My fuel pump decided to die late last year, so i ended up putting in a new TT fuel pump seeing as most threads i came across mentioned the TT fuel pump to be an upgrade/better option than the NA fuel pump & for the same price i figured why not. My zed is NA, & quite a few years back the FPCU was bypassed as per usual but i would like to get it fixed properly. Should i be using a TT FPCU as i am using a TT fuel pump in my NA zed? Or do i just keep using my NA FPCU? Is there any differences between the NA & TT FPCU? Is there a writeup on what to check & fix inside the FPCU once it gets opened up? As i would like to see if my FPCU can be repaired before buying a brand new one. Thanks in advance.
You are better off with TT FPCU if you wanna run TT pump just to be sure that fuel delivery is good. Although you may need to buy yourself an adjustable fuel reg to make up for that extra amount of fuel pressure being deliver otherwise will be running quite rich at idle etc. However I don't see the point of using TT bits into an N/A unless ur N/A is pushing some serious power. IMO I'd stick with N/A bits.
Abz.. I ran a TT Fuel pump with an NA FPCU in my old NA for many years. Never had a problem. Just means that the TT fuel pump will be running at full speed as the NA FPCU only has one speed. But its not going to oversupply your engine with fuel as thats governed by the fuel pressure regulator in the engine bay.
The Fuel Pump Control Unit (FPCU), controls voltage supply to the fuel pump. Battery voltage is supplied to both the NA & TT under the following conditions: For 1 second after the ignition switch is turned on. During engine cranking. [the voltage will drop to around 10 volts] In the case of a TT for 30 seconds, an NA for 5 seconds after the engine has been started & the engine temperature is above 50 degrees Celsius. [the voltage could be around 14 volts] The engine temperature is below 0 degrees Celsius. The engine is running under heavy load conditions. [eg: on a dyno, drag strip or going up a steep incline] When the engine is running under middle load conditions the TT pump is supplied with 7 volts, while the NA has battery voltage. [the battery voltage will be determined by the alternator output, so it will be above 12 volts, probably about 13 or 14 volts] Except for the above conditions, the TT will have approximately 6 volts & the NA approximately 8 volts. By referencing the voltage supply to the fuel pump during the above conditions, the FPCU can be diagnosed as working within the design parameters or not. Fuel pressure is controlled by the Fuel Pressure Regulator, engine vacuum, Fuel Temperature Sensor, Pressure Regular Vacuum Relief (P.R.V.R.) Solenoid Control Valve & the E.C.C.S. Control Unit (ECU). The fuel pressure is maintained at 43.5 psi, the amount of fuel delivered to the engine via the injectors is determined by the injector pulse width [how long the injector is open]. Fuel Pressure Regulator Control: The fuel "pressure up" control system briefly increases fuel pressure for the improved starting performance of a hot engine.
The tt has a additional wire from the ecu. Won't work properly in a na. Just use the Na fpcu or bypass it.
Thanks everybody for the replies. I shall stick with the NA FPCU. At times when i turn the key to ignition, i cannot hear the fuel pump priming & it takes a few extra seconds to start rather than the first turn start which is normal, including when ive driven the car & turned it off & back on, hence why i thought i would ask, as I'm certain the fpcu was bypassed quite a few years back, but this only started happening once i had the TT fuel pump put in, unless my mechanic reversed the bypass for some reason, is there any other suggestions or explanations? @Mark - cheers for that. So did you still have the original fpr or did you have an aftermarket one? Is there any write up or guide as to what exactly goes wrong with the FPCU that it needs to be bypassed inorder to get it started? Is there any way to fix the FPCU instead of buying a brand new FPCU? Is LHD & RHD FPCU all the same? @ East Coast Z - Does running the TT pump at full speed all the time cause its life span to get shorter at all? Thanks in advance, i really appreacite all the help.
Don't buy a brand new NA FPCU....... There must be hundreds of used NA controllers kicking around out there..... buy two and have one as a spare (at a fraction of the price). There's a writeup on TTnet about repairing FPCU's, but for all the trouble and expense it's just not worth it Bypassing the FPCU (either variety) is only meant to be a temporary measure, because it runs the pump at battery voltage ALL the time, which will theoretically shorten the life of the pump and will increase your fuel temperature because your pump sits inside the fuel tank
My TT has had its FPCU bypassed so the pump run full speed all the time. it's loud but I didn't mind. Generally it would wear the pump faster but saying that I've had the car running for quite a while without any problems with shortage of fuel supply. The trick for me is to buy an adjustable fuel reg to compensate for the excess pressure on idle so I won't run rich. I have fuel pressure gauge mechanical under the bonnet and electrical in cabin, works great. I think it's always good idea to have a guide to see what's going on with fuel pressure as preventative maintenance.
The original pressure regulator really should do the job fine, its more common to have problems with an adjustable reg because its possible to set it up incorrectly. Nissan designed theirs to work with both the NA and TT system, no need to change it until you go for a big pump like the 550lph.
Correct...... The only time the fuel pressure differential is increased above 43.5psi is when re-starting a hot motor (assuming your zed still has the PRVR solenoid valve fitted) Increasing voltage to your fuel pump will make it run faster, it will NOT increase your fuel pressure
Agree to disagree, yes the pump runs faster obviously means able to pressurise the fuel system faster/more however you wanna call it. The increased in pressure is noticeable at idle (idle once again). It pumps more fuel than the system is capable of returning excess fuel to the tank thus injecting slightly richer mixture at idle. Under heavy acceleration there will be small difference. That's why I decided to go for adjustable just to tweak the fuel delivery at idle. But then again it should run alright without adjustable.
It means more flow, the stock reg should be able to handle that flow without affecting pressure, if it can't its probably failing with age.
Yes that's true, factors such as age and condition of regulator etc contributes to such effect. Mine was probably just really old (like most as) and not so efficient as it used to be. Really happy with looks of this tomei regs though, looks cool sitting under the bonnet
I beg to disagree..... ......increasing the pump speed or installing a larger capacity pump will not increase fuel pressure. The pump provides flow, RESTRICTING flow creates pressure. The size of the return line to the tank will not increase pressure at the injectors, unless you severely RESTRICT the line. As an example, pumps are measured by the amount of fuel they can move, this is usually expressed in lbs. Pump efficiency is measured by the flow rate (lbs) against pressure. So if you have a pump & decrease the outlet diameter the pressure will rise & so will the current (amps). By decreasing the outlet diameter (increasing the pressure) further, the pump will eventually reach a point where it is unable to continue to supply the same amount of fuel & the flow rate of the pump will drop significantly. Therefore the maximum flow rate of the pump will be highest when there is no pressure on the outlet line of the pump. Increasing pressure on the same outlet line will reduce the flow rate & cause the amperage to rise. Pump curves are very much like dyno charts on engines.
