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Murray · Post by **Murray** » Mon Mar 14, 2005 12:20 pm

i'm just going over my baby in anticipation of that day when spring arrives and I have a question.Testing my fuel feed system and have installed a pressure gauge in the fuel line before the fuel rail.When I energize the pump by opening the AFM door all is well -pressure rises to 36 PSI.If I pinch off the return line after the regulator pressure rises quickly above 50PSI (I chicken out at that point !).When I pressurize the system to 36PSI and turn off the pump the pressure is not maintained.It steadily drops down to 15-20PSI in about 20 seconds.Is this OK or is my regulator failing to maintain proper pressure ?Everything is tight no leaks and my injectors are brand new.(Real new ala Greg Gordon not sort of new !)

Thanks

Greg Gordon · Post by **Greg Gordon** » Mon Mar 14, 2005 1:32 pm

I don't think you have any problem. I have seen cars that hold pressure for a really long time, and others that leak down in about the time period you experienced. I can't find any Alfa Spec for fuel pressure leak down, but here is what I have found on our personal cars. It's almost always a pressure regulator not sealing perfectly, but it really doesn't matter. As long as pressure doesn't drop to Zero in a few seconds the regulator will be able to hold pressure when the car is running.

Pinching the regulator return line really just checks to make sure the pump can hold a lot of pressure, but I wouldn't do that too much.

bmacf · Post by **bmacf** » Mon Mar 14, 2005 4:57 pm

Greg, you really sure? I saw that problem once and it turned I had a leaky injector. When I bought some new injectors the fuel pressure would stay up for at least an hour after I shut off the car.

Sounds like the regulator is ok, but I'd wonder where the fuel is going? Maybe the check valve in the pump is bad? Maybe a leaky injector?

Bill in MD

Greg Gordon · Post by **Greg Gordon** » Mon Mar 14, 2005 6:25 pm

A leaking injector usually manifests itself in some other way, poor idle, fouled plug on one cylinder etc. A regulator or fuel pump can allow pressure to bleed down without any other symptoms. I suspect that's why there is no actual spec for that, if it's happening it just doesn't matter.

I am not saying it can't be a leaking injector, and if it is I will send a replacement pronto! However I doubt it is.

Murray · Post by **Murray** » Tue Mar 15, 2005 1:55 am

Bill I'm pretty sure the pressure is bleeding off through the regulator because if I shut off the pump with the return line pinched shut, the pressure drops very slowly - probably due to incomplete closure of the return line (vice grips don't make a perfect valve

) I'll elect to go with Greg's suggestion and live with it.I'll order a replacement regulator just in case.

Greg Gordon · Post by **Greg Gordon** » Tue Mar 15, 2005 6:56 am

You can buy special clamps specifically for pinching lines shut. If you have any doubts or problems let me know and new injector(s) will be on the way.
Greg Gordon www.oldebottles.com/italiancars.htm

Murray · Post by **Murray** » Tue Mar 15, 2005 7:41 am

Thanks Greg I'm sure the injectors are fine.Car starts, idles and runs just fine.If my lap times are any longer this summer I'll blame it on you though

Fuel pressure regulator testing