Not getting FUEL??
01-18-2009, 06:11 PM
#23
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okay... clarification-
Voltage to the fuel pump should only be seen if the Circuit Opening Relay is being powered up. The Circuit Opening Relay acts as a "go-between" between the fuel pump and the rest of the truck. It get's turned on (humminy humminy) by EITHER the ignition switch (when cranking the engine) or the air-flow meter (when enough air is flowing through it to move the vane). If you get voltage at the fuel pump when the key is in the 'ON' position, not the 'START' position, and the engine is not running something's wrong.
To be even more specific- the COR has TWO coils in it- one powered up by the ignition switch and the other has power to it but can only turn on when the AFM has enough airflow to close a switch inside of it and ground that coil. Those coils, which ever way they operate, close the COR causing voltage to flow to the fuel pump. If the engine is not running and you're not cranking the engine over, there should be NO voltage at the fuel pump.
Voltage to the fuel pump should only be seen if the Circuit Opening Relay is being powered up. The Circuit Opening Relay acts as a "go-between" between the fuel pump and the rest of the truck. It get's turned on (humminy humminy) by EITHER the ignition switch (when cranking the engine) or the air-flow meter (when enough air is flowing through it to move the vane). If you get voltage at the fuel pump when the key is in the 'ON' position, not the 'START' position, and the engine is not running something's wrong.
To be even more specific- the COR has TWO coils in it- one powered up by the ignition switch and the other has power to it but can only turn on when the AFM has enough airflow to close a switch inside of it and ground that coil. Those coils, which ever way they operate, close the COR causing voltage to flow to the fuel pump. If the engine is not running and you're not cranking the engine over, there should be NO voltage at the fuel pump.
01-18-2009, 06:44 PM
#24
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okay... clarification-
Voltage to the fuel pump should only be seen if the Circuit Opening Relay is being powered up. The Circuit Opening Relay acts as a "go-between" between the fuel pump and the rest of the truck. It get's turned on (humminy humminy) by EITHER the ignition switch (when cranking the engine) or the air-flow meter (when enough air is flowing through it to move the vane). If you get voltage at the fuel pump when the key is in the 'ON' position, not the 'START' position, and the engine is not running something's wrong.
To be even more specific- the COR has TWO coils in it- one powered up by the ignition switch and the other has power to it but can only turn on when the AFM has enough airflow to close a switch inside of it and ground that coil. Those coils, which ever way they operate, close the COR causing voltage to flow to the fuel pump. If the engine is not running and you're not cranking the engine over, there should be NO voltage at the fuel pump.
Voltage to the fuel pump should only be seen if the Circuit Opening Relay is being powered up. The Circuit Opening Relay acts as a "go-between" between the fuel pump and the rest of the truck. It get's turned on (humminy humminy) by EITHER the ignition switch (when cranking the engine) or the air-flow meter (when enough air is flowing through it to move the vane). If you get voltage at the fuel pump when the key is in the 'ON' position, not the 'START' position, and the engine is not running something's wrong.
To be even more specific- the COR has TWO coils in it- one powered up by the ignition switch and the other has power to it but can only turn on when the AFM has enough airflow to close a switch inside of it and ground that coil. Those coils, which ever way they operate, close the COR causing voltage to flow to the fuel pump. If the engine is not running and you're not cranking the engine over, there should be NO voltage at the fuel pump.
I did get voltage with the key turned to the "ON" position BUT I had the paper clip in the diagnostic (without the paper clip I did NOT have voltage). I got roughly 12.1 Volts.....so is this would be an exception for having voltage at the fuel pump in the "ON" position, correct?? Not sure where to go from here.....EFI relay? COR? wiring?
01-18-2009, 06:48 PM
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if the jumper was in and you had voltage at the wires, that would be an exception to the rule. 
but with the jumper in, the fuel pump was not running, correct?
