External fuel pump
#121
Got the computer at RockAuto. It's the right computer according to the calibration. It is acting the same as the old computer. I'm leaning toward the wiring, possibly because I don't want to think I was sent a defective rebuild.
If I knew where I could buy a brand new one, if they're even made anymore, I'd have gladly paid the excessive cost versus a rebuild that might be defective.
If I knew where I could buy a brand new one, if they're even made anymore, I'd have gladly paid the excessive cost versus a rebuild that might be defective.
#122
Ya know, the dealerships had these really cool diagnostic tools for figuring out this kind of thing, you'd connect it into the main harness and look at the blinkenlights & meter readings. I'me borrowing something kinda similar from Bill Vose for my Taurii stuff but it's for diagnosing other electronic engine control stuff and isn't really designed to be testing harnesses (though I guess it could be used for that).
#123
Plus, I still can't pull any codes, I think my wiring must be screwed up and I'm tired of trying to figure out where there's a break. Aside from that, I'm not schooled in how to really see if there's a break. I know I use both connectors at each end to check continuity but I don't think I'm doing it right.
I ordered a new harness from Ron Francis harnesses. It's actually a Cobra harness that will fit my Ford (so they say) and will be configured to work with the MAP system instead of the MAF system. Hopefully, the new harness with fresh connectors and new wiring will make the difference. What a job that will be!!!
If the frame mounted fuel pump is running and the tank pump is not, you have a problem in the wiring between the fuel pump relay and the fuel pumps themselves. The ECM wiring harness does not include this wiring. I would look for a problem in the tank selector switch and associated wiring to the fuel pump relay and the tanks themselves.
#124
I can get to the internal pump easily. I have a wooden bed and a panel that easily is removed to get to the tank. The pink wire seems to have no current coming through it. I used the positive connector to my voltmeter connected to the pink wire and ground the black wire to the frame. I had the voltmeter set to 200 Volts. I turned the ignition to the on position, but not the run position. It read 00.0. I could pull the pump to check the wires (it's a new pump) but if there's no voltage coming into the pump it seems pointless.
When I rebuilt the engine I took the harness off and put it back. I have everything where it's supposed to be. I know this because I had everything clearly marked and had corresponding connectors marked as well. Still, I can't help but think something isn't quite right due to the internal pump not kicking on. In fact, I can disconnect the connector to the internal fuel pump and the engine runs just fine. The external pump is doing all of the work.
#126
#127
Do you have a 4 connector plug to your tank unit?
To be sure your meter is set up correctly (dc volts), measure your battery voltage (across Pos & Neg battery terminals), about 12vdc, about 14vdc with engine running.
So disconnect the connector, start your engine (Engine need to be running), measure dc voltage, about 20 Vdc range, positive meter lead to pink wire on the connector, negative meter connection to ground. You should read 10-14Vdc ?? (This is power for the motor)
It is handy to have alligator clips to attach to your meter leads, also its handy to have a black and red alligator clip lead set about 10' long (clips on each end), next time you are in your radio shack.
If you have a yellow wire at the connector you should have about 12 Vdc, with the negative test lead to ground? (This is power from the fuel gage)(ArdWrknTrk reports that the voltage may be as low as 5vdc) record your findings,
The other 2 wires/connectors are ground. But don't use them as your ground for those first two test. One of them is black and the other is ?? Orange?
While you are at it check the other two wires to see if there is any power, make a note if there is.
Test the two ground wires; (Turn your engine off) Scale Ohm's Rx100 or higher, test from each wire to Body ground, you should get full deflection of the needle. Connect between both ground wires and you should get a full deflection of the meter. If you read any resistance, make note of it.
Make a diagram, Pink wire to pin1, Yellow to pin 3, Black to pin ? Orange to pin ?
Do these checks and we will go from there. Can you hear the in-tank pump if it were running?
To be sure your meter is set up correctly (dc volts), measure your battery voltage (across Pos & Neg battery terminals), about 12vdc, about 14vdc with engine running.
So disconnect the connector, start your engine (Engine need to be running), measure dc voltage, about 20 Vdc range, positive meter lead to pink wire on the connector, negative meter connection to ground. You should read 10-14Vdc ?? (This is power for the motor)
It is handy to have alligator clips to attach to your meter leads, also its handy to have a black and red alligator clip lead set about 10' long (clips on each end), next time you are in your radio shack.
If you have a yellow wire at the connector you should have about 12 Vdc, with the negative test lead to ground? (This is power from the fuel gage)(ArdWrknTrk reports that the voltage may be as low as 5vdc) record your findings,
The other 2 wires/connectors are ground. But don't use them as your ground for those first two test. One of them is black and the other is ?? Orange?
While you are at it check the other two wires to see if there is any power, make a note if there is.
Test the two ground wires; (Turn your engine off) Scale Ohm's Rx100 or higher, test from each wire to Body ground, you should get full deflection of the needle. Connect between both ground wires and you should get a full deflection of the meter. If you read any resistance, make note of it.
Make a diagram, Pink wire to pin1, Yellow to pin 3, Black to pin ? Orange to pin ?
Do these checks and we will go from there. Can you hear the in-tank pump if it were running?
Last edited by vjsimone; 07-12-2016 at 10:29 PM. Reason: Adding text
#129
Yes the truck can run OK on just the frame pump. The only time you need the in tank pump is if you run out of fuel or go up steep hills or burn out starts.
