97 blazer fuel pump

[ia31638]

Two issues. Fisrt issue po305 misfire #5. Second issue fuel pump not holding pressure. Turn key on jumps to about 62 when pump is priming. When pump stops drops to zero immedialty. Its does start but takes quite a bit of cranking. Seems to run fine about 50-60psi while running. Also had a po300 last week. 138000 miles. Seperate issues or related?

[Rick Norwood]

Originally Posted by ia31638

Two issues. Fisrt issue po305 misfire #5. Second issue fuel pump not holding pressure. Turn key on jumps to about 62 when pump is priming. When pump stops drops to zero immedialty. Its does start but takes quite a bit of cranking. Seems to run fine about 50-60psi while running. Also had a po300 last week. 138000 miles. Seperate issues or related?

When was the last time you replaced your Distributor Cap? If your cap is old and/or not an AC Delco, you might try replacing your cap and Rotor. A bad cap will throw all kinds of codes.

Sounds like your Fuel Pump is going bad. When was the last time you changed your fuel filter? If you have good pressure, it should crank and run.

The fuel filter, new or not, will not cause the pressure drop, however, a new fuel filter might help if not enough fuel is getting through the old filter.

[ia31638]

new cap,rotor,wires,plugs going in tommorrow. All are ac/delco. New fuel filter last week. How and where are people plugging or pinching the return fuel line too see if its the fuel pump or fuel pressue regulator not holding pressure? Blazer will run if cranked long enough.

[mike2004tct]

Originally Posted by ia31638

new cap,rotor,wires,plugs going in tommorrow. All are ac/delco. New fuel filter last week. How and where are people plugging or pinching the return fuel line too see if its the fuel pump or fuel pressue regulator not holding pressure? Blazer will run if cranked long enough.

Thanks to write-up Old_master e-mailed me, I made a gauge to check the pump pressure.

The gauge was made with parts readily available from Napa and Ace Hardware.
Napa 730-5013 steel fuel line repair fitting, 3/8"
1 ft 3/8" hose, 2 clamps.
Ace - 3/8" ball valve
3/8" male to barb fitting (for the hose attachment)
3/8+ male/female adaptor (because the steel tube hit the ball of the valve)

Old Master's parts were somewhat different, but close to the valve (lower unit in the picture above). I clamped the open end of the hose onto the output of the fuel filter, and steel tube into the pipe to the injectors.
Once the fuel pump primed, I shut the valve as soon as the pump stopped.
Pressure gauge registered 52 psi steadily,indicating a good pressure regulator. As soon as the valve was opened, the gas went back thru the pump, and pressure went to 0 immediately. There was a small hole in the fuel pump line to fuel pump assembly top cover.

[Tech II]

Mike's setup is the same thing GM has, except it has fittings on both ends.....you just disconnect the outlet of the fuel filter and attach the shutoff valve.......can install this in the same area on the return line to check the regulator and injectors.....

As for the misfire, it could be secondary ignition or the injector.....

[ia31638]

Thanks for the info guys. I had a double whammy, fuel pump was leaking down, and #5 injector was leaking. Got them both replaced and all is good now.