Not getting fuel to the fuel pump

We have replaced the fuel pump and fuel filter. Checked all the relays, fuses. We are looking at the ECM to see if they may be why my truck is not starting. We know that the fuel pump is not getting fuel to it. Any suggestions?

 

You had the tank down, notice any thing out of the ordinary?

Tank has plenty of fuel to cover the strainer?

 

also check that the fuel pump is getting power then work your way back.

 

I really have nothing useful to add to this conversation, ...
I'm pretty sure this is some sort of internet voodoo myth.

I mean, I've been driving for 20 years (including professionally), and frequently (like, every 3rd or 4th tank of gas) run with the low fuel light on.

NEVER replaced a fuel pump. And to be honest, my parents haven't either.

...other than low fuel driving probably isn't the problem.

 

You should have opened with that line.

 

Assuming you mean pump not getting power.
You mentioned checking the relays. I don't know how or what you checked for.
You may be aware this already but the relay (circuit opening relay), does not close and initially power the pump until the ECM sees a signal from both the starter operating (STA) and the crank position sensor showing crank rotation (EN). It will then maintain power to the pump (thru the relay) as long as the crankshaft keeps turning.
I don't remember how the 4 is plumbed but on the 6 you should be able to pinch the fuel return line and "feel" fuel flow when the engine is running or in your case cranking.

One fellow on another forum replaced his bad pump only to mush one of the pins in the harness plug flat (at the tank).

This diagram is from a 99, should be the same for yours.

 

Edited just for you.






Don't worry, you can quote me too ...

 

It's ok, I obviously didn't have anything useful to add either, I just couldn't help myself

 

No worries. My butt isn't too hurt.

 

There is 3/4 tank still in the tank.

 

I went to replace the pump in my daughter's 99 and the one that O'Reilly auto parts gave me when installed would have been 1" further off the bottom of the tank. Went and bought one from the dealer and there was quite a bit of difference between the two.

The only reason I mentioned it.

 

its simple, if you have power to the pump then the new pump is defective and you need to replace it. new stuff is sometimes bad right out the box, you would be surprised how often.

also if you have a stuck pressure switch at the fuel rail it may not be sending power to run the pump thinking the line is already at full pressure.

also make sure you didn't switch the return line for the fuel to engine line, if you aren't sure the disconnect both and place them in a bucket and see if its pumping fuel then, if the lines are reversed I think there ids a check valve to prevent fuel from going the wrong way.

 

Stick a gauge on it other than that you are just guessing.

 

No matter what the ECM is doing the pump still should get power during the crank cycle. Once the key is released the ECM determines that the engine is running and keeps the pump running and it will continue to run as long as the engine is running. There is no such a thing as a submerged pump not getting fuel if there is no fuel delivery the pump is toes up or it has no power.

 

Possibly ground?

 

There is no such thing as a fuel pressure switch on a Tacoma. The pump runs all the time when the crankshaft is turning, with pressure regulated by the FPR.
The feed and return lines are different, feed is high pressure with the appropriate fittings while the return with little to no pressure uses spring type hose clamps.

That could very well be but read on.
According to the 99 FSM, Vol#1, Advanced Diagnostics, the ECM controls the fuel pump. It will not start the pump until it sees both cranking and rotation signals. It then grounds the COR powering the pump. The pump will then continue to run until the crankshaft stops turning. All that is nearly word for word from the FSM and seems to be confirmed by the factory diagram I posted. I never really thought much further about it until your post. Thanks a bunch.
EDIT 11/7/14
This is the whole page, note the text.


Now the interesting part is, how can us man trans folks push start the truck without using the starter at all? Several things come to mind, the FSM is wrong or the "STA" signal is generated by the ECM when the key is in the run position and only needs to see the crankshaft signal to allow the pump. The latter may hold some water when the detailed "actual" wiring diagram is compared to the "theory of operation" diagram from the diagnostics manual. This is where it starts to get foggy. The "actual" diagram is completely different and seems to show 2 sources of power for the COR coil with the neg side of the coil hard wired to ground. These being the clutch start switch and STA from the ECM.
The fog thickens.
The actual diagram shows a schematic of the COR with 2 sets of NO contacts and 2 coils further complicated by a resistor in one of the contact circuits.
More fog. In "testing the COR" the FSM says "12v on these 2 terminals should close one set of contacts while 12v on these other terminals will open the other contacts". This implies that there is 1 set of NC contacts contradicting the schematic.
It almost looks like the ECM will possibly allow the pump in the following condition, clutch start switch open, truck is moving (speed sensor?), key on and crankshaft rotating, like when push starting.
I would kinda like to figure this out and welcome any input but this is as far as I want to go before lunch.

 

Well, I had a bit to eat and thought I would compare my 99 paper FSM to the online 2000 and 2003, big mistake.
The 2000 looks almost identical to the 99 while the 2003 is completely different. The 00 shows the 5 wire circuit opening relay mentioned in the previous post while the 03 shows a more conventional 4 wire. Also in another section the "STA" signal is described as "12v from the starter as an input signal to the ECM".
Not sure I want to understand what's going on any more, at least until I have to. Darn sure not even going to look at 4 vs 6 cyl!

2000 Diagram, 2 pages of 8



2003 Diagram, 2 pages of 8

 

If you want to see if the pump will run remove the connector on the tank. Apply 12v to pin 4 and ground pin 5. I've drained several wrecked Tacomas and 4runners this way. At least you can rule out the pump.

 

The common practice is to run the pump during cranking this would reduce crank time. Some systems run the pump for a couple seconds then shut off only to re start during the crank cycle. Restarting the pump with a pressure switch would be problematic because of the pressure differences during a pump restart it takes time to move fuel and the entire injection system relies on a fixed pressure. I have no doubt that the signal comes through the ECM but it still is part of the cranking cycle. Regard less the pump needs power to run I believe the first thing I would do is check the related fuses. In the posted picture I see 3 fuses that could keep the pump from running.