Fuel Pump does not shut off
06-22-2010, 06:49 PM
#1
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Fuel Pump does not shut off
I've been trying to figure out my mpg issue.
Right now I'm getting around 10-12 mpg
So far I've cleaned MAF, TB
Also the car runs pretty well, no idle issues
Changed fuel filter
Changed o2 sensors
The main issue I cannot figure out happens when I go to start the car. When I turn the key to ignition, I hear the pump start and run, but it just keeps running, if I wait long enough, the car becomes more and more difficult to start as the pump keeps pumping. I'm sure its the pump because if I pull the pump fuse I hear it cut off (Brand new battery, starts easily if not left in ignition)
However, it works fine if I were to start the car, turn it and turn it back to ignition, in this case everything works fine, I hear the pump come on and shortly after shut off.
I thought could be a clogged filter preventing the line from pressurizing, however after changing that the issue still exists.
Any help would be appreciated.
Car is 03 Maxima, 80k miles
Right now I'm getting around 10-12 mpg
So far I've cleaned MAF, TB
Also the car runs pretty well, no idle issues
Changed fuel filter
Changed o2 sensors
The main issue I cannot figure out happens when I go to start the car. When I turn the key to ignition, I hear the pump start and run, but it just keeps running, if I wait long enough, the car becomes more and more difficult to start as the pump keeps pumping. I'm sure its the pump because if I pull the pump fuse I hear it cut off (Brand new battery, starts easily if not left in ignition)
However, it works fine if I were to start the car, turn it and turn it back to ignition, in this case everything works fine, I hear the pump come on and shortly after shut off.
I thought could be a clogged filter preventing the line from pressurizing, however after changing that the issue still exists.
Any help would be appreciated.
Car is 03 Maxima, 80k miles
07-24-2010, 09:58 PM
#7
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I'm desperate, only getting about 13 mpg in the city, and 15-16 on the highway, I don't know what else to change. I'm considering getting a used fuel pump assembly off ebay.
07-25-2010, 12:13 AM
#8
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Why are you thinking of changing the fuel pump which is running and developing fuel pressure and flow........the engine does run?? The ECM controls (grounds) the fuel pump relay which puts battery voltage to the pump. If the ECM does not get a signal from the camshaft position sensor (phase) when the engine starts/runs then the ECM is supposed to kill the pump operation after about a second. Are you sure that you changed the correct relay.......there is another relay close by it? Check the relay/ECM harness wiring between the relay terminal 2 and the ECM for damaged insulation that might be grounding the relay. If I'm reading the FSM correctly the only other cause for your issue could be the ECM. The condensor in the pump motor circuit is taped to the harness (like the ignition condensor) in the area of the left rear wheel well area in the trunk, I think. I can't see it being the cause of your issue.
07-25-2010, 09:36 AM
#9
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Why are you thinking of changing the fuel pump which is running and developing fuel pressure and flow........the engine does run?? The ECM controls (grounds) the fuel pump relay which puts battery voltage to the pump. If the ECM does not get a signal from the camshaft position sensor (phase) when the engine starts/runs then the ECM is supposed to kill the pump operation after about a second. Are you sure that you changed the correct relay.......there is another relay close by it? Check the relay/ECM harness wiring between the relay terminal 2 and the ECM for damaged insulation that might be grounding the relay. If I'm reading the FSM correctly the only other cause for your issue could be the ECM. The condensor in the pump motor circuit is taped to the harness (like the ignition condensor) in the area of the left rear wheel well area in the trunk, I think. I can't see it being the cause of your issue.
07-25-2010, 01:09 PM
#11
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UPDATE: If I pull the fuel pump relay while the car is running the car slowly dies in about 5-10 seconds. From my understanding the fuel pump relay only controls the fuel pump when the key is first put into ignition. Right? So what does this mean.
