throw_sparx

ok quick run down 89 gxl with 90 j-spec t2 since install iv been premixing a little just to make sure the omp is working properly but the fuel pump started going out so i swapped pumps and im guessing that the pump i installed is a non turbo fuel pump (i had a turbo one that went out) the fuel pressuer static was 25 psi and would go up about 40 psi on throttle,



so i just purchased a holley 255 LPH from summit racing, got it installed now my static fuel pressure is a little less than 25 psi and on a rev it drops about 5-10 psi then rises to just over 25 psi.



i pulled off the vacume line off of the sensor on the shock tower and with my vac testor i could get the pressure to rise a little and lvl at 25 psi at idle (the sensor came with the engine and is the proper numbers for the engine)



the reason i started trying to locate the issue is sometimes it seems like the car is running out of fuel has a light chug at low throttle lets say going down the road in 5th at 50mph it acts like it has a miss not a steady cycled miss but an ocational speratic miss like fuel pressure is not right at low rpm, and some times i get on it and it acts like its running out of fuel and pops a little. i havent been able to drive it much cause im too worried about it messing up, and if you know me and my history thats the last thing i need now lol



here are my questions



1 is the premix affecting the performance of the pump in any way?

2 would the problem im having be the factory regulator? would installing an aftermarket regulator help

3 or is my fps sensor bad?

4 or am i not looking in the right place to fix the problem





currently i want to get the new fuel pump in the pressure ranges that i need then i will go from there.

fcs13

I am going to take a stab at answering to the best of my knowledge. I can only assume since I dont know exactly which tower you are talking about that you mean the Boost Sensor on the passenger side of the engine bay. You said you are running a 90 J-spec engine with a matching sensor so it should be fine as far as that goes. But what I am thinking is happening since you said when you get on it that it has an occasional miss is that you are running too high a boost. Are you using an EBC of any sort? Are you running an FCD along with your setup? This just sounds like the villain named Boost Cut.



If you are not aware of what this is...What it does is after a certain PSI level of boost the ECU cuts fuel to the rear rotor. You may be experiencing this.



You also mentioned something about replacing the turbo fuel pump because you thought that might be the problem, which it may very well be. But, have you tried hard wiring your pump to a switch and try pumping fuel through the lines? You might try disconnecting the fuel lines under the hood and see if they are flowing nice and clean. Just dont forget to get something to catch those money signs coming out of the hoses from under the hood.



It could be a number of things concerning fuel systems. Also dont forget your injectors. They might not be suitable to keep up with the flow of your new fuel pump. If they are the stock 550cc's you might get them flow tested to see if they are in proper working condition. if so, they might not be big enough to compensate for the fuel flow. You could even have a filthy *** fuel filter. Just keep it simple stupid when it comes to something like fuel systems. I hope maybe something here helps you out.



-B.

j9fd3s

1. it can, but its more of a long term issue

2. possible, your fuel pressure sounds low, i think spec at idle is about 36-40psi

3. its not a fuel pressure sensor, its a boost sensor, it tells the ecu what vacuum or pressure is in the intake

throw_sparx

well i checked a couple things today first i think my voltage is a hair low to the pump spikes between around 9-11v tomorrow im going to pull the fuel filter and replace and check a few other things



but my biggest concern is that the pressure stays around 25psi which i know is bad thats why im not going to drive it till i get it fixed



the engine is stock the only thing changed from stock is the exhaust which isnt that great 2 1/2 all the way back form turbo ti a "Y" to dual thermal technologys mufflers (mufflers are awsome but piping is a little small) and a blitz air filter and adapter



i have a super afc installed and moderately tuned not by me but a reputable mechanic



i dont have my fuel cut defensor yet but im not driving the car hard cause of the underlying fuel issue and the studder at very low throttle and low fuel pressure once i get that issue solved i will start going from there



but why im at a loss is why i changed the fuel pump to an upgraded one and went down in fuel pressure thats why i was thingking about the filter that comes with the holley fuel pump and or the voltage i have an extra relay that i could put on the pump to add atleast a 30 amp steady flow of power to the pump using the origonal power supply to engage the relay



i was also informed that the factory fuel pressure regulator is on the fuel rail.



but like i stated above i really dont want to do any other mods to the car till the main issues are fixed so the problems dont compound you know



any input would be appreciated

throw_sparx

well i found the problem and made it better all the way around



the problem was the o-ring that was supplied with the pump was not seating properly between the pump and sending unit so i installed the origonal o-ring and re installed the pump and as a added bonus i installed a relay on the pump activated by the origonal power wire and eliminated the economy mode.



now i need to purchase a fuel cut defender any good suggestions or does anyone have one for a s5?

teknics

just to clear this up, which o-ring exactly?



kevin.

j9fd3s

on the s5 theres an o ring that seals the pump to the pickup assembly, seems easy to f-it up

teknics

yea...still not sure if i have that o-ring on my walbro but it was a miscommunication in terminology lol, im really involved in make a dual pump in-tank mount setup right now and i thought for a moment that i had lost some parts or something.



kevin.

throw_sparx

being that your using 2 of the walboros you should be fine but there not as good as they claim on ebay, the holley 255 from summit racing or jegs is the real deal costs about 139 each with free shipping unless you want it quicker just some fyi

teknics

lol, dont worry i know plenty about my setup and it's abilities. ive been building this specific car for 2 years, everything by me. and this car was making mid 300hp's with a single walbro with 0 problems before the buildup anywho. gotta buy the right walbro, not the cheap ebay ones.



kevin.