IW STi Forum banner

1 - 20 of 36 Posts

·
Registered
Joined
·
172 Posts
Discussion Starter #1
Guys, I need help. My car is a 2008 STI hatch with stage 2. Sunday I replaced the DW65c pump I installed a few months back with a dw300c pump. The reason for the change was that the car was running a little in the lean side and the tuner told me the problem could be the dw65c i installed. Anyways, I decided to replace the pump and the car ran fine Monday but yesterday it started to run too rich (way too rich) my AEM AFR gauge was reading 10.0 while idling. I stopped the car, and turned it off for a little while then I started up again and I could run but could not give much gas because it would go back to 10.0.

Today the car was running fine in the morning but it went back to the same in the afternoon. I had reset the ecu and nothing, change the map to another one and nothing. Of course when this happens the smell of gas is really strong. Could it be the pressure regulator? The car had the injectors and lines cleaned, new fuel filter, new fuel pump. Any help would be appreciated.
 

·
Premium Member
Joined
·
5,243 Posts
Yes it could be the FPR. But I'd try to determine the fault before replacing parts . . .
 

·
Registered
Joined
·
172 Posts
Discussion Starter #3
Thanks for your feedback. Definitely I would check first before replacing, but thats one of the parts left to replace on the fuel system. The car has 117,500 miles.
 

·
Registered
Joined
·
172 Posts
Discussion Starter #4
Well, I swapped the pumps again and installed back the DW65C and the car seems to be running normal. at WOT is reading 11.3 and goes down to 10.7 near redline. This was taken from AEM UEGO wideband.
 

·
Registered
Joined
·
1,557 Posts
Yes it could be the FPR. But I'd try to determine the fault before replacing parts . . .
I agree! Diag first before firing off the parts cannon.

The 320 lph pump is probably overrunning the FPR. I would verify fuel pressure. At higher IDC's, the FPR will be taxed less for flow and likely bring AFR's back in check... ish.
This! Fuel pressure needs to be checked. If need be, connect a mechanical gauge and tape to the windshield during your road test.
 

·
Registered
Joined
·
172 Posts
Discussion Starter #7
I will take it to my local shop to see if they can test the fuel pressure. I do know the car needs a protune soon, I have been running this ots map since I got the car (used from a dealership). However, this is the first time this problem happened.
 

·
Super Moderator
Joined
·
8,396 Posts
I agree! Diag first before firing off the parts cannon.



This! Fuel pressure needs to be checked. If need be, connect a mechanical gauge and tape to the windshield during your road test.
Shouldn't even need to go that far. An overrun FPR shows more issue with low IDC's where the injectors aren't using as much fuel allowing more to make it to the FPR. Just test base pressure.
 

·
Registered
Joined
·
172 Posts
Discussion Starter #12
Inline fuel pressure gauge installed and this is the reading at idle:
[/URL][/IMG]
 

·
Super Moderator
Joined
·
8,396 Posts
I'm willing to bet the fuel pressure is high with the larger pump and your current FPR.

As for your numbers, you'll have roughly -10 PSI of vacuum at your altitude, so your fuel pressure at that vacuum will be roughly 33 PSI.
 

·
Registered
Joined
·
172 Posts
Discussion Starter #18
I'm willing to bet the fuel pressure is high with the larger pump and your current FPR.

As for your numbers, you'll have roughly -10 PSI of vacuum at your altitude, so your fuel pressure at that vacuum will be roughly 33 PSI.
That's correct, the vacuum was -9.8 when tested. The car is currently working fine, so I will keep this pump and take it to the tuner. I will post the results.

Thanks again!
 

·
Registered
Joined
·
2,612 Posts
I'm willing to bet the fuel pressure is high with the larger pump and your current FPR.

As for your numbers, you'll have roughly -10 PSI of vacuum at your altitude, so your fuel pressure at that vacuum will be roughly 33 PSI.
What's the math behind determining your vacuum? I've always been curious about that.
 
1 - 20 of 36 Posts
Top