LUVTruck.com

OK, so now I am dealing with some carb issues. This thing just doesnt want to run right. It idles just fine. Well, let me describe the symptoms.

I have replaced the fuel filter, fuel line, and fuel pump on this truck, just as general tune up items since the truck has been sitting for so long. We also rebuilt the carb, but I admit we could have done a more thorough job. We should have let it all sit overnight in the Chem Tool. But we only had the help of my buddy that night, so the parts only sat in the stuff for 30 minutes or so. Anyway. At first I could not keep the truck running, and it was forever starving for fuel. I figured that out. It had something stuck in the float valve. Once I cleaned that out, it will now idle and I can drive it to work and all.

It runs OK when only the primary throttle valve is open, but as soon as I give it more throttle and start to open the secondary it bogs and looses power, sputters, etc. I thought this was the float level and it was flooding, as I noticed that the bowl was full, so I adjusted the float so the level was correct in the sight glass (at idle anyway). I then took it for a test drive and the bowl ran out of gas and the truck died before I got 4 blocks down the road!! Right now I have it set so that I can just barely see the fuel level at the top of the sight glass.

Now, if I hold the throttle down (WOT) it will eventually get through the bogging and begin to accelerate, but nothing like it should. At WOT it accelerates only moderately more than it does with the primary only, while in 3rd or 4th gear. Also, if I hold it at WOT and try to go as fast as possible, eventually the bowl will begin to run out of gas again and start starving for fuel and loosing power. I can back off and it will recover OK.

I am not real good with carbs, so I dont know if the bogging is from being rich or lean. I would guess that its from being lean, since eventually the bowl runs out of gas, and there is no real transition from condition A (bowl being too full) where I would expect it to run rich and condition B (bowl running out of fuel) which causes it to run lean. In other words, there's no where in between where it starts running good and accelerating like it should.

So since there was some junk stuck in the float valve, I can accept that there may be other junk in the carb causing problems. Does this sound right? What about the issue with it running out of fuel? This sounds like the fuel pump is not pumping enough, but its new! Should I go get it swapped? Or a higher capacity fuel pump? I wouldnt guess I should need this, but what do you guys think?

This might help to figure it out.Get a clear fuel filter and install it close to your carb.Then start the engine and keep an eye on it to see if it keeps gas in it. It should tell you if your fuel pump is working ok. It could be a number of things going wrong. Your fuel tank could be really dirty inside. If it sat to long . I rebuilt a carb for a 79 and it just wouldnt ever work right, so i put a new one on and it has never gave me a proublem. On my 80 4x4 i unhooked the gas tank and put another gas tank in the bed and hooked an external pump to it. Not recomended for hyway use though.

I pulled the tank on mine, and cleaned out the pre-filter on the fuel pickup line. Also, what type of carb do you have? If it is hitatchi, then it would make a nice shelf decoration in your shop. Buy a weber 32/36 dgev (the dgev designates electric choke) from Redline Weber. http://www.redlineweber.com. They are the people I bought mine from. I rebuilt the hitatchi on mine, 8 times in a month and a half trying to get it running right. Every time I got into the carb, I found something else wrong with it. I finally wised up and bought a weber. Out with the old, in with the new.

_________________
Hammer to fit, paint to match.
If it aint broke, don't fix it.
There's always room for duct tape and bailing wire.

WATCH YOUR PIEHOLE!!!!!!

OK UPDATE!

I swapped the vacuum hoses on the vacuum advance on the distributor. Now it runs much better. It still has some carb issues, namely in the morning it runs a bit rough until it warms up, and still has a bit of a stall in it when the secondary opens, but nothing like before. It has much power now.

So this is what I did. The hose that is providing vacuum at idle was on the top port of the diaphram. I swapped the hoses so it is now on the bottom port. Is this the way it is supposed to go? It is very possible that we got them swapped sometime during the motor swap/carb rebuild/vacuum hose replacement dance that we did.

