The first of PATCO's long-delayed refurbished railcars are now slated to begin service late next month, PATCO officials said Tuesday.

Persistent signal problems have been solved, PATCO president John Hanson said, so the first eight cars in the 120-car fleet to be rebuilt in a $194 million program can finally carry paying passengers.

The first cars will operate as two four-car trains during off-peak hours, PATCO general manager John Rink said. PATCO expects six more cars to be in service by late June and early July.

Then cars are supposed to arrive at the rate of four a month.

The return of the cars from an Alstom Transport Inc. factory in Hornell, N.Y., is more than a year behind schedule because of problems with communications, automatic train control, and propulsion and braking systems. The final hurdle was an automatic signal system that gives operating instructions to the train.

"We're all disappointed about how long this has taken," Hanson said Tuesday. "But we feel good that this problem has been solved. . . . It had the potential to be a deal-breaker. We insisted the cars be right before we would accept them."

Repeated tweaks in computer software that controls the automatic signaling were made at a Rochester, N.Y., lab and on PATCO test tracks, chief engineer Mike Venuto said. Now the testing equipment needs to be removed from the cars so they can operate with paying customers.

Once the eight cars return to service, PATCO will have 100 cars, up from the current 92. As rebuilt cars are returned to PATCO, the same number of old cars will be shipped to Alstom until the entire fleet is rebuilt.

PATCO's parent, the Delaware River Port Authority, hired Alstom in 2010 to rebuild the 40-year-old fleet. The DRPA decided to save money by rebuilding its cars, rather than buying new ones.

The rebuilt cars will have new interiors and communications and heating systems, but will retain the original stainless steel bodies and old wheel assemblies and traction motors.