fuel pressure bleeds off?

Coupe50h · 06-19-2003, 03:30 AM

is it normal for my fp guage to bleed off slowly after i turn the koeo? i heard it should hold pressure? it just bleeds off? it takes a few seconds, but eventually goes almost all the way down, car starts up good in the mornings. should i worry?

Mountain Main · 06-19-2003, 04:10 AM

How much time does it take to go from 40 psi to 0? What is the loss of psi every thirty seconds? You might have a leak some where? If you have a leak I would first check at the fuel pressure regulator. Next check for wetness around the lines. I would also make sure the shredder valve is secure. You can actually take the valve out of the line and clean it. I think it uses a 11/32 wrench. What kind of gauge do you have?

Coupe50h · 06-19-2003, 05:43 AM

I have the accell guage, i know it's not made for heat, but i leave it on for track duty, and just put a cap on it during the week, i have the needle part of the schrader pulled out.
i do not see, or smell any leaks, i would say it takes 5 minutes to drop off 40 lbs of pressure when i shut it down.

thanx for the help, maybe i shouldnt worry about it, my car ran 13.0 tonight, but it seems to hit a flat spot in the powerband at 5500 rpm, im thinking now it could be the stock springs floating, that will be another post.

tmoss · 06-19-2003, 07:42 AM

Mine takes hours to bleed down. If your sure there is not leak, I's suspect the FP regulator - or possibly a leaky injector but I'd think you would sense other problems with the leaky injector.

Coupe50h · 06-19-2003, 08:18 AM

the fpr is new? it is a cheaper holley though, not the best afpr on the market.

could an inproperly connected duckbill connector cause this? cuz i know when i installed my pump, i lost my duckbill clip, so i re-used an old chewed up one, i dont think it is even serving a purpose.

BilLster · 06-19-2003, 09:27 AM

mine drops to 0 in like .5 seconds and untill Chris posted a way to check the fuel pump i couldnt find it. my pump is letting fuel flow back into the tank as soon as it shuts down

this was from a earlier post of his

To check for a leaking injector, hook up the fuel pressure gauge, and turn the key on. After two seconds, turn it off, and then back on for another two seconds. Keep doing this until the gauge no longer goes up. Shut off the key, and watch the gauge. It should not drop at all for a minute. Does it? What about after 5 minutes? 10 minutes? let me know.

then he posted on which explained to take a old fuel filter cut out the ends insert some rubber line (i used vacum lime pressurerise the system use vise grips on the line to block any fuel returning from the pump)

when i did that my fuel pressure stayed all night , I dont know if thats a problem with the pump but i know what causes my fuel drop so im happy (I will replace the pump with a even larger one this summer)

'89GTStang · 06-19-2003, 08:51 PM

I belive that would be the FPR that's causing the problem because the fpr is what lets the gas go back down the return line. It works to hold a certain pressure by letting that pressure build up on the pressurized line and bleeding off just enough gas down the return line to keep it at that pressure with the fuel pump running.

BilLster · 06-19-2003, 10:12 PM

yes but below the set pressure a leak or improper seal will bleed presure down under the set pressure.

TMASTER · 06-19-2003, 10:35 PM

Mine bleeds down, about a few min or so i think, whats the big deal!?!?

PKRWUD · 06-19-2003, 10:37 PM

Wow. It's kinda cool reading my own advice written by someone else, and still giving me the credit for it. Makes me feel all warm inside.

BILster-
You have done well, Grasshopper! Your problem might be the pump, but it could also be a crack in the fuel line between the pump and where it exits the tank. Be sure to inspect it when you swap pumps.

Coupe50h-
You are developing an internal leak somewhere in your fuel system. While not critical now, it's only going to get worse, so you might want to start looking for it.

The fuel has only three places it can leak to, internally; through a leaky injector, past the FPR, or back through the pump or it's line before exiting the tank.

To determine which, you need to build up pressure, and start blocking off the paths to each of the three possibilities. When the pressure stabilizes, that means you've found the path to the leak, and you'll know what to replace.

