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The front suspension is basically the same for all Reatta years except that the 1991 has 16" wheels instead of 15" for previous years. The brake system was not updated for 1991, just changed over previous years (Teves vs. Bosch). The '91 Reatta engine is a L27 vs. previous years LN3. Most likely the 88-93 Riviera front suspension is equal, too. My '91 Reatta is also white with flame red interior. Yours has white belt molding vs. mine has black.

You might check with your local auto parts store, they may loan you a gauge.

I just have a good fuel pressure tester from the pre-Kmart Sears. You connect it to the rail shrader valve. Should be 35-40 psi at Idle. Might also check the fuel relief valve for gas in the vacuum line, they fail also.

The rpm signal comes from the ICM. Did the engine continue to run without the rpm display? The voltage displayed is normal with the engine running. By and large, the indicators are designed to be at approximately the middle of the range if everything is normal. The fuel level is of course variable. If oil pressure is normal with a proper sender, it rarely deviates one bar higher or lower than center, no matter the rpm or temperature. The pressures mentioned in the above post are for oil pressure, not fuel pressure as I had posted. Any possibility of mouse chewed wiring? Still need a fuel pressure gauge to establish if the pump is at fault or something else. At least it runs, which is a positive.

Just a little food for thought. I don't know if the following applies to a '91 model but it does to my '88 model. IF the ECM and fuel pump relay are working properly you should be able to unplug the oil pressure sensor/switch and the engine will start and run without problems. I have done it before to prove it. Here is what should happen for the car to start and run normally from a fuel pressure point of view... -When you turn the key to the run position the ECM should pick up the fuel pump relay for a few seconds to prime the system - then drop it out. This should happen each time your turn the key off and then to the run position. -Once the engine starts, the ECM gets a signal from the crankshaft position sensor that the engine is turning and it will pick up the fuel pump relay and keep it latched in to power the fuel pump as long as the engine is running. (blue circuit below) Now, here is where the oil pressure sensor/switch comes in... -As long as the engine has oil pressure the contacts in the oil pressure sensor bypass the fuel pump relay and power the fuel pump (yellow circuit) even if the relay is bad. If any of this is suspect, applying 12 volts to the prime connector will run the fuel pump so you can test the pressure. You can even start the car if the pump is capable of building adequate pressure.

LN3 spec is 40 psi at 1800. L27 is 60psi. "able to crank idled then sputtered " sure sounds like the 2 second prime shot is working but then the oil pressure switch is supposed to take over. Can monitor fuel pump voltage at prime connector. GM oil pressure senders are notorious for failing just make sure you get one for an L27 and not an LN3.