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help! 72 302 wont idle more than 10 seconds


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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/

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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.

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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.

http://www.7173mustangs.com/gallery/1_01_07_15_8_53_18.png

 

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!

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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.

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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.

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Just cruising along minding our own business when BAM!!! The LAWS show up.

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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!

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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

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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

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Well what i would do...Is hook a burp tank up to the carb and gravity feed your carb..If it starts up and runs well..You know it is still soming in your fuel system....gravity fed tank eliminates your fuel system..Take the normal fuel line and run it into a bucket and watch out much gas "if any" It pumps out while runing.

 

pretty much what i did below on a old mustang 2 below....just to get it runing..cause the tank was full of nasty stuff..I made a burp tank out of a radiator fluid bottle..and hung it up high and away from the car incase something happend...Bipassed all the fuel system...So if it keeps dieing in 10 min..You know it is something more than your fuel system..this will take it all out of the equation..cheaply too..without ripping your fuel system apart.

 

 

Ohh does sound a bit like a vac leak...Better get a vac gage on her..Almost sounds like a vacum advance problem.

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no doubt in my mind, it's a vac leak.

-Former 70 & 72 Mustang Owner.

-69 Torino GT, Formal Roof, 351W, Edelbrock 600 cfm, Edelbrock 351W Performer RPM intake, headers, AOD trans, dual flowmasters w/H pipe, Pertronix II Billet, 3.5 TRACLOC g/r, 15" Magnum 500s, 100A alt, aluminum radiator, electric fan, Pro-car seats, mini-starter...owned since Dec 13.

-70 Mach 1, 351W, Edelbrock E-Street EFI, VHX instrument cluster, Hooker headers, dual flowmasters, Pertronix II, 15" Magnum 500s, 150A alt, aluminum radiator, dual electric fans, Pro-car seats, mini-starter

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I didn't notice what ignition system you are running. But I use OEM style components. I've had the ignition condenser fail and result I'm the same symptoms. BTW replace the points also, condenser failure causes them to pit badly. Filing the points can get you about ten minutes of run time if you're stranded.

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  • 4 weeks later...

Hey after a long winter I'm startin to work on my mustang again, im having the same problem I had before winter hit, I tried starting it today and there are 2 problems that I see. One is that my battery doesn't seem to hold a charge at all, I charge it all the way and then it lasts for maybe 45 seconds total of cranking , but when I bring it to autozone it tests ok, idk why that would be. I figured I'll just get a new battery anyway, but that's not the main problem. The 2nd and main problem I've been having is that whenever I depress the throttle , no gas squirts into the carb. It used to work and I could hear feel and see the gas squirting into the carb and venturi when I depressed the throttle arm, but recently ( as in today and about a month before winter) it hasn't been working at all. When I depress the throttle arm now I can only hear air going into the carb, there is much less resistance also when pushing down on it ( its a lot easier to depress it now). It feels and looks and sounds like absolutely nothing is being squirted into the carb, but the filter is new, and the carb is newish, and the fuel pump is new. I tried using a generous amount of carb cleaner to get it to start for just a moment but it didn't start that way either, but I beleive this is because the battery wasn't good enough to crank it hard enough or long enough to start it after the winter. I'll start with a new battery , but I know that won't solve the problem with the gas , any thoughts or ideas would be greatly appreciated I really wanna get this thing running for spring. Thank you

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I'd put one if the clear inline fuel filters on your fuel line. It sounds like gas might not be making it to your carb and this would let you see visually if that's true or not

 

 

Sent from my iPhone using Tapatalk

2013 Ford Focus SE Flex Fuel 5spd - Daily Driver

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are your fuel lines from the pump to carp and pump to tank reversed?

http://www.7173mustangs.com/gallery/1_01_07_15_8_53_18.png

 

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!

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There's so many issues that could be at play here. A weird battery can cause all sorts of issues. How old is your carb? Has it been rebuilt. The accelerator pump diaphragm could be blown and not working hence no gas squirting into the engine.

 

Sent from my SCH-S960L using Tapatalk

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I had a car that would idle for 10 secs or so then die - it would restart just fine but then die again.

 

Turned out to be a weak rubber fuel line from the fuel sender to the hard fuel line back by the tank along with little or no tank venting.

 

The soft line would get sucked flat by the fuel pump shutting off the fuel, the car would stall, the pump would stop and the line would open back up letting the fuel flow again.

 

That was fun to figure out.

 

- Paul

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That's good information Paul. I'll remember that one. I would remove the top of the carb and put the eye on the fuel. I'm guessing there is none. That will direct the next steps. On the two barrel that's about 6 screws and the big air cleaner stud and choke linkage to remove the top. No fuel: line issue, filter, pickup or fuel pump and don't over look the needle and seat. If you have fuel carb blockages mentioned by others and rubber valves also mentioned. But you need to see if fuel is the bowl. Then move in one direction from there. This new fuel can cause some rubber to soften and create issues in carb and line connectors.

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Also, regarding the battery... A bad battery can read OK on a tester until it is put under a load. I had a battery that kept reading OK at the auto parts store, but wouldn't hold a charge. My mechanic buddy put a load test on it and it failed. The load trest creates a short, and measures the power while shorted. A bad battery will fail this test quickly, as may be the case with yours only providing 45 seconds of cranking.

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If the car has sat all winter and you have only been able to crank it for 45 seconds or so due to the battery issue, chances are you have no fuel in the fuel bowl. Get the battery straightened out and try it again. If you feel comfortable with it you can prime the carb by filling the fuel bowl through the vent. I use one of those baby snot suckers to do this.

73 conv. 460, D0VE large valve heads, Performer RPM manifold, Voodoo 227/233 cam, Holley 950 HP carb, C6 trans, 3.25 trak-loc.

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I fill fuel bowls with a piece of rubber hose pressed over the vents and fed up into a small funnel a jigger full of fuel into each one is usually plenty.

 

You can also hold a rag dampened with gas over the carb and get enough fuel into the system for it to fire over-but a backfire will light you up.

http://www.7173mustangs.com/gallery/1_01_07_15_8_53_18.png

 

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!

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Founded:
July 2010

By:
Webfinity Design

From:
Latrobe, PA

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