hoodxs6

I have a 99 astro van about a month ago the fuel pump went out so we replaced it.Still would not start so we replaced distrubuter,plugs,wires.We also replaced cap and rotor,fuel pressure regulator,crank shaft sensor.If you use starting fluid it will start and run but not very well.If you try and acclerate tries to die but if you spray starting fluid abd accelerate it runs fine.Does any one have any ideas?There are no codes.Thanks

old_master

Just because a part is new, is no guarantee that it's good. Replacing parts needlessly gets expensive. Before going any further, check the fuel pressure, it is critical on these engines. Here is a guideline:

Fuel pressure is not monitored by the On Board Diagnostic (OBD) system. Therefore it cannot set a Diagnostic Trouble Code (DTC), or illuminate the Service Engine Soon (SES) light. For example: If the engine will not run, or stalls, due to insufficient fuel pressure, no DTC’s will be set and the SES light will not come on.

Fuel pump operation:
The fuel pump circuits are designed to activate the fuel pump relay continuously any time the key is in the START position. When the key is in the RUN position, the fuel pump relay remains activated provided the Powertrain Control Module (PCM) is receiving a signal from the crankshaft position sensor. If the engine stalls, or is not running for any reason, the PCM will deactivate the fuel pump relay after approximately 2 to 3 seconds. The 2-3 second ON time is commonly referred to as “fuel pump prime”.

Fuel pressure test:
This test checks the pumps ability to build pressure, and the systems ability to hold it. Install the fuel pressure gauge to the test port near the distributor. Turn the key to the RUN position but do not start the engine. While the fuel pump is running, fuel pressure must be 60-66psi. After approximately 2 to 3 seconds, the fuel pump will shut off. Fuel pressure must remain between 55-60psi for several minutes. A drop in pressure below 55psi indicates excessive leak down.

Diagnosing leak down:
External fuel leaks include everything from the pressure line connection at the fuel pump, through the fuel filter, and up to the line going to the injector assembly. Internal fuel leaks can occur at the check valve in the fuel pump assembly, the fuel pressure regulator, the fuel lines under the upper intake manifold, or a fuel injector. Accurate diagnosis for pinpointing the cause of an internal leak, and testing the fuel pumps maximum output pressure requires the use of additional test equipment to isolate each component. In some cases it requires the removal of the upper intake manifold.

Here is a link to an adequate, inexpensive, fuel pressure tester: http://www.harborfreight.com/cpi/cta...emnumber=92699

Post your results and we can continue.

hoodxs6

Our fuel pressure is 50-52 key on engine off.50-55 when running.going down the road from stop step on petal goes between 55-60.Then back to 55.If you idling with a/c on very erratic 57 to 52.Turn off a/c goes to 54-55.Thanks apperciate any advice you have.

old_master

GM does not publish any specs for fuel pressure while the engine is running. The fuel system is to be diagnosed with the engine off. Your fuel pressure is too low, does the pressure hold when the pump stops running?

Follow the procedure "Fuel pressure test" as outlined in post #2 and post your results.

hoodxs6

no the fuel pressure does not hold when the pump shuts off.Will be interested in any advice you have.thanks

drew300

my '97 had a weak fuel pump. I had 59 psi, key on / engine off.
A GM service rep I spoke with said "minimum 60". He said it twice. I replaced the pump, and the van starts and runs fine.

old_master

Fuel pressure test:
This test checks the pumps ability to build sufficient pressure, and the systems ability to hold it. Install the fuel pressure gauge to the test port near the distributor. Turn the key to the RUN position but do not start the engine. While the fuel pump is running, fuel pressure must be 60-66psi. After approximately 2 to 3 seconds, the fuel pump will shut off. Fuel pressure must remain between 55-60psi for several minutes. A drop in pressure below 55psi indicates excessive leak down.

Diagnosing leak down:
External fuel leaks include everything from the pressure line connection at the fuel pump, through the fuel filter, and up to the line going to the injector assembly. Internal fuel leaks can occur at the check valve in the fuel pump assembly, the fuel pressure regulator, the fuel lines under the upper intake manifold, or a fuel injector. Accurate diagnosis for pinpointing the cause of an internal leak, and testing the fuel pumps maximum output pressure requires the use of additional test equipment to isolate each component. In some cases it requires the removal of the upper intake manifold.

An alternative if the special tools are not available, is to use a fused jumper wire to constantly energize the fuel pump. Then slowly restrict the fuel return line while the fuel pump is running. DO NOT allow the pressure to rise above 75psi or damage will occur to the fuel pressure regulator. The only thing this test checks is the fuel pumps ability to build pressure. It does not diagnose leak down. The only way to check the pumps maximum pressure is to connect the fuel pressure gauge to the fuel line where it enters the fuel filter. This method will also check for leakdown in the pump. This is a much safer way to check max pressure, but it takes some fooling around making up adapters so the gauge will connect to the fuel line. If you decide to check it this way, after the gauge is connected, BRIEFLY energize the fuel pump and check pressure. If the pressure is above 75psi and holds it when the pump is shut off, the leakdown is under the upper intake manifold. If pressure is less than 75psi or the pressure drops, the pump needs replacement.