'91 VR4 radio replacement

The CD on my '91 VR4 stopped working and my only reasonable choice is to replace the radio and CD player with a radio/CD player. Installed an Alpine receiver following all instructions, but I don't get any audio out of the speakers. Is there a separate amplifier that needs to wired in for the new radio to work? I noticed a plug with only one wire coming out of it that is coded yellow/white and am wondering if this is the remote connection to activate the amplifier. The new radio harness has an unused wire labeled 'REMO'.

did you install the headunit with an aftermarket wiring harness or did you cut and piece out each wire?
the yellow/white wire is for the steering wheel controls.
you can refer to jeff lucius' site, stealth316 (http://www.stealth316.com/2-sony_cdx-m800.htm), for some additional info

New unit came with 2 wiring harnesses, so I used butt end crimp connectors to connect all the wires per diagrams. Seller support suggested I cut all but on set of speaker wires to determine if their is a short in the speaker wiring, but the speakers were working fine with the factory unit and I buzzed out all the wires from new unit connector to wiring harness connectors and there were no shorts.

If the factory head unit had 3 wire harness plugs in addition to a round DIN plug than you will have an amp. If you only have 2 plugs than there is no amp in your system.

The wiring diagram is too big to upload to this site but you can download it from here (http://www.the12volt.com/installbay/file.asp?ID=1210).

It sounds like you may have wired up the head unit incorrectly. You can test the speakers by using a AAA battery. You will hear a pop if you touch the correct pair wires across the battery terminals.

The head unit does have 3 rectangular plugs with a 6 pin round plug (plus the antenna plug). From what I've read, I need to energize the separate amp to get the speakers to work. The new head unit has a remote wire that needs to be connected to turn on the amp but I have no idea to what on the factory wiring harness. Any suggestions?

have you checked your wiring against the diagram provided?
if you take a look at the diagram, the speaker outputs do not come out of the amp. the amp was only used for the cd player.
when checking the wiring make sure you check it with relations to the wiring harness not just color because there are duplicate colors.

I've isolated the problem to the left rear speaker wires. Cut all four speaker wires and then reconnected speaker front right, rear right, then front left and sound came out of each. Connected left rear and sound stopped. I will have to investigate wiring for rear left speaker to get all four working.

Bought the head unit from Crutchfield and they provided a harness. With some effort I found that connecting the left rear speaker caused the other speakers to stop working. I've left the left rear speaker disconnected for now so that I can used the radio and CD player. At some point I'll need to figure where the short is in the wiring to the left rear and fix/replace it.