Question about fuel starvation

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Model T Ford Forum: Forum 2010: Question about fuel starvation
Top of pagePrevious messageNext messageBottom of page Link to this message  By Mario Goldberg A. - Tenerife, Spain on Monday, November 22, 2010 - 03:19 pm:

Hello all,

Maybe it is a dumb question, but a so some of you said before: when working on the T, forget all you now about other cars mechanics.

Could I have the symptoms of fuel starvation, even though the carburetor bowl is full with fuel?, It is a 1923 with a Holly NH.

The engine quit, and I checked everythig, it has a distibutor, the spark looks OK, the timing is fine, the spark plugs are not fouled, there is compression in the cylinders, the carb has fuel but there is not much in the fuel tank, about 3 gallons; I pulled the carb out and inspected and looks OK.

But the engine wont start, so I asked again: it could be fuel stravation even if the carb bowl is full? maybe there is not enough pressure to vaporize the fuel?

If this doesn not work, I will revert back to fuel injection! :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Gelfer on Monday, November 22, 2010 - 03:40 pm:

If your mixture is too lean, the bowl will stay full, and you won't start. There could be some other kind of debris or clog in the carb too.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Christopher Lang - Brentwood Bay BC on Monday, November 22, 2010 - 03:42 pm:

I had this problem on my car, also with an NH. I removed the carb, and found that the spray nozzle had loosened. Tightened it back up, and away she went. Another time, I had the same trouble, and it was a piece of junk from the fuel tank, had gotten lodged between the spray nozzle, and spray needle. Both times, it took me a while to figure out what was happening, and a bright flashlight to look into the carb with, once it was off the car.

Just something to check.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mario Goldberg A. - Tenerife, Spain on Monday, November 22, 2010 - 04:00 pm:

Thank you for the answers but I adjusted the mxiture from lean to rich and fiddle with it a lot!

With the carb out I tried to dissasemble the spray nozzle and it was stuck so I did not want to force it, and without the spray needle you can see through the spray nozzle.

I have the carb out and I will work with it, maybe is what you say Christopher.

I have just purchased a fuel filter but the time consumed by tracing the trouble prevent me from istalling it; I will do it when I will put the carb back on.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Harry A. Daw on Monday, November 22, 2010 - 04:16 pm:

Mario, some might not recommend it but in such cases I have closed the choke as much as possible and cranked the engine until fuel dripped out of the carb. When this happens I am pretty sure that it is getting fuel.
Sometimes professional mechanics will take a propane torch (unlit of course), crank the engine while letting propane into the air intake. But please be careful since you may have raw gasoline coming out of the carb or in the case of propane, highly explosive gas. Definitely not something to try inside a garage.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert Conner - Sanford, NC on Monday, November 22, 2010 - 06:27 pm:

I was thinking something along the same lines as Harry, except I would use something like carb cleaner. Spray a little into the breather side of the carb and see if it will run. Another way is to to take a VERY small amount of gas and pour it into each cylinder, I'm talking about 1-3cc like what you would get out of a medicine dropper. If it fires and the quits in either scenario, fuel isn't getting into the engine for whatever reason.

I had an updraft engine do this to me a couple years ago, and I had talked to some people about it. One thing that came up was the fact that the intake was made of cast iron, and that if it had been sitting where water could get on it for a long period of time, it wouldn't let gas flow through it since it would be soaking it up faster than the vacuum could take it. They said to soak it in gas for a few minutes then try it again. I thought they were crazy, but after messing with it for another hour and a half in the middle of the summer, I decided to give the insane a try. I splashed a little bit of gas on the manifold, let it set for a couple of minutes and it started on the first try.

I wouldn't recommend the gas on the manifold, but I was wondering if anyone else had heard of such a thing. I don't know if it really soaked it up, or if it just ran through a small whole. That engine never gave me any problems after that.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Peter Claverie on Monday, November 22, 2010 - 06:38 pm:

You didn't say whether this problem suddenly arose after the engine ran well, or whether it has not run well since major work or sitting a long time.

I'll take a shot at the scenario that it either sat a while or major work was done on it---

Your intake manifold could be blocked or leaking. It could be a nest (wasps or their cousins) or a piece of trash that was sucked in, or an ill-fitting manifold-to-head joint.

The quick way to tell is to crank the engine with your palm over the carb intake. If it sucks hard enough to leave a red ring on your hand, this might not be the problem.

If it doesn't, then check for loose or blocked manifold.

Let us know what you find!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mario Goldberg A. - Tenerife, Spain on Tuesday, November 23, 2010 - 03:57 am:

I did not explain it properly, the engine was until that moment running well, the sitting period is long gone and it had no major work done.

I changed the bands a couple of months ago, because I sensed a lack of power and a little slippage, and was in the process of adjusting them, when it suddenly quit and did not start again. So the manifold is not blocked.

I also put a little gas on one cylinder and it fired when I tried to start it.

I also closed the choke for a while and fuel came out of the breather side of the carb when cranking.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Patrick Martin, Branch/Lafayette, LA on Tuesday, November 23, 2010 - 04:00 am:

Valve job needed?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Larry Smith on Tuesday, November 23, 2010 - 01:27 pm:

The problem I've found is the repro needle and seats. The seat is .100" on the repros, and is .125" originally.


Top of pagePrevious messageNext messageBottom of page Link to this message  By CharlieB-Toms River N.J. on Tuesday, November 23, 2010 - 02:16 pm:

Sounds like something in the carb Mario.You dump in fuel and it runs. That eliminates alot of other items. If fuel flow to the carb is OK you missed something internal in the carb. How about un-screwing the adj. needle and blowing thru the jet?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mario Goldberg A. - Tenerife, Spain on Tuesday, November 23, 2010 - 02:32 pm:

I blew trough every hole it has......

