Desperate for help re fuel starvation

[rjahunter]

Still got major problems with fuel flow. Can't even get from home to my mechanic pal to get my suspension fixed and getting a bit terminally fed up.

i get random good running and then lose power - feels like going down to 4 cylinders. When I stop and then put the ignition back on the fuel pump is thrashing away (and ticking like mad) in the boot. Tonight when I was checking fuel the fuel lines, I find that the pipe from the tank to the pump is firm and under pressure, but the one to the engine is soft. When I pinch the one going to the engine, the fuel pump immediately stops ticking.

I'm out of my depth here. I feel it could be a duff pump, or the wrong one, or a carburettor issue, although they've been stripped already. What is generally felt to be the best pump on the Stag ?

Someone tell me it would be impossible for the engine to get any petrol if the pump was running backwards.....

Any thoughts from you long suffering experts ?

Richard

[therat04]

Still got major problems with fuel flow. Can't even get from home to my mechanic pal to get my suspension fixed and getting a bit terminally fed up.

i get random good running and then lose power - feels like going down to 4 cylinders. When I stop and then put the ignition back on the fuel pump is thrashing away (and ticking like mad) in the boot. Tonight when I was checking fuel the fuel lines, I find that the pipe from the tank to the pump is firm and under pressure, but the one to the engine is soft. When I pinch the one going to the engine, the fuel pump immediately stops ticking.

I'm out of my depth here. I feel it could be a duff pump, or the wrong one, or a carburettor issue, although they've been stripped already. What is generally felt to be the best pump on the Stag ?

Someone tell me it would be impossible for the engine to get any petrol if the pump was running backwards.....

Any thoughts from you long suffering experts ?

Richard

Hello Richard i had a problem like this last year, i found i had a couple of problems, one was the pump which was only working intermittently, then it would be fine for a while then start playing up again, the other problem was a faulty fuel inertia switch which i temporarily bypassed.
I purchased a new fuel pump and fitted that, I have also fitted a new fuel inertia switch and i have had no problems since.
Just some thoughts Richard that are probably worth trying as your problems are very like mine were...Steve

[Firept]

Richard.
From you description it sounds like the pump is not picking up fuel.
2 things have you noticed if you open the fuel filler cap is there a sudden in rush of air sound? if yes then the fuel tank breather is blocked you can try running with the fuel cap slightly open dont go to far as it should always be shut. 2nd point have you got some rubbish in the tank that is floating around so that every so often it blocks the pick up pipe and when you stop, turn off the engine it settles back on the bottom of the tank. Last point what have you or any one done to the car recently as its a good starting point if it was OK before.

Paul.

[wilf]

Not many things to check, so logic should help you.

Fuel filter (under bonnet) - should be completely clean. Cheap thing to change so worth doing anyway if you never have.

Pump output - drop off the hose from the fuel filter to the carbs and put a suitable container under it and turn the ignition on (carefully!) - you should see a healthy flow of fuel and if you block the outlet off with your finger, feel the pressure being built up. Maybe have a helper here to turn the ignition on and off, or use the inertia switch to start/stop the pump yourself.

Blocked tank vent as above.

Collapsed (internally) fuel line fump to filter.

Sticking needle valves in the carbs (unlikely both would do it at the same time?)

Blocked tank pickup pipe as above.

Just work through he list, doing one thing at a time, and you should be smiling again soon.

