Fuel Pump Always On

[Manuel Kasko]

Hey guys

So my car when you turn the ignition you can hear the pump pump for around 10 seconds. My friends r33 seems to be making the pumping noise constantly.

He also thinks he is having fuel that has not been burnt coming out his exhaust.

Any ideas on what would cause this?

[Odium]

And its driving alright? Any mods?

[89CAL]

You mean when the car is running the fuel pump is constantly going?

Thats not a real big deal, Remember the injectors control fuel into the engine. My fuel pump runs constantly

Regulator controls pressure in the rail, injectors control fuel into the engine, pump creates the flow

[Rolls]

He probably has either an aftermarket pump or a pump that is dying, most aftermarkets are loud, dying pumps can also be loud.

Oh they also tend to be much louder in summer as well.

Unburnt fuel out the exhaust indicates a tune problem, probably due to an air leak causing the car to run rich, dead sensors, coupled with running more boost than standard putting the stock tune out.

Tell him to take it to a performance shop to get it looked at.

[Odium]

Yep if its dumping fuel into the engine, the fuel pump will need to be on more to keep up the pressure.

Also if the fuel pump is dying it'll be pumping less fuel, so it will need to be on more to keep up the pressure.

Question for someone more knowledgeable than myself:

If the sensor which measures the fuel rail pressure is dodgy and the pump is staying on because of that, would the pressure get way too high in the rail, and spit more fuel through the injectors? causing the rich condition the OP mentioned?

[kitto]

Yep if its dumping fuel into the engine, the fuel pump will need to be on more to keep up the pressure.

Also if the fuel pump is dying it'll be pumping less fuel, so it will need to be on more to keep up the pressure.

Question for someone more knowledgeable than myself:

If the sensor which measures the fuel rail pressure is dodgy and the pump is staying on because of that, would the pressure get way too high in the rail, and spit more fuel through the injectors? causing the rich condition the OP mentioned?

A lot of that is incorrect i'm sorry. In most EFI cars when you switch the ignition switch to on, but not start the engine, the fuel pump will prime for about 4 seconds to pressurize the fuel rail.

When you actually turn the key, the CAS sends a signal back to the ECU to say that the engine is rotating and trying to start. The ECU then sends a signal to either a relay or a Fuel Pump Control Module to run the pump.

Whenever there is a CAS signal, either when trying to start the engine or the engine is running, the fuel pump is always on.

Most EFI cars run the pump at a lower rate on idle (Fuel pump control module controls this). As soon as the ECU sees that the throttle is no longer on idle, the pump then runs at full speed until the engine returns to idle again.

Most people that put a larger pump in usually change the wiring and have it so that the pump runs at full speed all of the time as the fuel pump control modules tend to fail and wont usually support the current of a larger fuel pump. Unfortunately running the pump at full speed all of the time un-necessarily heats the fuel.

Some people do it dodgy and wire up the pump to be running ALL of the time whenever the ignition is on. This is not good for a few reasons. Firstly you heat the fuel up by pumping it around when you dont need to. But the more important one is in the event of an accident if the ECU controlled the fuel pump, when the engine stalls from being in a car crash, the fuel pump stops pumping, reducing any risk of fuel being spilt due to a ruptured fuel line.

If the pump is on all of the time, then you could have fuel pumping everywhere in the event of an accident.

Skylines do not have fuel pressure sensors, i am not sure about other vehicles, i would dare say most modern diesels the ECU would monitor fuel pressure. Maybe newer petrol vehicles monitor it aswell.

[Manuel Kasko]

Hey guys im going to get him to post on here so he can explain it a little more

Cheers for the current information

[DVS JEZ]

Where is he located

[Manuel Kasko]

Right now we are in the ACT but he lives on the coast in ulladulla

Why is that?

[Manuel Kasko]

Your up in Brissy aren't you

[89CAL]

Most newer diesels are Common Rail which require a pressure sensor on the rail. The machinery I work on will sometimes recieve a Low rail pressure warning if the pressure goes to low, and this can make the engine bog down.

Common rail pressure can get up near 40,000psi (I've worked on machinery where the pressure limiter (relief valve basically) is set to 38,000psi) So you dont want high pressure in here either. The pressure limiter can control this to a degree, its mainly there as a safety for spikes etc.

I assume most light vehicles run under similar principles just not as high pressures from memory.

Fuel pressure sensors arent needed in Skylines as the pressure regulator controls the pressure using the Vac/Boost feed. Its not a fool proof system, but 99% of the time its fine. Its only when something goes wrong that having a sensor would probably be benneficial

[Manuel Kasko]

So in regards to the air leak making it run rich. Just check all the hoses or inter cooler piping? Where should I be looking for this leak?

Also don't know about the aftermarket pump or not

His running stock everything except for front mount

Not even a boost controller

Newly purchased car so we will check if the pump is aftermarket or not. Might put it in my car to test if it's the pump.

[wilderboy]

Hey guys I'm Shane kaskos friends with the fuel problem

Thanks for all the posts it's given me alot to think about

I think I might problem solve by replacing the pump and checking the wiring to the pump

Because as I have been told it should only prime te car for about 5 to. 15 seconds and them turn off and it's fine but mine runs all the time but sometimes it doesn't every none and again tho do that the weird thing

I dont know of I should try and reset my ecu buy taking the battery out or something. But I think new fuel pump and chech the wiring!!

