Fatah is widely criticised as corrupt and ineffective
Palestinian Authority President Mahmoud Abbas's Fatah faction's first congress for 20 years has been extended amid rows between rival camps.
The meeting, which was originally scheduled to last three days, will go on for at least an extra day.
A spokesman described the meetings as "stormy", as delegates argued over voting procedures.
Younger members want to wrest more control from older leaders seen as corrupt and ineffective.
Participants have been divided over the process for voting in new members of Fatah's powerful 21-member central committee.
Delegates seeking to modernise Fatah have also accused the "old guard" of packing the conference with sympathisers to squeeze out younger members.
Tim Franks, BBC News, Jerusalem
After yesterday's "stormy" day, Fatah delegates decided to cool off today with a four-hour lunch-break. The message had clearly also gone out that now is the time to be more upbeat, and less angry.
Hazem Abu Shanab, Fatah's spokesman from Gaza, had just emerged from the morning session. "After the storm, we have rain," he said, approvingly. He changed the metaphor: "We are about to deliver a new baby. The baby will be very shiny, smiling, beautiful: the new Fatah, with the new leadership."
Voting for that new leadership may now drag on until Friday evening. And that could mean this congress could well creep, unscheduled, into Saturday.
But the approach seems to be: hang the timetable, we need the catharsis. One delegate, Mohammed Khorani, said it was only to be expected that after 20 years, "there should be some hard conversation, some angry feelings". But Fatah's poor image and self-criticism will abate, he insisted, "when we have a new leadership".
They accused those who control the Central Committee of adding hundreds of extra delegates to the original list of 1,550.
"They illegally keep adding new members. No-one knows the actual numbers," Fatah member Mansuor al-Sadi told Reuters news agency, accusing the committee of "trying to hijack the congress".
Proceedings have also been hindered by a row over the treatment of the votes of about 400 Gaza-based delegates who had been prevented from travelling to the congress in the West Bank town of Bethlehem by Fatah's rival faction Hamas.
Hamas controls the Gaza Strip, and refused to allow the delegates to leave unless Fatah released some 900 Hamas prisoners the Islamist movement says are being held in the West Bank.
The issue has been controversial as it could affect the chances of former Gaza security head Mohammad Dahlan, a younger but highly divisive figure, of being elected to the committee.
A Fatah spokesman said on Thursday that an agreement had been reached to allow the Gaza-based delegates to vote, but did not give further details "for security reasons".
Another row also broke out on Tuesday when another delegate, Hossam Khader, who has been critical of corruption among Fatah leaders, challenged Mr Abbas to provide a detailed report about the Central Committee's activities in the 20 years since the last conference.
Mr Abbas reportedly told him his lengthy opening speech on Tuesday should suffice and ordered him to sit down.
International interest in the conference has so far centred on whether Fatah will alter its charter, which calls for armed struggle to end the existence of Israel.
This dates back to Fatah's formation in the 1950s by the late Palestinian leader Yasser Arafat.
But by backing the Oslo peace process in the early 1990s, Fatah effectively renounced violence and recognised Israel.
On Tuesday Mr Abbas said Fatah was committed to peace, but maintained armed struggle as an option.
Correspondents say that without major reform Fatah will struggle to restore its image among Palestinians, which will be particularly important if elections scheduled for January 2010 go ahead.
Nonetheless, opinion polls suggest that Fatah is currently more popular than its main rival, Hamas.
It lost Palestinian parliamentary elections to Hamas in 2006.