[rjahunter]

Thanks for all these helpful ideas guys. I've been thinking over it and I'm going to start with the pump. I wonder if the mesh filters in the banjos are full of crap as I don't have the filter fitted between the tank and the pump which I think I need to change (didn't do it originally as it was a new tank). The fuel lines are all new so I'm not concerned about damage or collapse there. I don't think it's the inertia switch as the pump always runs flat out - it just clicks away all the time like it does when it's "pressurising" the system, and that's why I wonder if it's only getting a dribble through its output and thus the pipe to the engine is "soft" as I described. I'll post again when I make any progress. Richard

[pcoleman]

Hi Richard, you need to work through this problem methodically and eliminate 1 suspect at a time.I had similar experience and changed the pump for a new electronic type from LD parts and noticed the fuel filter in the engine bay was always full of fuel whereas before it was never more than half full. be aware that the carbs operate by feeding 2 cylinders on each side of the engine so if it feels like firing on 4 cylinders you may have still got a sticking needle valve on one carb,even though they may be new. bypass the fuel cut off switch by joining the two wires together to eliminate this as a problem.by compressing the engine bay fuel pipe you are creating pressure in the system and telling the pump to stop pumping. you may want to use a new lead from distributor to coil as this can give total failure as you describe ( this was 10% of the problem on my car ) if it was my car I and non of the above worked I would try the more obscure causes such as changing the fuel feed pipes all the way from the tank to carbs then fix a temporary fuel tank in the boot and pump from this to eliminate the tank. Dont try this unless you feel competent to do it safely. Dont overlook the fact that some new parts don't work as they should so never assume "it cant be that cuz I've changed it" good luck and let us know how you go on with the old girl.

regards. peter

[Princejohny]

Hi Richard,
To eliminate a potential fuel pump, tank and collapsed/blocked pipe problem a few years ago on my dad's V8 Rover, we used an old petrol lawnmower tank mounted high on the garage wall, next to the front of the car and ran a petrol proof pipe to the T joint, before the twin carbs.

I think it came from a Suffolk Super Colt and had a flow control valve to switch it on and off
No fuel pump was needed because it was gravity fed and enough pressure for the carbs.
On this occasion, the old V8 ran fine and trouble finally traced to pipes being gummed up with lack of use/evaporating old petrol from standing. Had to replace fuel pipe.
Cheers Johny

[V Mad]

......Tonight when I was checking fuel the fuel lines, I find that the pipe from the tank to the pump is firm and under pressure, but the one to the engine is soft.
Richard

Richard, the pipe from the tank to the pump cannot be under pressure, in fact it will be a very slight vacuum because the pump is sucking fuel from the tank. The one to the engine should be under a small pressure of about 3 psi when the carbs are full and needle valves shut. I dont think that feeling the hoses will help you.

You say when you turn ignition on fuel pump is ticking away like mad? Well if it doesnt slow down and virtually stop after about 10 secs then something is wrong; possibly carbs are flooding, or pickup pipe is not picking up fuel (air leak, low fuel, blockage etc etc. )

As the others have said, do some TESTS to see what is happening. First take off fuel pipe after filter and see if there is good fuel flow. Fill a small jar in 30 secs or so.

[staginhiding]

Hi Richard,if its the filter in the boot area you are talking about,it doesnt circulate fuel,its part of the venting system
Also your pump should not be ticking away all the time.If its ticking the same as when you first turn on(initially) your problem might be right there somewhere..

Thanks for all these helpful ideas guys. I've been thinking over it and I'm going to start with the pump. I wonder if the mesh filters in the banjos are full of crap as I don't have the filter fitted between the tank and the pump which I think I need to change (didn't do it originally as it was a new tank). The fuel lines are all new so I'm not concerned about damage or collapse there. I don't think it's the inertia switch as the pump always runs flat out - it just clicks away all the time like it does when it's "pressurising" the system, and that's why I wonder if it's only getting a dribble through its output and thus the pipe to the engine is "soft" as I described. I'll post again when I make any progress. Richard

[dasadrew]

Richard,

I'm a bit surprised when you talk about "soft" fuel lines where you can feel if they're under pressure and which can be pinched shut. My fuel lines are metal or hard plastic and the only rubbery connector bits could only be pinched shut in a vice. I'd be worried that one of your fuel lines could be pinched or bent over on itself somewhere or even sucking themselves shut when they see a small vacuum if they are really so soft.

Drew