Fuel pressure test results
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Fuel pressure test results
Well I did my fuel pressure test to try to figure out why it was leaning out at high RPMs during WOT. I also filled the tank to confirm that it wasn't because the gas was low. Anyway, when I tested fuel pressure, it was at 28 PSI with the vacuum hose connected, and 35 with the vacuum hose disconnected. I had set it to 43 about a month ago, but I guess the adjustment bolt must have vibrated out. I used a nut to secure it this time though. So I took it out to test the fuel pressure. I floored it at about 2500 RPMs. First the fuel pressure went to 34 and about half a second later went to 31 all the way to 6000 RPMs. Then I set the fuel pressure to 50 with the hose disconnected. This time when I floored it it was about 1500-2000 RPMs. At first it hit 49 PSI, and a second later dropped to 47 PSI all the way to 6000 RPMs. I did video tape this so I could make sure I was seeing everything correctly.
I figured I would start a new thread since it would get more attention. Hope no one gets mad.
So anyway, does that amount of pressure difference indicate a bad fuel pump? Or is it just the way vacuum pressure works during WOT?
Thanks guys!
I figured I would start a new thread since it would get more attention. Hope no one gets mad.
So anyway, does that amount of pressure difference indicate a bad fuel pump? Or is it just the way vacuum pressure works during WOT?
Thanks guys!
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
Well I did my fuel pressure test to try to figure out why it was leaning out at high RPMs during WOT. I also filled the tank to confirm that it wasn't because the gas was low. Anyway, when I tested fuel pressure, it was at 28 PSI with the vacuum hose connected, and 35 with the vacuum hose disconnected. I had set it to 43 about a month ago, but I guess the adjustment bolt must have vibrated out. I used a nut to secure it this time though. So I took it out to test the fuel pressure. I floored it at about 2500 RPMs. First the fuel pressure went to 34 and about half a second later went to 31 all the way to 6000 RPMs. Then I set the fuel pressure to 50 with the hose disconnected. This time when I floored it it was about 1500-2000 RPMs. At first it hit 49 PSI, and a second later dropped to 47 PSI all the way to 6000 RPMs. I did video tape this so I could make sure I was seeing everything correctly.
I figured I would start a new thread since it would get more attention. Hope no one gets mad.
So anyway, does that amount of pressure difference indicate a bad fuel pump? Or is it just the way vacuum pressure works during WOT?
Thanks guys!
I figured I would start a new thread since it would get more attention. Hope no one gets mad.
So anyway, does that amount of pressure difference indicate a bad fuel pump? Or is it just the way vacuum pressure works during WOT?
Thanks guys!
Fuel pressure is fine, so far. Go check your AFR and adjust the tune to hit your desired goal. If you cannot get to your desired goal and your fuel pressure is still 47 PSI (or above 43 PSI), you either have a tune problem or injectors that may be undersized. To determine that you will have to watch your duty cycle.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
Code:
LC310: FDB 111 ; Minimum Asynchronous Pulse Width, Cal = ms * 65.536, (1.69 ms) LC312: FDB 364 ; Maximum Asynchronous Pulse Width, Cal = ms * 65.536, (5.55 ms)
Last edited by Cliff Harris; Oct 29, 2014 at 02:34 AM.
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
I looked through the ECM code for my car and found these parameters. I knew there was a minimum injector pulse width but didn't know for sure if there was a maximum pulse width. You could be hitting that limit. Check your data logs for injector pulse width.
The asynchronous pulse width is used during WOT.
Code:
LC310: FDB 111 ; Minimum Asynchronous Pulse Width, Cal = ms * 65.536, (1.69 ms) LC312: FDB 364 ; Maximum Asynchronous Pulse Width, Cal = ms * 65.536, (5.55 ms)
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
Actually 92% duty cycle, don't forget the car is double fire system so you need to double your duty cycle.
