help! 72 302 wont idle more than 10 seconds

[mcampbell26915]

Alright sorry everyone I havnt posted in a while balancing between 2 jobs and school , anyway I disconected the coil and connected a long tube from the fuel line into a bucket and when I cranked it for 10 seconds , barely any fuel came out. Maybe 1 fluid ounce, and then I cranked it again for another 10 seconds and again to test it, and every time only a tiny bit of fuel came out. Therefore the carb is definatly not getting enough fuel , I'll try putting 5 gallons into the tank and trying again , but I know it has at least one gallon so I doubt that the gas is the problem. Maybe the fuel lines are partially clogged? The car still starts and runs for a little bit then dies, unless I give it starter fluid. If I start it and try to keep it alive by using the throttle arm and giving it gas, it dies instantly. As soon as I try to give it gas it dies, but when I give it starter fluid through the choke plate then it runs fine . I'm not sure what that means either. Thank you all very much for your help, I'm really hoping to work on it this week because next week is looking like snow . Thank you all again let me know what you guys think

 

[72HCODE]

get a 1 gallon gas can, and connect a hose to the fuel pump run the hose to the gas can. that will rule out if the main fuel lines are clogged.

 

[mcampbell26915]

Alright I will try that, there are 2 hoses coming out of the fuel pump, one is metal and one is rubber. Which one are you referring too?

 

[72HCODE]

rubber is the from the fuel tank. there is a hard line on the drivers side that is split in 2.

starting from the fuel tank:

you have the fuel sender, rubber hose, hardline up drivers side of chassis to master cylinder, Rubber hose, second hard line that runs down to the front Cross member, Rubber line goes to fuel pump, other side of fuel pump is a threaded connection and hard line runs up the engine block to rubber line that connects to the carb.

pull the rubber hose from the fuel pump and connect to a external fuel source and see if that solves it.

that would tell you the fuel pump is working and your hard lines are clogged if the engine runs.

everyone always asks why is the main fuel hard line in 2 pieces with a rubber hose at the master cylinder wall. This is in the event of a front collision the area will give and also pinch the rubber line and might kill the motor cutting fuel to the pump.


one other thing that can happen, if a rubber hose has cracked from age it will cause air to get into the system and the pump will not work right.

I actually did have 2 split fuel lines on my car when i first got it and one day i could not start my car i had to roll the car so the engine was down hill to get it to run

 

[mcampbell26915]

Alright wow thank you very much, alright so when you say to pull the rubber hose off the fuel pump do you mean to disconnect the hose from the fuel pump itself? Because if I do that then how will any fuel get to the fuel pump... Say I take the rubber hose off and put it in a gas can then there's no fuel like to the fuel pump. Or do you mean to disconnect the rubber line from the tank and put it in a gas can? I'm not exactly sure what to do I'm sorry

 

[Don C]

One of the tubes or hoses goes to the carburetor, leave it in place. Remove the other hose at the fuel pump. Connect a rubber hose, that is long enough to reach the gas can, to that connector.

 

[mcampbell26915]

Alright thank you, I will try that as soon as I get home and then post my results

 

[72HCODE]

yes remove the rubber hose going to the pump from the frame rail side, then hook the bypass hose to that so it will suck fuel from the external tank. this way the pump is being used to confirm it is working or not.

it is possible the pump is defective or wasn't installed correctly on the pump cam inside the engine.

i mean there could be other reasons things are not working.

 

[mcampbell26915]

Alright so I tried the external tank idea , I used a 5 ft long hose connected from the fuel pump into a gallon of gas. It started after a couple tries, then stayed running for a while ( maybe a whole minute) but I had to keep my foot about halfway down to all way down on the gas in order to keep it going. So that usually means I need to turn the idle up, so I let my foot off the gas and it died instantly. I turned the idle up a good amount, and it started again and ran but I still needed to keep my foot on the gas, even more then I did before I turned the idle up. Turning the idle up seemed to make it worse , I'm not sure why that is. When I hook up the external tank , and I push the throttle manually , I can hear a good amount of fuel squirting on the venturi. However when I hook up my regular gas tank , and I push the throttle manually, I can only sometimes hear fuel. Sometimes I can hear it just shooting air, and other times it squirts a little bit of fuel. I'm not sure exactly what that means either. Any suggestions are greatly appreciated ! Thank you very much for helping like always, I really want to get this thing done. By the way, when I hooked up the external tank , I was able to have the choke slightly open in order to start it. This is noteworthy because usually with the internal tank I have to have the choke all the way closed. Alright that's about all I can think of to say, let me know what you all think thank you very much!

