tedallen
Active Member
Hello. I posted about this issue in the Lincoln Forums and have had responses there from a couple of folks, but this forum has been much more active in the past, so I'm going to cross-post here.
I replaced the central junction box in this vehicle in February of 2018 due to a failure of the fuel pump relay. A couple of weeks ago, when I got in it after a doctor appointment it failed to start. The first crank or two there was a little sputtering, but not much. I had it towed home and when I started testing (I confirmed it was a fuel delivery issue when it started with starting fluid), I was initially seeing 12+v when back-probing the DG/YW wire in the blue-outlined connector on the central junction box (CJB) in the passenger front kick panel. However, it was dropping down into the 6v range in less than the 2 second fuel pump prime period when the key was turned to the KOEO position. I tried jumping 12v from the battery directly to the DG/YW wire in the connector and still did not hear the pump run.
I then took out enough rear trim to get to the inertia fuel shut-off switch and disconnect the connector and check the voltage there. It was reading the same as at the CJB.
At some point during testing I was no longer seeing even a momentary reading in the 12v range on the DG/YW wire at the CJB or inertia switch. At this point I decided to order replacement relays (a 2 pack) and removed and disassembled the CJB. I noted a burnt swollen section on the relay and felt confident I had found the issue.
However, after desoldering the old relay, soldering in the new one and installing the CJB back in the vehicle the symptoms remained the same. I was still only getting 6v on the DG/YW wire when back-probing at either the CJB or inertia fuel shut-off switch.
Even when running 12v directly to the DG/YW in the inertia switch connector (with it disconnected), I still do not hear the pump run and the vehicle will not start.
It seems like there is another issue impacting the voltage coming from the CJB even after replacing the bad relay, and it seems like there is quite possibly a problem with the fuel pump (or at least somewhere in the path between the inertia switch and the fuel pump) as well.
I replaced the fuel filter before I replaced the relay in the CJB while I knew it was not under pressure. I went to my local Pull-a-Part and got a complete CJB out of a 2004 Expedition today and am going to install it tomorrow and see if it behaves any differently.
Is there something else that could be influencing the voltage on the DG/YW coming out of the CJB (e.g. PCB)? Does anyone know which wire and (in which connector) the incoming power that should be going across the high voltage switched side of the fuel pump relay would be on and what components are in the chain that supplies that voltage?
I know @Hamfisted had a post 4 or so years ago where he mentioned having had to replace his CJB for the second time. It looked like he replaced it with one that was manufactured in 2020. Would that have been a special build replacement (aftermarket) or were Expys still using a common CJB that many years later? I would find that hard to believe.
I greatly appreciate any and all assistance.
Ted
I replaced the central junction box in this vehicle in February of 2018 due to a failure of the fuel pump relay. A couple of weeks ago, when I got in it after a doctor appointment it failed to start. The first crank or two there was a little sputtering, but not much. I had it towed home and when I started testing (I confirmed it was a fuel delivery issue when it started with starting fluid), I was initially seeing 12+v when back-probing the DG/YW wire in the blue-outlined connector on the central junction box (CJB) in the passenger front kick panel. However, it was dropping down into the 6v range in less than the 2 second fuel pump prime period when the key was turned to the KOEO position. I tried jumping 12v from the battery directly to the DG/YW wire in the connector and still did not hear the pump run.
I then took out enough rear trim to get to the inertia fuel shut-off switch and disconnect the connector and check the voltage there. It was reading the same as at the CJB.
At some point during testing I was no longer seeing even a momentary reading in the 12v range on the DG/YW wire at the CJB or inertia switch. At this point I decided to order replacement relays (a 2 pack) and removed and disassembled the CJB. I noted a burnt swollen section on the relay and felt confident I had found the issue.
However, after desoldering the old relay, soldering in the new one and installing the CJB back in the vehicle the symptoms remained the same. I was still only getting 6v on the DG/YW wire when back-probing at either the CJB or inertia fuel shut-off switch.
Even when running 12v directly to the DG/YW in the inertia switch connector (with it disconnected), I still do not hear the pump run and the vehicle will not start.
It seems like there is another issue impacting the voltage coming from the CJB even after replacing the bad relay, and it seems like there is quite possibly a problem with the fuel pump (or at least somewhere in the path between the inertia switch and the fuel pump) as well.
I replaced the fuel filter before I replaced the relay in the CJB while I knew it was not under pressure. I went to my local Pull-a-Part and got a complete CJB out of a 2004 Expedition today and am going to install it tomorrow and see if it behaves any differently.
Is there something else that could be influencing the voltage on the DG/YW coming out of the CJB (e.g. PCB)? Does anyone know which wire and (in which connector) the incoming power that should be going across the high voltage switched side of the fuel pump relay would be on and what components are in the chain that supplies that voltage?
I know @Hamfisted had a post 4 or so years ago where he mentioned having had to replace his CJB for the second time. It looked like he replaced it with one that was manufactured in 2020. Would that have been a special build replacement (aftermarket) or were Expys still using a common CJB that many years later? I would find that hard to believe.
I greatly appreciate any and all assistance.
Ted