07-25-2010, 07:32 PM
#12
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Why you have normal operation after going to ON the second time, I cannot explain. But, the ECM does control the fuel pump relay as I explained earlier. Looking at the FSMs of model years '00, '00.5, '01 and 02, only the '00.5 has the fuel pump control module that controls "high" and "low" voltage to the pump. But even with that system, the fuel pump relay still puts voltage directly to the FPCM and the pump as commanded by the ECM. The "timed one second" no run pump kill has got to be done with ECM circuitry.......but why it works on the second Ign. ON deal.......has got me. When you pull the pump fuse and kill the pump it just takes a few seconds for fuel pressure (and flow) to drop enough to kill the engine.
07-25-2010, 08:17 PM
#14
swap the fuel pump relay with another similar relay and see what it does......Or pull the relay and measure the two wires going to the pump and measure for any shorts, ground, etc.....measure the input side of the relay plug as well
07-25-2010, 09:10 PM
#15
your fuel damper at the rail could be bad, leaking pressure such that the fuel is being pushed through the injectors. this would especially explain the hard start if you leave the key on and pump running. would also explain poor mileage as you would always be getting extra fuel as a result of high fuel pressure
07-25-2010, 09:32 PM
#16
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your fuel damper at the rail could be bad, leaking pressure such that the fuel is being pushed through the injectors. this would especially explain the hard start if you leave the key on and pump running. would also explain poor mileage as you would always be getting extra fuel as a result of high fuel pressure
Hm how would I be able to test this, I was thinking this earlier, maybe leaking injectors or something which could be why the pump keeps running since it cant build pressure. Anyone know how to test this?
07-25-2010, 09:44 PM
#17
you could check the pressure with a fuel gauge. use the procedure outlined in the FSM. this would tell you if you are building pressure or if its leaking out somewhere. that would be the place to start. next option would be test the damper which i dont know how to do any other way than just replace it
07-25-2010, 11:13 PM
#19
Why do you turn the key to run and not start the car? My brother had a similar issue with his old Q45. His wife was leaving her work when someone came out to talk to her, she had already turned the key to run but hadn't actually started the car. After a 60 second conversation, she then tried to start the car but it wouldn't do anything. The fuel system pumped the cylinders full of gas and hydro-locked the engine. All the spark plugs had to be removed to pump the gas back out (then the engine power washed), before reinstalling the plugs and finally getting the engine to start. I thought it was only a Q45 issue (which is apparently somewhat well known according to the mechanic who worked on the car) but maybe it is a Nissan thing too.
07-26-2010, 06:36 AM
#21
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Why do you turn the key to run and not start the car? My brother had a similar issue with his old Q45. His wife was leaving her work when someone came out to talk to her, she had already turned the key to run but hadn't actually started the car. After a 60 second conversation, she then tried to start the car but it wouldn't do anything. The fuel system pumped the cylinders full of gas and hydro-locked the engine. All the spark plugs had to be removed to pump the gas back out (then the engine power washed), before reinstalling the plugs and finally getting the engine to start. I thought it was only a Q45 issue (which is apparently somewhat well known according to the mechanic who worked on the car) but maybe it is a Nissan thing too.
07-26-2010, 08:10 AM
#22
07-26-2010, 11:43 AM
#23
thats not the way to solve this problem since hard start is not his only symptom. If it was I would agree that is a good short term solution, but not leaving it on without starting it wont solve the MPG problem
07-26-2010, 01:26 PM
#24
I read the 2003 Infiniry Q45 manual and it seems to be the same as the maxima manual. The ECM uses the output from the camshaft position sensor sensor to decide to activate the fuel pump or not. No signal equals run the pump. Since the car runs, the sensor itself works.
.
If you want to download the manual, go here -
http://www.nicoclub.com/FSM/
.
There is also a fuel pressure regulator in the gas tank. It is not part of the fuel pump, it is a separate module that is inbetween the pump and the flange that holds everything in the tank. Maybe this regulator is not working.
.
If you want to download the manual, go here -
http://www.nicoclub.com/FSM/
.
There is also a fuel pressure regulator in the gas tank. It is not part of the fuel pump, it is a separate module that is inbetween the pump and the flange that holds everything in the tank. Maybe this regulator is not working.
