For the past couple of months I’ve been trying to chase a fuel system issue where I’m getting air in the fuel system that makes it’s way to the fuel rail. I purge it every so often with the Schrader valve when parked diagonally on a slight hill so the valve is the high point in the fuel system.
I do have VIDA. But barely know how to use it. Recently purchased a DICE unit and haven’t had time to learn it. Curious what I might be able to log in VIDA to possibly determine if it’s the fuel pump causing the issue.
Basically looking for suggestions on other things to check before replacing the pump.
The car just turned 130k miles. Got it October from an older couple that are retired college professors. They were the original owners. Always dealer maintained while they owned it. I think it sat for long periods since it was not their primary vehicle.
Diagnostic data (not from VIDA, values from TopDon BlueTooth dongle and Top Scan software) :
1) Fuel pressure stays right around 55psi while running. At engine speeds below 2k RPM pump duty cycle tends to be around 45%. Will drop to 43% at idle and go up over 50% at highway speeds.
2) fuel pressure will creep up to around 70psi within 5 mins after shutting down.
3) hard to verify what the pressure drops to when allowed to sit for several hours because the pressures starts to build before the live data page loads on the scan tool.
4) At cold start, If I wait approximately 10 seconds to start the engine after turning the key to position 2 it appears to be enough time for pressure to build to compress any air in the fuel rail so no codes are generated. Pressure will drop briefly, maybe 1 second or less, to 36-38psi range at initial start and then immediately recover. But it’s enough for a slightly rough idle for a few seconds. Typically no misfire codes are generated at a cold start.
5) Warm starts are problematic. Example would be after coming out of a store and the car has been sitting in the parking lot for 25 to 30 mins. Even if I wait with the key in position 2 for an extended time, there will be a long crank. It has always started on the first cranking cycle, never have to try again. But that’s likely because I tend to purge the air before it gets too bad. Misfire codes are random on these long cranks. 75% of the time it’s Cylinder 1, but it can be any cylinder. I think it’s related to how the car is sitting while parked. (level/incline, etc.) Seems like the heat soak causes the air to expand enough that it makes it’s way to the injectors when starting.
6) the car never throws any other codes or exhibits any other problems. Just a misfire at startup sometimes and a rough idle for 2 to 10 seconds at start.
7) I can’t find any fuel leaks. Not sure if it’s possible for air to make it into the system without fuel leaking when there’s 55+ psi of pressure there.
Here’s what I have done thus far:
-Replaced the fuel injectors & o-rings with rebuilds from Rock Auto
-Replaced the fuel pressure sensor on the fuel rail with a Bosch unit. I think OEM equivalent. The one that was in the car appeared to be working fine and I have saved it as a spare. Before and after pressure readings are the same. Was kinda taking a random shot with this part.
-Replaced all of the coil packs and plugs. IPD coils, Iridium plugs. Did this before I diagnosed the air problem because I was attempting to fix a rough idle.
-Replaced fuel filter.
Here’s what I have not done:
-Replace the fuel pipe-to-fuel-rail o-ring
-Replace the in-tank fuel pump
I haven’t had a chance to collect any data yet to see if the problem is related to tank fuel level yet.
Any thoughts or suggestions before I jump into replacing the fuel pump?