With a 255lph walbro fuel pump, fuel pressure drops very quickly after shutting off?

ojibway1972 · 03-12-2005

Anyone have a walbro 255 fuel pump and a fuel pressure guage? what im wondering is when I turn the key to prime the fuel pump if I dont start the car the fuel pressure starts to drop right off. When the car is running it holds pressure fine, but as soon as I shut it off the fuel pressure drops right down to 10 PSI. I checked all the fittings on the guage there tight, oh I have a Holley adjustable fuel pressure regulator. Im wondering this because when I had the stock regulator and fuel pump it would hold fuel pressure all night long after I shut it off.

GhostDog 5.0 · 03-12-2005

It should maintain pressure longer than that. It drops pressure within seconds of turning it off?

ojibway1972 · 03-12-2005

yes as soon as I turn it off it drops to like 10 PSI.

Quad · 03-13-2005

Did you change the regulator and pump at the same time? The pressure may be bleeding back through the pump but you would have to to contact the manufacturer to find out that. Most OEM fuel pumps will not bleed or should not bleed back. At least find out before you spend lot's of time trying to locate what's bleeding the pressure off.

ojibway1972 · 03-13-2005

I replaced the regulator first and I think it still held pressure when I replaced that im sure it was after I replaced the fuel pump that it started to bleed off pressure. I have been looking for tech info on the walbro pump but I cant find anything on the web about them. Thanks all for the info.

meangreen92 · 03-14-2005

I think there's a check valve in the supply side of the pump itself, which is
supposed to ensure that there is fuel for the motor upon startup. It's a
little ball bearing. I think that is the rattle you hear when you handle a fuel
pump.

Quad · 03-16-2005

Well don't think it's your regulator.. but you can always hook up the fuel pressure guage before the filter and see how it acts.. this will remove a lot of leak possibilitys and the fuel pressure regulator. Not familiar with the pump... is it a inline pump or internal pump in your tank? If internal are you sure you got the clamps tight on the hose going to your assembly?

ojibway1972 · 03-16-2005

I didnt put it in I had a tech put it in, it's a walbro in tank pump, I talked to summit on it and they said some leak down is going to happen, they didnt like the fact that it happened that quickly. Im just going to run it I worked it pretty hard and it keeps up well, I just dont like seeing the pressure drop off so quickly.

GhostDog 5.0 · 03-16-2005

I checked out my pressure yesterday I turned it off at 7 pm and checked it out at 7 am and it was at 25 psi.

ojibway1972 · 03-16-2005

Thanks Ghostdog, Im going to keep my eye on it.

ojibway1972 · 04-05-2005

UPDATE, After I filled the tank with a full tank of fuel it now will hold pressure alot longer than it did. I dont know why that is I cant seem to come up with a reason.