The guy I brought it from had a bootstrap controller and ever since I brought it I can always smell a really rich fuel smell

So I really don't know what to do iv had it a month and I'm finding problems

[Rolls]

Hey guys I'm Shane kaskos friends with the fuel problem

Thanks for all the posts it's given me alot to think about

I think I might problem solve by replacing the pump and checking the wiring to the pump

Because as I have been told it should only prime te car for about 5 to. 15 seconds and them turn off and it's fine but mine runs all the time but sometimes it doesn't every none and again tho do that the weird thing

I dont know of I should try and reset my ecu buy taking the battery out or something. But I think new fuel pump and chech the wiring!!

The guy I brought it from had a bootstrap controller and ever since I brought it I can always smell a really rich fuel smell

So I really don't know what to do iv had it a month and I'm finding problems

Think about this, if the fuel pump only runs when priming where does the fuel come from when you are driving along? Answer is it runs ALL the time on ALL cars. Standard I think they run at two speeds, lower at idle and normal the rest of the time. It is summer though so almost all fuel pumps are noisy this time of the year, aftermarket especially.

When you say runs all the time, do you mean when you put the ignition on but don't start the car it runs literally for ever and does not stop priming? If so then the previous owner has most likely installed an aftermarket pump and done very dodgy dangerous wiring keeping it on all the time, if so fix the wiring, however most aftermarket pumps are loud, nothing you can really do about this unless you go a nismo in tank pump, these are probably the quietest you can buy.

Do you mean boost controller? It will definitely run overly rich when on boost but at idle etc it won't change anything.

If it REALLY smells of fuel you may actually have a fuel leak, would explain why the pump is going mental and the car stinks. Most likely that you just have a car with dodgy sensors (O2, coolant temp etc) or a boost leak (old vac hoses leaking or silicon joiners split which are causing it to run extra rich as metered air is escaping under boost.

Steps to take:

Ask the previous owner if it has an aftermarket fuel pump, if aftermarket then nothing to worry about but check wiring.

Check for fuel leaks

If all the above checks out get someone who knows skylines to have a listen, chances are it isn't actually that loud and is normal, if not then you may have a failing pump, get a replacement

Fuel smell:

Check you have a cat converter, chances are it has been bashed out, car will always stink without a cat.

Check for fuel leak

Get a consult cable or go to a workshop that has one and check for sensor failures.

Check yourself for air leaks, if you cant find any pay a workshop to pressure test your intake, it is simple to do and will find 99% of leaks.

Let us know how you go

So in regards to the air leak making it run rich. Just check all the hoses or inter cooler piping? Where should I be looking for this leak?

Also don't know about the aftermarket pump or not

His running stock everything except for front mount

Not even a boost controller

Newly purchased car so we will check if the pump is aftermarket or not. Might put it in my car to test if it's the pump.

Check all silicon joiners, if you have an aftermarket FMIC chances are it has dodgy hose clamps that aren't sealing. Check all vac lines are on properly, if you have a boost gauge your vac should be -20 when throttling off or -16ish when idling, if it is lower you most certainly have an air leak, however you might have a minor leak that isn't obvious at idle, only on boost. Only 100% way to check for leaks is to pressure test intake with an adaptor on the pod, you will hear whistling when on boost if there is a leak.

No easy way to check pump is aftermarket, removing it is a pain in the ass, only do this if you are planning on changing it, most drop in pumps have similar/identical fittings to stock.

Honestly if you just bought this car and you aren't familiar with them nor a handy home mechanic I would take it to a performance workshop, they will be able to run a quick diagnostic with consult cable, check for air leaks, run it up on the dyno to check AFRs etc and just make sure there are no major problems with it. Shouldn't cost you more than $150 them to do some basic tests.

Edited December 24, 2011 by Rolls

[wilderboy]

Thank dude I will do and I'll have to check how long it stays on for when just on ignition is on! And I'll have to have a look a the fuel pump and see if it's after market or not

[Rolls]

Thank dude I will do and I'll have to check how long it stays on for when just on ignition is on! And I'll have to have a look a the fuel pump and see if it's after market or not

It is in the fuel tank, you can't see it unless you remove it, and removing it is a pain in the ass. There is a possibility that the previous owner installed an external pump, you'll be able to see that in about 3 seconds if you look in the boot though.

If he installed an external pump it will always be noisy and unless you get good quality lines it will also smell.

Edited December 24, 2011 by Rolls

[wilderboy]

Oh ok cool cool well I don't even have a boost gauge its all stock bar the fmic 3 and a half inch exhaust so I'll have to check all the hoses and lines

[wilderboy]

Yea iv done about 4 fuel pump chances on a few cars but never a skyline tho

[Rolls]

Just FYI a FMIC and 3.5" exhaust will increase the boost above standard, usually quite a bit as well. There is a chance the previous owner modifiied the stock boost solenoid to run 7psi all the time, not the 2 step 4/7psi where it switches over at 4500rpm. With the free flowing exhaust and intake it isn't uncommon to see the boost rise to 9-10psi.

If it has gone as high as 10psi the ECU will be running very rich when on boost, you will most likely see clouds of blackish smoke coming out the exhaust when giving it a bootfull, nothing wrong with this, in fact it means the engine is running quite safe and cool, it however won't make much power and will use slightly more fuel.

Edited December 24, 2011 by Rolls

[wilderboy]

Well I know for a fact it's got the 2 stage boost because before 4500rpm it's at 5 and above that its 7