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help! 72 302 wont idle more than 10 seconds


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It does sound like a severe vacuum leak.

What are you using for a gasket between the carb and intake? I have never had good luck with the thin paper ones and always use the thicker ones.

I would disconnect every vacuum line; brake booster, AT, PCV valve, AC etc. and plug all the ports. If the problem goes away reconnect one at a time...

 

Take pictures of your setup. Include multiple angles on the engine. Heed Rocketman Bob's note.

-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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ok try this,, real quick..

 

go to the back of the car, remove the fuel cap,

start engine....

 

if it runs right, your tank is forming a vacuum because the fuel vapor system is clogged up.

 

if there is no improvement then you should still see how much fuel the pump is generating out with a manual cranking of the starter.

and hunt for a vacuum leak to rule it out.

 

the engine is starving for fuel, the question is still why and you need to keep ruling things out.

 

try the cap removal.

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Alright so I tried the gas cap thing and it didn't work, it has gas, at least a gallon for sure. The gas is maybe a month old high octane ( the more exorcise type ) so I think the gas is good. I tried the fuel pressure check thing, I put a peoce of hose at the end of the fuel line and routed it into a plastic bag and then cranked it over. Not much came out , I don't think , I took a picture of what came out. The picture is what came out after 2 cranks each about 4 seconds long. Im not sure if that's the right amount or not, you guys tell me haha. Also the gas looks more yellow than it's supposed too... Idk what that is about but whatever. Also , does the AC draw vacuum? Because I just took out the AC but I couldn't get any of the cables or tubes or whatever out, so they are just sitting there not going to anything. I taped off the end of the AC cables with electric tape just in case. I used the thin paper gasket for the carb to manifold, and I used a thicker one for the carb to spacer. I'm not sure what you guys mean by " cranking it with the starter" ... Does that just mean start it with the key ? Thank you guys. I will add a couple more pictures to this to show you guys my set up


I'm not sure if I'm uploading these pictures right , let me know if they are showing up because I am new to this, here is a video of me trying to start it, hopefully this works. This video is me starting it, and then trying to keep it alive with starter fluid. This isn't a very good example, usually I can keep it alive as long as I spray starter fluid in it , but you can see that it idles good and then just dies randomly, also you can see the choke is almost all the way closed and still runs. Hope this helps, thank you guys

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cranking the engine with the starter either means using the key and cranking the engine that way or using a remote starter.

you crank the engine for 10-30 seconds with the coil disconnected. 2 cranks 4 seconds long isn't long enough to determine anything other then the pump is pumping fuel.

 

problem can still be, fuel, vacuum, or electrical.

 

try getting the engine to run as long as possible with the choke closed, disconnect the electric choke if you have one.

then cover the top of the carb with your hands and see if that kills the motor if it keeps running vaccuum leak from somewhere.

 

when you disconnected all the vacuum lines did you check the rear vacuum tree on the intake manifold to make sure those are capped off.

 

try disconnecting the vaccum booster if you have one and cap the line off the manifold as well.

if you have a PCV is it functioning correctly, you can cap that off as a possible vacuum leak source.

the idea is cap all vacuum accessories off the intake manifold for testing.

 

you may have a massive leak through the manifold base.

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alright ill disconnect the coil and try again, and ill also cover up the choke and try. im not exactly sure what all has vacuum, i think i know what the vacuum tree it, but it has 3 separate tubes going to it and none of them are cracked, im not sure what the vac booster is, and im not sure what line you are refering to off the manifold. is there some sort of diagram to show me what all has vacuum? im sorry im still new to this stuff, thank you. also did the pictures get uploaded? i cant tell

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alright ill disconnect the coil and try again, and ill also cover up the choke and try. im not exactly sure what all has vacuum, i think i know what the vacuum tree it, but it has 3 separate tubes going to it and none of them are cracked, im not sure what the vac booster is, and im not sure what line you are refering to off the manifold. is there some sort of diagram to show me what all has vacuum? im sorry im still new to this stuff, thank you. also did the pictures get uploaded? i cant tell

 

The video didn't post but just take several pictures and upload them. Obviously fuel is the main issue since it runs with starter fluid but I'm confident there is some type of vac issue. I think you mentioned that you pulled the manifold, you should have used RTV sealant on the front and back of the intake manifold or at worst the crappy little cork gaskets. If not, you have a massive air leak in there.

-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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hmm... did the pictures upload? i know the video didn't but i cant tell if the pictures went up either. if not, then i am not sure how to do it.

i used RTV sealant, however i re used the same gasket. when i took it out the first time, i scraped everything off with razor, putty knife, carb cleaner, the works. once i got it all clean i put the rtv on all the correct spots and laid brand new gaskets down and put everything back together. when i fired it up, it ran great except there was a huuuuuuge oil leak ( oil squirting out so fast it reached 1 foot away from the car) because i didnt put the right amount of sealant on the front and back of the valley, where the crappy cork ones would go if i had put them there. so i had to take everything apart again. so i took everything apart, re-scraped everything clean, and then re aplied the RTV only this time using the correct amount of sealant. however, i re used the same gasket that i used last time. it still looked relatively new, because it was only in the car for about a day. however i have been told ex-post-facto that i should never re-use gaskets, i just thought i would because they were really expensive and i didn't want to buy more. oil stopped leaking by the way, but now it could have a vacuum leak. but I am not sure why the vacuum leak would be causeing the much of a problem now, because it was running the other day, after the intake manifold swap. so im just confused as to what changed from a week or 2 ago to now, a week ago it was idleing ok, and just needed to be adjusted to be able to be driven, but now it wont even idle. the only thing i changed since then was the alternator, because it was a bad alternator and needed to be fixed because i couldnt troubleshoot my car because the battery kept dying before i could test anything. hopefully this information helps. thank you very much.

