Only runs for 30 sec...

[esquivelia]

71 series 2a runs only when using the manual prime on the fuel pump. Weber carb is rebuilt, new filter. Any suggestions would be awesome!

Thanks! Cory-

[SafeAirOne]

My guess is that your fuel pump needs rebuilding or replacement, since it doesn't seem to provide enough fuel on the normal stroke, but does on a comparatively lengthy manual (primer) stroke.

[artpeck]

Building on that it might be a worn cam arm which would cause the pump stroke to be short limiting the fuel pumped. That would I believe require a new pump.

Alternatively you might have a filter that is partially blocked and therefore the not enough is getting though on the regular stroke.

[Apis Mellifera]

Or the fuel pump lobe is worn on the cam.
Or the fuel pump drive lever is worn/broken.
Or the carb is jetted wacky such that the fuel pump can't provide the flow it needs.
Or the float jet is sticking closed and the priming pressure is high enough to unstick it and running pressure can't.

Check the fuel pump.

[esquivelia]

Well the fuel pump is new. I'm curious as to the thought that maybe the carb is demanding too much fuel;wouldn't that make the engine race...i'm confused.

I'm also curious about what actually goes on in the fuel tank and why the two fuel lines?

I like the sound of the smaller stroke idea but that would mean a worn cam on the cam shaft. Since it is a new pump and everything was working until it sat for a year this would have to be good timing for this issue to arise at this time.

Thanks for your responses!!

[siiirhd88]

If the fuel pump was recently replaced check to see if the arm is even reaching the cam lobe. I've found out that the later (no glass bowl) and aftermarket type fuel pumps aren't to use the phenolic insulator that mounts between the carb and engine block.....

It would run when the bowl was filled using the primer, but the cam wasn't actuating the arm.

Bob

[esquivelia]

It's the type with the glass bowl and the glass bowl is always filled. Also there is no insulator between the pump and the block, just a thin gasket. (I do have one between the carb and the intake manifold...was a little confused which you were talking about)

When I mount it I do feel it touching the cam shaft.

Also when it is running I can keep it running by actuating the primer lever.
When I do this I would think you should be able to feel the pump working and I don't really feel much...not sure if that matters or not.

[Terrys]

Can you pull the fuel line off the carb, stick it in a soda bottle and crank the engine to see if any fuel is being pumped.
Did you take the fuel pump off the engine? if so, did you put it back on with the lever to the outside of the cam.
Whwen you lift up on the priming arm, you won't feel the cam as the pump lever is being pulled away from the cam by the manual lever.

[siiirhd88]

Sorry, I meant the insulator between the fuel pump and block. That's not the problem if you don't have one anyway....

Bob

It's the type with the glass bowl and the glass bowl is always filled. Also there is no insulator between the pump and the block, just a thin gasket. (I do have one between the carb and the intake manifold...was a little confused which you were talking about)

When I mount it I do feel it touching the cam shaft.

Also when it is running I can keep it running by actuating the primer lever.
When I do this I would think you should be able to feel the pump working and I don't really feel much...not sure if that matters or not.

[esquivelia]

I will def try the soda bottle trick. I'm not sure I understand your question about reinstalling the pump. I could feel the bottom of the arm touching the top of the cam shaft.

Quick question...how full should the filter be?

I seem to remember it being about half full but now I can only get it a quarter at the most.

Thanks again to everyone!!

[Apis Mellifera]

Well the fuel pump is new. I'm curious as to the thought that maybe the carb is demanding too much fuel;wouldn't that make the engine race...i'm confused.

Without getting into flow vs. pressure relating to fuel supply, did the truck run with the carb before? Did you rebuild the carb AND fit a new fuel pump? Webers require a lot of flow at relatively low pressure. If you don't have the pump to match the carb, it can do a number of things including: flood the engine, blow out from the carb, cause a high speed miss, or run briefly and quit. A clogged fuel filter will do the last two as well.

The second fuel line is likely the vapor line. I don't know about SIIas, but my III (and other English cars of this vintage) use a second fuel line that runs to a charcoal canister in the engine compartment.

Unless you bought a Genuine FP, it could be that either the operating arm isn't shaped properly or the GPM/PSI is too low. However, it could be that the fuel filter is partially clogged. Try bypassing it. I wouldn't worry that the filter isn't all the way full. However, just because it has fuel in it, doesn't mean it is flowing enough.

[albersj51]

really dumb thought...didn't someone have a somewhat similar issue that turned out to be because the gas tank wasn't venting properly, causing too much pressure to build up?

[ccmohan]

Dual fuel tanks?

If you have dual tanks you might want to check the selector switch. I had a similar problem when the cork seal in my military fuel tank selector went bad - it was sucking air when wouldn't allow fuel to flow. I could manually pump fuel to the carb but when it was running it would stall after a few seconds.

[Sputnicker]

There has been a lot of discussion in previous threads about defects in brand new fuel pumps. These are the after-market mechanical pumps that look identical to the AC original. I gave up after two failures and converted to electric. Try removing the spark plugs and using the starter motor to see how much flow you get from the pump. Route the output hose into a glass jar. If you get low/no flow try Routing the pump inlet into a clean can of gas. If that yields good flow, then your problem may be the lines or venting from the tank(s).

[MikeJW]

Check the selector switch. I've just chased erratic starting/running problems I've had for the last couple of months to a leak at the selector. My fix was simply to bypass the switch.