Fuel pressure gauge still bounces a lot???

jubelands · 10-11-2008, 07:16 PM

I have been having a bouncing fuel pressure issue for a very long time that i just cant figure out. The gauge has been doing this for over a year and i have no clue what the cause is. I've already tried a different gauge and everything and it still does it. The needle is at around 42psi at idle but bounces +/- 6psi to 8psi constantly. When at full throttle it bounces even worse. It only does it when the car is running. When I'm installing a tune and the pumps are running at full the needle is not bouncy at all, it just sits at 60psi.
The funny thing is that whenever i depressurize my fuel system by removing any part of the fuel system (aeromotive regulator, injectors, rails) the problem goes away for a day or so but then comes back.

It doesn't seem to be effecting the driveability much considering i just got tuned the other day and made pretty good power, but i just know that its not normal.

Fuel mods are: walbro pumps w/ stainless y, aeromotive regulator, fuel rails, 60lb injectors, KB boost a pump.

The problem was occurring before and after i added any of these fuel mods. Nothing seems to get rid of it. I also just recently gut checked for vacuum leaks which i did have but are gone now yet the problem persists.

Also my vacuum at idle bounces between -20 and -21. Vacuum in drive is around -18 to -19. Do these vacuum #'s sound normal?

What could this issue be?

rhynotune · 10-12-2008, 09:31 PM

Your vacuum sounds fine. Your FP issue could be the cause of a couple of things, probably your regulator. Otherwise it could be your battery or something in your charging system.

skidmarkracing · 10-12-2008, 09:53 PM

mechanical fuel pressure Gage or electric

jubelands · 10-13-2008, 02:58 PM

It is a mechanical gauge mounted in the cowl of my hood. Is it possible that the regulator could go bad so quick?

gnarlyfox001 · 10-14-2008, 09:02 PM

ur vacuum sounds fine dont see a problem with that. ur injectors did u put them in new or used? also even new parts can go bad i have had that accurance happen plenty of times. injectors might be dirty causing them not to open and close efficently.

Wilderyzed · 11-12-2008, 08:50 PM

There is a high speed relay for the pumps its right next to the master cylinder under a little cover. Theres 2 relays its the front one. Sorry I don't have a pic but it took me forever to fix this re did the pumps, tank, filters, rails everything over a 2 dollar relay. This is exactly what it was doing. You get to a certain throttle and the pressure bounces at 43psi thats when the high speed circuit is supposed to jump in from that relay. I know thats your prob. good luck

10-11-2008, 07:16 PM	#1 (permalink)
jubelands Registered User Join Date: Apr 2004 Posts: 564 View this user's gallery iTrader: 7 / 100%	Fuel pressure gauge still bounces a lot??? I have been having a bouncing fuel pressure issue for a very long time that i just cant figure out. The gauge has been doing this for over a year and i have no clue what the cause is. I've already tried a different gauge and everything and it still does it. The needle is at around 42psi at idle but bounces +/- 6psi to 8psi constantly. When at full throttle it bounces even worse. It only does it when the car is running. When I'm installing a tune and the pumps are running at full the needle is not bouncy at all, it just sits at 60psi. The funny thing is that whenever i depressurize my fuel system by removing any part of the fuel system (aeromotive regulator, injectors, rails) the problem goes away for a day or so but then comes back. It doesn't seem to be effecting the driveability much considering i just got tuned the other day and made pretty good power, but i just know that its not normal. Fuel mods are: walbro pumps w/ stainless y, aeromotive regulator, fuel rails, 60lb injectors, KB boost a pump. The problem was occurring before and after i added any of these fuel mods. Nothing seems to get rid of it. I also just recently gut checked for vacuum leaks which i did have but are gone now yet the problem persists. Also my vacuum at idle bounces between -20 and -21. Vacuum in drive is around -18 to -19. Do these vacuum #'s sound normal? What could this issue be? Last edited by jubelands; 10-11-2008 at 08:31 PM.

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10-12-2008, 09:31 PM	#2 (permalink)
rhynotune Registered User Paid Member Join Date: Jul 2007 Posts: 100 NLOC member #: 2625 View this user's gallery iTrader: 0 / 0%	Your vacuum sounds fine. Your FP issue could be the cause of a couple of things, probably your regulator. Otherwise it could be your battery or something in your charging system.

10-12-2008, 09:53 PM	#3 (permalink)
skidmarkracing My wife says i'm retarded Join Date: Dec 2005 Location: Wylie, TX Posts: 965 View this user's gallery iTrader: 12 / 100%	mechanical fuel pressure Gage or electric

10-13-2008, 02:58 PM	#4 (permalink)
jubelands Registered User Join Date: Apr 2004 Posts: 564 View this user's gallery iTrader: 7 / 100%	It is a mechanical gauge mounted in the cowl of my hood. Is it possible that the regulator could go bad so quick?

10-14-2008, 09:02 PM	#5 (permalink)
gnarlyfox001 Registered User Join Date: Oct 2008 Location: Chicago Posts: 12 View this user's gallery iTrader: 0 / 0%	ur vacuum sounds fine dont see a problem with that. ur injectors did u put them in new or used? also even new parts can go bad i have had that accurance happen plenty of times. injectors might be dirty causing them not to open and close efficently.

11-12-2008, 08:50 PM	#6 (permalink)
Wilderyzed wildman Join Date: Jul 2008 Location: Davie, Fl Posts: 142 View this user's gallery iTrader: 0 / 0%	There is a high speed relay for the pumps its right next to the master cylinder under a little cover. Theres 2 relays its the front one. Sorry I don't have a pic but it took me forever to fix this re did the pumps, tank, filters, rails everything over a 2 dollar relay. This is exactly what it was doing. You get to a certain throttle and the pressure bounces at 43psi thats when the high speed circuit is supposed to jump in from that relay. I know thats your prob. good luck