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just wondering, you said you twisted the "terminal pass thru the top" is that the little fitting on the top of the fuel pump where the blue positive wire enters the sending unit?
The whole apparatus is "fuel pump sub assembly", "sending unit" referes to the fuel guage sensor. But thats just quibling over terms, should be easy to figure out which you mean with some context.
just wondering, you said you twisted the "terminal pass thru the top" is that the little fitting on the top of the fuel pump where the blue positive wire enters the sending unit?
Anyways, yeah something like that. One of the power supply wires grounding to the tank thru the plate/cap. Should be easy to figure out which one with a meter at the harness plug.
I cant even remember what exactly I did, besides insulate the wiring in the sending unit, and its worked fine ever since. Look up cable glands, I used some plastic ones I had laying around.
did you take the sending unit out? (9 small bolds holding it in) and insulate wires inside of it, or just the ones leading to it? i'm hesitant to take it off because of how dirty my tank is and fear of getting dirt particles inside the unit and also the lines running off of it are so rusted on i think i'll just break the corroded metal before I get the bolts off.
i'm assuming it was not actually the sending unit you are speaking of but the fuel pump mount... took mine off, broke corroded pipe (Sh*#t) (gonna have to get a new one) but when i plug it in directly it runs fine and does not blow fuse, no visible wire shorting locations whatsoever... totally stumped. now truck wont turn over, just makes electrical clicks within the engine. I fear i'm a little bit ˟˟˟˟ed.
Yeah the metal cap in the top of the gas tank is where his short was. He just added some insulation like he said. But you didn't test it and now you broke it and have to replace it anyway. Lesson learned? Test first!
1: Disconnect battery and/or pull EFI fuse.
2: Disconnect wireing harnes plug to gas tank.
3: Attach multimeter ground probe to body.
4: Turn meter to continuity/diode-test/Ohms.
5: Probe each wire on both sides of the harness plugs. Write down which wires show ground continuity.
6: Post results here, for more directions.
basicly you poke around with the meter till you find the wire that is shorted to ground, inspect this wire it's whole length, and repair the short or replace the whole wire.
Likely places for body rub damage are in the cab at the rear grommet, and in the electrical channel under the trim at the bottom of the door.
yeah lesson learned, i put it all back together and am back to square one only worse because now when I turn the key it wont even turn over, nothing happens except for some clicking from the engine. I dont think its the battery as I have tried it with jumpers and still nothing, seems like battery has juice... crap.
Or wires, yep you sound like you're on the right track. I'll also add make sure your lower switch on the clutch is working, and/or wiggle the "clutch start cancel" sw onthe dash if you have one.
got it! putting a new fuel pump mount did fix the problem, though I couldnt tell because it wasnt cranking now. but upon whacking starter with a hammer it cranked over and started once I put gas back in it.
stoked on that however now I have the starter issue, what exactly does the "whack with a hammer technique" tell me about the starter?
I'm going to hijack this thread since its a good one and I have the same issue. This way, when someone searches for answers like me maybe this will come up.
In my case, I did a cursory look at the O2 sensor, nothing unusual there but will look again with full light tomorrow.
Seems to have happened after I pushed the "clutch cancel" button. Started car fine, it idled for 10 minutes as I was warming it up. Turned it off, came back five minutes later to drive off and it wouldn't start.
The 15 AMP EFI fuse keeps blowing.
Newer Optima Red battery
Need to test fuel pump and wiring
Need to jump +B and Fp connector
Noticed that some of the driver's side relay integration fuses/relays look very used and in need of replacement. Will replace this weekend with junkyard finds. Will also replace the OCR relay.
I also found that there is an old alarm in the car that I'm going to look at further and disassemble. As I type this I recall there were two wires connected to a diode, to indicate power I suppose, and I cut these from the knockout panel where the diode was but didn't connect them again. So maybe I need to remove this entire system instead since now the circuit is open.
Will update with my solution to help others when I figure it out.
My specs: 1993 3.0 4x4 4Runner 250K
Last edited by Just_ Rollin'; 04-23-2018 at 08:09 PM.
Below are captures of schematic from 1994 3VZ-E. Should be close to yours.
Measure resistance to ground at negative side of EFI fuse as you inspect and wiggle wires traced in red AND all components connected to them downstream. See if anything causes resistance to be 0.8 ohm or close or less.
Originally Posted by Just_ Rollin'
...This way, when someone searches for answers like me maybe this will come up...
...Will update with my solution to help others when I figure it out.
Good point, and thanks a lot!
...The 15 AMP EFI fuse keeps blowing.
