fuel tank theory?

[laguna80]

So, I've searched extensively and could not find an answer to several questions. Sorry if these seem too simple and if they are, then feel free to rip me a new one.
My predicament: I put in a new gas tank/carb and tried to start. Truck won't turn over. We, my father and I, tried putting gas directly into the carb and it wouldn't turn over, but I don't think the carb is the problem. We may not have put enough gas into it. When I disconnected the fuel line from the carb, there was no fuel in the line. When I disconnected the line from the pump, there was no fuel in the line. This leads me to believe that the fuel pump is the problem. However, I have a question regarding how the pump sucks fuel from the tank. From what I can tell, the fuel line comes out of the side of the tank, near the center. How does the pump suck fuel and not air that is inside the tank? If the gas is below the level of the fuel line, how can the gas be sucked up? If the lines are completely dry, how long does it take of cranking the motor before the carb will get gas and turn over? Lastly, is my reasoning right in thinking that it is my fuel pump that is not working? Sorry for the long post.

 

[homchz]

If you pump the gas pedal and have someone look down the throat of the carb do you see gas squirt in?? You could also take the line off the carb and try turning the motor over and see if fuel comes out. Just be sure to have a can to catch the gas.

Tank outlet hose/tube should be close to the bottom of the tank, so if the pump is working and the fuel level is above the outlet it will pull the gas through no matter where the line is position, even on top.

Should not take to long to get gas to the carb on a dry system. 10-20 seconds, as a guestimate, on the long side.

It has been a while since i have worked on a 40 so hopefully more educated people will chime in.

 

[laguna80]

If you pump the gas pedal and have someone look down the throat of the carb do you see gas squirt in?? You could also take the line off the carb and try turning the motor over and see if fuel comes out. Just be sure to have a can to catch the gas.

Tank outlet hose/tube should be close to the bottom of the tank, so if the pump is working and the fuel level is above the outlet it will pull the gas through no matter where the line is position, even on top.

Should not take to long to get gas to the carb on a dry system. 10-20 seconds, as a guestimate, on the long side.

It has been a while since i have worked on a 40 so hopefully more educated people will chime in.

No gas going into the carb. removed fuel line from linkage to carb. and no gas came out. Think I'll start looking for a new fuel pump. Will take it out tomorrow and check out the internals. As for the tank outlet. I wouldn't say that it's close to the bottom mainly because of the extra dip in the tank. I put 4 gal. in the tank so far. Is this enough to get the lines to suck fuel. I suppose I should fill it up to 3/4 full, ya?

 

[snailwagon]

Is it a tank that has two nipples on it. Depending on the year, many cruisers came with a gas outlet to the carb and a return line for overflow. I'm not sure, but they might not be at the same level. Fuel tank theory is that despite the external nipple location, it should be routed inside the tank to be near the bottom.

 

[laguna80]

Is it a tank that has two nipples on it. Depending on the year, many cruisers came with a gas outlet to the carb and a return line for overflow. I'm not sure, but they might not be at the same level. Fuel tank theory is that despite the external nipple location, it should be routed inside the tank to be near the bottom.

It's a tank to a 72 FJ40. Sorry for not mentioning that earlier. The tank only has one nipple on it for the fuel line. Gotcha on the theory, seems so simple now that I can visualize it. I thought that it might have been sucked up when a vacuum was created by the pump and that the fuel was limited to one of the chambers. In the words of Homer Simpson.

 

[Pin_Head]

Here is the reasoning:

If it won't turn over, it is a starter motor or battery problem.
If it turns over, but it doesn't start and run, it is either a gas or ignition problem.
If you pour gas into the carb and it won't even fire, it is probably an ignition problem.

 

[Benson]

Pin_Head is a guru so try what he says first.

In addition, if you pull the fuel line off of the filter (input side) gas should simply drain out of the hose even without the fuel pump running as it sits below the tank. This is an easy way to tell if you have a blockage before the filter. If nothing comes out try blowing some air through the line to clear it and see if that helps. If you get gas spilling out then move onto the fuel pump. Unhook the line from the carb and turn it over and see if gas squirts out.

I replaced all of my lines and had a slight kink in one of them that wasn't readily apparent. Something that silly can hold you up for a while.

Good luck.

