Hi, grateful for this forum!
I have a 1990 toyota 4runner 3 liter 6 cylinder efi engine 3vfe
It won't start in spite of a new fuel filter, new fuel pump, new efi relay, new battery. All fuses are ok, tested for spark and that's ok. Tested and found very low voltage going to fuel pump and it is brand new so ok there. Where else do I look?

 

I would try to figure out why there is low voltage to the fuel pump. If you put a jumper wire in the check connector under the hood from B+ to FP, it should turn on the fuel pump under normal circumstances

 

the factory fuel pump style was designed for a 12v and a lower volt setting that the fuel relay switches to on low draw (idle, low rpm)
check to see if the injectors are firing. will it run on starter fluid being sprayed into the mass air with no air filter?

 

Some other things to check: loosen the fuel rail flange bolt before the regulator, ever so slightly as it should be under high pressure after you have turned the engine over. Be careful to not start a fire obviously. If no fuel or low pressure go down the line towards the tank, plugged line, or fuel pump issue... If good fuel pressure at the rail go the other way, are the plugs wet with fuel after turning the motor over? If yes, you know which direction to keep looking. If no, then you have an injector issue.

Hopefully this works for you.... At least this makes sense in my head. Lol

 

You really should replace the crush washers (two) whenever you loosen a fuel line fitting. Yes, even if it doesn't seem to leak when you tighten it. They're only about a dollar each at the dealer, but you have to get them. So I would leave loosening fuel lines farther down the list.

Checking for wet plugs is a good idea (plugs can be removed and reinstalled lots of times, and you're not worried about leaking fuel.) j2the-e's suggestion is where I'd start; Kimbo already knows he has a fuel-pump-power problem, so run the diagnostics on that.

 

Should have mentioned that we connected B+ to FP and it didn't fire the fuel pump. After the pump was replaced we were getting 12v to the pump, it started and we thought it was fixed. Took it for a short drive and it wouldn't start for the return trip without a jump. Now it is only getting 2.2v to the pump.

 

Sounds like a short or charging issue.
Inspect the harness run to the pump from the relay for shorts or other insulation damage, check battery voltage and alternator output. Need to figure out where the voltage is going or why the battery is draining.

PS. Test parts before you replace them, throwing parts at a vehicle is a waste of money and effort.

 

Actually tested fuel pump before replacing, Co_94_PU. And the fuel filter was in backwards...I bought this used. The battery had been weak for a long time so it seemed like the right time to put a new one in. The issue is no power from the fuel pump.

 

Fuel pump is powered up by the circuit opening relay. May want to check for voltage to the relay, and doing a voltage drop test across the switched side of the relay. Or you can remove the relay and install a jumper wire to bypass it and see if that gets you power to the pump. A good wiring diagram will help tremendously. Some relays have a diagram on the side that shows which terminals are switched, so that may help as well if you understand how the circuit works. Just make sure you don't jump the wrong terminals as it can cause other problems