Fuel Pressure Falling

[szewczyd]

So I got a 97 Talon. All the basic mods. Supra TT fuel pump. aeromotive afpr. Car was running funny so I was going through it. Checked the base fuel pressure and was 10psi less that it should be with the vac line pulled. So I adjusted it back up to 43. Did a little tunning drove for about 100 miles. Car started acting funny again so we pulled up dsmlink and see the fuel trims were way off. Checked fuel pressure again and it was now down 20 psi. Readjusted it up and now runs good again. What is causing it to keep dropping?

 

[gofer]

Sounds like your fuel pumps dieing, you should replace the pump ASAP before it leaves you on the road stranded.

 

[szewczyd]

Do fuel pumps slowly die? I thought they kind of just were good or dead.

 

[gofer]

When was the last time you checked your fuel filter? After I posted last night and went to bed I was thinking that would probably be the first thing I'd replace losing fuel pressure like that. The filter might be gummed up and considerably dropping your fuel pressure once it makes its way to the rail. Just be careful removing it you don't twist any of those fittings on the stock fuel line.

 

[szewczyd]

The fuel filter is my main suspect. Unfortunately it is a aeromotive and I need to figure out which one so I can order a new one. All the fuel lines are stainless steel so I don't have to worry about twisting them.

 

[gofer]

Thats perfect then, and you don't have to replace the entire fuel filter if its an Aeromotive you can just replace the filter element inside of it. You might also check for kinks in the SS line wherever you have it running since that would also cause some fuel pressure issues, even if its in the return line back to the tank.

 

[99gst_racer]

How did you seal the outlet of the fuel pump on the hanger assembly? If there's a leak there, it will bleed off pressure.

 

[szewczyd]

That was the owner before me so I will have to check. I want to be able to drive this car frequently so I might as well just get a fuel filter, rebuild the afpr, and a fuel pump. All those parts have been on the car for quite some time.

 

[NOSLO2PT0]

I'd swap in a diff. regulator myself. See if the spring/diaphragm was bad on the regulator.

 

[szewczyd]

I'd swap in a diff. regulator myself. See if the spring/diaphragm was bad on the regulator.

That would be easy enough other than I don't have a spare or know of anybody with a spare so I think I will just spend the 20 bucks and rebuild this one.

 

[99gst_racer]

If a new/rebuilt regulator doesn't solve the issue, then make sure the pump is installed correctly and properly sealing. Here's a good thread with some info regarding the Supra pump on a 2G: http://www.dsmtuners.com/forums/newbie-forum/355980-question-regarding-supra-fuel-pump-2g-awd.html

 

[LiquidX]

Not to thread jack but I'm having a similar issue. My fuel pressure is good while driving but it drops after I turn the car off and let it sit. It'll loose all pressure in about an hour or less. I just pulled off the return hose to see if it was draining out of the regulator but it wasn't. Where else should I check?

I have a 255 wally that was put in a couple years ago but the car sat for almost a year with not start up. Could something be wrong with the fuel pump now that I've started to drive it again?

 

[ramsack]

Bleeding pressure off after you turn the car off:

1. AFPR
2. Fuel pump check valve
3. Injector(s) not shutting all the way

 

[9!'clipseDOHC]

I have zero fuel pressure immediately after shutting it off. And just recently it's gotten hard to start. I've posted on a similar thread recently, still no conclusion.

 

[LiquidX]

Ramsack, how would I be able to find test #2 and #3?

 

[szewczyd]

Wowzers. Seriously guys? I keep getting emails with updates and now your trying to solve your problems in my thread!

 

[gofer]

Not to thread jack but I'm having a similar issue. My fuel pressure is good while driving but it drops after I turn the car off and let it sit. It'll loose all pressure in about an hour or less. I just pulled off the return hose to see if it was draining out of the regulator but it wasn't. Where else should I check?

I have a 255 wally that was put in a couple years ago but the car sat for almost a year with not start up. Could something be wrong with the fuel pump now that I've started to drive it again?

I have zero fuel pressure immediately after shutting it off. And just recently it's gotten hard to start. I've posted on a similar thread recently, still no conclusion.

He does have a good point, both of you should no better especially since the SEARCH button hasn't moved and you both frequent these forums. I've posted in a few "Losing Fuel Pressure After Cars Off" threads with the information above so I know neither of you searched. Cold Start No Fuel Pressure Issues

I'm not trying to scold either of you but this guy must be getting emails letting him know someone has posted on this thread to help him. Here it is that its just someone asking another question that doesn't even pertain to his issue to fix their problem.


To the OP, there are only a few possibilities to the problem your seeing so just check the diaphragm inside the AFPR and replace the fuel filter and see if that fixes things.

 

[ramsack]

It sounds to me like the AFPR is wearing out. Fuel filter would be better to do first if you haven't done it in a while. Both are around the same cost.

 

[szewczyd]

It sounds to me like the AFPR is wearing out. Fuel filter would be better to do first if you haven't done it in a while. Both are around the same cost.

Thanks guys, I pulled the fuel filter and cleaned it as it was a cleanable one. It was very clean already but got any little specs of grime I could find off of it. I have the afpr rebuild kit on the way.

 

[turboglenn]

I had this same issue when installing my new aeromitive AFPR.. it would constantly change FP on it's own... after a few months and many many heat cycles it settled on it's own but i have threads bitching about this myself.. I think when the aeromotive is new the spring is effected by engine bay heat untill it "sacks out" enough to stabilize.

I even swapped to a customers AFPR just to make sure it wasn't my pumps, lines, filters etc... but they are all good to check, and believe me... the AFPR will change it's setting by like 5 - 7 psi for a few months when new (for me it did anyway) I was running 720's on pump gsa and batch fire so i could always tell the idle difference and woudl get so tired of checking the FP every damn time i drove the car and finally set it up left it and drove through the changes and it stabilized as i said after many heating cycles

 

[szewczyd]

I had this same issue when installing my new aeromitive AFPR.. it would constantly change FP on it's own... after a few months and many many heat cycles it settled on it's own but i have threads bitching about this myself.. I think when the aeromotive is new the spring is effected by engine bay heat untill it "sacks out" enough to stabilize.

I even swapped to a customers AFPR just to make sure it wasn't my pumps, lines, filters etc... but they are all good to check, and believe me... the AFPR will change it's setting by like 5 - 7 psi for a few months when new (for me it did anyway) I was running 720's on pump gsa and batch fire so i could always tell the idle difference and woudl get so tired of checking the FP every damn time i drove the car and finally set it up left it and drove through the changes and it stabilized as i said after many heating cycles

Well mine is well heat cycled and pretty damn old so I am hoping it is just the rebuild.

 

[szewczyd]

Hrmm. Well I torn into the afpr to do a rebuild and discovered this:

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I am 100% sure this had to be causing the problem, wish I would have pulled it apart before I just ordered the rebuild kit!