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2000 l67 Park Ave fuel pressure

A

ayeb

New member
I've uploaded a video of my fuel pressure readings on youtbe. Can any watch it and let me know if my specs are in good order, thanks.
 


checking your fuel pressure should take like 30 seconds. you check it with key in on position and the engine not running, and then you check it with the engine running. with the key on engine off it should be about 48 to 54, and with the engine running it should be about 38 to 51.

these specs are for my 2001 GTP, I think it is the same for you park ave, but ive been wrong before.
 
If you don't want to change the pump, change the filter instead. There are 2 checks one with the vacuum line connected and then with the vacuum line disconnected with the engine running of course. When you remove the line from the fuel pressure regulator the pressure should rise.

Jeff
 
J57ltr said:
If you don't want to change the pump, change the filter instead. There are 2 checks one with the vacuum line connected and then with the vacuum line disconnected with the engine running of course. When you remove the line from the fuel pressure regulator the pressure should rise.

Jeff
Click to expand...

Thanks for reminding me, completely forgot about removing that vac line. I already changed the fuel filter. So my problem relies with the injectors or fuel pump which I already have on hand
 
I just watched the video and everything looks fine. What I saw was you turn on the key several times and the fuel pressure rises as the regulator reacts to the extra fuel deadheaded it drops back to 46 psi. Then you start the engine and the pressure drops slightly as the injectors open and when the engine starts and idles the pressure steadies out at 46 psi. As you rev it it goes to 50 psi after you shut the engine off at idle the injectors and pump stop, but there is vacuum in the manifold and as the pressure rises back to atmospheric it is still pulling on the regulator causing the pressure to drop to 40 psi then holds steady. I'm not seeing a problem, checking it under load is the best way to test a pump. Idle is the easiest on a pump as vacuum keeps the regulator held more open. The injectors do their thing and the regulator, well regulates the pressure. As you near atmospheric pressure spring pressure pushes the regulator more closed and pressure rises. As you start going into boost (assuming it's supercharged) the pressure on the regulator is increased which increases fuel pressure usually at a 1:1 ratio, so at 10# boost you would be 10psi higher than your Atmospheric pressure.

think of the regulator as a garden hose with some small holes in it. As you place your thumb over the end less water comes out, but the pressure in the hose rises and the pinholes spray more water as well. The water coming out where your thumb is just returns to the tank.

Jeff
 


Thanks for the explanation. Maybe I could tape the gauge down to the window. Still kind of lost on the psi atmospheric and boost ratio along with the fuel pressure. What should the gauge read during normal driving and at 5 psi of boost? Just trying to figure out my sluggishness and kind of starts
 
Basically atmospheric pressure is the air pressure all around us just when we are standing around which is 14.7 psi at sea level (slightly less the higher you go). When an engine is running the throttle plate limits how much air can enter the engine (ignore the IAC for now) because the throttle plate partially closed it is basically starving air from entering the manifold and cylinders so this is where the system is under vacuum or negative in relation to atmospheric pressure so it is usually expressed as Inches of Mercury. Normally an engine will idle at a negative pressure of about 20"/Hg as you apply throttle more air is allowed into the engine and the vacuum moves up closer to atmospheric pressure (usually it is 0 on a gauge, that is also where it sits when the engine is off), as you keep applying throttle you get to a point where the atmospheric pressure inside the engine is he same as the outside, as you keep feeding throttle you are turning the supercharger faster and it starts building pressure inside the manifold that is higher than atmospheric pressure. This is where you get into positive manifold pressure or PSI the more throttle you give it the more pressure it develops until you either reach the drive ratio's ability to force more air into the engine or you reach the maximum engine rpm. Usually when you are running around the pressure will be lower in the 39-40 range at idle and low vacuum times and as you get to atmospheric pressure it will go up to the higher pressure of I seem to renumber about 48 psi then the pressure should rise 1# per # of boost. So lets say for the sake of the conversation your atmospheric pressure (line disconnected and engine running and plugged line) you are at 50 psi of you run 5psi of boost then your fuel pressure should then be 55 psi. if you were running 10 psi boost then your fuel pressure should be 60 psi. Bascially it is a net of 0 above the preset atmospheric pressure.

What I mean by that is that if you had 50 psi and 10 psi boost the injectors would see a net pressure of 40psi since the boost pressure would try to force some of the fuel back into the injector. So 50 base pressure plus 10 psi boost pressure and fuel pressure regulator raising 1:1 you would still have 50 psi Net pressure. Gauge pressure and manifold pressure are different things entirely. Just remember 1 psi boost gives you 1 psi more fuel pressure and so on.

Clear as mud?

Jeff
 
Got it, thanks for the time and teaching. Going to go out here now and check the pressure while driving.
 
Good luck seeing it under driving conditions. What I did which I do not recommend to someone that is not familiar with fuel issues and is not going to take the time to do it correctly, is I bought an electric oil pressure gauge and unscrewed the mechanical gauge from the fuel pressure tester and screwed the oil sender in it's place. I ran a wire from the sender to the gauge inside the cab and connected power for the gauge to a cigarette lighter so I could just plug it in temporary and without dealing with actually wiring it in permanently. I grounded the sender using wire and electrical tape and wire tied everything solid and went for a drive. That way I didnt have fuel passing into the cab, I didn't have to spend a mint on a fuel pressure gauge and since it was just temporary I could remove everything in a few minutes.

Jeff
 
Well everything is ok with the fuel pressure. Im leaning towards the injectors for my sluggishness and slight hard start.
 


it would have to be really bad for that. I will have my injector test stand up and running in a couple of weeks.
Wife had me doing honeydoos this weekend.

Jeff
 
Im thinking theyre just leaking internally. I was going to get some rebuilt one from aus which are priced about $30 a pc. If this doesn't anything Im afraid Im going to parts ways with the car. I bareley like driving it anymore, it stresses me out to drive it any where lol.
 
Really bad huh? It idles ok, if you sit there and listen/feel for slight misfires you can notice it sometimes. My coil packs are at 5.9 except for one which measured at 6.0. I did my own smoke test and seal whatever leaks I had with rtv. My ltft is at -1.52%. 16mpg and sluggishness is not a good combination.
 
They can't leak internally without it getting out of back to the rail. Have you pulled the plug? Are you running rich (are they black)? What about timing?
 


Unless you have one just barely leaking then it could cause that, but at speed it shouldn't kill your mileage like that. You would leak enough that it would get past the rings and you would smell gas on the dipstick. I actually just had an injector fail open so bad it hydrolocked the engine and had about 2 quarts of fuel in my oil. But it was wide open. How long does the system hold pressure?

Jeff
 
I just changed the plugs so Ill post a pic of those, they look fine had them in for about 2 months. A little hint of white thats all. It holds pressure for about 10 to 15 mins before it drops very slow

EDIT: So if I had a leaky injector I would most likely smell it in the oil? Im thinking it could be something with the exhaust in the front by the rear manifold and front pipe, because when I do start it, it sounds ragedy in that area. Some type of exhaust leak.
 
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A leaking injector will sometimes drip into the cylinder if the intake valve is open and it will leak past the rings, so you will get gas in the oil, but if it is just a little bit then it is possible for it to vaporize out over time. I just had to drain about 2 quarts of fuel from my oil because of an injector that was stuck open.

Jeff
 
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