DiZ86

Hello all,

I'm a bit of a newbie, so bear with me; also, let me know if I posted this in the wrong place..

My issue:

My truck was running normal (compared to how it was when I got it) until I ran out of gas. (Note, this had happened before, and I had no problems after putting gas in it previously) This time, I put gas in it (premium) and it ran fine to my house. The next day, I went to start it up, and it would crank over for a few seconds and then die. Also, it dies more suddenly when I step on the gas. If I pump the pedal, it goes a bit before dying again.

I have a stock Aisan carb, which I just rebuilt (mostly), I replaced the fuel pump and filters, replaced vacuum lines. Before the carb rebuild, there was a new whistle I could hear, so I thought the carb was the problem. Now, that whistle is gone, but I still have the same problem. I've checked the basics (plugs, wires, electrical connections, intake bolts, linkages) and all seems to be in order. I rebuilt the head a few months back, so the related gaskets there are all new and seem fine. I'm totally stumped here and a bit frustrated.

I should also note that my gas tank has a few pinholes in the top (due to previous owner's lack of care), which I have tried several times, and failed, to patch. However, that has been an issue since having it, and like I said it ran fine before.

I'm sorry for the wordiness, I just wanted to make sure I gave an accurate description...

Do you have any suggestions of what to do next?

Thank you for reading!

83

It's always hard when someone has done all the work you've just done. Because we don't know you and don't know how well you did the work, and there are a lot of places you might or might not have messed something up.

Assuming you did everything right, I would say to definitely check the fuel side of things. You may have sucked up some gunk at the bottom of the tank when you ran it dry, and clogged the fuel filter (you replaced that before running out of gas, not after, right?) or some passage in the carb.

I'd try another new fuel filter and some carb cleaner in the carb.

Also, unless your emissions stuff is all up to snuff, I'd consider a Weber (not sure if Oregon requires emissions testing). When everything is working correctly, you can't beat the stock Aisin carb. But on a 1978, things are pretty much never all working correctly. A Weber allows you to do a way with all the clogged, non functioning emissions stuff which is likely screwing with the functioning of your carb. Or you can read up on the emissions removal stuff and keep the Aisin, and just plug off unused ports.

Anyway, pretty clearly sounds to be a fuel issue.

How exactly did you try to patch the holes in the gas tank?

83

Just to be sure: everything worked fine after you rebuilt the carb? It wasn't until running out of gas that it started acting up?

DiZ86

I understand, it's difficult to explain without being here in person, and my apologies if my explanation is confusing. Actually, I rebuilt the carb just the other day, which was after this issue cropped up. Everything worked fine before the carb rebuild. this issue started before the rebuild and after running out of gas that time (the most recent). The thing is, I had run low on/out of gas previously to all this and I had no problems when I would put gas in). Also, the fuel pump is an electric drop-in tank style, and it has a mesh filter on that. When I replaced the pump (since this issue started), I made sure the tank was clean and installed a new pump pre-filter with the new fuel pump. The smog pump and related connections were already disconnected when I got the truck, and I cleaned the hell out of the EGR connections and intake passages when I redid the head as well. The carb has been iffy since getting the truck, it would sputter frequently and backfire at times, but otherwise it would work well enough.

When rebuilding the carb, I say 'mostly' because for one, the kit didn't come with everything, including the secondary diaphragm, and jets. Also, I got as far as separating the air horn and body. I replaced gaskets up to that point, and the AAP, choke gasket, needle valve, pump piston. I cleaned everything in carb cleaner, I checked the diaphragms I couldn't replace with kit (choke breaker, secondary, throttle positioner) and each seemed to check out fine. I triple checked each step according to the diagrams in the tech manual I have (it's an old Toyota brand manual). I didn't want to go too deep and damage something, because it looked pretty decent on the inside of the body. I took the air horn pieces apart and cleaned all. I took out the venturis and soaked them, checked passages, and sprayed them down inside and out. I did not take out the main or secondary jets, because they looked clean and seemed clear when I blew through areas I could. When reassembling, I took care to follow each step carefully and not torque too heavily as to mess up adjustments. Another point is that I don't have the carb driver/guage tools that the book calls for (SST 09860-11010/ 09240-00011)

When I tried patching the tank (this was a couple months ago, and it had been running fine apart from this), first I tried a fuel patch kit that came with a mylar type fabric and epoxy. I made sure the surface was well cleaned and sanded/prepped, and waited for cure time before putting gas in. Failed. I then tried Magnum Steel, which was specifically rated for fuel repair, and again same deal; I made sure the surface was clean/prepped and followed all instructions and waited even longer than recommended for curing. Failed. I just learned of 'PC-7' (a 'dry mix' type epoxy) and am told that should work. Do you have any experience with it?

I agree with you about the Weber; I've heard a lot say its the best/simplest way to go. For me, the main reason for all this struggle is that I don't have a lot of cash to spare. I like a challenge to fix things and learn as well, and I've learned a lot by doing the work myself. I intend to eventually go with a Weber, but $50 for a rebuild kit is more immediately appealing than $200, also considering I need the vehicle to use for work and make enough money to save up.

