Hesitation Problem On My Gt-t

[TriniGT]

I have had some issues with my GT-T lately and was wondering. I recently had a failed fuel pump, car was witched off and the timer running and the pumped failed. I replaced the fuel filter and fuel pump (replaced with a Walbro) and that eliminated the starting problem. Now my new problem is that ever since the fuel pump install I get a hesitation problem on cruising and light throttle, usually around 1500-2000rpm. Is it the fact that I have more fuel going to my system? I decided to change my plugs eventually, put in some BKR7E-11 Iridiums and gapped them down to 0.8mm to see if that would help but still no go. I then decided to wire up my AEM Wideband to see how my car is running at my low boost setting and I get an AFR of 10.2.

My car has a Blitz Access ECU, Blitz SSBC, Trust Air Filter (recently cleaned), HKS FMIC, Trust Oil Cooler and a Pivot ACS-M to control my air flow. I have since decided to adjust the pivot to see f it will help the situation; it was currently set to +2 (this is just a single dial setup, yes it may be junk but it is all I have a the moment) so I decided to lower it to between -1 and -2. Now on full boost which is 0.6 bar my AFR is about 11.4-11.6 and my idle is around 14.7. My concern I have is that when I am boosting and I come off the throttle that I get a lean area, it automatically jumps to off the lean side of the gauge and then comes back to around 13.5 AFR. On slight throttle out of boost around 0.2 bar vacuum I am seeing AFRs between 14 and 16, should I worry?

Since the plugs have been changed and the Pivot adjusted the car has been noticably peppy but I still have this hesitation at low rpm and cruising that is quite annoying. I have also noticed as of recently that my battery has developed a weak start, the car starts every time but it feels sluggish to start, can a weak battery have any relation to my hesitation problems or may it be a combination of weak grounding? I am stumped and before my fuel pump failed I never had a problem. Any help will be greatly appreciated.

Jason.

[EliSun]

First problem here would be your walboro pump.

Check that it has the correct voltage going to it, and since you're going to be doing that, you'd might aswell ground it properly and redo the wiring.

Also copper plugs would be fine, you dont really need iridiums or platinums

An AFR ratio of 10.2 is also quite lean, AFR ratio on idle should naturally be 14.7 and when on boost it should be between 12.7-13.3

In short, you definately need to get your car tuned, which can be a good or bad thing.

bad because you have to pay for it and good because your car should be running sweet.

sorry i dont have time to be more in depth, im on a busy schedule at work,

hope this helps

Edited May 13, 2009 by EliSun

[TriniGT]

I thought that 10.2 AFR would have been a rich state and 17 is on the lean side? Gonna be checking the Walbro voltage at the connector tomorrow, swapped a new battery in as the other one was on the way out. I am gonna swap out the plugs for coppers in an effort to correct my problem but this problem happened only when the fuel pump failed initially and I swapped in a Walbro to replace the stock fuel pump. On light throttle I encounter the hesitation and it seems to be getting worse and more annoying. I am taking tomorrow off to further investigate. I wanna run a direct for the pump with a new relay to see if that helps anyone with a diagram to help a situation on the relay wiring?

[EliSun]

I thought that 10.2 AFR would have been a rich state and 17 is on the lean side?

whoops, yea thats what i meant, funny how getting one word wrong could make it sound so bad.

also adjust your fuel pressure regulator, and if you dont have one, you should get one

however, you'll still need to get it tuned so that your car gets the correct fuel throughout the whole rev range.

Edited May 13, 2009 by EliSun

[R31Nismoid]

^^ Why should be get a fuel pressure regulator exactly?

Because simply put - there is absolutely NO reason for him to buy one, the stock Nissan one if perfectly FINE even for 400rwkw+ applications if injectors are correctly sized.

To say he needs a FPR is wrong.

[TriniGT]

^^ Why should be get a fuel pressure regulator exactly?

Because simply put - there is absolutely NO reason for him to buy one, the stock Nissan one if perfectly FINE even for 400rwkw+ applications if injectors are correctly sized.

To say he needs a FPR is wrong.

