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help! 72 302 won't idle more than 10 seconds
#1
runninpony 
I'm new to this forum and I am having serious trouble with my 1972 mustang 302, it starts up and idles well for about 10 seconds then rpms slow down and die almost instantly, I have replaced a lot of things on it so I don't know what could cause this problem. if anyone else has had a similar problem and could help me that would be greatly appreciated, I have tried everything that I know! thank you, if you need additional information I would be glad to give it out, just let me know what you need to know. ps: I've never used a forum before, so bear with me
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#2
Sounds like a fuel supply issue.

Could be many things... Fuel pump going bad. Carb not set properly. Fuel tank not vented properly.

Can you keep it running if you give it some gas?

Once it stalls, does it start right back up, then stall another 10 seconds later, or is it hard to start after it stalls?
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#3
I agree that it sounds like a fuel issue. It also sounds like it is running on the fast idle/choke cam for a moment and then dying. To me that is a signal that there is a vacuum leak somewhere, or the internal circuits in the carb aren't drawing fuel through the idle circuit.

Has the car ever idled properly during the time you have owned it?

[Image: 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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#4
Remove the air cleaner and spray starter fluid in it when it starts to die. If it keeps running you have a fuel supply issue. If it dies then I'd look into a vac leak. I'd also make sure that your choke isn't wide open at cold startup.
If there are no leaks that you can find (use starter fluid to spray around the carb and vac lines) then I'd look at the timing.

-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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#5
All of the above. just do one at a time then move on. make a list and check them off.

Live, Laugh, love
ECTA, Ohio mile Landspeed record holder
C/GALT-136.36, AA/FALT 159.38 mph, New B/GALT Record 180.577mph- speed is the need !
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#6

Fuel...but make sure you have 6 volts at your coil....I believe that is 6 volts between the + side of the coil and a source for ground.

Could be worse. Consistent issues like this are relatively easy compared to a car that runs great in the driveway and peters out at 110 on the freeway.

[Image: 11jmcuc.png]
351C Bold Manners, Brash Attitude
Favorite Teams: Michigan Wolverines and Whoever Is Playing Ohio State.

When I drive past a herd of cows, the cows MOO at me
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#7
Thank all of you for responding so quickly! To answer as many questions as I can, I just replaced fuel pump and filter, just replaced carb with a 500 cfm Holley, just replaced intake manifold and valve covers, relplaced exhaust ( just listing everything that I replaced) replaced spark plugs, replaced coil, 3 push rods that were bent , alternator, and re set timing . It runs for 10 seconds then dies, during those 10 seconds if I give it any gas at all it dies almost instantly. Also it will not start unless the choke is Completly closed, not even a hair open. If it is open at all then it will not start, and If I open it a little when it is started then It dies instantly. It ran before, it ran horribly rough but it ran, then it randomly stopped running ( I thought because of the carb) so I rebuilt the carb and it still didn't work so I replaced the carb and that still didn't fix it. So I tried all those other things i listed above and none of them fixed it so now I am here... Also I think it is noteworthy that when I set the timing I had it set at 30 degrees advanced which is crazy high, but that's where it ran best. It ran for about 10 minutes the other day no problem, but for some reason the very next day, after not touching it at all, it starts doing this. I thought I was extremely close a couple days ago, because it idled awesome but just died as soon as I put it in gear, so with a few minor adjustments to the carb screws I was able to take it around the block by 2 footing it. But now I can't even set the screws because it won't run long enough to do anything. I can't check for a vacuum leak because it dies too fast to spray around the intake. Alright so that's the end of my rant haha, thank you guys again for your responses, this car is really stressing me out that it won't run! So any ideas would be greatly appreciated, thank you very much
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#8
I say vac leak as evidence by the choke. I'd still start with starter fluid to rule out fuel starvation.

I had the EXACT same problem with my 289 and it ended up being that the carb spacer was letting massive air in due to the shape. I used a stock 4 bbl spacer and fixed it by going with a cheapo 4 BBL spacer from Chinazone. I later went to an Edelbrock version due to hot start issues.

Check for air leaks @: transmission to manifold (modulator to metal tube & metal tube to manifold), any open holes on the manifold (my Edelbrock manifold came with 4 or 5 open holes to accessories), carb to carb spacer, carb spacer to manifold, brake booster to manifold, PCV to carb/manifold, valve cover to PCV, any open ports that needed to be blocked off on the carb (Edelbrock has one on the front for the PCV and one on back for accessory), manifold to block (front and back) and valve covers.

30 degrees is WAYYYYYYYYY too much timing at idle. Set idle mixture screws to 1.5 turns out and make sure your idle screw is around 3/4 in (as a start). For sh*ts and giggles, I'd try to back off timing a tad without starting it if you are confident your balancer & timing marks were right on.

KR

-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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#9
Are you sure the accelerator pump and the power valve are perfect?
The timing is wrong...

Maybe you're running on 6 or 7 cyl, check all leads for spark...
Worse case scenario, you've got worn lobe(s) on the cam.?

[Image: Image3.png]
Jim
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#10
thanks again guys for the help,
the starter fluid idea is a good idea however i wouldnt be able to test it because as soon as i would open the choke to spray the fluid into the carb it dies, so i couldnt really check that unfortunatly, are there any other ways of testing if its the fuel delivery problem? I thought about getting a fuel pressure gauge to check if i am getting pressure but let me know what you think. the float could possibly be stuck which would cause it to not get very much fuel and explain why it dies every time, but it shouldnt be stuck because it is a new carb and it ran the other day pretty well, so it would have had to have gotten stuck within the past couple days so i dont think that is it. i have a spacer on it aswell, it is a 2bbl though. maybe the spacer is upside down or something, but i doubt it. it has brand new gaskets so there shouldnt be a leak on the carb spacer, do you recomend i take out the spacer completley and see if it changes anything? a couple other things worth mentioning is when i replaced the intake manifold and gaskets, i had a bad oil leak so i took manifold off again and re put it back on but i used the same gaskets, which i heard is not a good thing to do. the oil leak stopped, which is good but apparently using the same gaskets could cause a vacuum leak. i also took out the AC compressor and pully to take weight off the front and to have more room in the engine comp, i dont think that matter just letting everyone know. im not sure how i would check for any air leaks in any of those places you mentioned because i cant keep it running long enough to do a test with the carb spray, are there any other methods of checking for vacuum leaks without the car running? and the carb screws are already 1.5 turns out, im not sure about the idle though, i just tuned it untill it sounded best for those 10 seconds and left it there. i will try to retard the timing a little bit and see if that fixes anything, the way it is now, at 30 degrees, was when it ran the best however and didnt backfire at all so if i move it back i have the feeling it will start to backfire again, but i will give it a shot. thank you so much for your help, to answer jimniki ,
the accleerator pump should be good, it is pretty much a brand new carb, only used for a couple weeks before i bought it. im not sure what the power valve is exactly , sorry :/. also how would i check if I am only running 6 or 7 cylinders? these seem like dumb questions so i apologize ... thank you so much both of you for helping me with this (:
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