From 1967 to 1981, Mr. Diehl was assistant manager of the mechanical-engineering division for Catalytic Inc., which designed and built chemical plants, oil refineries, pharmaceutical manufacturing plants, and desalination facilities across the globe. His office was at 1528 Walnut St. in Philadelphia.
From 1982 to 1996, at Diehl & Associates, he provided expert witness and consulting services for equipment-makers, insurance companies, and law firms.
The firm was in his Springfield, Delaware County, home, where he lived before moving to Maris Grove in 2006.
He was a member of the International Electro-Technical Commission in Geneva, Switzerland, a lecturer for the Continuing Education Program for Professional Engineers, and the author of many papers. He held numerous patents.
Born in Philadelphia, he graduated from Northeast High School, and earned a bachelor's degree in civil engineering from Drexel University. He completed a master of science degree in civil engineering at the University of Pennsylvania.
He was a veteran of World War II, serving in the Army Air Corps.
He had been active with the First Presbyterian Church of Springfield since 1950, serving as an elder, board of trustees president, and a Sunday school teacher.
A family man, he enjoyed participating in his children's activities, Shore vacations, piloting his sailboat, and being a handyman and chef.
He traveled to Russia, England, and Ireland and took cruises to various parts of the world.
He was married for 62 years to the former Elizabeth Devitt. She and the couple's son, James C. Diehl, died earlier.
Surviving are a daughter, Nancy Diehl Larkin; two grandsons; and a great-granddaughter.
A memorial service will be Friday, Sept. 27, at 2 p.m. in the Chapel of Maris Grove, 200 Maris Grove Way, Glen Mills, Pa. 19342. Interment is private.
Contributions may be made to the Maris Grove Resident Care Fund at the address above.