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I wouldn't reuse the gaskets but they shouldn't be causing THAT much of a problem. Check one of my earlier posts about what should have line running to it to check. I wouldn't be checking without at least 5 gallons of gas. As far as the yellow colored gas, you probably have some rust in the fuel tank. I'd make a few trips to give her at least 5 gallons before going through anything else.

 

No pictures uploaded. Make sure you click to "Insert in post"

-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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The vacuum booster is the large diameter can the brake master cylinder attaches to, provides the power brakes, and has the large hose running from the vacuum tree at the back of the manifold. It would probably take a vacuum leak that big to make it stall.

The wrong carb spacer, say one for an EGR and you don't have an EGR valve, will cause a huge leak. The PCV line and valve is also a potential source for a large leak, if not properly connected.

 

The other vacuum lines run to the vacuum advance on the distributor, the vacuum modulator for an automatic transmission, and to a vacuum reservoir if you have an air conditioner. I don't believe any of these are large enough to cause a leak big enough to kill the engine that fast.

 

 

“If you can't explain it simply, you don't understand it well enough.”

--Albert Einstein

 

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If you want to be a real bush mechanic, just get someone to hold a piece of carboard so the air from the motor's fan won't interfere and just light a smoke and move it around slowly around the manifold... You'll soon see the smoke being sucked in if you have a leak...

Do the whole manifold and then also do all the other fittings connected to the manifold if you don't want to unplug stuff...

Image3.png

Jim

 

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Hi everyone , I took several videos and I have been trying to upload them and I cant seem to figure it out, when I try to post them it says that the attachment isn't allowed... im not sure why. anyway, if someone could help me figure out how to post the videos that would be good because I took videos of me trying to start it and a walkthrough of my engine and everything so that everyone could see what I was working with and hear what it sounds like.

anyway, I tried the idea of masking off the top of the carb with duct tape to keep any air from going inside of it at all, and it didn't run, or even start. so I need to have at least a small amount of air going through the choke in order for it to start, which means vacuum leak is less of a suspect. once I took the duct tape off and opened the choke about a 1/10 inch then it fired up and ran for about 40 seconds, then eventually died randomly. to keep it alive for those 40 seconds, I had to mess around with the choke. when it was loosing RPM I closed the choke more and it picked back up, and eventually after about 40 seconds of that it died. I checked some of the vacuum lines, the big drum looking think that the master cylinder attatches too ( I think it might be called the vacuum booster or some thing) and the line was good. the grommet that connects that tube to the drum think was cracked, but it was still air tight I believe, because when I removed the hose to check if it made a difference, it didn't run for more then 2 seconds. so that tells me that that hose is ok, and there are 2 more hoses other than that one , on the vacuum tree. both of those hoses I looked at and there are no cracks in them either, and there is a 3rd nozzle on the vacuum tree that is capped off. all together on the vacuum tree there are 4 nozzles, 1 is the vacuum booster ( the big circular drum thing) and 2 others go to different things that I am not sure what the name is, and the 4th nozzle is capped off. it ran before without that one connected to anything, so I doubt that's a problem , im just telling everything I know. I checked the pcv tubes, one is good and the other pcv thing I switched out for a breather so its not a tube anymore, so that's good also. I sprayed starter fluid around base of carb while it was running and I didn't notice any dramatic change in rpm, I might have heard a small amount but it could have been just in my head. I switched around the carb spacer thinking I could have had it on backwards, so i flipped it around and put it back on and now i think it is definitely on wrong because i am unable to push the throttle cable back. so i will flip that back around, and while i am at it i will replace the gasket. how would i know if i have the wrong spacer? it fits exactly right and looks exactly right. alright let me know what you guys think, thank you so much for all your guys help!

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I'd say not worry about the video, just post pictures. I'd sure move that timing down a good bit as well.

-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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Have you confirmed that you are getting a proper amount of fuel to the carb? That should be your first job.

You stated that you put 1 gal of fuel in the tank and that the fuel that came out of the pump into the plastic bag looked " too yellow".

Follow the recomendations that several people have posted and confirm that you are getting enough fuel to the carb.

I would try running the car off a 5 gal can connected to the fuel pump and see what happens. Then you know you have 1) enough fuel to start with and 2) clean uncontaminated fuel.

Then you can start looking for vacuum leaks and/or timing issues.

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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

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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

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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

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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.

 

 

“If you can't explain it simply, you don't understand it well enough.”

--Albert Einstein

 

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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.

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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!

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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.

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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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!

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