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 Post subject: Fuel pressure problem
PostPosted: Mon Jul 25, 2011 8:36 am 
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Fuel system consists of a walbro with a spoolboy canister. -6 feed and the stock fuel line as the return. A laronzo(sp?) fuel rail and a chill factory rrfpr.

The problem, I tightened the fuel pressure adjustment screw all the way in. I make 30-20 psi. Which means, it's either holding 20psi or it holds 30psi and any number in between. It does not fluctuate.

I loosen the screw all the way out and the car made no fuel pressure at all. The gauge on the fuel rail read 0psi. So I tightened it back up.

Things to note, there is an electrical problem as once the car is running it's only holding 10v and the battery before I start is hold ~11.7v

I'm going to fix the electrical problem during lunch but I'd like to hear some idea's so that once the electrical issue is fixed I have other trouble shooting test I can perform.

Thanks

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 Post subject: Re: Fuel pressure problem
PostPosted: Mon Jul 25, 2011 10:34 am 
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Neon Mechanic
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How much base pressure do you need?

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 Post subject: Re: Fuel pressure problem
PostPosted: Mon Jul 25, 2011 11:32 am 
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Well I was hoping to get up to 43-45ish psi for the baseline.

Once I get all the electrical figured out I'll pretty much be stumped if the fuel pressure doesn't change.

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 Post subject: Re: Fuel pressure problem
PostPosted: Mon Jul 25, 2011 12:55 pm 
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Neon Mechanic
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Usually a RRFPR is used to facilitate using larger than stock injectors.
The RRFPR drops the fuel pressure out of boost so the engine runs clean.
The RRFPR raises the fuel pressure in boost so the motor does not burn up.

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 Post subject: Re: Fuel pressure problem
PostPosted: Mon Jul 25, 2011 2:14 pm 
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So the fuel pressure has decreased and now it's only hitting 10psi. So I'm sure there is a fuel leak in the canister.

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 Post subject: Re: Fuel pressure problem
PostPosted: Mon Jul 25, 2011 2:35 pm 
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Neon Mechanic
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Pinch off the return line momentarily with a gauge on the fuel pressure and you will see if the pressure is available.

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 Post subject: Re: Fuel pressure problem
PostPosted: Mon Jul 25, 2011 2:47 pm 
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Already did that, most definitely leaking in the canister.

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 Post subject: Re: Fuel pressure problem
PostPosted: Mon Jul 25, 2011 9:36 pm 
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So I fixed the leak in the canister. Once I prime the system it goes up to 80psi and holds it.

Once I start the car though, the first time it was running at 20psi, then it was running at 25psi. I'm pretty much stumped as I can't tighten the chill factory anymore then what it's set at.

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 Post subject: Re: Fuel pressure problem
PostPosted: Mon Jul 25, 2011 10:39 pm 
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You don't have a check valve on your vacuum line. So you're referencing vacuum, not just boost.

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 Post subject: Re: Fuel pressure problem
PostPosted: Tue Jul 26, 2011 7:19 am 
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esteinmaier wrote:
You don't have a check valve on your vacuum line. So you're referencing vacuum, not just boost.


That's correct.

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 Post subject: Re: Fuel pressure problem
PostPosted: Tue Jul 26, 2011 7:31 am 
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So that means you need to fix that. If our cars were vacuum referenced at the factory, you would need to account for that, but they were not. The way to make them work is to keep the pressure in vacuum steady. To command that, use a check valve with the arrow pointed toward the regulator.

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 Post subject: Re: Fuel pressure problem
PostPosted: Tue Jul 26, 2011 8:04 am 
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That's great! Thanks for the info.... Now where can I find a small enough check valve though? I had the hardest time finding one for the break booster. I'm using a vw 1.8t one that is much too big for the fuel pressure regulator.

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 Post subject: Re: Fuel pressure problem
PostPosted: Tue Jul 26, 2011 11:32 pm 
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so I disconnected the vac line hoping to be able to increase the fuel pressure. It bounces between 25-30psi and if I try to raise it any higher the fuel gauge goes crazy bouncing from one side of the gauge to the other side of the gauge and the AFR's go lean by a point.

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 Post subject: Re: Fuel pressure problem
PostPosted: Wed Jul 27, 2011 6:16 am 
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Goes lean by a full point, 14.7 to 15.5ish. I've tried googling this, but I haven't gotta a clue as to what I need to do to get the fuel pressure up.

Debating about buying a 1:1 fuel pressure regulator and calling it quits for the chill factory.

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 Post subject: Re: Fuel pressure problem
PostPosted: Wed Jul 27, 2011 9:54 am 
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Fuel pressure is bouncy with aftermarket fuel rail. The stock rail has a damper on it which helps smooth out the pressure. That bouncing is because the injectors are opening and closing which causes a change in fuel pressure.


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 Post subject: Re: Fuel pressure problem
PostPosted: Wed Jul 27, 2011 10:16 am 
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boost junkie wrote:
The stock rail has a damper on it which helps smooth out the pressure.


Huh.... never knew that great info !!!

My fuel pressure on my car is very very steady, I'm using a stock rail with welded -6an on the ends....

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 Post subject: Re: Fuel pressure problem
PostPosted: Wed Jul 27, 2011 10:52 am 
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boost junkie wrote:
Fuel pressure is bouncy with aftermarket fuel rail. The stock rail has a damper on it which helps smooth out the pressure. That bouncing is because the injectors are opening and closing which causes a change in fuel pressure.


