homewrecker

As the title says, my brand new fuel pump doesnt seem to pump any fuel to the engine. I had another thread about my car not starting but this was related to other symptoms.

Why I think my car has fuel delivery issues:
- I sprayed a tiny amount of brake fluid (act as starter fluid) in my throttle body and it started the car.
- Having tried to start the car many times, when I pulled out the fuel hose at the tank in the backseat it was dry with no fuel going the fuel feed or return hose.

More infos:
- Brand new pump
- Brand new filter
- Can hear pump turn on when turning key on "accessory" position
- Fuel feed is not clogged
- There is power and ground

What would be the next thing to check before putting another pump, and/or filter?

Thanks !!

DennisMik

iTrader: (2)

The next step is to get your voltmeter and start troubleshooting by doing some voltage measurements.

First, check that the car is not disabled by the NATS security system. If the red led in with the clock is on while you try to crank the engine over, the car is disabled. This causes the ECU to cut off the gas to the engine.

Then check the 2 fuses that make the fuel pump run. They are 10 amp fuse # 17 and 15 amp fuse # 29. Just don't look at them, test them or swap them out.



If the car is not disabled and the fuses are good, remove the rear seat cushion and the access plate for the gas tank. Set the voltmeter to DC volts and locate the black with yellow stripe wire in the wire harness connector. Connect the black, negative meter probe to a good chassis ground spot and the red, positive meter probe on the black with yellow stripe wire.

It may be a little easier to unplug the gas tank connector and use the pin side. It doesn't matter which way you do it. Then, be watching the meter as you turn the ignition key to the ON position. The ECU will send 12 volts to the fuel pump for only a second or 2.

If the meter shows voltage, the fuel pump should be running for this second or 2. Disconnect the output hose for the fuel pump and attach a longer hose and put the other end in a bucket or jar or something. Turn the ignition key to the ON position again and see if any gas comes out of the hose from the fuel pump. If you get gas, the fuel pump is good. If no gas, the fuel pump is no good.

If you did not measure any voltage at the fuel pump, that is another avenue for troubleshooting.

If the fuel pump pumps gas, then this is a different avenue of troubleshooting.

homewrecker

There is voltage at the connector 12v with the key "ON" but it drops to around 7v when cranking but I've tried 2 different pumps and still not pumping any gas.

I swaped fuse and relays and it didnt do anything.

Apparently the fuel pump control module could be my problem.

DennisMik

iTrader: (2)

If you have a fuel pump control module, that means you have a 2000 Maxima, last half of the production. No other 5th gen had that. It was an ill advised experiment that Nissan tried for a few months and gave up on it.

That you have 12 volts going to the fuel pump is good. When you crank the engine, the battery voltage will drop, although 7 volts is lower than normal. Your battery probably is not fully charged.

The fuel pump control module works in a similar manner as the dash light dimmer control, it removes ground from the fuel pump motor. I don't have any experience with the fuel pump control module, so anything I say will be based on theory and/or guesswork.

Try this first. Unplug the control module and see if the pump runs when you try to start the car. I don't know if it will or not.

Have everything plugged in and get out the voltmeter. Go to the plug on the gas tank. Connect the black lead of the voltmeter to chassis ground. Connect the red lead of the voltmeter to the green with red stripe wire. This is the ground wire for the fuel pump motor. Crank the engine. The voltage on the green/red wire should be almost 0 volts, allowing the fuel pump to run.

If the voltage reading is significantly higher, (I'm guessing it will) the the fuel pump control module is not letting the pump run. But is the fuel pump control module being told to do this or is it bad?

Go into the trunk to the fuel pump control module. Connect the black lead of the voltmeter to chassis ground or the solid black wire in the fuel pump control module. Connect the voltmeter red lead to the blue with white stripe wire. (In your photo, this is the wire hiding underneath the black with yellow stripe wire in the lower right corner.) This is the wire that tells the module what to do. Now crank the engine (you may need a helper if your arms are not 12 feet long). The voltage should read about .4 volt. If the voltage is in the .4 volt range, then the fuel pump control module is bad.