Take care,
~Chris

06-19-2003, 03:30 AM	#1
Coupe50h Registered Member Join Date: Aug 2002 Location: SanAntonio, Tx Posts: 957	fuel pressure bleeds off? is it normal for my fp guage to bleed off slowly after i turn the koeo? i heard it should hold pressure? it just bleeds off? it takes a few seconds, but eventually goes almost all the way down, car starts up good in the mornings. should i worry? __________________ X-Texas highway patrol ssp 1990 coupe - exploder Gt-40 iron heads, Explorer intake, 19 lber's. E-cam. crane 1.7 rollers. 190fp. 75mm maf. 65mm tb, tubular subframe connectors, mac cai, Asp crank pulley, T-5, king cobra clutch, flowtech 1-5/8 unequals, mac X-pipe Frpp driveshaft, lakewood Lca's. race weight 3,160 12.69 @ 107.35, 1.71 60' 26x8.5 drag's 3.90 gear 13.20 @ 106.91 - 235/60/15 firestones 2.3 60' 3.27 gear

06-19-2003, 04:10 AM	#2
Mountain Main Registered Member Join Date: Feb 2003 Location: Minturn, CO 81645 Posts: 109	More detail How much time does it take to go from 40 psi to 0? What is the loss of psi every thirty seconds? You might have a leak some where? If you have a leak I would first check at the fuel pressure regulator. Next check for wetness around the lines. I would also make sure the shredder valve is secure. You can actually take the valve out of the line and clean it. I think it uses a 11/32 wrench. What kind of gauge do you have?

06-19-2003, 05:43 AM	#3
Coupe50h Registered Member Join Date: Aug 2002 Location: SanAntonio, Tx Posts: 957	I have the accell guage, i know it's not made for heat, but i leave it on for track duty, and just put a cap on it during the week, i have the needle part of the schrader pulled out. i do not see, or smell any leaks, i would say it takes 5 minutes to drop off 40 lbs of pressure when i shut it down. thanx for the help, maybe i shouldnt worry about it, my car ran 13.0 tonight, but it seems to hit a flat spot in the powerband at 5500 rpm, im thinking now it could be the stock springs floating, that will be another post. __________________ X-Texas highway patrol ssp 1990 coupe - exploder Gt-40 iron heads, Explorer intake, 19 lber's. E-cam. crane 1.7 rollers. 190fp. 75mm maf. 65mm tb, tubular subframe connectors, mac cai, Asp crank pulley, T-5, king cobra clutch, flowtech 1-5/8 unequals, mac X-pipe Frpp driveshaft, lakewood Lca's. race weight 3,160 12.69 @ 107.35, 1.71 60' 26x8.5 drag's 3.90 gear 13.20 @ 106.91 - 235/60/15 firestones 2.3 60' 3.27 gear

06-19-2003, 07:42 AM	#4
tmoss Registered Member Join Date: Mar 2003 Location: Saint Louis, MO Posts: 634	Mine takes hours to bleed down. If your sure there is not leak, I's suspect the FP regulator - or possibly a leaky injector but I'd think you would sense other problems with the leaky injector. __________________ Tom (Torque) Moss 88Gt 5spd Vert, FLowmaster Catbacks, stock cam advanced 4° @ 108.5° ICL, NMRA prepped GT40P heads 1.85/1.55 valves and 1.7 rockers, MAC P headers Jet-Hot coated, 97 Exlporer intake (ported lower), TB and injectors. 277RWHP/330RWTQ (SAE). http://www.fastlanecars.com/

06-19-2003, 08:18 AM	#5
Coupe50h Registered Member Join Date: Aug 2002 Location: SanAntonio, Tx Posts: 957	the fpr is new? it is a cheaper holley though, not the best afpr on the market. could an inproperly connected duckbill connector cause this? cuz i know when i installed my pump, i lost my duckbill clip, so i re-used an old chewed up one, i dont think it is even serving a purpose. __________________ X-Texas highway patrol ssp 1990 coupe - exploder Gt-40 iron heads, Explorer intake, 19 lber's. E-cam. crane 1.7 rollers. 190fp. 75mm maf. 65mm tb, tubular subframe connectors, mac cai, Asp crank pulley, T-5, king cobra clutch, flowtech 1-5/8 unequals, mac X-pipe Frpp driveshaft, lakewood Lca's. race weight 3,160 12.69 @ 107.35, 1.71 60' 26x8.5 drag's 3.90 gear 13.20 @ 106.91 - 235/60/15 firestones 2.3 60' 3.27 gear

