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How long should fuel pressure last with key off? by Tweeder
Started on: 09-12-2013 12:13 AM
Replies: 23 (4444 views)
Last post by: Tweeder on 05-15-2014 10:32 PM
Tweeder
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Report this Post09-12-2013 12:13 AM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
I was wondering on a 3800sc when you shut the engine off, how long should the fuel pressure hold?

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86 SE Convertible 3800sc 4t65e HD.

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Report this Post09-12-2013 12:25 AM Click Here to See the Profile for trotterlgClick Here to Email trotterlgSend a Private Message to trotterlgEdit/Delete MessageReply w/QuoteDirect Link to This Post
Don't know if there is a spec for it. It should not just instantly fall to zero, but it probably will not stay high for a minute. I think if it just slowly falls over a few seconds or longer that things are good. Larry
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Tweeder
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Report this Post09-12-2013 12:32 AM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by trotterlg:

Don't know if there is a spec for it. It should not just instantly fall to zero, but it probably will not stay high for a minute. I think if it just slowly falls over a few seconds or longer that things are good. Larry


Yeah it takes a few mins to completely bleed off, that's good then. Now I'm wondering about my KOEO & engine running, it's just under 45 psi at KOEO and is around 40 psi blipping the throttle. I have a 300lph fuel pump.

EDIT: I forgot to mention that I do not have the pulsator installed.
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[This message has been edited by Tweeder (edited 09-12-2013).]

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DefEddie
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Report this Post09-13-2013 02:08 AM Click Here to See the Profile for DefEddieClick Here to Email DefEddieSend a Private Message to DefEddieEdit/Delete MessageReply w/QuoteDirect Link to This Post
Pressure should stay constant indefinately.
If it's bleeding off a few psi (engine hot) than it is just a little vaporization.
Any more than that you need to see where it's leaking down. Disconnect the guage and put it on the filter line to narrow it down.
If it leaks down connected to filter than you check valve on your fuel pump is bad or possibly the hose on the pump.
If it doesn't leak down attached to the filter line,than it is likely an injector leaking down.
Your pressure should NOT just slowly leak down to nothing,this will show up generally as long crank on cold startup or after it has sat awhile because it needs to fill the line back up.
A few psi is nothing to worry about,but it should stabilize and not leak more than that.
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Tweeder
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Report this Post09-13-2013 11:55 AM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by DefEddie:

Pressure should stay constant indefinately.
If it's bleeding off a few psi (engine hot) than it is just a little vaporization.
Any more than that you need to see where it's leaking down. Disconnect the guage and put it on the filter line to narrow it down.
If it leaks down connected to filter than you check valve on your fuel pump is bad or possibly the hose on the pump.
If it doesn't leak down attached to the filter line,than it is likely an injector leaking down.
Your pressure should NOT just slowly leak down to nothing,this will show up generally as long crank on cold startup or after it has sat awhile because it needs to fill the line back up.
A few psi is nothing to worry about,but it should stabilize and not leak more than that.


What is this filter your talking about. I will have to time it but it will eventually (half hour?) goto zero. This is a brand new pump but that don't mean much. I did not install that pulsator thingy back in with the new pump. I haven't noticed it being hard to start when it sits for about 12 hours.
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Report this Post09-14-2013 12:53 AM Click Here to See the Profile for DefEddieClick Here to Email DefEddieSend a Private Message to DefEddieEdit/Delete MessageReply w/QuoteDirect Link to This Post
The fuel filter.
You can disconnect it and hook a fuel pressure guage on the line to the tank to deadhead the pump and isolate the two side of the system.
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DimeMachine
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Report this Post09-14-2013 07:40 AM Click Here to See the Profile for DimeMachineSend a Private Message to DimeMachineEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by DefEddie:

The fuel filter.
You can disconnect it and hook a fuel pressure guage on the line to the tank to deadhead the pump and isolate the two side of the system.


There are 7 possible bleed down leaks - right.
1. hole in line -would be easy to find.
2. 6 fuel injectors
3. fuel pump.

I would have to make up an adaptor to connect to the fuel line coming from the pump - or can you buy this adaptor? Is it a good idea to deadhead a fuel pump intended to have its pressure regulated by a fuel pressure regulator?

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84/87 NB, 3800SC, E-85, VS Cam, 2.8 Pulley, 4T65E-HD, HP Tuners, AEM Wideband, Regal GS Gauges, S-10 Brake Booster. 1/4 mile -11.906 at 111.93mph

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Report this Post09-14-2013 07:02 PM Click Here to See the Profile for DefEddieClick Here to Email DefEddieSend a Private Message to DefEddieEdit/Delete MessageReply w/QuoteDirect Link to This Post
Yes,you should be fine deadheading the pump. I've done it to new vehicles (via the manual) even with pwm fuel pumps at the dealer.
Just be careful and clamp the line well,most fuel pumps can generally exceed 80psi max when not regulated.
I've had a line blow out in my face while looking at guage when it hit 90psi pressure,couldn't see well for the rest of the day and man it really burned.

If you don't have the proper fitting,AZ has a master fuel pump kit that is on loaner tool program.
I'm not sure where I got my adapters,I have a master fuel guage kits as well as 2-3 others and I generally seem to have the fittings i need.
Or you can usually get a brass fitting or steel replacement line and make an adapter.

