81 FI runs out of gas but 3/4 tank full

[whiterabbit]

I topped it off this morning and ran the p*ss out of it non stop with the gas cap just laying on the filler neck. At about 1/2 tank it lost power/sputtered to a stop. Can't be vac lock. Maybe electronics over heating? Checked the connection to the control module behind the coil. It's good but the coil was hotter than hell . It's the original. Could barely touch it. Coil overheating maybe? Was planning on upgrading the coil and module this winter anyhow but might have to push my plans forward a few months.

[bobplyler]

When it dies, are you getting spark? It's easy to check.

[aj81spider]

If it's electronics overheating then it should start with the half tank after everything has cooled down again. If it doesn't start the next morning with a half tank then it isn't overheating.

[whiterabbit]

Going to swing by the parts store and grab an Acell 8145,MSD 8202, or Mallory 29216 coil and a 4 pin ignition module Acell35361 or Mallory607. Been searching the posts here and it kind'a sounds like a coil or module problem. Module connector did come loose a few months ago on the road. Fried it maybe?? From dealing with kantankerious motorcycles (old Harleys),I've realized the carb gets blamed for alot of ignition problems. Soooo, hiho,hiho,it's off to the parts store I go..

[dfuehrer]

I have a thought for you here... Perhaps you have an older piece of rubber fuel line SOMEWHERE that is flattening out under the slight vacuum produced on the entire fuel system as it runs and the level of the tank goes down?

i just had a "visit" from an old friend last night. The '79 MG I sold when I bought my Spider. It had a weird stalling problem when i sold her. I scratched my head for 2 years over it and never figured it out. The new owner told me he discovered that there was about a 1" (straight) length of fuel line that would suck flat and starve the engine at any given moment. Who would have thought that that short of a piece of line would be so troublesome?

Might be as simple as that on your car. I would replace any old fuel line I had not already replaced myself, even if it looks good on the outside, with new from the tank to the carb (where ever there is a rubber or plastic line).

My 2 cents...

[whiterabbit]

Thanks for the advice. I checked all the hoses on it and replaced all the rubber lines from the tank to the filter. The only soft and mushy line I have now is the one that goes behind the engine to the heater hard line from the intake. Don't know how you're supposed to reach that darn thing! I need a trained monkey with a flashlight to loosen that clamp!
Picked up a coil,module and wires today. The battle of witts continues!

[124JOE]

when mine started to stall out often it was a small break in the insulation on one of the wires to the dizzy.
shorting out whenever it felt,and just died then id crank and nothing no spark. i taped it all up and no more problems.joe

[124cso]

I have a thought for you here... Perhaps you have an older piece of rubber fuel line SOMEWHERE that is flattening out under the slight vacuum produced on the entire fuel system as it runs and the level of the tank goes down?

...

This is unlikely as the fuel system on a FI car is pressurised from the pump forwards and all the way back to the tank. The Vacuum tap off the plenum box just controls a bypass valve but that line is pressurised.

[So Cal Mark]

on an FI car it is possible to have a hose that has inner deterioration and if a flap of rubber is torn it can be affected by fuel flow. Usually the deterioration ends up plugging the injectors