So now we're at a problem with the fuel pump or the wiring to/from the pump / ground.
but with the jumper in, the fuel pump was not running, correct?
So now we're at a problem with the fuel pump or the wiring to/from the pump / ground.
01-18-2009, 07:01 PM
#26
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Thanks for all the help/ideas!!!
01-18-2009, 08:29 PM
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makes no sense... the FP terminal in the test connector is meant to show that the COR is working, supplying voltage for the pump. jumpering it to B+ to make the pump run is a side effect of how it's wired.
So I'm guessing that if you had a test light or meter connected to the FP terminal and were cranking the engine over, the light would light up or the meter would show voltage. But your pump won't run....
So I'm guessing that if you had a test light or meter connected to the FP terminal and were cranking the engine over, the light would light up or the meter would show voltage. But your pump won't run....
01-19-2009, 06:04 AM
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makes no sense... the FP terminal in the test connector is meant to show that the COR is working, supplying voltage for the pump. jumpering it to B+ to make the pump run is a side effect of how it's wired.
So I'm guessing that if you had a test light or meter connected to the FP terminal and were cranking the engine over, the light would light up or the meter would show voltage. But your pump won't run....
So I'm guessing that if you had a test light or meter connected to the FP terminal and were cranking the engine over, the light would light up or the meter would show voltage. But your pump won't run....
01-19-2009, 07:08 AM
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Looking at the wiring charts it looks like a light blue and a white with a black strip wire go to the fuel pump....is this correct?? Also there is a solid black and a solid white wire in a protected gray case...what does this go to?
01-19-2009, 08:00 AM
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After messing with the wires for an hour I think I might be getting somewhere. When the key is "ON" and the diagnostic jumper is in I can hear the fuel pump working!! Also when I try to start the truck the engine runs for 2 seconds EVERY time and then shuts off (without using starter fluid). But the truck won't stay running for more than that.....
01-19-2009, 08:02 AM
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According to both the Haynes and wiring chart in the "1990 to 1995 Toyota 4Runner OEM Repair and Wiring Manuals" the light blue is the supply side and the white with black stripe is the ground side of the fuel pump. The other two wires could be the fuel sender gauge. Though the colours in the Haynes manual indicates these should be yellow with red stripe going to the fuel gauge and yellow-blue going to the low fuel warning light and brown on the ground side. (which I know is three wires!)
Last edited by spitfiremkiii; 01-19-2009 at 08:04 AM.
01-19-2009, 08:06 AM
#33
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Yes, everything sounds correct Duckky. The paperclip bypasses the Circuit Opening Relay (COR) completely, and lets you send power down the line to diagnose problems (thus, the Diagnostic Connector 
). You can also use it in a pinch to get you home if your COR fails, or you loose the ground from the MAF sensor.
Anyway, if you're getting 12V at the pump, and you've checked the ground at the pump, then the pump itself has failed. You should be able to remove the entire pump assembly from the access port under the rear seat (no need to drop the tank again).
). You can also use it in a pinch to get you home if your COR fails, or you loose the ground from the MAF sensor.Anyway, if you're getting 12V at the pump, and you've checked the ground at the pump, then the pump itself has failed. You should be able to remove the entire pump assembly from the access port under the rear seat (no need to drop the tank again).
01-19-2009, 08:38 AM
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Yes, everything sounds correct Duckky. The paperclip bypasses the Circuit Opening Relay (COR) completely, and lets you send power down the line to diagnose problems (thus, the Diagnostic Connector ). You can also use it in a pinch to get you home if your COR fails, or you loose the ground from the MAF sensor.
Anyway, if you're getting 12V at the pump, and you've checked the ground at the pump, then the pump itself has failed. You should be able to remove the entire pump assembly from the access port under the rear seat (no need to drop the tank again).
