'73 911T engine hesitation on acceleration

[rgv67]

Hi!

I have owned and driven this car since December 2015. It has the original 2.4T engine with MFI. Two months ago, I noticed engine hesitation on sudden/heavy acceleration on all gears. I had the fuel tank cleaned (basic cleaning only using sand and gasoline as media, 2 people shook it back and forth for 1 hour) and had the old fuel lines checked for clogs, etc. Fuel pump pressure tested fine as well. Engine hesitation went away.

Yesterday, the old symptom came back after some spirited driving on the hills. Engine hesitates on sudden/heavy acceleration but is fine on final gear and idling.

I am thinking of having the same fuel lines re checked and the old fuel tank cleaned again. I'm having doubts on replacing my fuel pump because the pressure test came out fine, but the discernible noise on the pump makes me think otherwise.

What could be causing this engine hesitation?

Thanks in advance.

Randy

[RSTarga]

You put sand in the tank?
Check all your fuel filters including the one on the tank. Change all rubber fuel hoses.
Check your timing and dwell.

[rgv67]

You put sand in the tank?
Check all your fuel filters including the one on the tank. Change all rubber fuel hoses.
Check your timing and dwell.

Thanks for your inputs David. Sand was supposed to act as abrasive to loosen rust inside tank. They used a lot of gasoline to flush out the sand.
I will replace all rubber fuel hoses since I think they have not been replaced since new.

Thanks again!

[classic]

Ummmmm sand, really????

[rv1967]

Ummmmm sand, really????

I know Tony it sounds stupid :-). We used coarse sand and I have yet to find out on how effective the flushing was. I will let you know once we get to the tank again this week.

Randy

[steve shea]

You should use shot for loading shotgun shells. You can buy it by the bag at hunting supply stores. Try it next time. About BB size or bigger.

[Frank Beck]

What could be causing this engine hesitation?

The low compression from excessively worn pistons and cylinders?

Sand? What part of Arkansas do you hail from?

If you're not kidding I would do a leakdown ASAP and not run the engine another second.

Is it smoking?

[rv1967]

Thank you Steve and Frank for the tip. Let me see the condition of the tank and I will let you know after.
Engine has just been recently rebuilt when I got it last December, does not smoke, and pulls fast. This hesitation happened the next day after a spirited hillclimb. Like I said, same old symptoms before I cleaned the tank. Right now, I'm thinking of the tank and the old fuel lines. I will sort them out this week.

Thanks again!

[rv1967]

Hi everyone!

We split the tank open and found a lot of rust inside. The swirl cup contained more rust when we opened the lid. I couldn't tell if some of the fine particles were sand left from the initial cleaning though. Cleaned and and scrubbed everything until bare metal showed up. Also blasted the lines with air, and found more fine debris! We welded the tank back and painted it in similar colour as the old patina.

It now runs nice and smooooooth!

Problem solved.

Thanks everyone for your inputs! Good people, great forum!

Randy