Just as the title says, I had my fuel pressure tested today and it is sitting at 40 psi at idle...

and one thing that would be obvious from this is my car is on occasion running lean. Here is the thing that confuses me, the only time my car throws the lean code is if i get above 3k rpms when it is in open loop, where as yesterday i went from slowing down for a stop light, then just about floored it, had it down shift twice, and ran it up to 5.5k rpms for 2 gears and it didn't throw the lean code.

I am thinking the fuel pump is giving enough fuel, just not enough pressure, is that at all possible, since it only leans out when in open loop, since the o2 sensor isn't giving any input for injector flow?

Oh and one other thing, I bought the pump from these guys, http://autoperformanceengineering.com/, but I don't think I bought the high pressure pump, is that where I messed up... I just looked and what I bought from them only cost $97 for everthing so i didn't buy the high pressure.


So I am now guessing I need to replace my fuel pump... joy, the pump I got last time is from what I understand is the gear driven kind, that make alot of noise, i really don't car about the cost anymore, I want to get a pump that meets the 3800s need and is very quiet. If you think that is my problem with my fuel pressure let me know, and if you have a different pump to suggest that is quiet and good enough for my engine please let me know.


Thanks, Chris

bocsh 044 pump. it's a pain in the butt to get it in the basket, but it's pretty quiet and supports 700ish hp. i'm running one now and i'm spraying a 100 shot to my car and it's trapping 122 in the 1/4. with no signs of fp loss.

another thing to consider is i run a much high fp then you do. with vaccum hooked up i believe mine is 45lbs. it then ramps all the way up to almost 70lbs from my rising rate fpr. try to bump your fuel pressure a tiny bit to 45lbs and if that doesn't work can you tune around it. if you have a tuner...

treperformance.com

After looking at the site I got the pump from, it clearly says that the pump I bought is rated at 40 psi... kinda like I have seen that number somewhere else... I am gonna buy the pump from the site rideZlightning posted... only problem is I am not sure which kit to get, I assume the universal kit will work.


Thanks, very much for the help, Chris

There are TWO different Walbro 255GPH fuel pumps. Both are high flow but only one is high pressure AND high flow. The high pressure high flow pump is the one to use for boosted applications. What P/N did you purchase?

------------------
87GT - with 3800SC Series III engine, 4T65eHD
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

I really don't know what the part number was, but I am almost 100% sure, since the fuel pressure is 40 psi, and my bill from them was $97 that it is the high flow with normal pressure one.


I just need to know which of the kits from that site lightning gave to buy, thanks.


Chris

quote Originally posted by eph_kay: I really don't know what the part number was, but I am almost 100% sure, since the fuel pressure is 40 psi, and my bill from them was $97 that it is the high flow with normal pressure one. I just need to know which of the kits from that site lightning gave to buy, thanks. Chris

I believe that you need the Walbro pump that is made for the GM Grand National turbocharged 3.8L V6. Believe part number is Walbro 340M

------------------
87GT - with 3800SC Series III engine, 4T65eHD
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

the 340 seems to have been discontinued or something, and is replaced by F20000169 atleast i hope it has :P ebay has them for 97 bucks, and you can pic them up around the net for the sameish price

The deal is I have a walbro pump and they are insanely noisy, rideZlightning gave a site that he said, in other treads, that he has used in many swaps and worked fine, and it is a silent pump, they just have every different kit for every different car, just no fiero, and I was curious as to which of the kits they have will have the stuff I need.

Here is the link to the grand national one, I think I am gonna go ahead and get it, http://treperformance.com/i...5-lph-fuel-pump.html

chris

dont get that one, he has it listed incorrectly, you dont want that big ass plastic tube. Get a ford one instead. If you liok, the only difference is the tube, the fiero uses a short rubber.

http://treperformance.com/i...5-lph-fuel-pump.html

quote Originally posted by darkhorizon: dont get that one, he has it listed incorrectly, you dont want that big ass plastic tube. Get a ford one instead. If you liok, the only difference is the tube, the fiero uses a short rubber. http://treperformance.com/i...5-lph-fuel-pump.html

haha rubber...

Will do, thanks.


Chris

i told you the best single pump out there. that bosch.

At $2-300 that is alittle more than I plan on spending right now, and in honesty all I plan to do to my engine is new valve train and possibly a smaller pulley.

Thanks for the info on the pump though, does it make alot of noise or is it a rather quiet pump?


Chris

I thought the spec for the L67 was 40PSI. Im questioning this though, as I would have assumed someone here would have pointed that out by now.

If that were the case, it wouldnt matter what pump you put on there, the regulator would keep it at 40PSI. Try blocking the return line and see what pressure is then, if it goes up, the regualtor is holding it down, but I never knew it was diffrent.

At any rate, if you are only having problems in open loop, its a tuning problem, not a delivery probelm.

Im going to go find my pressure guage and check my L67

I remember low 50's at idle, and low 60's at 0psi.

Idle should be around 42 PSI, 48 PSI with vacum line pulled off and like 60 PSI at WOT but this depends on how much boost.

Ok, I would like to correct my statement about the only being a problem in open loop, I think it had more to do with the fact that I reset the fuel trims, and they hadn't finished calibrating, or something of that nature, because right now I have the code on, and it has been on since it showed up, not going away and coming back like it was.

According to AllData the fuel pressure, with key on engine off is 55-60 psi, when I put the fuel pressure tester on it was at 40 at idle, and when we clamped the return line it jumped to like 42 or 44psi. To which my instructor said, means the fuel pump is at it's limit, which is further confirmed by the site from where I got the pump.


I already bought this pump, my car is a stock tune, and I am hoping that when I switch it out it fixes my problem, Chris

Turns out I loaned out my pressure gauge and it (apparently) hasnt been returned yet, so im no help there.

I really think it should be ~40PSI when out of boost. Thats the norm for most all cars, and I cant see any reason why it would need to run at a higher pressure outside of boost. Im going off instict there though, I dont know for sure.

But if you're sure you've completely blocked off the return line, then thats an indicator, but I wouldnt have expected that, not at all.

What you can try, get a vacuum pump and hook it to the FPR, test FP under both vac and boost to the FPR. If I get my gauge back soon, I'll take some measurements and let you know

Sounds good, and if all else fails, other than being unhappy that I don't know why my car is running lean, I will now have a silent fuel pump....


Chris

Those TRE's are damn nice IMO, very good china knockoff product (heh).

If you are not getting a decent drop and rise when you go from engine running and not running, then something could be up. One of the more common posts I have seen on here involves a FPR full of crap btw.

well, when I bought my fuel rail it didnt come with the fpr so I went and bought a new one, so I really hope that isn't the problem.


Chris

my pump is pretty quiet. you can barely hear it inside the car. it's actually quieter then my stock pump of my suburban. if you don't plan on more then valvetrain then a 255 should be enough. i just don't like being near the limits. the bosch was rated @70psi vs the walbro's 30. also the bosch is what most of the rally cars use because of it's reliability.