[This message has been edited by DefEddie (edited 09-14-2013).]

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Tweeder
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Report this Post05-05-2014 11:06 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
Forgot all about this thread, guess it's still an issue as I never got a definite answer. Once the pump finishes priming after koeo it takes about 40-50 seconds from full to zero. But with the koer, it stays at 45 ish.

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Tweeder
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Report this Post05-06-2014 07:32 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
Bump.

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86 SE Convertible 3800sc 4t65e HD.

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Tweeder
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Report this Post05-13-2014 01:19 AM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
Anyone? I need to find out if the pumps going south so I can get it warranted before it runs out next month.

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Report this Post05-13-2014 03:33 AM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Tweeder:

Anyone?


I have no idea what you were trying to say. It's possible no one else knows what you're talking about either.

 
quote
Originally posted by Tweeder:

Once the pump finishes priming after koeo it takes about 40-50 seconds from full to zero. But with the koer, it stays at 45 ish.


Not trying to be a smartass, but what language is that?
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MulletproofMonk
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Report this Post05-13-2014 08:22 AM Click Here to See the Profile for MulletproofMonkClick Here to visit MulletproofMonk's HomePageSend a Private Message to MulletproofMonkEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Tweeder:

Once the pump finishes priming after koeo it takes about 40-50 seconds from full to zero. But with the koer, it stays at 45 ish.

 
quote
Originally posted by Patrick:

Not trying to be a smartass, but what language is that?


I am assumed koeo "key on, engine off" and koer "key on, engine running"
Edit: koeo could be "key on, engine on"
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[This message has been edited by MulletproofMonk (edited 05-13-2014).]

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Report this Post05-13-2014 09:15 AM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
I'm gonna guess 'key off engine running' for the R.....which means the other one is OFF. This is harder to decipher than the fuel pressure.... .

Most fuel systems will keep pressure for about 5 minutes after being shut off, but anything over about a minute works fine.
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Report this Post05-13-2014 12:24 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by MulletproofMonk:


I am assumed koeo "key on, engine off" and koer "key on, engine running"
on"



Correct

[This message has been edited by Tweeder (edited 05-13-2014).]

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Tweeder
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Report this Post05-13-2014 12:27 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post

Tweeder

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Member since Aug 2012
 
quote
Originally posted by Gall757:

I'm gonna guess 'key off engine running' for the R.....which means the other one is OFF. This is harder to decipher than the fuel pressure.... .

Most fuel systems will keep pressure for about 5 minutes after being shut off, but anything over about a minute works fine.


Once I turn the key on and the fuel pump primes then stops. The engine is off at this point. Once the pump finishes priming the fuel pressure slowly goes down to zero in just under a minute. I"m just wondering if that's normal or not?
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MulletproofMonk
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Report this Post05-13-2014 12:36 PM Click Here to See the Profile for MulletproofMonkClick Here to visit MulletproofMonk's HomePageSend a Private Message to MulletproofMonkEdit/Delete MessageReply w/QuoteDirect Link to This Post
Read this> http://performancefuelsyste...ch-leakdowntest.html

Sounds like you have a problem. Not not the fuel pump though...

EDIT: I just read on another forum that the check valve in the fuel pump can go bad and also cause the leak.

-Brian

[This message has been edited by MulletproofMonk (edited 05-13-2014).]

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Tweeder
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Report this Post05-13-2014 01:36 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by MulletproofMonk:

Read this> http://performancefuelsyste...ch-leakdowntest.html

Sounds like you have a problem. Not not the fuel pump though...

EDIT: I just read on another forum that the check valve in the fuel pump can go bad and also cause the leak.

-Brian

Thanks I will read that thread. I also heard of a bad check valve and was thinking that also, but how yo check that?


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Patrick
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Report this Post05-13-2014 03:39 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by MulletproofMonk:

I am assumed koeo "key on, engine off" and koer "key on, engine running"


Acronyms are normally capitalized, not that I was familiar with those two anyway. I thought they were words from some foreign language.
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Tweeder
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Report this Post05-13-2014 03:45 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
Oh and it has a new fuel pressure regulator also.
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Tweeder
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Report this Post05-13-2014 09:13 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
i have the pump out in a bucket of fuel, how do i test it without the car? And what am I looking for?
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Tweeder
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Report this Post05-14-2014 02:57 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
Looks like I got my answer from another forum. It appears that high flow pumps don't have the anti-bleed back valve. So it sounds that the bleed back within the minute is acceptable.

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Report this Post05-15-2014 10:23 PM Click Here to See the Profile for SpoonSend a Private Message to SpoonEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Tweeder:

i have the pump out in a bucket of fuel, how do i test it without the car? And what am I looking for?


Probably a big Boooom!!

I wouldn't try that If I were you. Whatever "that" might be. The bucket of fuels got me worried.

Spoon

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Report this Post05-15-2014 10:32 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
Never thought of that... Oh well I used my power probe and grounded the ground terminal and then applied power to the furthest plug and watched the fuel go from one bucket through the pump and into the other bucket with the hose ends.
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