Fuel pressure problem that i cant make heads or tails of

[Mr.Spool]

I must say I really can't believe this thread.keeping the combo simple especially with a mild build is one best things about these cars.it is unbelievably easy to get these cars to run good with the stock stuff and a little know how.

 

[Mr.Spool]

Car ran the same. Recently I installed more parts:

Fast XFI
120lb precision injectors
GM flex fuel sensor in the return line
car is now on e85

Problem is you never fixed the problem and threw more parts at it that future complicate things.

 

[Mr.Spool]

I suspect It is not raising under boost either but i cant see the gauge while driving. I

You need to see the fuel pressure in real time or your guessing and chasing your tail.fp must rise one to one period.put a gauge in the car or outside of it or things are going to get even more expensive.

 

[Boost231]

If it were me, I would test the regulator. Pull a vac. on it with a gauge you can read and monitor fuel pressure and then apply pressure and monitor. This can all be done in the garage. Report back.

Sent from my SM-G935T using Tapatalk

 

[Mr.Spool]

I am looking for any advice to speed up the diagnosis.

Verify fuel pressure rise 1 to 1 in real time and work from there.

 

[turbo89]

I must say I really can't believe this thread.keeping the combo simple especially with a mild build is one best things about these cars.it is unbelievably easy to get these cars to run good with the stock stuff and a little know how.

you said the magic words .. a little know how

It's just easier to put twin 450L pumps , fed by welder cables , dual -12 feeds, to 3/4" rails, -8 twin returns, to feed 300 lb Moran Atomizers .. All on a 11 second car at best

common sense isn't so common just more shit for people to hang themselves with

 

[GNRick]

Toby can you elaborate on where to buy a stock style FP hanger? I had a couple where the bulk head burned. On the last one, I removed the burned piece and installed the Racetronix intermediate harness. It looks like the same harness that Jack uses on his new hangers, so I'm not expecting anymore burnt bulk heads. After 4 months, so far so good.

 

[Toby_Goodmk]

Toby can you elaborate on where to buy a stock style FP hanger? I had a couple where the bulk head burned. On the last one, I removed the burned piece and installed the Racetronix intermediate harness. It looks like the same harness that Jack uses on his new hangers, so I'm not expecting anymore burnt bulk heads. After 4 months, so far so good.

buy a spectra

 

[ttribejr]

IMG_1036

• ttribejr
• Dec 29, 2016

IMG_1031

• ttribejr
• Dec 29, 2016

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• ttribejr
• Dec 29, 2016

Anything out of place here? I noticed the return line is the smallest of the bunch. I followed it and the vent line all the way to the charcoal canister and fpr and didn't see any kinks. (I could not see behind the ac compressor too well) Previous owner doesn't know much because he had shops do the work for him. Is the return line hose I.D. Supposed to be smaller than the vapor line?

I clamped the return line shut and pressure shot up as you would suspect. Next I partially clamped the feed line and brought the static pressure down in the mid 40s

I turned up the static pressure to 55 psi just for grins and plugged in the vacuum line and it dropped pressure like it should.

I only had an hour tonight to play with it. I'm positive it's a return restriction, just not positive where. Maybe somebody can chime in and see if those hoses look too small?

On the picture where they are stacked the top is feed, middle return, bottom is vent

On the right to left picture right feed, middle return, left is vent

 

[ttribejr]

As far as verify the 1:1 rise. I will, just don't have the equipment yet.

 

[Mr.Spool]

IMG_1036

• ttribejr
• Dec 29, 2016

IMG_1031

• ttribejr
• Dec 29, 2016

IMG_1030

• ttribejr
• Dec 29, 2016

Anything out of place here? I noticed the return line is the smallest of the bunch. I followed it and the vent line all the way to the charcoal canister and fpr and didn't see any kinks. (I could not see behind the ac compressor too well) Previous owner doesn't know much because he had shops do the work for him. Is the return line hose I.D. Supposed to be smaller than the vapor line?

I clamped the return line shut and pressure shot up as you would suspect. Next I partially clamped the feed line and brought the static pressure down in the mid 40s

I turned up the static pressure to 55 psi just for grins and plugged in the vacuum line and it dropped pressure like it should.

