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How hard would it be to replace all of the vacuum hoses? They are all in place now, but they are almost 30 years old, and my truck hasn't been running in over 4 months because it is missing on 2 cylinders... I was thinking it wouldnt be too hard if I took them off one at a time and replaced them as I took them off so I knew where they went. I'm not sure what is causing the miss so that is why I wanted to replace these (thinking there may be a hole or clogged line or something).

I replaced the points and plugs, and still nothing. I'm going to do a compression check on it this weekend, but its on cylinders 1 and 4 (I think) and I dont think it would be a head gasket (heard it usually went out between 2 and 3).

Any ideas on what it could be? I need to smog my truck by mid March so I need to get it running!

Oh and what size is the hose? That might be important if I replace it

Thanks!

There should be a sticker on the inside of your hood showing the vacuum line routing. How it's connected now may, or may not actually be correct.

If you need a copy of the diagram, let us know what year truck you've got and I'm sure someone can post a pic or a drawing.

I replaced all the vacuum lines on my '85 Olds Custom Cruiser not too long ago, and it was all 5/32" tubing. It actually ran worse until I cleaned out the EGR.

Have a pair of needle nose handy for when you break off that one tube that runs from the passenger side of the valve cover to the base of the carb....lol..

Have fun...

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"If we did the things we are capable of, we would astound ourselves" - Thomas Edison

Ok, update.

I drove it today... it runs pretty good, when you on the gas, or it's not idling...

I think we narrowed it down to a gas issue (may be carbed related) but I was thinking the gas filter may be clogged. Since it may not be getting enough gas through the filter with the lower pressure...

Any thoughts?

Make sure the idle cut off solenoid is getting power. It's the round thing on the side of the carb. with one wire coming out of it. It goes ( with other wires) to a plug on the fire wall. It should have 12 volts when the key is on.

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OK, I'm over it. Where's the beer?

Ok, I replaced most of the vacuum lines, which made the truck run a little better, but it still wont run good.

I also pulled the carb off and cleaned it out (was really clean to begin with) and that didn't do much.

I checked the idle cut off solenoid, and I'm not sure it had power with the key on, but it had power when the truck was running. Does this matter?

Any other ideas on what it could be? I need to smog my truck this week

Here is some more info, I can pull any 2 spark plug wires off and it runs the same as before. So it's not just certain cylinders missing, its like an all over thing.

Also, since it runs fine when its at speed, would I be able to smog it how it is? It idles, just not well, and I think it will pass the 15mph and 25mph part of the test, I'm just worried that by law they can't smog it if it's not running good. Anyone know about this?

Also, did the LUV come with a fuel filter? And where is it?

Thanks! and sorry for all of the questions.

My LUV just spent three weeks at the mechanic's trying to get it to pass smog. It was running great when I took it in, but they said it failed because of the CO (carbon monoxide) level. It turns out that it was a carb problem. Good luck with your LUV, make sure it is running the best it can, when you take it in for a test. Do not take it to a "test only" facility, take it to a place that can do the repairs on the vehicle, I think they're called "Gold Shield" smog facilities. Someone else could probably chime in on this. Make sure all of your emissions equipment is on the vehicle and operating correctly.
Dano

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Garage is empty;
Between trucks

Well its never had a problem before. It has always passed with about a quarter of the max. Its just that I cant get it to run now.

If it runs ok when driving but not at idle it is not a gas filter problem. Have you tried adjusting the idle mixture? Sounds like it is running too lean. Turn the idle mixture screw out about one more turn with the engine warmed up and idleing, then back in or out slowly until it runs the smoothest/best. Give this a try if you haven't already.
If this dosen't help--remove the mixture screw completly with the engine stopped of course. Use a spray can of carb cleaner with a plastic spray nozzel like Gumout or something. Poke it into the hole and give it a shot of cleaner (carefull, cover your eyes.) This will flush out the idle circuit. Reinstall the mixture screw seating it lightly, then back it out about 2 turns and start the engine and adjust in or out like before for the best idle. ---- I have had good luck with this if something is plugged in the carb.

Ok, I'll have to give that a try.

Which screw is the idle screw? I know there are 2 on the bottom of the cab on the pass. side. Is it either of those? and if it is, is it the one in front, or the one in the rear?

forwardmost one.. other one is for the idle setting.

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Tact is for people not funny enough to be sarcastic.

So the back on would relate to RPM at idle? Just checking.

and thanks for all the help guys

Bob is correct. The front one with the spring around it. Proper way to adjust is-- with the engine warmed up to normal, turn mixture in or out until the best idle. If it speeds up then slow the idle speed back down with the other screw and go back and readjust the mixture again for the best idle. Go back and forth between the two, keeping the idle the smoothest at 900 rpm.
Then to make sure it passes emissions, slowly turn in the mixture screw until the speed just starts to slow a bit, then turn it back to the left about 1/4 turn. If this corrects everything you can now call youself an expert carb man.