 

[Jeff73Mach1]

I believe you have a massive vacuum leak either in the intake manifold gaskets or internally in your carburetor. I also suspect your return line (vent) is plugged or your fuel lines are in bad shape, or your pick up is plugged or has fallen off.

I would replace the fuel filter then remove the fuel sending unit and check it's condition. I would next blow compressed air through the fuel lines (10-15 PSI is enough to test), the vent lines and then I would pull the intake, clean the surfaces, replace the gaskets and torque everything in sequence. Finally I would rebuild the carburetor.

All in all I've outlined 4 hours of work or less to completely vet your fuel system problems. If you can't do these things yourself, it is time to get hands on help.

 

[mcampbell26915]

Dang, the carb should be perfect Becuase I just got it. It's only a month old, and the fuel sending unit I'm not sure how I would replace... I know it doesn't work because no matter how much gas I have in the tank the fuel gauge always says empty. And alrfht I'll blow out all of the lines and replace the filter. I'll pull the intake off again and replace the gaskets , should I buy any thing new? Like should I buy a new fuel tank or anything. Thank you for the help, I think I can handle all of those tanks , I'm not sure about the fuel sending unit though because I am not exactly sure what that all is. Thank you again for the help and extremely quick response! I would really rather not rebuild the carb because it's really expensive and I would probably just end up making it worse. It should be a good carb. Thank you!

 

[Wasagachris]

Your new carb probably got fouled with old fuel/gum/rust from the old tank and bad fuel. The needle seats probably just need cleaning out.

Here is a link to a fuel tank kit. It contains everything needed to change the tank/sending unit, etc:

http://www.cjponyparts.com/fuel-tank-kit-1971-1973/p/FTK4/

Tank Straps:

http://www.cjponyparts.com/fuel-tank-straps-1971-1973/p/FTS1/

Fuel lines:

http://www.cjponyparts.com/fuel-line-tank-to-pump-v8-2-pc-3-8-om-1971-1973/p/MUF1012O/

 

[72HCODE]

again like wasagachris said and others have suggested. your fuel lines are most likely in bad shape along with the tank and vapor system.

when you ran off the external tank everything got better even though you had problems, so your looking at a complete fuel system overhaul.

and i would replace all the lines the tank and the sender and the vapor return system.

as for the carb,,, you most likely have clogged it up with junk from the original fuel system, so it will need to be opened and cleaned throughout, blowing out all the passageways and ventricle points and reassembled for testing. then you will want to test it from the external tank only.

i would also remove the hard line from the fuel pump to the carb, and blow it out with compressed air for a couple of minutes. and blow out the fuel rail going to the carb itself getting any garbage out, or you could flush things out with gas or alcohol too.

at this point any filters you have inline with the original fuel system should be discarded and replaced, and do not use them with the original fuel system again.

you want a fresh 100% clean re-start to the fuel system, before you hook everything back up outside of testing.

that still does not rule out a massive vacuum leak, or adjustment issue.

you can disconnect the throttle cable and try making adjustments from the engine bay instead of having to get inside the car and hold the pedal.

just use one hand on the throttle linkage to keep it going and make adjustments,, what is happening is you need to hold the throttle way open to try and get the engine to keep running. that isn't good but for diagnostics you need to get that engine to stay running to figure out what is wrong.

you want to get a vacuum gauge and timing light on it and maybe an external tach/dwell gauge so you can work on the problem from the engine itself.

i would again disconnect all Vacuum accessories and plug everything up to rule them out as a problem source.

good chance you have a bad seal between the intake manifold and the cylinder heads. or a massive leak at the carb base.

but you can also have internal leaks in the carb from the choke. or base.

some carbs have a vacuum line on the front right under the fuel bowl, and people forget to cap it, but your leak would be much larger if present.