As soon as it is connected?
as soon as you turn on IGN?
As soon as you get it running?
Random?
...Noticed that some of the driver's side relay integration fuses/relays look very used and in need of replacement.
... Will replace this weekend with junkyard finds. Will also replace the OCR relay.
..maybe I need to remove this entire system instead since now the circuit is open.
I do not think it's the COR (See signature)
Inspect but do not replace components that you are not certain are bad with components that you are not certain are good. (Pls see signature).
Yes, absolutely remove and/or insulate open wires.
Last edited by RAD4Runner; 04-24-2018 at 03:50 PM.
Thank you for the extremely detailed reply. I still haven't had time to look during daylight but under spotlight, I discovered a few things tonight.
The 15 amp EFI fuse blows only when I try to start the car. Not randomly, not when I turn the ignition to on. Only when I kick the engine over does it predictably blow.
I also tried to jump the +B and Fp with ignition on. This had no effect, did not hear the fuel pump go on.
The EFI relay in the engine bay was warm to the touch.
I temporarily replaced the EFI relay with another. This had no effect.
When reinserting the original EFI relay, I noticed that it made a clicking sound typical of a relay when the prongs touched the insert with the ignition power on. So this does not seem to be the culprit.
I investigated the O2 sensor more closely and see no signs of issue there.
I need to watch some Youtube videos before I completely understand the electrical testing. I do have a multimeter but need to practice with it before I know how to look at that schematic and actually do anything with it. But I will learn.
Seems so strange to start a car, keep it parked while running, turn it off and then it fails to turn on again without having moved anything including the car.
... The 15 amp EFI fuse blows only when I try to start the car. Not randomly, not when I turn the ignition to on. Only when I kick the engine over does it predictably blow.
I also tried to jump the +B and Fp with ignition on. This had no effect, did not hear the fuel pump go on.
The EFI relay in the engine bay was warm to the touch....
Excellent problem statement!^^^ Helps us help you more effectively. But did you hear/feel the EFI relay click when you turned IGN on?
B+ gets its power from the EFI fuse via the EFI relay (Wht-Red wire in schematic).
If EFI relay clicks, check for12V at output of EFI relay. That same 12V should go to B+ pin of fuel pump test connector.
Also try connecting fuel pump directly to battery to test it.
Also measure resistance to ground of fuel pump, and compare with fellow owners' measurement or vs FSM.
Pull the access panel for the fuel pump (4runner feature), unplug the connector and check for shorts to ground..
This was just covered recently, or above..
The bulkhead isolator has been know to fail, this shorts the pumps power input to ground via the fuel tank. No pump, blown fuse. Other likely locations depend on wire routing (model year), iirc on some this wire bundle runs along the frame farther than others.. Chase the wires forward from the tank, visually and electrical test everywhere it passes through the body, rubs, or shows signs of damage or alteration (electrical tape).
...check for shorts to ground..
This was just covered recently, or above..
...The bulkhead isolator has been know to fail, this shorts the pumps power input to ground via the fuel tank. No pump, blown fuse. ....
My truck had a bad wire going to the fuel pump. I just ran fresh wires from the battery back to the pump with a switch mounted in the dash for now. I’m thinking of getting fuse box with a few spots for aux stuff and a fuel pump fuse. For now I just have an in-line fuse. Is this a bad idea? Sorry if this is hijacking thread but I figure this could be an alternative?
this is only if the problem is outside of the tank.
Last edited by Drewandhis89Yota; 04-28-2018 at 05:07 PM.
Reason: Add more
My truck had a bad wire going to the fuel pump. I just ran fresh wires from the battery back to the pump with a switch mounted in the dash for now. I’m thinking of getting fuse box with a few spots for aux stuff and a fuel pump fuse. For now I just have an in-line fuse. Is this a bad idea? Sorry if this is hijacking thread but I figure this could be an alternative?
this is only if the problem is outside of the tank.
It's a very, very, bad idea! Bypassing fuel system safety systems put people in danger. You, your family, fellow drivers and first responder's!
Fixing it properly would have cost you less money also..
Just to join with Co_94_PU to explain WHY it is such a bad idea:
What happens if you get in an accident that breaks a fuel line? You'll be hanging upside down in your seatbelt, and the fuel pump will keep pumping fuel all over the place. You'll try to reach your red-neck pump switch, but you'll be too late ....
By design, as soon as the engine stops sucking air, the fuel pump shuts off. And as Co_94_PU pointed out, it probably would have been cheaper to fix it correctly. So fix it now.
02-21-2013, 04:50 PM