83

There's also supposed to be a filter/sock type thing in the gas tank on the pickup tube. Could be that it's clogged. But I don't know. I run out of gas all the time in my 78 and haven't had any issues, but it also doesn't have a corroded gas tank.

DiZ86

The inside of the tank didn't look too shabby, no internal rust that I could see. The most recent patch attempt still has a layer of epoxy over the bad area, it just leaks if the tank is more than 3/4 full. Of course, that also means there is less air pressure I realize. I've had a difficult time locating a matching tank and again being able to afford a new replacement.

Also, I cleaned and painted the entire outside of the tank (after the recent patch cured).

I have blown out the lines (with mouth, don't own a compressor), and checked fuel flow from pump to/through fuel filter (with line disconnected at carb inlet).

83

Well, either it has something to do with running out of gas, or it doesn't. If it does, it seems like it's got to be something clogged. Since you've checked all that, it seems you've ruled it out. So I think that the problem starting after running out of gas is just a coincidence.

The fact that giving it a lot of gas makes it die, but pumping the gas keeps it running is strange to me. Almost like a choke issue. Or a weak spark issue. I would make sure the choke is moving freely. How did you test the plugs/wires/distributer cap/rotor/coil? Are all the grounds properly connected on the engine?

The fact that it just started out of nowhere, after running fine right after all the work you did, is making it hard for me. I'm not sure what's up. How long after all the other work you did was it running fine? A few days? Longer?

Why are you running out of gas so often?

DiZ86

I can only put in about 7 gal. max and my fuel level sensor works intermittently due to partially worn contacts in the tank sensor. I keep spare gas with me in a can at all times though.

So, an update: I had a friend crank it for me so I could poke around under the hood. With air housing off, and after blowing out the lines again, it puffed white smoke out the top of the carb, then it started up great! Issue=resolved. It must have been a blockage I missed..

Thank you very much for your responses/suggestions! Again, I'm sorry if my posts are too wordy; I try to give the best descriptions I can when necessary. I'm fairly new to forum use, and I really appreciate this resource and do not wish to clog things up or whatever.

As for the other issues, well, time and money are my hurdles for that.

83

NIIIICE. Great.

Yeah I hear you. I've traveled a lot in my 78. Only takes 11 gallons, gas gauge drops to zero at about 3/4 of a tank. I run out of gas all the time. And yep, that's why I carry a spare 5 gallons. You know it's time to pull over and fill up when the truck starts bucking!

Wordiness is a tricky thing. You want to cover everything you've done and noticed, so that people can hone in on the problem. But if you type too much, people just take one look and close out of the topic...Not everybody has the time to get in depth.

Find your own balance, but the best thing is to be complete. Let people know what the vehicle is, what modifications are done to it, what you have done lately as far as repairs, what led up to the problem, and what you've already checked/tried. But do it in as few words as possible; small paragraphs, bullet points if possible. Keep the reader in mind...just give as much info as possible in as short and as easy-to-read way as possible.

Long descriptions don't get read as much. Short descriptions with no punctuation...no periods, questions marks, no way to tell when one sentence/thought ends and another begins...get read even less.

kawazx636

iTrader: (3)

Glad to see that you figured out your issue, but as a side note, if you are putting premium fuel in your engine then you are wasting your money. Premium fuel does NOT equal more performance. In fact, in an engine not designed for use of premium fuel will inhibit your engines performance. Here is a little octane lesson for you in case you were unaware. The higher the octane, the more resistant to combustion the fuel is. So 87 octane (Regular) is more combustible than 93 octane (Premium). Engines that use higher octane fuels will have a higher compression ratio. The fuel in those engines must resist premature combustion during compression or they will start pinging or detonating prior to the spark. The compression ratio for a 20R is 8.4:1 which these days would be considered a moderate to low compression ratio. You typically don't see vehicles requiring premium fuel (93 octane) until upwards of 12:1 ratio. However, technology these days can throw out all of the rules of octane with things like variable valve timing, electronic timing, etc.

I'm not saying that your truck will not run on premium, but it would likely run better on regular fuel. I personally run Shell's mid grade (89 octane) in my 22R. For one, it is ethanol free and two, my compression ratio is 9.84:1 after I rebuilt it. On regular fuel, I was getting a slight knock which went away with the higher octane.

83Toyota88

iTrader: (1)

Saaaaayyyyyyy what?? Are all their stations that way with the ethanol free? I would def buy that if that's true.

kawazx636

iTrader: (3)

Yep! No, ethanol for this guy! I'm not sure all shell stations are like that, but the ones around here say "ethanol free" on the pump - I think they have to by law.

Johnsoline

My carburetor does the same things, but I do not know the problems exactly. However, when you push the gas in, about halfway in you will feel a "bump." This is where the choke plate catches and from there advances to wide open. After the truck is started, push the gas in, but not in far enough so that you feel the bump; push gas until about halfway to the bump. After the engine reaches 2500 RPM or so, floor it all the way. The engine will lag for a second and then rev real fast. Right when it stops lagging and begins to rev, release the pedal immediately and allow to idle.

The carburetor is still messed up, but this is how I keep mine going until I can afford to rebuild.

As for the pinholes in the gas tank, I emptied the tank and got a 1/4" wide wood screw and coated it in JB Weld then screwed it into the pinhole.