Idle drop/fuel starved question

[Pro198]

Hi folks,
I’m pretty sure I’ve tracked an occasional idle issue to when the fuel is low in the tank. I don’t want you guys to beat this one to death but what are the simple things to check. It stalled a few times as I down shifted and rolled up to stoplight so I started to realize it might be starved a bit when fuel is lower. Performance when on throttle didn’t change.

Tony

[SkiVT]

I dont think fuel pressure or delivery volume changes at low fuel tank (1/8, 1/4 for example) levels. The problem would be tied to something else. My 83 euro died when the decel valve wasnt performing. A small adjustment kept the idle from dropping to zero with clutch engaged approaching stoplights, etc. Does this happen whem the engine is cold and/or warm? Have you checked the fuel pressures for warm, cold, system?

[steely]

Just in case your initial hunch is correct, you could inspect or change the tank filter.
Crud would be immediately evident. see pic. It is accessible under the tank and I forget the size, but you can use a spark plug wrench socket (the type with the hex head on top) to remove the filter screen. (with tank drained).

I'd recommend a search here to see how to inspect the tank from the top for crud or the condition of the tank wall itself. The float would have to come out and I've never done it, hence the suggestion to research it.

Check pressure like SKiVT recommends, change your filter, check out your pump, have your injectors tested/cleaned (if applicable) by an injector svc place.

BTW what year is yours?

[Pro198]

Originally Posted by SkiVT

I dont think fuel pressure or delivery volume changes at low fuel tank (1/8, 1/4 for example) levels. The problem would be tied to something else. My 83 euro died when the decel valve wasnt performing. A small adjustment kept the idle from dropping to zero with clutch engaged approaching stoplights, etc. Does this happen whem the engine is cold and/or warm? Have you checked the fuel pressures for warm, cold, system?

You are describing the exact issue better than I did. Tends to be when cold, but it didn’t happen for almost a week now regardless of air temp and engine temp. Now today with 1/4 tank it acted up. It appeared to have disappeared with a full tank and air temp was warm.

[Pro198]

Originally Posted by steely

Just in case your initial hunch is correct, you could inspect or change the tank filter.
Crud would be immediately evident. see pic. It is accessible under the tank and I forget the size, but you can use a spark plug wrench socket (the type with the hex head on top) to remove the filter screen. (with tank drained).

I'd recommend a search here to see how to inspect the tank from the top for crud or the condition of the tank wall itself. The float would have to come out and I've never done it, hence the suggestion to research it.

Check pressure like SKiVT recommends, change your filter, check out your pump, have your injectors tested/cleaned (if applicable) by an injector svc place.

BTW what year is yours?

Ok this is all within my scope and the prelim before more expensive. Thank you.
1978 911SC