That's what I thought as well. I have researched and saw that AFPRs are not needed unless you absolutely want to squeeze every ounce out of the system. Anyway, It is 6:00AM over here so I wanna get an early start on this, I am going to scrap the back of the trunk area and measure the voltage at the pump when the switch is in the ON position and when the car is started and when the A/C and the music and every accessory is on to have an idea what voltage is reaching the Walbro. Before when I was wiring the Wideband and I used my deleted VSS switch to pull an ignition signal and I measured the voltage it was 12.5 and when I tumbled the car it dropped to 7.6V, I am thinking the battery was failing and that may have caused the fuel pump to die from not getting enough voltage.

A new battery is in now so that is eliminated, Walbro in as well. I noticed when I installed the Walbro that it was a tight fit and the top of the walbro butted the hard line that goes to the line supplying the engine. I don't see it being a potential problem but today I am going to be installing a fuel gauge in the engine bay to see what is really going on when the throttle is feathered. Any suggestions and also how to wire the fuel pump directly, I have never wired a relay but I am handy with electronics. Thanks again for the help otherwise.

[raps86]

pm sent regarding relay wiring

[TriniGT]

Thanks for the diagram. I did some other checks today. I installed a Fuel Gauge in the engine bay and to my surprise when I tumbled the car I saw a reading of 20 psi. This is a new Walbro pump, I am noe wondering if I am not getting the proper voltage going to the pump but even then it should still have a 40 psi reading or thereabouts even if the voltage was lower. I checked the voltage on both harnesses going to the fuel cover as I am not sure which one goes to the pump and which to the fuel gauge, thinking the thicker ones were for the fuel pump. When I started the car and took a reading on the two thick wires the black w/ yellow stripe read 12.87V on slight throttle it was rising to around 12.91V; when I took the reading on the white with the green stripe I got a next reading when I was thinking I should have gotten a ground reading, the readin was about 9.35V and on light throttle it dropped to around 8.9V.

Which wire is suppose to be the power wire for the pump and why am I getting a second reading on the other wire or is it because everything is connected and the car on? Is it that the Walbro is just defective and I should just replace it?

[TriniGT]

Anyone can advise me?

[TriniGT]

Anyone can shed some light and ideas?

[jsh58home]

that could be a tough one given it seems you've got plenty of air and it also seems doubtful that your new fuel pump is pumping too little fuel. i'd check the grounds on your ignition amp. which engine do you have again?

[Guilt-Toy]

cheers for the PM, this is my suggestion.

Sometimes people don't install the fuel pumps properly or put them back in the tank properly. open the inspection hole and check to make sure the pump bracket is sitting in there correctly. if its not it can cause you some issues. if you are unsure then take it out and put it back in properly and make sure everything is 100% in there. if you are not sure then its not 100%

wire your pump to a relay and its own earth, use the current power wire to switch the relay on. This is needed for ANY walbro pump as they are not rated to run at 12v they need 13 14v ???

next thing to do is buy a set of COPPER plugs. you cannot gap those irridums or platnum spark plugs properly because it stuffs them! NGK BCPR7ES gapped to .8 is a good start. this is a must also.

good luck with it

[TriniGT]

Thanks a lot for taking the time to reply, I already bought the coppers to swap in they are NGK V-Power BKR7E-11 and I'll gap them to 0.8mm. Can you by chance sned a diagram illustrating the relay wiring, I have one but just to emphasize it seeing that you have probably done it already. Also next question, when the wires are connected to the pump and I check the voltage on the thick black wire with the yellow stripe I get 12.87V and when I measure on the White wire with the green stripe I get 9.3V, both are on the same pair and they are thick so I am thinking they go to power the pump but why both have a voltage, is it because the car was started when I measure the voltage? Anyone got a schematic for the ER34 pump wiring? Thanks again for the response people.

I see there is a relay already for the fuel pump so that means I am taking the supply form the first relay and using it to power the second relay? This is what raps86 sent me can you just confirm as I wanna ensure that everything is proper in the end, not doubting you raps86 but I just want a confirmation before I go about cutting my wires. Also I have located a used Walbro from a friend to use for testing purposes as it is a known working one. Also any particular brand relay?