Sounds about right. Kinda hard to tell without seeing it. What about on the block side , those have to be connected good to.

OK another update on this.

I replaced the fuel filter tonight. I blew the old filter out backwards from the flow, and quite a few bits of junk blew out all over the garage floor. Looks like rust. Also, the filter I have now is clear, and I can already see small bits of trash in it too, although they are much smaller than the junk from the old filter. So anyway, changing the filter didn't help much.

I have also checked to make sure the fuel is being fed to the carb via the larger fuel line, and not the smaller return line (but thanks for the idea anyway Blue Meanie). Also, a friend of mine thought maybe the choke flap was getting sucked closed on the carb, so I tied it wide open. Still no difference. I even tried taking the air filter off and test driving it. A noticeable power increase of course, but the carb problem (or whatever it is) is still there.

So I noticed some basic repeatable behavior tonight, as I was trying different things and test driving. My problem only seems to rear its ugly head when I open up the secondary on the carb. Both 1st and 2nd gear were pretty good. It would bog just a little here, but acceleration is acceptable. In 3rd once i open up the secondary it immediately looses power, then it comes back but I have to floor it in order to get more power than with the primary open only, and even then the power gain is barely noticeable. Also, if I hold it to the floor in third, it will seriously start to loose power around 4000-4500 RPM. This whole series of events is from a dead stop. Addtionally, I get the same results in 4th, but more pronounced. Also, if I let off the throttle when I start really loosing power, it will recover. If I dont let off, but shift into 4th right away, the power is still not there, and I have to let off.

What I think is happening is that the bowl on the carb is running out of fuel, and all the bogging and stuff is the engine running on the wrong amount of fuel. Although I have to admit that I have never seen any white or black smoke, which should be indicators of a lean or rich condition. I also changed the spark plugs after running 500 miles with this problem and they did not look fouled or abnormal.

I dont know if I mentioned it in my earlier posts, but I have to set my float so that it is way over the mark on the site glass, or I cannot even drive the truck a few blocks without the engine dying (like it is running out of fuel really fast). With it set the way it is now, at least the truck stays running and I can drive to work and stuff.

So basically, it sounds like I have some sort of restriction going on. For some reason, inadequate fuel is being pumped to the carb. I have replaced the pump with a new one. It was one of those universal ones you get from AutoZone. It was called out for the truck, but I did notice it is a "universal" unit. Looking at the pump, it says "2.5-4 PSI". My shop manual calls for 3.56psi at the carb. To me, this says that at idle, the pump is able to provide enough fuel, but under wide open throttle, the flow goes to the max and the pressure drops to 2.5psi, so the carb is going to run out of fuel. Does that make sense?

Also, this is wierd. AutoZone.com lists the required fuel pressure for the LUV as 4-5psi. I wonder why they would sell me a pump that will barely fit their own spec?

I'm also not quite sure about the ignition system. I have replaced the plugs, plug wires, distributor cap and rotor. This engine came with an electronic ignition from a later model auto, probably a newer LUV or an Opel. It has a coil that looks just like the older style, but has an ignition control module that is piggy back on the coil. It says that it is an "ignitor". I am wondering if this old thing is crapping out on me.

Well, anyone have any ideas? My next steps are to blow out the fuel lines and drop the gas tank and wash that sucker out. This is getting really agravating.

Try this. Run a jumper wire from your battery to your fuel pump. First, get a bucket or something to catch the fuel. Remove the fuel line off of the side of the fuel pump that goes to the Carb. Unhook the hot wire from the fuel pump. Hook up your jumper wire when you are ready to test the pump. If fuel doesn't pump at a decent rate, then you may have a bad pump, or trash pluggin up your prefilter on the fuel pickup tube in the tank. After you unhook the jumper wire, take the inlet fuel line off of the pump. Try blowing a little shop air (low pressure with fuel cap off) into the tank. Maybe this will clean the sock off and help you determine if the tank needs to be removed.