The nozzle was to tight to unscrew, I will try to loosen it and check.

I do not think it need a valve job, well not urgently.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Fred Dimock, Newfields NH on Tuesday, November 23, 2010 - 04:08 pm:

FYI -- Motors do not run on carb cleaner but they do a good job of removing dirt and buildup.

Since it fired when you poured gas in the cylinder I assume that the ignition is OK.

The next thing is to make sure the gas is getting from the manifold to the combustion chamber.
I'd try spraying a bit of starting fluid in the carb to see if it fires.
If it does the manifold is clear.

Next is the carb itself -
I once read an automotive repair book that boldly stated
"The Carburator is a French word the means Leave it alone"
but I don't believe it.

Most of the posts about cleaning the carb etc are correct.
The only thing I would add is make sure that the gas is flowing from the tank to the carb.


Top of pagePrevious messageNext messageBottom of page Link to this message  By CharlieB-Toms River N.J. on Tuesday, November 23, 2010 - 04:57 pm:

You probably have to loosen the clamp nut on the carb to free up the adjusting needle. It is tightened to keep the needle from un-screwing by itself. You can un-screw the nut and remove the needle with it in one step. Be aware that you have to un-screw the needle before reinstalling it to avoid driving it into the jet when installing. You can blow down thru the jet with a straw without removing the carb.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David J. Holland on Tuesday, November 23, 2010 - 05:19 pm:

All of the above, but if you installed a modern fuel filter it could be the problem. Not enough presure with gravity feed to have a good flow.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Tuesday, November 23, 2010 - 06:16 pm:

Check for a loose connection in your distributor circuit. Could be you are getting fire sometimes and sometimes not.

Another possibility is your cylinders are flooded. What do your plugs look like?

As for the Model T, forgot all you know about computers and remember all you know about engines and automobiles.

Start at the beginning and retrace your steps, you must be missing something. If you are in time, with spark, compression and gas in the NH you should be able to get it to start.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mario Goldberg A. - Tenerife, Spain on Monday, December 20, 2010 - 08:28 am:

Hi Fellas,

I have not still resolved this matter.

I checked everythig, compression, ignition timing, intake, and carb gaskets and I am going nuts.

Definitely I am sure that fuel is not getting to the cylinders, the spark plugs are dry and when I pour a little fuel directly on them, it fires.

I have taken out the carb plenty of times, and dissaembled and reassembled it, and everything looks OK, but there must be something I am not seeing.

Is there any passage or hole that could be blocked?

The needle and jet seems unobstructed, the float is OK.

Its been a couple of months and no progress.

It is no fuel pressure either.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenny Edmondson, Indy on Monday, December 20, 2010 - 08:59 am:

Mario, have you had the intake manifold off recently. I worked on a T that wouldn't start or run and I found the intake manifold was not seated on the copper glands (gaskets) properly. There was a vacuum leak bad enough that fuel wasn't being pulled into the cylinders. If you weren't so far away I'd tell you to send your carb to me and I'd check it out. Can you take some pictures of your carb parts and post those?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Dufault on Monday, December 20, 2010 - 09:34 am:

Hi Mario,
Frustrating sometimes, isn't it? Especially with the pleasant weather you are having, Christmas coming, and I'm sure there is a desire to take those beautiful daughters of yours for a Christmas drive!
After you have checked Kenny's suggestion, think about this.... you said:
"there is compression in the cylinders"
- but is there SUCTION ?
Take out a spark plug or two, and hold your finger lightly over the hole while someone activates the starter. If that works, then....Confession time for me...I once had a devil of a time starting my auto....went thru all sorts of checks (like you have done), then finally realized that I had one of the two gas line shut offs in the OFF position. Mental cramp, I guess...just completely forgot. Is/are your gas line shut-offs in the ON position? put a container under the installed carb, and undo the carb drain plug....assure yoourself that the gasoline flows freely.
Good Luck to you, and I hope that yoou soon solve your problem.
Merry Christmas,
Dave


Top of pagePrevious messageNext messageBottom of page Link to this message  By willie k cordes on Monday, December 20, 2010 - 12:03 pm:

Mario, a compression gauge might be a good to verify that you do have proper compression. A reading of 45PSI minimum is required. Leaky valves can cause severe starting problems.
Some auto parts stores used to have rental service equipment available to customers or just buy a tester, I do not think they are that expensive.
Leaky valves will also result in loss of power which you said you had.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis - Lyons, GA on Monday, December 20, 2010 - 12:49 pm:

Removing the drain cock from the bottom of the carb and letting the fuel flow for a several seconds into a jar or bucket will tell you whether you are getting gas to the carburetor in enough volume to run the engine. That should eliminate any fuel filter or inlet needle and seat problems.

Peter's 'hand over the carb inlet' trick should verify if you have enough suction to draw fuel into the cylinders.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Henry Petrino on Monday, December 20, 2010 - 01:29 pm:

Lot's of really good suggestions. IMHO, even if the flow from the tank to the carb is obstructed to the extent not enough fuel is flowing to keep the engine runing, a full carb bowl should contian enough gas to run the engine at a brisk idle for a full minute or two. After reading this string from start to its current end it sure sounds to me like it must be 1 of 2 problems:

1. There is an intake vacuum leak. This could be the manifold glands, but it also could be at the manifold to carb gasket.
2. The fuel mixture is not getting from the carb to the intalke manifold probably due to a problem or obstruction at the needle valve.

Cupping your hand over the carb and cranking it a turn or two (with switch OFF) will prove or disprove item 1. If it has good strong suction, then I'd pull the carb again and look for damaged part(s) and/or foriegn material.

Just my $.02. Good luck and let us know how it turns out!


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