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mike gaines
01-06-2007, 01:23 AM
Hi Guys, my current challenge is ; after travelling on the motor way for some distance at about 70mph ,when I get to the end of the motorway and decellarate , the engine cuts out , it restarts easisily but if I dont rev the engine it immediately stalls when I try to pull off.I have a 58 silverhawk with the standard mechanical pump. I am assuming it is a fuel starvation problem but is it caused by the pump not having sufficient pumping capacity to keep the carb level high enough on decellaration over an extended distance or could it be as a result of fuel evaporation in the line before the carb. Would an electric pump sort the problem and is this neccessary ?

chocolate turkey
01-06-2007, 09:04 AM
Mike, If the car is running fine at 70mph, your problem is not the fuel pump. I would suspect the carburetor, providing it is a fuel problem. I'm not much on carburetor problems, but I'm sure that someone else will chime in and help out.


Brian K. Curtis

CHAMP
01-06-2007, 09:32 AM
You could have a vapor-lock problem.

GARY H 2DR.SEDAN 48 STUDEBAKER CHAMPION NORTHEAST MD.

N8N
01-06-2007, 09:43 AM
I've found that this happens when "setting up" a car for the first time, the idle speed and mixture must be set with the engine *full hot.* Often idling in a driveway will simply not get the engine as hot as taking it out and driving it for 10-15 minutes; I'd reset the idle after doing so.

Also, is your car supposed to have a dashpot on the carb, and is it present and functional?

nate

--
55 Commander Starlight
http://home.comcast.net/~njnagel

John Kirchhoff
01-06-2007, 10:47 AM
I've had the level in the float bowl being too low cause problems exactly like yours. I'm not saying that's what your problem is, but if the carb has been worked on recently it could be. Otherwise, with years of use the fuel level tends to raise due to wear and age. I don't know what sort of additives are in your fuel, but over here ethanol is added to much of it anymore. On carbs built pre-1980, the alcohol would sometimes swell rubber parts, not always, but often enough that the rubber compound was changed. If you folks have any ethanol in your gas and you have an old carb or one repaired with an old kit, the rubber tip on the float needle could have swelled and thus lowers the fuel level.

In my experience, with vapor lock the engine usually doesn't start for a while. However, Champ could be on the right track. You might take a look at how close the fuel line exiting the fuel pump is to the exhaust manifold. I put power steering on mine and I don't know if I bent the line in the process or it was already that way, but the line is far too close to the manifold for my liking.

mike gaines
01-06-2007, 12:43 PM
Thanks guys , I will move the fuel line further from the manifold and see if this solves the problem. I didnt mention that I dont have this problem with normal non motorway driving , and it only happens when there has been a long period of coasting before coming to a stop.It also happens when I change down from 3rd to 2nd with the revs on the high side.Some times the starter has to crank more than normal to get the motor re started but not always.My car is fitted with a 4 barrel Holley and I dont know to much about carbs but it was reconditioned about 6 months ago.The car idles fine cold or hot.We dont have any ethanol in our fuel.

CHAMP
01-06-2007, 12:53 PM
You might want to check the fuel pump, not just the PSI but volume also.

GARY H 2DR.SEDAN 48 STUDEBAKER CHAMPION NORTHEAST MD.

Rerun
01-06-2007, 01:40 PM
Check to see that the fuel tank is properly vented. I had a similar problem due to a plugged vent tube. I don't know if your Hawk has a tube or uses a vented filler cap, but you don't want to create a vacuum in the tank as fuel is consumed.

Jim Bradley
'64 Daytona HT "Rerun"
http://home.earthlink.net/~bradley71771/images/Rerun.jpg

Rosstude
01-06-2007, 05:20 PM
Two thoughts come to mind, 1-too much fuel, or 2- too little fuel. Do you have to pump the accelerator in order to restart? Do you have any indication of flooding? I.E. having to hold the accelerator to the floor to restart, black smoke when it restarts, or having to rev-it up to blow out raw fuel prior to getting it to idle?

[img=left]http://i52.photobucket.com/albums/g27/Rosstude/11-27-061.jpg[/img=left]
Ross.
Riverside, Ca.
1957 Provincial X2
1958 Transtar

PackardV8
01-06-2007, 07:24 PM
If the carb functions well under hard acceleration, it is not low fuel level causing it to stall. Closed throttle decel uses next to no fuel compared to full throttle acceleration.

Look for problems caused by high manifold vacuum. High manifold vacuum causes a vacuum advance distributor to go to full advance. Could your distributor vacuum advance be sticking? Holley vacuum operated secondary throttle bores and power valves are connected to and operated by high vacuum. Did these problems start after the carburetor was reconditioned six months ago? Does your car have power brakes? Could there be a faulty check valve in the system? Check your intake manifold for leaking gaskets.

One other possibility is too cold spark plugs. Prolonged high RPM decelleration dumps fuel onto the plugs. If the plugs are too cold a heat range, the fuel literally douses the fire. Does the engine ever backfire on this decelleration? That is a sign of unburned fuel going into the exhaust system.

thnx, jv.



PackardV8

gordr
01-07-2007, 01:56 AM
Mike, I'd be inclined to suspect the fuel pump is overpowering the needle and seat, and causing flooding when you have a low fuel demand, as wheh decelerating. Might be pump pressure too high, or a worn needle and seat, or possibly the float not floating well enough in today's less dense fuel.

If you can get a fuel pressure gauge, try that first. I doubt vapor lock is the problem. That usually occurs after a hot soak, or in hard pulling in hot weather.

Gord Richmond, within Weasel range of the Alberta Badlands

mike gaines
01-07-2007, 01:48 PM
Thanks for the helpful replies, I have noticed a vacuum when I remove the filler cap , which is an aftermaket unit. I will drill a small hole into it in the morning. I have also found a leak in the left side exhaust manifold gasket where it joins the exhaust , will seal that in the morning as well.Also found that the pin securing the fuel pump lever to the pump body was sliding out of its hole by about half its length , I dont know whether this could have an effect but it was allowing oil to escape and I had thought it was the pump/timing gear cover gasket and have redone the gasket several times trying to sort the problem !The car does backfire on decellaration but it is more of a low burble than actual back firing. Unfortunately the car was not driveable before the carb refurb.The plugs in the car are Champion H14Y and are burning quite a dark brown colour , I have adjusted the mix to run a little leaner to see if the colour wont lighten a bit.

mike gaines
01-10-2007, 02:04 PM
A small hole in the filler cap sorted the cut out problem and sealing the exhaust leak required re setting the mixture on the carb. Thanks for all the help.