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]

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.

[esquivelia]

Wow! I didn't see this had gone to a second page. All of your suggestions seem very much worth trying out. I will try a few this weekend.

Just to recap: Rebuilt Weber carb, new replica pump; the glass bowl type, new fuel filter.

Thanks again for all the input..will report back! :thumb-up:

[esquivelia]

Still no results...next step, electric fuel pump. I'm going to mount it close to the fuel tank with an inline filter just before the pump. Probably pick one up at Pep Boys. If anyone has any suggestions for me fire away. I saw that they had a few models there. I'm not sure what I should be looking for as far as the specs of the fuel pump.

Both fuel pumps (the old one and the new one) move fuel when I manually pump them either with the priming lever or the actual arm. This leads me to believe that maybe I have a worn lobe on the cam shaft.

Thanks! Cory-

[esquivelia]

also...I haven't even thought about wiring the fuel pump. Not sure where to tap into. :confused:

[albersj51]

Ill try digging up my part number for you. I ran it off of the ignition so that it comes on when I turn the key.

[I Leak Oil]

Napa used to carry a relay that you could use to tap into the oil pressure idiot light. That way if you're in an accident the pump will shut off when the motor does. Even if you don't use something like this run a dedicated fused circuit.

[SafeAirOne]

In the 109 6-cylinders, they ran the factory electric boost pump right off the white primary wire for the coil.

I seriously doubt that the cam lobe for the fuel pump is worn out. Do you realize what it would take to wear it down to an extent that the pump becomes ineffective? You'd have to have play sand in the oil or a cutting edge on the pump lever for that to happen IMHO. I'd suggest you look elsewhere for the cause of your fuel supply, personally...

[Sputnicker]

I did a pretty thorough web search on electric pumps and decided to use the Facet Posi-Flo. They are available at NAPA. Get the lower pressure version (1-4 PSI). Here's a link:

http://www.facet-purolator.com/images/technology/hd_pdfs/Posi-Flo_sheet.pdf

[Wander]

That's the one-low pressure pump should be about $50. Mine is directly down line from the tank and mounted on the seat box front wall. I'm not crazy about this spot as it is just above the tranny and transfer case so if I had a leak it could get ugly. I've seen others place it along the frame rail.

Mine is wired wih the ignition-turn the key and you can hear it pumping away. Having the return line will be great with an e-pump and a webber. You'll need a filter with a bypass to run the return line from. This will help you avoid vapor lock and dieseling aftger shut down when it's warm out. The new fuels with the alcohol don't burn off as much and so I get dieseling after shut down as I don't have a return line to the tank.

[kevkon]

I seriously doubt that the cam lobe for the fuel pump is worn out. Do you realize what it would take to wear it down to an extent that the pump becomes ineffective? You'd have to have play sand in the oil or a cutting edge on the pump lever for that to happen IMHO. I'd suggest you look elsewhere for the cause of your fuel supply, personally...

X2
I doubt it too. I know that many have had issues with some of the replacement mech. pumps, but there should be no reason why a properly functioning one can't do the job. Especially since these carbs don't need much fuel and don't like much pressure.

[Apis Mellifera]

I wouldn't rule out a worn cam. Anyone who has taken apart an MGB engine will likely have found a very worn cam. I've seen lobes basically worn round. That said, it's a gradual problem. What specifically has changed since the truck last ran well?

I have the above Facet pump on my MGB and while it works well, it makes a continuous audible buzz. For this reason, I do not care for the pump despite the fact that it works well. I would recommend an SU fuel pump or the replacement mentioned here:

http://www.mgexperience.net/phorum/read.php?1,1638176

Facet pumps are also discussed.

[bobzinak]

I too had a problem with a new fuel pump. worked like a champ when I first rut it on, but over a period of weeks my power and top speed started dropping. to the point where it would barely run. turned out that one of the small one way valves was shut and no amount of fiddling would let work. a proper fuel pump should develop a good amount of both suction and pressure. if you have the pump off the suction side should hold your finger, in the inlet, the pressure side push air out around you finger. it seems to me that if you can run it with the manual primer says that your not getting enough fuel. I had one pump that had a bad valve an the fuel would bleed out of the line when it sat for awhile. also make sure that the two small flat wedges that hold the pump pivot pie are properly peened in place.I don't think the problem is in the camshaft. and unfortunately even the best parts can have defects. Hope this helps. bobzinak.

[cousindave]

I have had the facet pump and now I have a mr gasket pump. Both are great pumps! Went mr. Gasket when facet died after 8 years of sucking rust through the pump with no filter or screen to the pump. Don't forget to get a pressure regulator and relay while you're at it.

[gudjeon]

I tried the mechanical and had 2 fail to work from new. I had it and went to an electric from Napa and created my own recirculating system. No more vapour lock. It keeps the fuel constantly moving, filtered, and under pressure right up to where it needs to be. Modern fuels are made for high pressure injection and are not suited for carbs. New fuel is more volatile in an open carb system and gets worse with heat and altitude. I used a lower pressure pump from Napa (made for carbs) and a recirc filter from 1980 Chrysler spec. I did not even worry about mounting it low and it work just fine.

P.S. its on the bulkhead.:thumb-up:

it ain't pretty, but it works pretty good.
http://i35.photobucket.com/albums/d187/gudjeon/fuelpump1-1.jpg