I understand that it's bouncy. At 20-25psi it bounces, when I try to bring the pressure up to 30+psi the gauge goes from 100+psi to 0psi repeated very quickly and will continue to do that until I turn down the pressure screw on the regulator.

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 Post subject: Re: Fuel pressure problem
PostPosted: Wed Jul 27, 2011 7:39 pm 
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Anyone have any ideas of the erratic fuel pressure above 30+psi?

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 Post subject: Re: Fuel pressure problem
PostPosted: Wed Jul 27, 2011 8:54 pm 
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Your pump just does not sound healthy....

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 Post subject: Re: Fuel pressure problem
PostPosted: Wed Jul 27, 2011 8:59 pm 
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Brand new walbro?

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 Post subject: Re: Fuel pressure problem
PostPosted: Wed Jul 27, 2011 9:01 pm 
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Neon Mechanic
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I wonder if the regulator doesn't have a problem.

If you gradually raise fuel pressure by pinching return hose does the pressure fluctuate?

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 Post subject: Re: Fuel pressure problem
PostPosted: Wed Jul 27, 2011 9:11 pm 
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I'm going to try that tomorrow:)

I'm thinking the pump isn't sealed properly in the canister.

I'm pretty much leaning towards a fuel pump issue too.

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 Post subject: Re: Fuel pressure problem
PostPosted: Thu Jul 28, 2011 7:23 am 
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I'd bet money that the fuel pressure really isn't jumping that much. Are you sure that's a good quality fuel pressure gauge?


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 Post subject: Re: Fuel pressure problem
PostPosted: Thu Jul 28, 2011 8:00 am 
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whity89 wrote:
Brand new walbro?


Ahh didn't read that it was new, umm what kind of fuel pressure gauge are you using ?

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 Post subject: Re: Fuel pressure problem
PostPosted: Thu Jul 28, 2011 8:23 am 
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Even if it was the worst gauge in the world, which it may very well be, the whole fuel system pulsates when it becomes erratic, 100psi-0psi.

I just hooked up a vacuum line to the port on the regulator and blew into it. It would go up to 30psi and then start pulsating, and I could feel it pulsing through the vacuum port.
(should also be known that I was able to create enough fuel pressure to stop the car from idling with the fuel pressure being erratic.)

I'm going to block off the return tonight and see what changes.

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 Post subject: Re: Fuel pressure problem
PostPosted: Thu Jul 28, 2011 12:47 pm 
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Try taking apart and re-lubing the regulator


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 Post subject: Re: Fuel pressure problem
PostPosted: Thu Jul 28, 2011 2:19 pm 
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What lube should I use and..... Where should I put it :blush:

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 Post subject: Re: Fuel pressure problem
PostPosted: Thu Jul 28, 2011 3:02 pm 
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viewtopic.php?f=47&t=256868


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 Post subject: Re: Fuel pressure problem
PostPosted: Thu Jul 28, 2011 3:37 pm 
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Before I pull out the fuel pressure regulator, if I cap the return line, the pressure should stay constant, correct?

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 Post subject: Re: Fuel pressure problem
PostPosted: Thu Jul 28, 2011 3:55 pm 
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If you cap the return line the pressure is going to shoot to maximum.


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 Post subject: Re: Fuel pressure problem
PostPosted: Thu Jul 28, 2011 4:34 pm 
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boost junkie wrote:
If you cap the return line the pressure is going to shoot to maximum.


Okay, so I'm hoping that happens. That way I know it's the regulator without a doubt.

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 Post subject: Re: Fuel pressure problem
PostPosted: Thu Jul 28, 2011 6:28 pm 
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Did you ever fix your electrical issue? The voltage to the pump directly dictates the amount of volume and pressure it delivers.

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 Post subject: Re: Fuel pressure problem
PostPosted: Thu Jul 28, 2011 6:41 pm 
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Can't you just pinch the return hose gradually and watch the gauge?

Capping the return is very hard on the pump and may blow the pump off the hose inside the canister.

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 Post subject: Re: Fuel pressure problem
PostPosted: Thu Jul 28, 2011 8:27 pm 
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Capped the fuel return, and it built 80psi.

I took apart the regulator and did the maintenance and it is now holding pressure fine, gonna put everything back and test drive the car and see if I can have it hold 45ish psi while driving.

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 Post subject: Re: Fuel pressure problem
PostPosted: Thu Jul 28, 2011 10:07 pm 
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whity89 wrote:
Capped the fuel return, and it built 80psi.

I took apart the regulator and did the maintenance and it is now holding pressure fine, gonna put everything back and test drive the car and see if I can have it hold 45ish psi while driving.


When I tighten the screw, it held 80 psi well. Then I loosen the screw quite a bit and it still held 80psi. Then I loosened it as much as I could and it was back to 20psi, so I tried to raise it, and as soon as I hit 30psi, it started going erratic and pulsing 100psi-0psi

I give up,

I'm buying a new regulator tomorrow.

(it should also be noted: in the link there is a picture of the regulator in pieces and in one of the half sections there is a blue ring that cover the bottom bolts. My regulator doesn't have that ring. I bought it used, it's the only thing that makes sense to me.)

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 Post subject: Re: Fuel pressure problem
PostPosted: Wed Aug 10, 2011 5:01 pm 
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I just want to post a conclusion for this thread, it was infact the fuel pressure regulator.

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