 

[Jeff73Mach1]

Please don't take this the wrong way, but I would strongly suggest you find a local hobbyist to give you a hand. When you are afraid to rebuild a carb for fear of making it worse, I suspect you lack experience and without a certain amount, all of the information we provide gets very hard to digest and process.

Also long distance diagnosis is hard-we respond to the information you provide, but being there in person, I would bet we could narrow down the cause(s) of your problems quite quickly.

 

[72HCODE]

I would add. Don't be scared but be informed.

When I started a couple of years ago I never touched a carb in my life, never changed engine oil, never changed a filter, never touched a spark plug.

I knew I was over my head very fast but what I did was read, read a lot, watched videos online, asked for advice, then I made many many mistakes but I learned from them and built up my knowledge and experance.

You could look up your type of carb and within a couple of minutes find a detailed rebuild article or video showing what to do. I mean it's not rocket science , take photos for each step you do, take a video of you working on it on the bench so you remember where parts go. Do one area at a time, you don't have to take everything apart start simple open a fuel bowl and see how full of junk it is.

Or save the carb for last and remove it and Inspect the gasket it sat on does it have an imprint of a seal on both sides for the carb base and the intake base that would tell you that area is sealing. With the carb back out of the way you inspect the seal for the intake manifold see if you have new leaks. Check to make sure you installed all the correct hardware.

There was a issue on v4 heads with aftermarket intake manifolds were 2 of the bolts needed to be longer because the heads were deeply tapped in those 2 areas and it caused a massive internal vacuum leak with the lifter valley. And people confused where those long bolts were suppose to go.so people would go insane and couldn't figure it out I remember edelbrock started to include supplemental directions talking about it.

I remember you said the car ran better before so you have to assume the work you did is the problem and then backtrack it to the source of the problem.

We are diagnosing through the internet based in what you tell us so something you think is not important might be.

Please don't take this the wrong way, but I would strongly suggest you find a local hobbyist to give you a hand. When you are afraid to rebuild a carb for fear of making it worse, I suspect you lack experience and without a certain amount, all of the information we provide gets very hard to digest and process.

Also long distance diagnosis is hard-we respond to the information you provide, but being there in person, I would bet we could narrow down the cause(s) of your problems quite quickly.

 

[marks73]

The sending unit is on the DS of the tank. Easy enough to change once you drain the tank. Me personally, I'd get the thing running first. You have already eliminated the carb and the line from the tank to the fuel pump as being the problem. Pull the intake and carb and have some help there to reinstall the intake. You would not be the first person to have trouble setting the intake without messing up the gasket placement.

 

[mcampbell26915]

Ok so this is really weird but I started it today and it actually idled great. Didn't change a thing at all, very strange. It idled smoothly so I put it into reverse, it took a second and then I felt it switch gears into reverse. So I reversed it and all and it went well , I backed it up around 20 ft to the end of my driveway and I put it in drive and it went forward pretty much no problem either , however after several trials of this I noticed that whenever I gave it gas in drive or reverse it didn't do anything except make the engine slow down or die. If I give it any gas while it's in drive or reverse it Completely dies, but when I give it gas in park it revs up fine and sounds good. Not sure what this means exactly, thanks for all the help!

 

[marks73]

Vacuum leak!!!!!

 

[mcampbell26915]

Alright I'm having a mechanic come over tomorrow to find the vacuum leak for me, seeing as I've been unsuccessful in finding it myself. Cross fingers hopefully once i take care of this vacuum leak it'll be running well. I'll update as soon as I can thanks guys

 

[72HCODE]

Check that the vacuum line to the transmission modualar didn't fall off. You will have to look under the car.

Alright I'm having a mechanic come over tomorrow to find the vacuum leak for me, seeing as I've been unsuccessful in finding it myself. Cross fingers hopefully once i take care of this vacuum leak it'll be running well. I'll update as soon as I can thanks guys