|08-19-2015, 11:20 AM||#1|
Join Date: Aug 2015
2002 l300 fuel pump no prime condition
So I am working on a 2002 l300 with and have p0171 p0174. I built a smoke test rig and found a few vacuum leaks. One with the brake booster (brakes are working great again after replacement by a bone yard special) and another on the vacation hose connecting to the fuel pressure regulator. No other leaks were found. Fuel trims look good but still have a lean code .
The car has a rough start since the pump is not priming for the 3s when the key is initially in the on position. I also confirmed with a fuel pressure gauge. I checked the relay by energizing and testing BOTH the energized and non energized circuits for continuity. Working fine. I still need to test the fuse box with a DVOM to make sure the pcm sends the signal to energize for the 3s to prime
My obd2 adaptor does not show a pid for the AF output on the banks but I see the fuel trims are responding nicely. Based on this, I assume the sensors are OK. I should add propane to verify and will do this soon. There are no other drivability problems to speak of other than leaking oil, suspected to be leaking from the valve covers.
With the provided info, the trouble codes seem a bit mysterious and the no prime condition may point to an electrical issue.
Can anyone point me to another circuit to test for the no prime condition if the relay is working and the fuse box gets a signal from the pcm?
Can anyone comment on the trouble codes and my situation and whether or not the fuel pump may be complimenting this problem?
Thanks in advance, James
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|08-19-2015, 12:46 PM||#2|
Join Date: Jan 2006
2003 L-Series 3.0L Sedan
Re: 2002 l300 fuel pump no prime condition
Mileage? What's actual fuel pressure? Specs are 39-49 psi, regulated. 65 psi unregulated. Fuel filter replaced every 100k miles?
To test for the 12v/START/run signal from the ecm to fuel pump relay, remove the relay and note pins 85 and 86. One of them is the 12v START or run signal from the ecm. Carefully probe relay terminals 85 or 86 for the 2-second fuel pump signal when someone turns the ignition switch to the ON/RUN position. You may have to wait around 15 seconds when repeating cycling the ignition switch as a timer prevents cycling the pump several times in quick succession. You can probe both terminals (one is ground with polarity unimportant with dmm's) or use engine/chassis ground.
Pins 85/86 are the control signals to power the pump relay. 30 and 87 send 12 volts to power the pump.
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