Car Stereos: no sound from stereo in 1991 Ford E 350, pioneer head units, pioneer head unit

Question
I installed a pioneer head unit in my 91 Ford E 350 van; purchased the correct wiring connectors,and have installed stereos before. Tried 2 different Pioneer head units. Will power on but no sound. Re-connected factory stereo and got sound. Re-checked all connections. Still no sound from either Pioneers. This particular E 350 utilizes one common ground for all speakers, therefore only 1 ground for four (4) speakers. Please help!

Answer
Hi Keith,

Some of my previous research has found that some of the old E350s had factory amplifiers!  You might have to do a little digging to see if yours does.  In that case, you might find yourself having to bypass it entirely to make an aftermarket deck work in it.

(Or find an integration harness, which sounds easier than it might be.)

Justin