UPDATE

Ok, I tried twisting the mizture screw with the idle screw, and it didn't do much of anything, and it got to the point where it was all the way backed out.

So, any new ideas?

The truck has a lot of hesitation when you hit the gas also if that helps at all... I dont know if that is just a given, or if it may be able to help determine what it is...

Here are some pictures of the carb, is the "door" (not sure of the term) supposed to be open at idle?

The door in the picture is the choke plate. Yes, it should be open when warm and will close when the engine is cold.
If you haven't already, do the spray cleaning procedure with carb cleaner as I mentioned above. One more thing, was the idle speed slow? Like about 900 rpm or lower? If it is running too fast the idle mixture screw will have no effect. It only effects low idle.
Accelerator pump piston cup may need replacing. This will cause a hesitation. Sometimes will dry out and not seal proper. This can happen if the truck sat for a long time unused. If you need to get inside the carb, you may as well get a rebuild kit and just do the whole thing with new gaskets and all.

I have a rebuild kit in my garage. I looked at it, looked at the carb, looked at it again and decided that was way over my head.

What is the Accelerator pump piston cup? Would that explain the lean running, or just the hesitation?

Don't let the carb intimedate (sp?) you. If you need to, take pictures of the linkage first. That is the hardest part for me. Be careful of turning upside down while taking apart because parts (springs, check valve balls) tend to fall out. Put your parts and screws in piles, in a line, in order so that you can put back together in the same order.



egg, my acc pump is solid brass with no o-ring or leather gasket. Is that normal for Hitachi carbs?

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1980 4x4 - Hunt'n truck 9yrs only seen pavement to the gas station. Gets a little spooked when it sees another vehicle.

Accelerator pump will cause a hesitation but not lean running normally. You brass one is the factory original one. Replacement kit may be rubber or leather type. Tuffluv is right--don't let the kit scare you. You won't use all the parts in the kit. Just the ones you need. Probably the accerator pump, needle and seat, and gaskets about covers it.

the rebuild is not hard even if you no nothing about it... when I was 16 and had my first luv a 74' i rebuilt the carb, i knew nothing about cars and my dad couldnt even change the oil or knew where it went so he was no help (dad had money and if it didn’t work off to the shop it went) any way long story short . i rebuilt the carb had 2 screws and one spring left over and the thing ran better then new for 3 or 4 years till i sold it… or there is this rebuilt one for a luv http://cgi.ebay.com/ebaymotors/CHEVROLE ... 0181137881

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My old but now gone Luv...

Here's a couple of random thoughts:

Did the problem suddenly occur, or did it get gradually worse? Did it just occur or did it happen after you did something?

Rebuilding the carb is kind of a last resort. After 40 years of working on cars, I've found that most of the time, when you think rebuilding the carb will fix the problem, rebuilding the carb doesn't fix the problem.

I was thinking about what you said about the spark plug wires. If you pull any spark plug wire, the engine should run worse. If not, then that cylinder is not firing correctly.

Are you sure the distributer cap is on right and the firing order is right. I've bought caps before where the cap is marked 180 degrees wrong. (The #1 marking is really where the #3 wire should go.)

A common problem is a head gasket that blows between #3 and #4. The symptom of this would be no change in performance when you pull either #3 or #4 plug wires.

Another common problem is a vacuum leak from the brake booster hose. It is a big hose that comes into the manifold right between #4&4 cylinders. It will cause a real bad idle that smooths out (a bit) at speed.

A friend showed me a trick once, but you have to be careful you don't blow yourself up. Use a propane torch. Turn the gas on but don't light it. Hold it near likely vacuum leak spots. If the engine speeds up or smooths out, it's sucking propane in through a leak. As I said though, be careful you don't fill the garage with propane and blow yourself up.

Hope one of these will point you in the right direction.

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You went there in that?!?!

I second okie's thoughts on this, almost sounds like either the distributor is 180 out, or the cap is. I had an old 302 once that did pretty much what you've described, and it was due to a worn dizzy shaft, so there is a possibility of a wear problem also.

How are you checking the timing? The vacuum to the distributor needs to be removed and plugged. It will run poorly at speed if you forget to put it back.

There is a post on baselining the Hitachi here somewhere, I can't seem to find it...
Something like, 3 turns out on the mixture screw, 2 to 2 1/2 on the idle and then set the timing. From there adjust only the carb... I think...

Vacuum leaks will frustrate the heck out of anyone, so make sure you check the brake booster vacuum as okie said. There is also a 3 way, T-fitting on the passenger side firewall that goes to the intake, it's larger hose and can get really hard and crack.

Oh, and on the propane torch thing, you can just use a can of ether (starting fluid) or WD-40 and get the same results without quite as much hazard. On my 4x4 the problem was the EGR gasket leaking. Took a while to find it, becuase it's down low on the intake manifold and whenever the ether would drift down it would rev up.

Good luck.

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"If we did the things we are capable of, we would astound ourselves" - Thomas Edison