Fuel Leak Down Test

1.Depressurize the gas line by opening the gas cap.2. Tee in a fuel pressure gauge between the fuel filter and the injector rail. 3. Replace gas cap.4.Once installed and tightly sealed, turn the key to the "ON" position [dont start the car]. The gauge should pop up to around 40 psi and hold. If after the pump shuts off [about 5 secs] the gauge starts to fall off rapidly or more then 10 psi in 10secs you have a leak down somewhere in the system.5.You now need to repeat the process but pinch off the fuel line between the fuel filter and your pressure gauge as soon as it reaches pressure. If it continues to leak down you have now eliminated the fuel pump check valve and your problem lies in the rail or the pressure regulator. If it didnt leak down you have a fuel pump check valve problem.

6. If leak down still occured ,you now need to do the test again ; this time pinch off the return line. If it still leaks down, you need to redo the test and pinch both the lines . If at this point it still leaks down, you have a leaking injector. If when you pinched the return line and it didnt leak down, your pressure regulator is leaking.

Fuel pressure regulator( this article has the specs for fuel pressure ie 34/43psiFuel Injector Leak test



You need the fuel injector gauge. Normal gas gauges are much lower pressure.



Modified by vancouverbc at 10:39 PM 11/24/2007

Modified by vancouverbc at 3:54 PM 11/25/2007

Modified by vancouverbc at 12:29 AM 11/29/2007
Modified by vancouverbc at 7:24 PM 1/19/2008

Sweet and wonderful. I'll be using it this weekend.

Quick question, where'd you get the T-bar that you have connected to your fuel pressure gauge? The only fuel pressure gauges I can purchase have that shrader connector on them. So, rather than manufacture my own T-bar, if I can purchase one....

Thanks.

RamonetB wrote:Sweet and wonderful. I'll be using it this weekend.

Quick question, where'd you get the T-bar that you have connected to your fuel pressure gauge? The only fuel pressure gauges I can purchase have that shrader connector on them. So, rather than manufacture my own T-bar, if I can purchase one....

Thanks.

Mine came with the gauge. Make sure your gauge goes up to 100 psi or you have the wrong kind.

Hello:

This is my first posting to NICO and I hope I get this request to the right place.

My son has a 1989 240sx. His first car. It is stock and is a bit rough. He took it to highschool shop class and I have spent a lot of time fixing up what they did there.

I am not a mechanic. It was running very rough and I put in new plugs, wires, cap, rotor. I replaced this injectors with a fairly new set from a wreck. It now runs on all 4 cyclinders and runs very well.

There are two problems however.

1. It is very hard to start, but after cranking for say up to 20 - 30 seconds, even in sequences of 3 or 4, 8 second intervals, it fires up. When running it runs smooth.

2. I noticed yesterday the fuel pressure regulator was wet with gasoline around the edge after the car had been running in the garage. I replaced the pressure regulator with one from a wreck. It also gets wet around the edges after the car is shut down. Today I opened the hood and noticed it still was getting a bit of gasoline around the fuel pressure regulator, even though it had not run for 15 hours.

When I remove the gas cap, there is pressure in the tank.

I am at a loss on how to stop this gas from leaking around the pressure regulator.

Does anyone have any suggestions on what to look at next or advice on what keeps the pressure in the line and yet it is so hard to start (hot or cold)?

Thanks, and have a great day.
Modified by digger12 at 7:16 PM 12/16/2008