HELLO, I’AM STUCK HERE AND IN NEED OF SOME ASSISTANCE, I HAVE A 1993 CHEVY ASTRO 4.3L ENGINE CODE “Z”, NOW I CHANGED THE RELAY, THE FUEL PUMP, FUEL TANK SENDING UNIT, CHECKED THE FUSE AND STILL I HAVE NO POWER GOING TO THE PUMP, NORMALLY WHEN YOU TURN THE KEY YOU WOULD HERE THE PUMP COME ON, AND YOU DONT HERE THAT, RUNING OUT OF IDEAS, ANY SUGGESTIONS WOULD BE VERY VERY HELPFULL…THANK YOU VERY MUCH…
I know I am a pest about it, but ALL CAPS are difficult to read. Using standard case and paragraph spacing makes messages much easier to read. Making them easier to read means more people will read it and you are more likely to get a good answer. I suggest you start at the pump and start measuring voltage until you find where it starts. Throwing parts at a problem is usually the expensive and time consuming solution.
Are you sure you checked the right fuse for the fuel pump? It should be a 10 amp fuse. You can jump the relay also and see if you have power to the fuel pump that way. We changed a fuel pump a few months ago in a GM and when we were done it had no power to the fuel pump and found out it was the little RED 10 amp fuse causing the problem, changed the fuse and then it was fine. It is not uncommon to have a fuse go out if a fuel pump goes bad.
cars have an inertia switch in the power to the fuel pump. if this switch get tripped it shuts off the electricity. unless you reset this switch nothing will work.
sorry, i don’t know where it is on your vehicle, but some other knowledgeable responders on here might.
i found out about these switches when my son was in the front seat kicking the dashboard. terrible twos!! when i came back out of the drug store the truck wouldn’t start. had it towed to the mechanic and he showed me how to reset the switch, under the dash, above the brake pedal. sort of made me feel stupid. but… that never happened to me again!
Check the ECM-B 15 amp fuse, it powers the fuel pump circuit.
The Astro does not have a inertia switch, it uses the oil pressure switch to shut down the fuel pump.
Willey has the right type of circuit. There is NO inertia switch.
The wiring diagram is at: http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c152800a824a Click on Fig.10.
The ECM/Batt 15A fuse provides power to the fuel pump relay and the Fuel Pump/Oil Pressure Switch. The fuel pump relay provides power to the fuel pump ONLY during cranking. As oil pressure builds to a certain value, the Fuel Pump/Oil Pressure Switch provides power to the fuel pump.
If oil pressure falls too low, or if the Fuel Pump/Oil Pressure Switch faults, power will be lost to the fuel pump; and, the fuel pump won’t run. This is a good thing. An engine will self-destruct if it doesn’t have oil pressure. Use the wiring diagram and check the wiring, fuse, and the FP/Oil Press. Sw., when oil pressure to close the switch (which sends power to the FP).
How do you know you have no power to the fuel pump?
From your post it appears that you’re assuming that you have no power because you don’t hear the pump running. It is very possible that you have plenty of power going to a failed fuel pump.
Check the fuel pump power at the connector going into the fuel tank. If you’ve got power there, you’ve got a bad pump.
When you disconnect the electrical connector, at the fuel pump, which carries the 12 volts power to the pump, someone has to be cranking the engine; otherwise, there won’t be 12 volts on the gray wire.
The OP won’t need to be CRANKING the engine.
Fuel pump power is typically applied for about 2 seconds following turning the key to the “ON” position. “START” position is not required. Just have someone turn the key to “ON”. 12 volts should be seen at the fuel pump plug for 2 seconds. If it’s there and the pump isn’t running, change the pump. Want to see it again? Turn the key off, then back to “ON”.
Yes, JayWP is correct: there will be power (12 volts) for two seconds each time the ignition key is turned from OFF to RUN. AND, power will be there as long as the engine is cranking.
i know i do not have power, because i was cranking while my dad was testing for power, today actually about 10pm we tested the fuel pump with a jump wire, and it worked. so then we checked the relay, and of course no power, all the fuses are fine, i was told that it might be the computer, any advice on what else to check for i would really appreciate it.thank you very much…
Here is the description of operation for the fuel pump from ALLDATA…
The fuel pump is a turbine type, low pressure electric pump, mounted in the fuel tank. Fuel is pumped at a positive pressure from the fuel pump through the in-line filter to the pressure regulator. Excess fuel is returned to the fuel tank through the fuel return line.
The fuel pump is attached to the fuel gage sender assembly. A fuel strainer is attached to the fuel pump inlet line and prevents dirt particles from entering the fuel line and tends to separate water from the fuel.
When the key is first turned “ON” without the engine running, the control module turns a fuel pump relay “ON” for two seconds. This builds up the fuel pressure quickly. If the engine is not started within two seconds, the control module shuts the fuel pump “OFF” and waits until the engine starts. As soon as the engine is cranked, the control module turns the relay “ON” and runs the fuel pump.
When the engine is cranking or running, the control module receives distributor ignited reference pulses which in turn energize the fuel injectors.
As a backup system to the fuel pump relay, the fuel pump is also turned “ON” by an oil pressure switch. When the engine oil pressure reaches about 28 kPa (4 psi), through cranking the oil pressure switch will close to complete the circuit to the fuel pump.
It keeps the responses in chronological order if you click on POST YOUR REPLY.
You, “checked the relay, and…no power.” How did you check power (to?, from?) the fuel pump relay, and on which wire?
Fig. 10 shows the wires to, and from, the fuel pump relay: http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c152800a824a .
There is an oil pressure light on the dash, right? Near the fuel pump relay is a single, loose, red wire just “hanging there”. This, lone, red wire is the fuel pressure prime wire. You can jump power, to the red wire, from the battery positive, to cause the fuel pump to run. You can, also, check for power (12 volts) to this red wire, WHEN the fuel pump/oil pressure switch closes during cranking, after the oil pressure light (on the dash) goes off. Results? Let us know.