Edited May 14, 2009 by TriniGT

[Guilt-Toy]

Thanks a lot for taking the time to reply, I already bought the coppers to swap in they are NGK V-Power BKR7E-11 and I'll gap them to 0.8mm. Can you by chance sned a diagram illustrating the relay wiring, I have one but just to emphasize it seeing that you have probably done it already. Also next question, when the wires are connected to the pump and I check the voltage on the thick black wire with the yellow stripe I get 12.87V and when I measure on the White wire with the green stripe I get 9.3V, both are on the same pair and they are thick so I am thinking they go to power the pump but why both have a voltage, is it because the car was started when I measure the voltage? Anyone got a schematic for the ER34 pump wiring? Thanks again for the response people.

maybe you should see a auto electrician? get him to wire it up for you ? look in the DIY "Do it yourself" section of SAU, there would have to be a guide on there on how to do this with pictures.

I dont have any diagrams mate, sorry

12.87v is not enough for a walbro, you need 14 volts

[TriniGT]

This is what you're talking about Guilt-Toy?

http://www.skylinesaustralia.com/forums/Fu...ml&hl=relay

http://www.skylinesaustralia.com/forums/wi...ml&hl=relay

Edited May 14, 2009 by TriniGT

[Guilt-Toy]

yes

[TriniGT]

So I removed the pump once again, something is definitely wrong, everything checks out good just not sure on the voltages. Is there any chance that the fuel lines can be connect wrong on the top of the fuel tank cover? I removed the setup again only to realise that my friends pump was a GSS341 and has the setup on the wrong side so fitment was too much trouble. I decided to do what Guilt-Toy said and take my time and install the pump again. This time I am 100% sure of the install and it still gives the same 20psi reading on idle. Could it possibly be a clog fuel hard line? Has anyone ever encountered that problem? I mean getting bad voltage may be one thing but getting 20psi is something else. Also what is this round plastic float thing on the pump supply line?

I also found a harness in the tank with three wires that is clipped together in there, anyone know what it's for?

Edited May 15, 2009 by TriniGT

[R31Nismoid]

The FI Guide has a fully detailed link to wiring for fuel pumps..

have a read of it.

FI Guide should be the first stop for everyone, it has links to VERY good info

[TriniGT]

Hmmm ... will check it again.

Edited May 15, 2009 by TriniGT

[TriniGT]

Okay did some more checks and here are my findings. I replaced the walbro I had with a replacement known working walbro from a friends car and initially when I allow the pump to prime it swings the fuel gauge to 36psi. So I am thinking great it's the pump. I tumble it and it maintains it for a while and then drops to about 33psi. I leave it and let it warm up to see what's going on, afterwhich I rev it to see how the fuel gauge goes. I notice the fuel gauge dips to about 20psi and then when I let off it jumps to 40psi and then goes back to 30psi. I do the low psi checks from the manual, I check for pulsing in the supply line and it is there and I try pinching the return to see if the fuel gauge will spike and there is no go, it remains dead at 30psi, WTF???? I am trying to come up with why the fuel pressure is low, I am thinking the FPCM may be dropping the voltage to the pump as the car is idling as if in traffic but the stock psi is 0.25bar with vacuum and without it is .3bar so between 36 and 40 so now I am stomped. I took the car for a drive and the hesitation has cleared up considerably but the car is really flat in second gear but no hesitation in first so I can see the lack of proper fuel is the main problem and causing the hesitation, just need to solve the issue now though.

Other things suggested were a faulty pump which I eliminated, faulty fuel filter which I eliminated, so just now are the regulators and damper or a clogged supply line. In the morning I am going to disconnect the front of the supply and the rear of the supply and send compressed air through it to see if it may have a clog, same for the return. Has anyone experienced a fauly damper on the return line or faulty regulator and what are the symptoms? Also, the two thick wires going to the fuel pump have a voltage on them, the black w/yellow has 12.87V and the white w/green has 9.1V, which wires is which in the event that I have to snip the wire to install the relay? Someone with an ER34 that wired the relay for the fuel pump please chime in here.