck
1984 2wd isuzu pup parts truck

"A man who says it can't be done shouldn't interrupt a man doing it."

I took the carb off and put new gaskets on it and tightened them down good and tight, still leaked. But yeah, I have a ton of slack in both the carbs I have.

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Richard Barnes Salt Lake, Utah
1980 Luv Mikado 4X4
http://geocities.com/luvtruck2004/

<<<<<<double post>>>>>>>>

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no the carb isn't the reason i put the weber on...i wanted something that would breath enough for my bore and cam. you could just bolt it on and hook it up.....i have it listed in the classified section at the moment but not for long.
the only reason i'd sell it would be cause nobody really needs it and i can't seem to throw things away(drives my wife nuts). but since you need it well..........do unto others right?

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I've got my carb taken off and I'm gonna try one last thing. I checked the trouble shooting section of my Haynes manual and the only reasons that would cause a flat spot and the erratic idle is clogged jets and secondary throttle plate misadjustment so I'm gonna check 'em and set them to spec and see if this helps. One question though:

When I took off the carb I felt around in the intake manifold cause it looked a little shiny and there is a film of oil covering it. The only things that go from the engine to the manifold are the big hose from the back of the rocker cover to the air cleaner and the little vacuum hose that goes to the inside of the intake under the carb. Does this light off any light bulbs?

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Richard Barnes Salt Lake, Utah
1980 Luv Mikado 4X4
http://geocities.com/luvtruck2004/

Also, I've got on vac line coming out of the bottom of my carb. What is that supposed to be attached too? It had the vacuum advance on it but I put it directly on the manifold cause it looked cleaner, but now I'm not so sure if that was right to do, cause the one on the carb doesn't look like it's the same as the ones on the manifold. Anyone know what it's there for?

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Richard Barnes Salt Lake, Utah
1980 Luv Mikado 4X4
http://geocities.com/luvtruck2004/

Have read this long discussion and it sounds a lot like what my experience has been trying to get a carb working on my 74. I worked on it for about 4 months and it was running like a sewing machine before the carb crapped out in June, and since then I've had nothing but problems trying to get it right.

I've got a theory about what the design problem is with the Hitachi 340 carbs but haven't gotten far enough into one yet to know for sure. These carbs have a power piston setup that controls a power valve in the base of the float bowl that, when depressed, dumps gas into the air stream below the venturi, if I'm not mistaken. On some carbs, like the Motorcraft 5200, a piston like that is controlled by a replaceable diaphragm that so when it leaks vacuum and won't stay up you can replace it. On the Hitachi it's just an aluminum piston in a bore in the air horn, so it can either (a) stick, or (b) wear out so it sits on the power valve most of the time, or drops on it when it shouldn't. My local carb shop, which wants $70 just to look at it, isn't so sure and says that there isn't a bushing kit for the power piston anyway, so fixing it would be a small, custom precision machining job, but probably still cheaper than buying a Weber. If anybody knows more about this or has a manual that specifies what the maximum clearance between the power piston and the bore is supposed to be I'd be interested in hearing about it.