Bought this vehicle with symptoms that it would simply quit running. Replaced main wiring harness, turbo, fuel relay and had in shop several times. Still, there are starting problems, mostly when cold. When this happens, it will crank and crank until I hear what I believe to be the main fuel pump come on, then it will usually start. Sometimes, I have to let it sit for some time before it will finally start. There will also be times when it will cut out and nearly quit as I'm driving at highway speeds.

Whether related or not, the Boost sensor never moves from the center position.

Any ideas?

 

Was the fuel pump relay new? If so, other options could be: fuel injection relay (called radio suppression relay) mounted on the overflow bottle). Two relays there, identical...often you can swap 'em and diagnose. Also, the ignition module mounted on driver's inner fender near battery. Fumes can cause corrosion on terminals or it could be failing. As for the boost gauge it is mechanical. Check to see if the vac hose going thru the firewall is connected to the manifold. It should show vacuum even when not in boost. Won't cause your symptoms however. Don't despair, your car is 23 years old. Turbos, with their heat, are particularly hard on vacuum/pressure hoses and wiring...especially wiring on the passenger inner fender. Would be good to replace your fuel filter if you have no idea when it was last serviced. Let us know!
p.s. A failing ignition switch could theoretically cause the symptoms as well. Usually, there are other symptoms. When you start the car, do all the warning lights stay on or radio not work etc. until you wiggle the key? If so, it is the electrical portion of the ignition switch worn out. It plugs into the back side of the actual lock. It sounds exactly like a fuel pump relay. If it was a used one you swapped in, I'd start there.

 

Thanks for the excellent guidance. I have a number of things to check out. I'll keep you posted.