Electronic fuel pump dont come on?

Welcome, do you have spark at the plugs, engine cranking? Also, use a gage and check fuel pressure. There should be a fuel pump relay in the power distribution center, under the hood. Voltage for the load side of relay is hot all the time, voltage for the coil side of relay goes hot with engine cranking and a couple of seconds when you first turn key on, no crank. This guide should help us get started https://www.2carpros.com/articles/car-cranks-but-wont-start

My info showed the above for underhood fuse block. no reset that I'm aware of.

I am having the exact same problem. The manual says to first listen to the whirring sound of the pump when ignition is first on.

If pump does not come on, check the fuel pump fuse which governs the fuel pump relay, the fuel pump, the injectors, the ignition system and the PCM.

If fuse is good, check for an open circuit between the relay and the fuel pump. With the ignition key on (engine not running), check for battery voltage at the relay connector. This is located behind the glove box inside the relay control box.

(I am having problems determining what the relay looks like behind the glove box. I see a large harness that I believe connects to the ECM, and to the right of this is a black box that may or may not be the relay I'm looking for. I am wondering if I need to remove the relay in order to test for power to the relay, if this is actually the relay at all). I digress....

If battery voltage exists, replace the relay with a known good relay and retest. If necessary, have the relay checked by a qualified automotive parts store.

If the fuel pump does not activate, check for power to the fuel pump at the fuel tank. Access to the fuel pump is difficult but it is possible to check for battery voltage at the electrical connector near the tank.

If oil pressure drops below the specified pressure level, the oil pressure switch will act as a feul pressure cut off device.

I know this is an older thread, but I am posting this for those that stumble upon it.

As previously stated, the manual says the fuel pump relay is behind the glove box. Mine was actually in the fuse panel in the engine bay. I went online and after appxomately 1 hour, I was able to understand how to test the relay to see if it is working. An easier way is to put your finger on the relay itself and have someone turn the ignition on (engine not running). You can feel the relay click if it is working properly. You can also hear the click. If the relay is in close proximity to another relay, it may be difficult to hear if the relay you are trouble shooting is the one that you clicking. That's why it is good to follow up with the feel method.

Once I was sure my relay was working properly, I was able to reach above the fuel tank at the back end of the tank and reach the connector at the fuel pump. I unplugged the connector and was able to place a multimeter on the pins to read voltage. Use your manual to determine which of the four pins are power and ground. The important thing to remember is that when the ignition is on (engine not running), the fuel pump relay kicks on and provides temporary voltage to the fuel pump to prime the lines. If the fuel pump works properly you can hear this momentary prime. The relay only provides power for a couple of seconds. You cannot turn on the ignition and then crawl under the car to test the connector for power. There will be no power by the time you get there. You must be under the car with the probes from the multimeter hooked up while somebody else turns on the ignition for you. You should see near 12v of power momentarily and then no power. If you have power, and your fuel pump does not work, drop the fuel tank and change the pump. If the voltage is excessively low (more than .5 volts lower than what your battery is giving), a relay could still be the problem.

If you check the connecting harness and see 5 volts of power to the pump, be certain you are reading the correct probes at the connector. The connector for a 2001 GMC jimmy has 4 terminals. Two are for the fuel pump and two are for the sending unit. The sending unit should read 5 volts with the ignition on at all times.

Word of caution when changing the fuel pump. There are three feed ports on top of the pump assembly. They are very brittle. If you are not careful you can break one of the plastic ports when attempting to connect the fuel lines to it. Be sure the tank is high enough and only attempt to connect the fuel lines from the fuel lines to the pump ports. This means you should connect the flexible fuel lines to the rigid fuel lines along the body of the car first, then once the tank is high enough, reach up and connect the flexible fuel lines to the pump ports. When connecting them the other way around, when you pull on the flexible fuel line from the port nipple, in an effort to connect to the rigid line along the body of the car, it takes very little force to snap the port clean off and will likely have to replace the pump.

Hope this helps.

:)

What should you check if there is no power to the fuel pump fuse next to the relay?

Are you talking about 99 Jimmy? ECM B fuse, goes hot when you turn on the key. I can't say if ignition switch is faulty? I'd have to check the feed to and from the switch.

[quote:6da71d58bd="jdl123"]Are you talking about 99 Jimmy? ECM B fuse, goes hot when you turn on the key. I can't say if ignition switch is faulty? I'd have to check the feed to and from the switch.[/quote:6da71d58bd]


It's a 98 but same set up


Should have constant power per the wiring diagram
Get nothing from either side of the fuse, but when I pull the fuse and check the hot side it barely lights up the circuit tester
Isn't there a wire somewhere along the fire wall that goes directly to the pump to test it?

Mod shows fuel pump test connector, if there is one, in the underhood bussed electrical center. I don't know why the ecm B fuse isn't hot, have to track the circuit. There is a 175 amp mega fuse, one of the positive battery cables, lead to it, Don't have exact location. That fuse serves several circuits, including ecm b fuse.

Where is this located. I'm looking at the picture in the Haynes manual and it says it's on the block behind the intake manifold, but I don't see it. Could it be on the valve cover? I see something there that looks like it.

Sorry, my info didn't give exact location. I'd have to track it down.

[quote:fa7e2f8add="jdl123"]Sorry, my info didn't give exact location. I'd have to track it down.[/quote:fa7e2f8add]


I was talking about the oil pressure sensor.


I didn't see it listed on my previous post!

If your talking about the oil pressure switch in the fuel pump circuit? It's just a redundant power supply to the pump, as long as the relay is function, that switch can't kill the engine or keep it from starting. That sensor is near the distributor and you can see the wiring colors.

I was told that it could go bad and continuously send a low pressure reading to the computer causing the fuel system to stay shut down! Is it under the distributor or am I just blind? Would it be easier to reach from under the vehicle?

Just a tidbit, mine is a 2000 SLE a retired state vehicle. It's a little bit of a catch 22 but I was told by a State mechanic who used to work on these if the vehicle has been sitting for a while ( more than a week) if you don't hear the fuel pump when you turn the key on you have to get someone to sit in the driver seat and then then you have to climb underneath and as the person is cycling the key on and off, if you can get access to where the fuel pump is you take a wrench and very lightly tap on the fuel pump until you hear it on. I stress very lightly because as someone pointed out that there are fragile lines that you can break. Mine is a new pump so don't have the issue. This means do not go under there with a sledgehammer or jack hammer. A small wrench or screwdriver handle should do the trick but tap very lightly and make sure to add fuel first otherwise you will have to repeat. I would assume tapping on the fuel tank would work as well if you can't access the fuel pump. Mine I can get to the fuel pump, but it is a tight squeeze. Now my question there is sheet metal shield under the fuel pump, would I be safe removing this? I would think that it is for off roading to protect the tank, but I am not planning on doing any rock climbing. My only off roading will be in some farmers field as I am a volunteer firefighter, but my only job is directing traffic and unless they need me to direct cow traffic I might not be there either. I believe the only time would be on a search and rescue.

Yep, you should be okay, but I can tell you I would drop the tank and replace the fuel pump, one time the pump will not work even with tapping the fuel tank. Here is how to do the job is done in case you want to fix it:

https://youtu.be/bCcueO4ALxQ?si=0zIhliEyQYcLfuKv

Check out the images (below). Let us know if you need anything else.