fuel pressure question
07-05-06, 04:30 PM
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fuel pressure question
What would cause a pressure gauge to bounce (a little) at idle and cruise?
I seem to be having a hesitation problem and I got it traced to that I think.
At decel, the gauge is solid but when I get on the gas even slightly, the needle bounces. Not a whole lot but enough to notice. The regulator is an HKS and there's no leak in any connections. Te other night I noticed the gauge read 2.0 bar which seemed low at cruise and idle. I tried to raise the pressure but it's almost at it's max setting. The gause reads fine on boost and rises to proper pressure and stays solid. What would cause this? The gauge is a Greddy electric unit. Thanks for any help.
I seem to be having a hesitation problem and I got it traced to that I think.
At decel, the gauge is solid but when I get on the gas even slightly, the needle bounces. Not a whole lot but enough to notice. The regulator is an HKS and there's no leak in any connections. Te other night I noticed the gauge read 2.0 bar which seemed low at cruise and idle. I tried to raise the pressure but it's almost at it's max setting. The gause reads fine on boost and rises to proper pressure and stays solid. What would cause this? The gauge is a Greddy electric unit. Thanks for any help.
07-05-06, 06:12 PM
#2
What are you running for your entire fuel setup? and how recent are these items?
I've noticed very slight fluxuation in fuel gauges before and it seems to be something that just is, however there are a few things that can cause this syptom.
The first that comes to mind would be a lack of a pulsation dampner - but it would seem to me that you wuld be seeing MORE fluxuation at higher pressure than at idle, so I dunno.
What is the problem you are trying to trace down anyways?
I've noticed very slight fluxuation in fuel gauges before and it seems to be something that just is, however there are a few things that can cause this syptom.
The first that comes to mind would be a lack of a pulsation dampner - but it would seem to me that you wuld be seeing MORE fluxuation at higher pressure than at idle, so I dunno.
What is the problem you are trying to trace down anyways?
07-05-06, 06:41 PM
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Originally Posted by classicauto
What are you running for your entire fuel setup? and how recent are these items?
I've noticed very slight fluxuation in fuel gauges before and it seems to be something that just is, however there are a few things that can cause this syptom.
The first that comes to mind would be a lack of a pulsation dampner - but it would seem to me that you wuld be seeing MORE fluxuation at higher pressure than at idle, so I dunno.
What is the problem you are trying to trace down anyways?
I've noticed very slight fluxuation in fuel gauges before and it seems to be something that just is, however there are a few things that can cause this syptom.
The first that comes to mind would be a lack of a pulsation dampner - but it would seem to me that you wuld be seeing MORE fluxuation at higher pressure than at idle, so I dunno.
What is the problem you are trying to trace down anyways?
I noticed the pressure was low and I noticed the needle bouncing a little which hasn't done that before. It was reading at 2.0 bar and when I tried to raise the pressure, it barely went up. The screw to adjust is sitting at it's maximum. I got it to 2.5 bar and it's running a little better but I can't raise it any higher.
The setup is a 255 walbro, -6AN s/s lines all around.
I'm not sure if it's the pump that is failing?? The regulator (I doubt it). I pulled the vaccum hose off and the pressure dropped enough to have an erratic idle. It's supposed to raise pressure to atmospheric but it drops. Is the regulator bad?
I know I didn't have any trouble raising the pressure since I had it the screw halfway and I could raise it if I wanted to.
07-06-06, 06:20 AM
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The slight bouncing is normal.
It's the pulsations from the fuel injectors opening and closing.
At decel, the fuel injectors don't fire, so you get no pulsations.
Do you still have the PD still there?
-Ted
It's the pulsations from the fuel injectors opening and closing.
At decel, the fuel injectors don't fire, so you get no pulsations.
Do you still have the PD still there?
-Ted
07-06-06, 05:08 PM
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Originally Posted by RETed
The slight bouncing is normal.
It's the pulsations from the fuel injectors opening and closing.
At decel, the fuel injectors don't fire, so you get no pulsations.
Do you still have the PD still there?
-Ted
It's the pulsations from the fuel injectors opening and closing.
At decel, the fuel injectors don't fire, so you get no pulsations.
Do you still have the PD still there?
-Ted
I thought the injectors could be sticking since on decel the injectors cut out.
Although the fuel pump has been re-wired, I'm going to check the voltage again and swap out fuel pump. Whatever the hesitation is, it seemed to be getting worse and raising the pressure to proper level cured most of it but now and then it comes up at low load as in shifting 1st to 2nd half throttle.
And another, the A/F gauge (using for idle A/F monitoring) reads low. Maybe a dying Walbro pump? It's about 2 years old though.
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