I only had an hour tonight to play with it. I'm positive it's a return restriction, just not positive where. Maybe somebody can chime in and see if those hoses look too small?

On the picture where they are stacked the top is feed, middle return, bottom is vent

On the right to left picture right feed, middle return, left is vent

Check the pump and volts.

 

[Chuck Leeper]

BTW, the Accuflub has known machining issues

^^^^
A new Accufab I installed did exactly the same thing. Took ir apart, found alum chips in it, cleaned it up...OK.

 

[ttribejr]

^^^^
A new Accufab I installed did exactly the same thing. Took ir apart, found alum chips in it, cleaned it up...OK.

will it reseal fine or do you have to buy a rebuild kit for it?

 

[turbo89]

^^^^
A new Accufab I installed did exactly the same thing. Took ir apart, found alum chips in it, cleaned it up...OK.

THIS X 2 ..

 

[turbo89]

will it reseal fine or do you have to buy a rebuild kit for it?

Be careful taking it apart and it will re-seal fine ... just take your time and be careful with the membrane.

 

[zapp240]

Sorry, just saw this post. I might be throwing a damper on all the theories flying around but have the same exact issue and came to the conclusion the fuel pump is overpowering the return line. tried several FPR's (holly, accufab) and they do the same exact thing, will not adjust to below 50psi when started and after running her for 20 or so minutes, have no problem dialing it in to 43psi with vacuum off. monitored alternator voltage and saw it at 14.6 at startup and 13.7 after 20 minutes. new hotwire and fuel pump on a 21k mile car. issue is high voltage at startup and drops when the alternator runs a bit. got the braided -6 line to run back to new tank that is on the car, will someday put it on when it bothers me that I have to let car warm up for 30 minutes before i get on it (since the irregular fuel pressure is playing havoc on the computer during startup). hope this helps you out a bit. take a look at your volts and see what it is doing at startup and after warmed up

 

[ttribejr]

Sorry, just saw this post. I might be throwing a damper on all the theories flying around but have the same exact issue and came to the conclusion the fuel pump is overpowering the return line. tried several FPR's (holly, accufab) and they do the same exact thing, will not adjust to below 50psi when started and after running her for 20 or so minutes, have no problem dialing it in to 43psi with vacuum off. monitored alternator voltage and saw it at 14.6 at startup and 13.7 after 20 minutes. new hotwire and fuel pump on a 21k mile car. issue is high voltage at startup and drops when the alternator runs a bit. got the braided -6 line to run back to new tank that is on the car, will someday put it on when it bothers me that I have to let car warm up for 30 minutes before i get on it (since the irregular fuel pressure is playing havoc on the computer during startup). hope this helps you out a bit. take a look at your volts and see what it is doing at startup and after warmed up

You are correct sir. The lowest pressure I can run is 50psi static without the Hotwire and 54psi with the Hotwire. At those static pressures the Fuel pressure drops about 4-5psi at idle and raises when you blip the throttle.

If I set it any lower, the FPR does not function properly.

crazy. All I have is a 255LPH walbro. Maybe I have a blockage somewhere. Don't know. I replaced the 1/4 rubber lines with new 5/16 and I cut off the crimp in the return line on the hanger. But the above results are the lowest I could go.

 

[ttribejr]

I am still going to open up the fpr and look inside after reading what others said about their accufab. I just ran out of time tonight.

 

[zapp240]

thanks for giving me the heads up on the hanger return line, was going to try and cut off the end where it restricts the most, but since you had no gains there, will just opt for the braided line return. if you search for return line upgrade fix, you should be able to find a few good write ups on how to do it, i have it bookmarked somewhere, will have to try and find it.

found this one, this is where i got my parts list from

http://buickturboregal.com/install-6-braided-return-line-buick-grand-national.html

 

[Mr.Spool]

I have run strong in tank pumps and even when you run higher intial fp say 50psi it still raises 1to1 with boost ,It just makes the curve richer.there have been cases where bigger return lines are needed on the higher flowing pumps.