If the voltage is higher, like towards 12 volts, that means the ECU is telling the fuel pump control module to shut off the fuel pump. I sure as hell hope not.

homewrecker

1-Yes I have a 2000 SE Maxima
2- My battery almost dead (I crank it with the help of a booster pack)
3- Havent cranked the car but the reading at the blue wire is .6v with the key on "Accessory" position.

If its my ECU that is bad should I just scrap the car or spend more time at the junkyard?

DennisMik

iTrader: (2)

Your answer # 3 is saying that the ECU is telling the fuel pump control module to pump gas.

Did you measure the voltage on the green/red stripe wire? This would confirm that the fuel pump control module is bad.

You might want to know that the fuel pump control module is a $305 part at the dealer if they don't discount. This would be a junkyard part if you need one.

homewrecker

I dont get any reading at the green/red wire. Still getting .5 at the blue one.

Is it possible in any way to bypass the module?

Btw, I dont get any reading on the black/yellow wire at the relay or the module but I get 12V at the pump which is weird cause I would assume no V at the relay would mean no V at the pump. Heres my voltage results at the relay with the key on "accessory" position:
- Black/yellow : 0V
- Black/pink : 0V
- Black/brown : 11.85V
- Black/white : 11.85v

I tried to connect the black/yellow to the black/white with a pin and managed to get 11.85v at the black/yellow but the car still did not start. I think I would either have a wiring issue or my module is bad. I have found one for 40$ on ebay but I feel like im just throwing parts again as Im not certain its the module. What do you guys think should I check the wiring first??

DennisMik

iTrader: (2)

I kind of think that you are OK on the green/red wire. This wire is the ground side of the fuel pump motor. According to the service manual, and I quote, you should measure "almost 0 volts". If you don't have an auto ranging voltmeter and you had it set on the 20 volt scale, it probably would not show you a decimal point voltage such as .1 or .2. You would have to use the 2 volt scale.

Now the part about the relay and the black/yellow wire. This doesn't make any sense to me, either. I suppose the first thing I would do is check wire continuity on the black/yellow wire. Since this wire goes to 3 spots, you will have to do 2 checks: fuel pump to control module and fuel pump to relay. You could also do relay to control module and control module to fuel pump. It accomplishes the same thing.

I don't know if you can bypass the control module. Did you try just unplugging it? But there is a feed back wire from the control module to the ECU, so I don't know if this would work. Without the feedback, the ECU might de-energize the fuel pump relay.

Do you have any pick & pull junkyards in your area? They would most likely be cheaper than the ebay one. Maybe they have a last half production 2000. If you find one, when you are checking out, don't tell them it is a control module. Tell them it is a dropping resistor or a current limiting resistor to prevent shorts. They might charge less that way.

MichMaxFan

I scanned the replies here rather quickly but didn't understand the testing jargon but what I DO know is the rubber grommet had to be at the pump and filter connection. I just changed my filter last weekend and missed it and I could hear the pump run but no start. Gotta have the grommet or no fuel gets out of the tank.

Check for the grommet unless u know for sure it's there.

homewrecker

Ok I have tested the black/yellow wie at the relay and I do get 12V for the second it turns on before cranking. It drops to 7-8v while cranking on both the relay and the fuel pump connector. My battery is dead but im doing the tests plugged to a booster pack so its like I have a functionnal 12v battery.

I will redo the same test on the module.

Where can I find a wiring diagram for the fuel system WITH THE MODULE cause I cant seem to find any ???

homewrecker

Are you talking about that little cap?? Its the only piece that came with the new pump and im pretty sure there wasnt anything of the sort on my old pump.

homewrecker

This is exaclty the pump ive ordered from Rock Auto

DennisMik

iTrader: (2)

Here is the complete FSM for your car:
http://boredmder.com/FSMs/Nissan/Maxima/2000.5/

Specifically, you want section EC, page 717:
http://boredmder.com/FSMs/Nissan/Maxima/2000.5/EC.pdf

MichMaxFan

No. Mine was about half inch long and had a small flange on it. Grommet probably isn't the best word for it but it fits on the round output of the pump and seals the connection to the filter so fuel gets forced into the filter and up thru the lines. If u have no such rubber piece at the mating connection into the filter then that's almost certainly your problem.