I know of guys that have drove their trucks for years in Fla with the in tank boost pump not running. It is very flat land there I am told.
That said a place you might check to see if you may have a one tank jumper behind the dash that plugs into the place that the two tank switch goes and see if it is missing.
Newer trucks have this jumper with a one tank system but I do not know about a 1985 truck.
I know of guys that have drove their trucks for years in Fla with the in tank boost pump not running. It is very flat land there I am told.
That said a place you might check to see if you may have a one tank jumper behind the dash that plugs into the place that the two tank switch goes and see if it is missing.
Newer trucks have this jumper with a one tank system but I do not know about a 1985 truck.
#130
There was the BOB (60 pin Brake Out Box) that plug into the harness between the Computer and the wiring harness but it has no blinking lights or a meter. I use mine a lot.
There was also the Monitor, I have one but very seldom use it.
I have the Recorder that goes with it and I use it even less.
All of these units go between the computer and the wiring harness.
#131
This is a thermal switching regulator and should show a (buffered) ~5.2V according to Gary's testing.
Gauges are thermal indicating.
Yes, that's right..
They warm up and tension against the needle reduces to indicate fuel level (oil pressure or water temperature)
This provides a measure of damping because of the time needed to heat or cool.
If these gauges saw full battery voltage for any length of time they would be off scale and quickly fail.
#132
Got the computer at RockAuto. It's the right computer according to the calibration. It is acting the same as the old computer. I'm leaning toward the wiring, possibly because I don't want to think I was sent a defective rebuild.
If I knew where I could buy a brand new one, if they're even made anymore, I'd have gladly paid the excessive cost versus a rebuild that might be defective.
If I knew where I could buy a brand new one, if they're even made anymore, I'd have gladly paid the excessive cost versus a rebuild that might be defective.
I think I have almost the same truck as yours: 85 5.0 EFI 2wd. I think the only difference is that I have 2 fuel tanks and you have one.
I'm a little confused when you say you can't measure any voltage at your tank, but you say that you can hear the pump running. In my truck, I have 2 pumps; one is on the frame rail and there's another one in each tank. I don't want to offend you, but when you are checking voltages have you ensured the meter is set to DC and not AC? If it was accidentally set to AC (usually a little squiggle instead of a straight line) then you probably wouldn't measure anything.
Also, I recently replaced my original computer with a rock auto one and ... unfortunately, I'm getting exactly the same problem you report. It has only happened twice; once right after I put the computer in and (unfortunately) yesterday. Pump runs for a very long time. If i try to start the truck before the pump stops the truck doesn't start. This is purely a guess on my part, but it's like the injectors never work. The computer is stuck in some funky state. Just to be clear I never experienced this problem with my original computer, so I'm pretty sure my problem is not wiring. This would suggest your replacement computer could have the same problem as your old (but not original) computer.
We have to figure out why it only happens every once in a while.
#133
How did you get the pump to not run forever?
#134
I must admit it's a little hard to follow everything that's going on here, but I might have a little bit of information that may be of use.
I think I have almost the same truck as yours: 85 5.0 EFI 2wd. I think the only difference is that I have 2 fuel tanks and you have one.
I'm a little confused when you say you can't measure any voltage at your tank, but you say that you can hear the pump running. In my truck, I have 2 pumps; one is on the frame rail and there's another one in each tank. I don't want to offend you, but when you are checking voltages have you ensured the meter is set to DC and not AC? If it was accidentally set to AC (usually a little squiggle instead of a straight line) then you probably wouldn't measure anything.
Also, I recently replaced my original computer with a rock auto one and ... unfortunately, I'm getting exactly the same problem you report. It has only happened twice; once right after I put the computer in and (unfortunately) yesterday. Pump runs for a very long time. If i try to start the truck before the pump stops the truck doesn't start. This is purely a guess on my part, but it's like the injectors never work. The computer is stuck in some funky state. Just to be clear I never experienced this problem with my original computer, so I'm pretty sure my problem is not wiring. This would suggest your replacement computer could have the same problem as your old (but not original) computer.
We have to figure out why it only happens every once in a while.
I think I have almost the same truck as yours: 85 5.0 EFI 2wd. I think the only difference is that I have 2 fuel tanks and you have one.
I'm a little confused when you say you can't measure any voltage at your tank, but you say that you can hear the pump running. In my truck, I have 2 pumps; one is on the frame rail and there's another one in each tank. I don't want to offend you, but when you are checking voltages have you ensured the meter is set to DC and not AC? If it was accidentally set to AC (usually a little squiggle instead of a straight line) then you probably wouldn't measure anything.
Also, I recently replaced my original computer with a rock auto one and ... unfortunately, I'm getting exactly the same problem you report. It has only happened twice; once right after I put the computer in and (unfortunately) yesterday. Pump runs for a very long time. If i try to start the truck before the pump stops the truck doesn't start. This is purely a guess on my part, but it's like the injectors never work. The computer is stuck in some funky state. Just to be clear I never experienced this problem with my original computer, so I'm pretty sure my problem is not wiring. This would suggest your replacement computer could have the same problem as your old (but not original) computer.
We have to figure out why it only happens every once in a while.
Good point making sure the correct range is set on the meter.
Last edited by vjsimone; 07-13-2016 at 07:44 AM. Reason: Adding text