07-26-2010, 02:29 PM
#25
I'm just saying to prevent possible hydro-locking the engine like happened in my brother's Q45, for right now, either start the car or leave the key in the off position.
07-27-2010, 01:06 PM
#28
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The fuel pump isn't causing your MPG issue.
If you were running rich (to much gas) or lean (not enough pressure) you'd get a CEL.
When was the last tune up? What did the plugs look like?
What mods do you have on your engine?
What is your style of driving? City, Highway??
What rims, tires are you running and are they inflated correctly?
Alignment checked?
If you were running rich (to much gas) or lean (not enough pressure) you'd get a CEL.
When was the last tune up? What did the plugs look like?
What mods do you have on your engine?
What is your style of driving? City, Highway??
What rims, tires are you running and are they inflated correctly?
Alignment checked?
07-27-2010, 02:51 PM
#29
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Just changed the plugs, no difference, had oil on two of the rear plugs, gonna change the valve cover soon, I have no mods to the engine other than the ghetto air box, I drive mostly highway, doing around 60-70 mpg, driving it gently, the tires are new but the rims are all bent, alignment has been done.
07-28-2010, 10:55 PM
#32
this is incorrect. trust me, you will only throw a CEL for lean/rich under limited circumstances. if you are in a situation where you run very rich for just a bit and then it catches up, you will get bad mileage and no CEL...personal experience
08-02-2010, 06:30 PM
#33
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Figured it out today. Seems person who installed the remote start before I got the car mixed up the start signal and ignition wires. Therefore, whenever the car was in ignition, the ECM thought the car was cranking so it ran the pump constantly. This is also why why memory seats werent working, they dont function when the start signal wire is energized.
08-02-2010, 06:32 PM
#34
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After getting, 12-14 mpg combined highway and city for the past 5 months, I fixed the wiring today and took her on the highway and the on dash display was reading upwards of 24 mpg 
WIN!
WIN!
10-21-2010, 05:51 PM
#38
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Fuel Pump Weirdness
So today, I experienced something similar with my 5th gen. I stepped out of the car and noticed a loud pulsing vibrating noise coming from my car....I think, My cell phone must be on vibrate inside my console. Nope, cell phone is in my back pocket. I walk around the car....definitely sounds as if the noise is coming from underneath the car in the area of the gas tank. I sat down in the car and turned the ignition on. I hear the normal high pitched wine I'm used to hearing from the pump and I continue to hear the pulsing vibrating buzzing noise every few seconds. I turned the car back off and removed the gas cap and the noise stops almost immediately. I screwed the cap back on and closed the lid and started walking and before I reached the door of the house, it started up again. I searched, found this post and returned to the car to remove the fuel pump fuse which did indeed stop the pump. Everything electrical in my car is stock with the exception of my poineer head unit which is mated to the Factory bose amps. What is wrong with my car? Do I need to call an exorcist?
10-21-2010, 05:54 PM
#39
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So today, I experienced something similar with my 5th gen. I stepped out of the car and noticed a loud pulsing vibrating noise coming from my car....I think, My cell phone must be on vibrate inside my console. Nope, cell phone is in my back pocket. I walk around the car....definitely sounds as if the noise is coming from underneath the car in the area of the gas tank. I sat down in the car and turned the ignition on. I hear the normal high pitched wine I'm used to hearing from the pump and I continue to hear the pulsing vibrating buzzing noise every few seconds. I turned the car back off and removed the gas cap and the noise stops almost immediately. I screwed the cap back on and closed the lid and started walking and before I reached the door of the house, it started up again. I searched, found this post and returned to the car to remove the fuel pump fuse which did indeed stop the pump. Everything electrical in my car is stock with the exception of my poineer head unit which is mated to the Factory bose amps. What is wrong with my car? Do I need to call an exorcist?
I'd try changing the fuel pump relay first
10-21-2010, 09:03 PM
#40
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I think I will go for the relay, looking at courtesy nissan, it looks like it will only be about $20 or less. I put the fuse back in after about a few hours and I haven't heard the demon since. I was concerned the fuel pump would burn itself out or drain my battery if I didnt stop it.