Engine/Transmission (1998.5 - 2002) Walbro/FASS hard start problem-better solution than using power window circuit IF...

[zman]

Hey all. I've been trying to find a better solution to my Walbro pump hard start problem than using the power window circuit to trigger the relay. The PW circuit does work UNLESS you are using some sort of turbo cool down system like what is built into the Edge Juice box.



The main problem is that once the ignition is shut off, the power to the pump is cut if the relay is triggered via the PW circuit leaving you with ZERO pressure during cool down. The other problem is that the pump will run constantly if you need to have the key on but engine off for some reason. My other goal was to use the original lift pump wiring harness to trigger the main relay.



My solution was to install a second relay that turned off the pump ONLY while the ignition is cranking.



The typical relay setup is like this:



RELAY 1 (SPST type shipped with GDP and FASS systems):

pins 85 & 86 --> stock fuel pump wiring harness (or PW window circuit & ground)

pin 30 --> battery (+)

pin 87 --> fuel pump







My two relay setup is like this:



RELAY 1 (SPST type shipped with GDP and FASS systems):

pins 85 & 86 --> stock fuel pump wiring harness

pin 30 --> battery (+)

pin 87 --> pin 30 on RELAY 2



RELAY 2 (SPDT type set up for normally closed use):

pin 85 --> starter solenoid post on starter (small wire)

pin 86 --> ground

pin 30 --> pin 87 on RELAY 1

pin 87a --> fuel pump



The dual relay setup shuts down the pump only while cranking but allows the pump to continue to run once the ignition is shut off IF you are using a turbo cool down system. If you don't use a turbo cool down system, this will still work for you and you won't have to worry about the pump running while the key is on and the engine is off.



So far this setup works perfect, but I'll be doing more testing tomorrow and will report back.



Steve

 

[PRout]

Nice improvement. . Sounds like a spare relay is on the items needed list when we're out in the boonies.

 

[zman]

OK, after the third start, I threw a code P1899 and my cruise quit working. After some research I found another post where the installation of a relay caused both of those symptoms to occur. Apparently the grounding of the coil in the new relay causes some sort of interference that the ECM sees.



I moved the connection of pin 85 on RELAY 2 to the starter solenoid post on the starter and it appears that problem is solved. I had previously connected pin 85 to the 14 ga yellow ignition wire that runs down the steering column.



So far, no more codes. I'll report back with the results of this change. I've updated my first post to reflect the change.



Steve

 

[zman]

I drove the truck all weekend and have thrown no codes since moving the RELAY 2 trigger wire to the starter solenoid post. The best news is I didn't have any hard starts or stalls when going into gear. Hopefully everything is back to normal!