 

[rusty_tlc]

Pin Head really summed it up well.

I would suggest using starter fluid rather than gas. There is less chance of flooding the engine than just pouring gas into the carb.

 

[camcruiser13]

first, if its not even turning over you got other probs,

 

[laguna80]

Thanks for the replies people. Yes, the engine is turning over that much I'm sure of. It won't start and run though. It seems to be a fuel delivery problem. So far, no gas has been squirting into the carb from the fuel lines. I will take the line off the fuel pump from the tank side and see if gas pours out. We have tried pouring some gas into the carb to get it started but it wouldn't start. That's an ignition prob. like pin_head said right? I replaced spark plugs/wires. They were properly gapped. Replaced rotor/condensor/breaker points and gapped the points as well. The wire going from condensor to ignition coil is partially severed at the condensor end. Could this cause the starting problem? I'm taking the fuel pump off today and inspecting it and if need be, I will get a new one. Furthermore, the choke cable is extremely sticky. It will not pull out easily. We have to pull it out by pulling on the wire on the carb side while simultaneously pulling on the knob. This shouldn't lead to starting problems though, right? Right now, we have left it with the knob pulled out. I know that Napa sells cheap choke cables.

 

[kfrosty]

Severed wire, yes it could cause you problems. Have you tested to make sure the plugs are firing?

 

[laguna80]

Haven't tested the plugs yet. I will definitely try that too. Do you know any good threads offhand that tell the procedure. Otherwise I can search for it. Thanks.

 

[theo]

Haven't tested the plugs yet. I will definitely try that too. Do you know any good threads offhand that tell the procedure. Otherwise I can search for it. Thanks.

Pull one spark plug out, put the wire back on, and lay the plug down so the metal threads are grounded (touching the head or block). Turn the engine over with the key and watch for a spark. Simple.

 

[laguna80]

Couple of problems now. I pulled the spark plugs and checked for spark, but unfortunately there is none. What does this mean for me? Breaker points gap off? Ignition coil broke? That wire that runs between the ignition coil and condensor is only partially severed, the circular loop is still intact although barely. Secondly, gas isn't flowing. I blew air into the tank and could hear the gas sloshing around. Blew air through the lines and felt air coming out the other side. They're not clogged. However, gas isn't flowing out when I disconnect the line from the filter. I think that I have to get gas into the line first. Like an IV bag, if the bag is upside down, but no blood is in the line, it won't get sucked up into the line no matter how far below the bag the line is. I'm pulling my fuel pump now and taking a look at it. Sorry for the long post.

 

[laguna80]

Alright, got the fuel pump off. Diaphragm looks to be intact. Cracked in a few places on one side, but no holes, pin or otherwise. All the parts appear to be in good working order. I still can't figure out why it wasn't pumping fuel. Think I'll get a new one when I get a new choke cable.

 

[laguna80]

Dammit things have taken a turn for the worse. I put the fuel pump back in after inspecting it and thought I might give the engine another try. Turned the key and CHcgggcggrrrrggrrrr. Not starting. Try again. CLICK. Shoot, Try again, CLICK. No try again, no sound. Where is that drain dangit. D/c the battery cable and test the terminals with my voltmeter. 12V is what it reads. Any ideas as to what went wrong? Starter gone bad? Ignition coil gone bad?

 

[Pin_Head]

Charge your battery first.

Make sure that the fuel pump is pumping fuel.

Check for spark.

 

[thewatergoblin]

Find a buddy thats a pretty good mechanic and buy him some beer and have him figure it out. Just a thought.

 

[laguna80]

Find a buddy thats a pretty good mechanic and buy him some beer and have him figure it out. Just a thought.

I would love to, but this is my first cruiser and I'm trying to do everything myself. My own learning ecperience.

 

[laguna80]

Charge your battery first.

Make sure that the fuel pump is pumping fuel.

Check for spark.

Well, now it looks like my fuel delivery is the least of my problems. Charged my battery last night and now I'm still getting nothing when I turn the key. No sounds whatsoever. I tried tapping on the starter with a hammer and that didn't help. I know for sure that the battery is good and fully charged. All wires are properly connected and grounded. I think I'll have to pull my starter and inspect it or should I just get a new starter? I don't understand how the thing can be turning over one day and then the next day nothing happens.