I have recently been having some starting issues with my 91 first intermittent, and now it wont start at all. It has spark but no fuel pressure at the banjo fitting on top of the fuel pump. Is there a way to test the pump?
3FE fuel issue
- Thread starter hawaiicruz
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
Jump pins 1 to 8 on the check connector. This feeds the fuel pump +12 directly and bypasses all the FP logic. Don't leave this jumper in for any length of time without the motor running as the fuel pump will not turn off, but you should get fuel pressure at the cold start injector banjo fitting. That's an easier place to check for fuel.
- Thread starter
- #3
Thanks Jon. Please bear with me as I am a total 3fe newb is the check connector the diagnostic port? if so my lid is labeled with multiple letters
The check connector is on the right side of the firewall, below and to the left of the wiper motor. The picture below is from the FSM.
- Thread starter
- #5
Thanks I'm guessing that pin 1 is the lower left and pin 8 is one of the middle ones? Mine are only labeled with letters.
- Thread starter
- #6
never mind I figured it out from my 94 fsm, testing now
Uhhh...look at the picture. B+ is top right and FP is bottom right.
Last edited:
- Thread starter
- #8
ok no fuel. since I have a check engine light and spark, I can rule out efi relay fuses and fusible links?
- Thread starter
- #9
I'm thinking it might be wiring related, is there a way to test for voltage at the fuel pump wiring connector just above the fuel pump?
The fuel pump motor +12 is the red/green stripe. Ground is white/black stripe.
Check for +12 at the pump with the jumper in between pins 1 and 8 so you bypass the logic.
Check for +12 at the pump with the jumper in between pins 1 and 8 so you bypass the logic.
- Thread starter
- #11
Only 3.1 at the connector so I guess I will work backward from there. Thanks again
- Thread starter
- #12
I traced the wires back to the large connector in the drivers kick panel but I cant seem to identify the correct wire to the fuel pump. I was thinking of just running a new hot wire to the fuel pump, I'm looking for a circuit that's only hot with the ignition on. Any suggestions on this, or a different approach?
The fuel pump is fired from the circuit opening relay (COR) in the driver's kick panel. The COR is fired both from the starter signal (runs the fuel pump during starter cranking) and the flap in the AFM. This ensures that in the event of an accident, the fuel pump is shut down if the motor stalls.
I strongly suggest fixing the problem correctly.
Pin 14 of connector ID2 (the one in the driver's kick) is the FP hot lead. It changes color from red/green stripe on the FP side to red/black stripe on the COR side.
You should also verify that you're seeing a strong +12 at the check connector pin 8.
I strongly suggest fixing the problem correctly.
Pin 14 of connector ID2 (the one in the driver's kick) is the FP hot lead. It changes color from red/green stripe on the FP side to red/black stripe on the COR side.
You should also verify that you're seeing a strong +12 at the check connector pin 8.
- Thread starter
- #14
I'm only getting 9.6v at pin 8
Under what conditions? Be specific.
You should be seeing a strong +12 at the check connector with the key in the ON position, motor off. No jumpers, no nothing.
If you are not getting +12 then something is loading down that circuit or there is poor connectivity from the EFI relay. It's passing enough to satisfy the ECU logic, but not enough to fire the fuel pump.
I would start by making sure the EFI relay is getting the proper voltage on the load side coming from the fuse (pin 2). You can pull the relay and jump pins 2-4 on the socket and see what the voltage is a the check connector.
If it's still low, start pulling connectors off of the 3 VSV valves; ISC valve; O2 sensors, while monitoring the voltage at the check connector.
Hang on a minute. If the fuel pump itself is faulty, it might be loading down that circuit as well. Try disconnecting the FP while monitoring the voltage as well.
I have a hard time believing something is loading down that circuit as it's not logic, it's battery power. The 15 amp EFI fuse would blow before you had a severe voltage drop.
I'm just sipping my tea and theorizing here.
If you are not getting +12 then something is loading down that circuit or there is poor connectivity from the EFI relay. It's passing enough to satisfy the ECU logic, but not enough to fire the fuel pump.
I would start by making sure the EFI relay is getting the proper voltage on the load side coming from the fuse (pin 2). You can pull the relay and jump pins 2-4 on the socket and see what the voltage is a the check connector.
If it's still low, start pulling connectors off of the 3 VSV valves; ISC valve; O2 sensors, while monitoring the voltage at the check connector.
Hang on a minute. If the fuel pump itself is faulty, it might be loading down that circuit as well. Try disconnecting the FP while monitoring the voltage as well.
I have a hard time believing something is loading down that circuit as it's not logic, it's battery power. The 15 amp EFI fuse would blow before you had a severe voltage drop.
I'm just sipping my tea and theorizing here.
Jon you crack me up. "...sipping my tea and theorizing"
You are so patient and helpful. I can't pass up your posts, in fear I might miss reading something I don't know already, and that info will most likely save my ass one day.
Example: I was on Cinnamon Pass in Colorado on the Alpine loop with my wife, 2 kids, my parents and sister. We had just bought the Landcruiser and drove to Colorado on our summer trip. Well after lunch I get in and crank but no start. Well before our trip I got on this new forum, ih8mud and read and read for hours and some how I remembered about the EFI relay Jon wrote about, I took out the relay, it was hot, tapped it on my hand and plugged it back in and a way we go!!
Your in good hands hawaiicruz...
You are so patient and helpful. I can't pass up your posts, in fear I might miss reading something I don't know already, and that info will most likely save my ass one day.
Example: I was on Cinnamon Pass in Colorado on the Alpine loop with my wife, 2 kids, my parents and sister. We had just bought the Landcruiser and drove to Colorado on our summer trip. Well after lunch I get in and crank but no start. Well before our trip I got on this new forum, ih8mud and read and read for hours and some how I remembered about the EFI relay Jon wrote about, I took out the relay, it was hot, tapped it on my hand and plugged it back in and a way we go!!
Your in good hands hawaiicruz...
- Thread starter
- #18
x2 thanks again Jon. Key on, motor off, fuel pump unplugged, no jumper = low voltage at pin 8. off to perform other tests as mentioned...Wait let me try it with the fuel pump plugged in correctly.
- Thread starter
- #19
Did I mention that it's this truck? https://forum.ih8mud.com/80-series-tech/512254-750-cruiser.html?highlight=750 hence the ease of performing tests directly to the fuel pump. ( fuel pump resistance is good)
- Thread starter
- #20
Well, it appears that the fuel pump is bad. I put 12v directly to it and got nothing, but that still doesn't explain the odd voltage readings elsewhere
it also appears that someone has been in there before me, as the fuel return hose is missing the clamp
it also appears that someone has been in there before me, as the fuel return hose is missing the clamp
Last edited:
