Question about 1995 Buick Riviera

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FUEL PRESURE / FUEL GAUGE

PART 1 ( fuel pressure )
this ia a stock 5.0 HO . i have 30 psi of fuel at idle . it will increase to 40 psi if i remove the vacuum from the fuel regulator and it does go back to 30 psi when vacuum is replaced . if i close/ pinch of the fuel return from fuel regulator to the tank my fuel pressure does not increase ( i beleive it should ). with the fuel gauge still attached to the fuel line i drive the car and the fuel pressure drops down to 20 psi and lower. this is my problem, under mid to heavy acceloration i get popping / backfire out of the throttle body . i noticed it is only when the fuel pressure is low. by the way this is with a new fuel pump . ( i think i have a defective fuel pump ) . and i beleive the fuel pressure should rise under acceloration. can someone confirm this?

PART 2 ( fuel guage )
the gauge did not ( always read full ) . i got a boneyard sending unit and it tested 12 ohms full and 74 ohms empty ( i beleive this to be the correct specs ). once the tank was back up and filled with gas, the dash gauge reads closer to empty with the more gas i put in. can anyone help here?

IS IT POSIABLE THE TWO HAVE ANYTHING RELATED IN A SHORTING OUT / LOSE OF POWER KIND OF WAY?

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  • Anonymous Mar 17, 2009

    3.8 liter buick riviera cuts out when accelerating. already changed coil packs,plugs,wire and fuel filter.tried gas cap also. Whats next

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  • Buick Master
  • 6,982 Answers

Buick with a 5.0?? OK, regardless, pressure should not drop like that. Possible that fuel filter is full of **** & should be changed, or, you may indeed have a bad pump... (can happen). Sending unit: sounds like you have the leads reversed or the unit is somehow different than the one you replaced.

Posted on Dec 26, 2008

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2 Answers

How to check fuel pressure 91 geo storm gsi


1.6L DOHC (same way as the ISUZU impulse ) same car.
4XE1 engine twin cam.
has MPI injection with fuel rail, regulator and loop
disconnecting the feed line and stuffing it with guage only does 1 of 5 tests. done on MPI. it does JUST the shut test.
the correct way it to check it at the filter or rail tests ports on most cars.
in some cases you must add it.
they sell banjo fittings with test ports at summit racing dot com.
so the first question on all MPI cars, is , where is the stock fittings.
other cars the rail has a schrader valve or a plugged hole to add one. (test port) did you look first for this?
to test the FPR, unplug the vacuum line running
and pressure will jump up 6 to 10 psi.
this simulates wide open throttle pressure, a key fact in getting full power from engine, i test cranking presssure, idle, 3000rpm
and wot pressures to be sure the PFR is working, not just the pump.



the spec at the rail is.

Late 1986 to 1993 I-TEC MPFI system (after VIN 0908197)
Regulator vacuum line connected-36 psi
Regulator vacuum line disconnected-42.5 to 45 psi

the shunt test can hit 60 pis easy. do so for only 5sec.
as this stresses the pump .

the only rail drawing , shows no fittings (cheap buggers)



not even a cheap plug...

24024302-wtht4tipiqsxmsfaksxjx4vs-4-0.jpg below is the twin cam, 1.6L
buy a TEE feeting, and put it at upper, red arrow.
use clamps rated for fuel injection, not chezzy screw band clamps as seen on carb cars. use the correct parts.
or you will get leak and it will not be pretty,
the filter as at 14 ID. this is the pressure feed side of the loop.
30 to 60psi , so all parts must be rated over 60, psi, (100psi is a nice goal)

24024302-wtht4tipiqsxmsfaksxjx4vs-4-1.jpg

now the words directly from the IMPULSE FSM.

Testing
  1. Relieve the fuel pressure.
  2. Disconnect the fuel line near the engine and install fuel pressure gauge T-connector in the line.
  3. Connect the fuel pressure gauge to the T-connector.
  4. Start the engine and check the fuel pressure, it should be:
  5. 4XC1-Turbo and DOHC I-Mark, G200Z Impulse: 35.6 psi with the vacuum hose of the pressure regulator disconnected and plugged. 28.4 psi with the vacuum hose connected and at idle.
  6. 4ZC1-Turbo, 4ZD1 Impulse and 4ZE1 engine: 42.6 psi with the vacuum hose at the pressure regulator disconnected and plugged. 35.6 psi with the vacuum hose connected at idle. Disconnect the VSV before checking pressure.
  7. V6 engine: 9.13 psi at the fuel pressure line after the fuel filter.
  8. 4XE1 SOHC and DOHC engine: Flow test, disconnect the hose from the EFI fuel feed line at the engine and place in a suitable container. Apply battery voltage to the fuel pump. Pump should supply 1/4 quart (0.24L) within 15 seconds. Pressure test, connect a pressure gauge in the fuel pressure line after the fuel filter, located at the driver's side frame rail. Disconnect the vacuum hose from the pressure regulator. Apply battery voltage to the pump. After the pump stabilizes, the pressure should be 35-38 psi (245-256 kPa) and hold steady.

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