Technical X1/9 stalls low rpm - runs fine high rpm

[erisajd]

OK - this car sat for 14 years - has been fixed up to run [clean fuel lines, new brakes, new belts, plugs, rotor, wires, cap etc.] We have verified ignition, at least at idle and revved up standing still. Timing fine, vacuum advance works (using the old suck the hose method!] all vacuum hoses are brand new.

This cars runs GREAT - does not overheat, but has a chronic problem with stumbling, stalling etc.

What happens is that it runs fine and then all of a sudden the engine stumbles and loses power. I'll pull it out of gear and when I hammer at the accelerator pump it'll catch and then run fine up high above 3500-4000 rpm. But when I ease up to put the clutch in, it stumbles and will not run at the lower RPMs needed to get and keep the car going.

This is a pretty constant problem now and seriously affects driveablilty and my desire to drive away from the immediate neighborhood.

So, the fuel filter shows about 1/2 full when the engine is idling and does not get any more fuel in it when I goose it - but when it is idling it will run fine and rev up fine with that amount of fuel in the see-through filter.

I am thinking carb . . . after sitting all those years there was probably dirt or sediment in the gas tank [this gets worse going up hill] and the float or jets are getting plugged and not delievering fuel except when the secondaries are open. I have an extra carb that I can rebuild and swap out - but does anyone have any experiences or ideas- I do not want to go thru the effort of rebuilding a perfectly good carb [I know - there is no such animal] .

This 'extra' carb had a problem with the fuel return line being inop - so all fuel was returned to the tank instead of going into the carb - is this fixable???

Also, how EZ is it to drain and flush the fuel tank???

thanks - Joe

 

[polecat]

Could also be blown inlet manifold gasket or similar.

There is usually a drain plug on fuel tanks, this is sometimes flush fitting and hard to find, especially when painted over with underseal. Not sure about X1/9.
If its a plastic tank then you will probably have to drop it and wash it out with paraffin.

 

[scaltec]

got grit in the needle valve ie float chamber its a pain when it hapens it picks it up from the fuel tank from being stood for so long

 

[erisajd]

compression is fine - intake manifold gasket??? howzat gonna create these symptoms??? over lean I can see -

 

[Mr. X]

It could be you are having a vac leak when the car is running... like a cracked hose that happens to move in the wrong way when the motor torques over... Or the intake manifold leak...

The X tank does not have a drain... it is easily removed "IF" you can get the car leaning high enough on a side angle to drop it out the bottom...

Does the problem only happen when you are driving it or does it also happen in the driveway? At speed? only when hot?

 

[erisajd]

I think that we figured out the main issue - now the repair . . .

The engine is running too lean. [Like I said - I replaced ALL of the vacuum hoses with NEW hose - not the problem]

With the air cleaner off @ normal op temp, when I closed off the choke butterfly RPM increased immediately and the engine ran smoothly, albeit at a much higher RPM.

When I opened the valve, it again stumbled. When I then took at tie and tied the butterfly closed and drove the car - it drove PERFECTLY. No loss of power, still not real good acceleration, but no issue with stalling or running rough. Lack of power was apparently lack of fuel.

So, issue is - what caused it to all of a sudden run lean to the point of not running?

any ideas??? Idle mixture and idle are set -

Plugged jets? float problems? Dirt?

Joe

 

[VanHine]

you probably need to rebuild the carb and you do need to clean out the gas tank because after 14 years if there was any gas left in it it will be quite nasty, also check the fuel pump to verify it is working properly