). You can also use it in a pinch to get you home if your COR fails, or you loose the ground from the MAF sensor.Anyway, if you're getting 12V at the pump, and you've checked the ground at the pump, then the pump itself has failed. You should be able to remove the entire pump assembly from the access port under the rear seat (no need to drop the tank again).
01-19-2009, 09:06 AM
#35
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Ok, so the pump is HUMMING with the diagnostic jumper? Does the truck run?
If yes, suspect your circuit opening relay to be faulty. Further diagnosis can be done to confirm it, or you can swap with a known good (or a few wrecker parts) and check for startup.
If yes, suspect your circuit opening relay to be faulty. Further diagnosis can be done to confirm it, or you can swap with a known good (or a few wrecker parts) and check for startup.
01-19-2009, 09:17 AM
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Yes it runs for 2 seconds and the quits EVERY time now. How and where do I check the COR?? I'll see if I can find a previous post describing the procedure.....thanks!
01-19-2009, 09:32 AM
#37
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It really sounds like a bad ground side connection to me. You get battery voltage to the pump connector, but it still does not work. You also say that it does work when connected directly to the + and - terminals of a battery. Really sounds like a ground problem. inspect your wires to make sure that they aren't damaged, particularly the white with black stripe. Use your Ohmmeter to look for continuity between the connectors before the COR.
The COR is basically located directly behind the front passenger speaker. Remove the glove box and it is right there. The connector is the only part of it that you can see. There are a few relays for the A/C below it.
The COR is basically located directly behind the front passenger speaker. Remove the glove box and it is right there. The connector is the only part of it that you can see. There are a few relays for the A/C below it.
01-19-2009, 09:55 AM
#38
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It really sounds like a bad ground side connection to me. You get battery voltage to the pump connector, but it still does not work. You also say that it does work when connected directly to the + and - terminals of a battery. Really sounds like a ground problem. inspect your wires to make sure that they aren't damaged, particularly the white with black stripe. Use your Ohmmeter to look for continuity between the connectors before the COR.
The COR is basically located directly behind the front passenger speaker. Remove the glove box and it is right there. The connector is the only part of it that you can see. There are a few relays for the A/C below it.
The COR is basically located directly behind the front passenger speaker. Remove the glove box and it is right there. The connector is the only part of it that you can see. There are a few relays for the A/C below it.
01-19-2009, 10:05 AM
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"If problems suspected, test the relay resistances (relay removed from socket) as follows:
STA - E1 = 17 - 25 ohms
+B - Fc = 88 - 132 ohms
+B - Fp = Infinite ohms (i.e. open circuit) w/ relay off
+B - Fp = 0 ohms w/ relay on
Jumper +B - Fp in socket to send power to fuel pump for testing wiring
CO Relay Pins/Wire Colors "
Source: http://www.4crawler.com/4x4/CheapTri...shtml#FuelPump
I tested my COR and it was all within the parameters not sure if it could still be bad if its not opening/closing correctly though.
STA - E1 = 17 - 25 ohms
+B - Fc = 88 - 132 ohms
+B - Fp = Infinite ohms (i.e. open circuit) w/ relay off
+B - Fp = 0 ohms w/ relay on
Jumper +B - Fp in socket to send power to fuel pump for testing wiring
CO Relay Pins/Wire Colors "
Source: http://www.4crawler.com/4x4/CheapTri...shtml#FuelPump
I tested my COR and it was all within the parameters not sure if it could still be bad if its not opening/closing correctly though.
01-19-2009, 10:23 AM
#40
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applying 12 volts to the coil of a relay will activate it. Use your battery to get 12 volts to terminal STA or B+ and the negative side of the battery to E1 or Fc. You can leave the relay hooked up to the battery all day if you wanted to and nothing would be hurt. Also, do as you posted and jumper B+ to Fp in the socket and see if your truck runs. If it does then it is probably the COR. If not then you have a wiring problem. Jumping those two literally bypasses the COR but uses the same wires that the relay would, unlike the Diagnostic B+ and Fp.
