90 Mustang GT, trouble code 96, help??

[hrdbdy38]

Hey guys,

I'm new to the board but not to cars. They've been my passion and hobby for nearly 25yrs now. I can pretty much do anything with them but I hate chasing down possible electrical problems and/or trying to hunt down various problems that cause trouble codes.

~background info and upgrades~

My car has 270,000+ miles on it and still runs strong except for 1 cylinder that oil fouls a sparkplug once every 6-12 mos. Only parts that have worn out which I've recently changed is the: aluminum radiator, thermostat, water pump, alternator, battery, distributor cap/rotor, MSD coil, MSD wires, plugs, fuel pump, fuel pump relay, and most recently replaced my worn OEM timing chain set with a gear drive. Rest is totally stock except for cold air, air intake setup, C&L mass air meter, and BBK X-pipe with high flow cats.

~ whats going on ~

I had a "hot" problem this past summer with the car. IE- for some reason, when my car would idle for long periods of time in traffic jams, or after about an hour of regular driving it would just die for no reason. I could try to start it and the engine would turn over and over but it would never fire.
After letting it sit with the power off for 5-10 minutes then it would fire right back up and I'd be back on the road.

After banging my head on the wall REPEATEDLY over this one (and yelling lots of obscenities), I finally came to the conclusion that my OEM fuel pump relay- located under the driver seat - was acting up. I presume it would get hot then malfunction internally. Once allowing it to cool (me letting it sit for 5-10 min) it would start working again. So I replaced this relay with a new one about 3+ mos ago and have not had the problem since.

That is until 2 days ago when I had been driving for 45 minutes on the freeway then got caught in a traffic jam. Bumper to bumper, barely moving. After about 30 minutes of idling and going no where it died on me again. I didnt want to be broken down in a traffic jam on the freeway (what a nightmare!) so I immediately started cranking over the engine and praying it would start. After several minutes it finally started again. It was running rough (coughing and sputtering) for the first 30 seconds like it was either super lean or super rich, but then finally smoothed out.

Any clues to what would cause this new engine dying situation? I had plenty of fuel and my temp gauge was in its normal position.

When I got home I scanned my computer. There was a new code, CODE 96. According to my definitions book this means "Fuel pump secondary circuit fault and/or high speed fuel pump relay open"

How do I chase this thing down? Has anyone else had this problem with the EEC-IV vehicles? What's the quick fix, to drop in a new wire harness going to the fuel pump relay or ?? Only thing I can think of, is that either the stock wiring to the relay, or the fuel pump relay is getting hot for some reason again.

Any help is appreciated, thanks!




PS.
I changed the fuel pump to a Walbro 255LPH about 6-12 mos ago. I know it still works because when i first turn the key to prime the engine before I start my car, I hear it running for a few seconds until correct fuel pressure is achieved. So I dont think the fuel pump is the problem.