06-19-2003, 09:27 AM	#6
BilLster Registered Member Join Date: Oct 2000 Location: Ontario canada Posts: 446	mine drops to 0 in like .5 seconds and untill Chris posted a way to check the fuel pump i couldnt find it. my pump is letting fuel flow back into the tank as soon as it shuts down this was from a earlier post of his To check for a leaking injector, hook up the fuel pressure gauge, and turn the key on. After two seconds, turn it off, and then back on for another two seconds. Keep doing this until the gauge no longer goes up. Shut off the key, and watch the gauge. It should not drop at all for a minute. Does it? What about after 5 minutes? 10 minutes? let me know. then he posted on which explained to take a old fuel filter cut out the ends insert some rubber line (i used vacum lime pressurerise the system use vise grips on the line to block any fuel returning from the pump) when i did that my fuel pressure stayed all night , I dont know if thats a problem with the pump but i know what causes my fuel drop so im happy (I will replace the pump with a even larger one this summer) __________________ 89 with 331 t3'/t4 hybrids. upr Suspention worked out finnaly . 9.89 144 mph .

06-19-2003, 08:51 PM	#7
'89GTStang Registered Member Join Date: Apr 1999 Location: greenwood, ar Posts: 118	I belive that would be the FPR that's causing the problem because the fpr is what lets the gas go back down the return line. It works to hold a certain pressure by letting that pressure build up on the pressurized line and bleeding off just enough gas down the return line to keep it at that pressure with the fuel pump running. __________________ '89 GT K&N, Twisted Wedge heads, TFS intake,FMS 1.7 rockers, Trick Flow stage 1 cam(221/225 .530in\.542in) , 3.73's, headers, off road H-pipe, Flowmasters, FMS Clutch, Tremec, PRO-5.0, FMS driveshaft, fluidyne alum. radiator, and more to come.

06-19-2003, 10:12 PM	#8
BilLster Registered Member Join Date: Oct 2000 Location: Ontario canada Posts: 446	yes but below the set pressure a leak or improper seal will bleed presure down under the set pressure. __________________ 89 with 331 t3'/t4 hybrids. upr Suspention worked out finnaly . 9.89 144 mph .

06-19-2003, 10:35 PM	#9
TMASTER Registered Member Join Date: Sep 2002 Location: TEXAS Posts: 161	heh Mine bleeds down, about a few min or so i think, whats the big deal!?!?

06-19-2003, 10:37 PM	#10
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	Wow. It's kinda cool reading my own advice written by someone else, and still giving me the credit for it. Makes me feel all warm inside. BILster- You have done well, Grasshopper! Your problem might be the pump, but it could also be a crack in the fuel line between the pump and where it exits the tank. Be sure to inspect it when you swap pumps. Coupe50h- You are developing an internal leak somewhere in your fuel system. While not critical now, it's only going to get worse, so you might want to start looking for it. The fuel has only three places it can leak to, internally; through a leaky injector, past the FPR, or back through the pump or it's line before exiting the tank. To determine which, you need to build up pressure, and start blocking off the paths to each of the three possibilities. When the pressure stabilizes, that means you've found the path to the leak, and you'll know what to replace. Take care, ~Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Fuel Pump Pressure?	Swarzkopf1	Windsor Power	3	08-31-2004 02:07 PM
fuel pressure issues	mustang98gt	Modular Madness	3	07-05-2003 10:43 PM
Rising Fuel Pressure with Rising RPM?	StreetStang37	Windsor Power	1	05-21-2002 03:49 AM
Fuel pressure at high altitude. etc...	Dark_5.0	Windsor Power	5	04-19-2002 07:52 AM
Please Help...Fuel pressure keeps moving.	Dark_5.0	Windsor Power	2	04-06-2002 01:31 AM