_________________
Hammer to fit, paint to match.
If it aint broke, don't fix it.
There's always room for duct tape and bailing wire.

WATCH YOUR PIEHOLE!!!!!!

hey grimace. do you have some special luv book sitting around. how long have you been working on cars.you help alot of people out.

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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

Well, I have the original repair manual for the truck. I have been working on cars for about 12 years. I have built all kinds of stuff. I guess it's my hobby. Somepeople dig in a garden, some collect stamps, I bust my knuckles and cuss alot I didn't have alot of help when I was younger, and now that I can share some of my info, I do whenever possible.

_________________
Hammer to fit, paint to match.
If it aint broke, don't fix it.
There's always room for duct tape and bailing wire.

WATCH YOUR PIEHOLE!!!!!!

I had a similar problem with my 79 4X4. The truck had been sitting for a couple of years and the inside of the tank had rusted. The first time the tank was filled all the rust broke loose and settled to the bottom of the tank. The truck would start up and run fine at idle. As soon as I sped up, it would starve for gas and die. I finally removed the tank (after replacing the fuel filter and pump) and there was about an inch of rusty sludge in the bottom. I basically blasted the tank out at a car wash and let it dry real good. Seems to have fixed the problem so far.

Yes, I'm beginning to believe this is my fate. I just know that when I blow out the fuel lines, its not going to help. I hope the inside is not too bad, or I may end up buying another tank.

Grimace, yeah I tried that, and it looks like it is pumping good, but that is at idle. Now at WOT is where my problem is, and that is a bit harder to observe while you are truckin at 70mph.

One observation I did make, since my filter is clear, that while at idle, the filter has air inside of it. I would think that sooner or later all of the air would get sucked through, unless the fuel flow was not adequate...

You do have an electric pump right? If so, then it won't pump anymore at 70 than it does at idle. That is what the return line from the carb is for. Do the same thing, but disconnect the fuel line from the inlet side of the carb. If it pumps the same amount of fuel, then I would not suspect the fuel lines. Cleaning them won't hurt but if you are getting good fuel to the carb, then I would think the problem lies in the carb itself.

That was me just now. Forgot to log in.

_________________
Hammer to fit, paint to match.
If it aint broke, don't fix it.
There's always room for duct tape and bailing wire.

WATCH YOUR PIEHOLE!!!!!!

At least on the stock carb in my 79 4x4 the secondary is vacuum, not mechanical. Maybe the vacuum solenoid has a leak...

-DK

Ok Tuftluv I just had a thought on my long drive home. Do you have the stock hitatchi carb? If you do, have you rebuilt it? If you have, did you thoroughly clean the last ditch filter in the banjo fitting (the fuel inlet fitting with two nipples, one large, one small)? I found a buildup of tan sediment caked in mine. I had to blow it out gently with shop air, and use a fine bristle toothbrush dipped in gas to clean it all out. You could always try this. Take a length of fuel line, I think it's 5/16", and run it from the fuel pump to the carb. bypassing your stock metal lines. Make sure you tie the temporary line up out of the way so it doesn't come loose while you drive. This might also tell you if your stock lines are full of sediment. I was talking to a guy at work who once owned a luv. He said his truck would run good for a while, then start to sputter and die for lack of fuel. He did a hundred things, and finally removed the steel fuel lines put rubber lines on in their place. He said the truck ran great. Hope some of my rambling gives you some help.

_________________
Hammer to fit, paint to match.
If it aint broke, don't fix it.
There's always room for duct tape and bailing wire.

WATCH YOUR PIEHOLE!!!!!!

Yes, it was rebuilt, and that filter is clean. The carb might have junk in it now, if the tank or the lines had alot of crap in them. Well, I will find out if its the lines are tank this weekend....

Also, yes my secondary is vacuum actuated. I will have to try and trouble shoot that this weekend also, if blowing out the lines and cleaning the tank doesnt work...