Best way to find carburetor vacuum leak

Use an UNLIT propane torch. Just open the valve SLIGHTLY and move it around the area you think there is a leak. When you hear the engine rev up your near the leak.

When was the gas filter last changed?

You can spray WD40 around the seams in a running engine, otherwise folks use a smoke generator that blows smoke into it.

Mike

Not sure when the fuel filter was changed...the car has 2 of them, i replaced one, the other is old. The float bowl seems to stay full of gas, though.

I can't keep the engine running for more than a couple seconds so I can't really check for revving.

I tried blow> When was the gas filter last changed?

Thanks for reply. I can't keep the engine running long enough to do this, it dies within a couple seconds regardless if i'm giving it throttle or not.

Masospaghetti wrote in news:emf4df$idh$ snipped-for-privacy@news-int2.gatech.edu:

me thinks you have a problem not of vacuum leak origin. even with the brake booster vac hose open (large vac leak) you should be able to run engine with throttle opened up. BUT, a non flammable vac leak finder = shampoo bottle full of water, squirt it around suspect area and you will hear it start sucking water when you find leak.......whistling you mentioned may equal exhaust stoppage. all that goes in must come out grasshopper...............

First, determine if you do even HAVE an intake leak. Hold a piece of notebook paper over the carb--not air-tight, but just enough to 'choke it' a bit while someone else starts it. By varying the amount of air you allow into the carb, you should be able to keep it running if it does have that suspected leak.. IE, by letting in less air, you are making it run richer to compensate for any intake leak which makes it run too lean. Then, when you get it levelled out(assuming you find it to have an intake leak) , spray your wd-40 or whatever around possible-leak areas. When you reach the leak, as others have said, the engine will suddenly speed up (or if you now have correct flow of gas/air by use of paper, it may try to slow down from suddenly being way too rich!). Anyway, when the spray hits the leak, the rpm's will try to change quickly. HTH, s

Your symptoms are more likely fuel starvation than a vacuum leak. Even with a vacuum leak, you should be able to make it run with throttle.

I would change the fuel filter before spending any more money or time on it.

Mike

Masospaghetti wrote:

If you suspect a clogged fuel intake as some suggest you could disconnect the fuel line and crank the engine (mechanical fuel pump) or just turn the key in the ignition (electric fuel pump). You can also take off the air cleaner and look into the carb while pullign on the throttle control to see if a jet of fuel squirts into the trottle with every pull.

Just for the record, another way to search for vaccum leaks is to use a water mist from opne of those house plant sprayers. That will slow the engine down if there is a leak.

In your case you might try sealing all the hose connections with by wrapping them with masking tape to see if that stops the leak. If ti works then remove them one by one to see which causes the problem.

Can we assume you'e done a carefull visual inspection of the hoses, pinching them between the fingers to check for cracks, and pushign each onto it's connector in case one is loose? I sometimes have hoses come loose when I'm working in the engine compartment. It's so crowded in there I don't notice if one has been jarred loose.

I have checked the hoses and have not found any that are broken. I tried disconnecting the fuel line and cranking; a LOT of fuel came out. Its definitely not starving for fuel.

I tried spraying both WD40 and carb cleaner around the suspected leak areas and did not find anything.

I did try disconnecting the vacuum lines and taping them off and seeing it the engine would run better. There was one line that made the engine somewhat better (it could be kept running with the throttle) but certainly not completely right.

thanks for your input. I appreciate any and all help.

-J

Wm Watt wrote:

I tried disconnecting the fuel line and cranking the engine and a lot of fuel came out. I dont think its starving for fuel.

I also tried putting some cardboard above the primary barrel and effectively choked the intake while a friend cranked the engine. it started and ran much better, it was racing at idle and didn't quit. So im thinking that points back at a large vacuum leak?

Thanks

-J

Mike Roma> Your symptoms are more likely fuel starvation than a vacuum leak. Even

That would almost have to be the brake booster blown or it's line with a hole in it. Maybe the charcoal canister if it has it or PCV line open also.

Mike

Masospaghetti wrote:

Honestly, reaching here, but does your carb have a fuel-pump mechanical spring operated, mechanically [throttle pressing] activated feed system? I realize I am reaching , but do you have a pump plunger? Or a fuel shut-off valve? It is mounted on the carb, a diaphragm and spring inside a plate, that is activated [pressed] by a mechanical rod or lever when you press the throttle pedal.

carb cleaner is best way to find vacuum leak..just don't spray on exhaust...unless you got a vacuum guage..if idles up when spraying you'll know your getting close too leak......

Take some clamps and clamp the hoses down. Does it start? Now start opening 'em.

--scott

It has never sounded like you have an engine that is starving for fuel so why do you have everyone looking for a vacuum leak?

When you do get the engine started and running for a few seconds, Does it produce any smoke out the tail pipe when it does run? Does it rev up and cut off immediately or does it just sputter along and slowly die? Does it take a lot of cranking and charging the battery to get it started? Why did you just install a different carburator? I'm guessing it wasn't because the engine was running beautifully before. It's best to describe the symptoms of the problem clearly and completely rather than asking "why is my solution not working?" The reason you can't find a vacuum leak is probably because that is not what is causing your engine not to run.

-jim

Whose idea was it that WD40 was a good product to use? It'll leave an oily residue everywhere you use it and that residue will be flamable.

Use carb cleaner instead. It'll evaporate and leave no bad residue.

Umm, we 'regularly' have to spray the 'insides' of our distributor caps when off roading in the Canadian bogs with a good 'water displacement' fluid and we use WD40.

If it left a flammable residue, our distributor caps would explode.

It 'does' have a flammable carrier when in spray mist form, but not once on the surface and liquid or evaporated leftovers, hence folks using it for vacuum leak detection.

Mike