Just took advantage of the relatively warm afternoon to spend some quality time under the truck. I also picked up a new pump at the parts store to be ready in case it was the pump. Since I had it, I took a look at the connector and figured out which two pins go to the pump (there are three, my DMM says it's the outer two. The middle is presumably the fuel level sender).
Having determined that, I got under and disconnected the plug that's nestled between the tank and the frame rail. No volts. I got Mrs. Juror to toggle the ignition switch from on to off while I checked and I got no volts.
I popped the lid on the under hood fuse and relay box. I pulled the fuel pump relay, checked the pinout, and bench tested it in the shop with a 12 volt power supply. It clicks as it should. I didn't have enough hands to check continuity on the NO contact, but having gotten a click, I figured I'd check if there was 12V to the coil in the truck. No luck. I got Mrs. Juror to toggle the key from off to on a couple of times and confirmed that it wasn't turning the pump on briefly when you turn the key on.
I got back under the truck, reconnected the pump to the harness, and jumpered the relay contacts. The fuel pump runs, and I get a 4-6" high fountain at the schrader valve if I depress it with the pump running. So I guess I can return that new pump and filter, and I don't need to worry about dropping the tank for the time being either.
Having tried the carb cleaner in the intake trick last night, I got no running/sputtering/other signs of life. I pulled a plug, grounded it on a confirmed-good ground, and had Mrs. Juror crank again. No spark.
Nuts.
A couple other observations:
The under-hood fuses are all good. I didn't test any of the passenger compartment ones because they all appear to be non-essential for the engine to run. I'm open to being corrected on that though.
The volt meter on the dash was previously working (i.e. reading middle of scale at 14V when running, off-scale low when the truck is off). It currently reads off-scale low whether the key is off or on.
The gas gauge at least had some passing resemblance to reality. It's currently off-scale high with the needle around 4 o-clock. No difference if the key is on or off
The coolant temperature gauge is middle of scale at 210 degrees. No change with the key on or off. This is clearly a bogus reading. It got up to something like 50 today.
The oil pressure gauge is at 22 psi. No change key on or off.
The hazards work.
The headlights work. The buzzer beeps when you have the headlights on, the key off, and the door open. The buzzer *also* beeps with the key on and the headlights on. <- Is this a clue that the ignition switch is bad? AIUI, the PO replaced it, but I don't necessarily have a good way to confirm that.
The fan blower was previously working (high only). It is not working at the moment, even with the key on. <- Another clue that the ignition switch is bad?
How do we feel about the ignition switch hypothesis? Is there a master circuit list in the giant service manual that'll tell me what circuits should be on when the key switch is on and off when the key switch is off?
Having determined that, I got under and disconnected the plug that's nestled between the tank and the frame rail. No volts. I got Mrs. Juror to toggle the ignition switch from on to off while I checked and I got no volts.
I popped the lid on the under hood fuse and relay box. I pulled the fuel pump relay, checked the pinout, and bench tested it in the shop with a 12 volt power supply. It clicks as it should. I didn't have enough hands to check continuity on the NO contact, but having gotten a click, I figured I'd check if there was 12V to the coil in the truck. No luck. I got Mrs. Juror to toggle the key from off to on a couple of times and confirmed that it wasn't turning the pump on briefly when you turn the key on.
I got back under the truck, reconnected the pump to the harness, and jumpered the relay contacts. The fuel pump runs, and I get a 4-6" high fountain at the schrader valve if I depress it with the pump running. So I guess I can return that new pump and filter, and I don't need to worry about dropping the tank for the time being either.
Having tried the carb cleaner in the intake trick last night, I got no running/sputtering/other signs of life. I pulled a plug, grounded it on a confirmed-good ground, and had Mrs. Juror crank again. No spark.
Nuts.
A couple other observations:
The under-hood fuses are all good. I didn't test any of the passenger compartment ones because they all appear to be non-essential for the engine to run. I'm open to being corrected on that though.
The volt meter on the dash was previously working (i.e. reading middle of scale at 14V when running, off-scale low when the truck is off). It currently reads off-scale low whether the key is off or on.
The gas gauge at least had some passing resemblance to reality. It's currently off-scale high with the needle around 4 o-clock. No difference if the key is on or off
The coolant temperature gauge is middle of scale at 210 degrees. No change with the key on or off. This is clearly a bogus reading. It got up to something like 50 today.
The oil pressure gauge is at 22 psi. No change key on or off.
The hazards work.
The headlights work. The buzzer beeps when you have the headlights on, the key off, and the door open. The buzzer *also* beeps with the key on and the headlights on. <- Is this a clue that the ignition switch is bad? AIUI, the PO replaced it, but I don't necessarily have a good way to confirm that.
The fan blower was previously working (high only). It is not working at the moment, even with the key on. <- Another clue that the ignition switch is bad?
How do we feel about the ignition switch hypothesis? Is there a master circuit list in the giant service manual that'll tell me what circuits should be on when the key switch is on and off when the key switch is off?
