kleinqpro

I have a 1996 4runner 3.4 liter, all stock. It has been starting hard after a hot soak . 15-30 min. Runs perfect after start up. No codes in pcm. I Intalled a fuel pressure guage. Engine running fuel pressure is 46 psi. When I shut the key off it bleeds back to 0 in less than a minute. I pinched off the fuel return line near the left inner fenderwell right at the moment I shut the key off. It then holds pressure, so I thought it would be the regulator, however when I let go , it still holds pressure? If I drive it a while and retest, fuel pressure drops again. If I pinch off the supply hose, It also holds pressure. So much for pinpointing problem.
So my questions. Fuel pressure listings in haynes manual seem way off. With the regulator vacume going to the air box, unplugging it at idle does not change pressure? how could it. Does 46psi sound right. If I pinch off the return line with it running it jumps to 85psi so the pump is strong. Does the pump have a check ball to prevent drainback on the supply side?
Also, when I turn my key on just to run, the fuel pump does not run for a few seconds like other Non toyotas i'm familiar with, It does immediately run when cranking, and when the engine is running. Is this correct?

Any thoughts on which to replace first, the pump or the regulator?

Thanks, Chris

RandyÄ

The fuel pump provides the check valve internally. It only pumps during start/run, On will not power it. I've got my old one from when I upgraded to a 190. You can have it for postage. Send me a P/M if you want it.

kleinqpro

Well , I got the fuel pump from RandyA, Thank you very much, and its fixed. The fuel pump check valve is right in the outlet port. I stuck a piece of hose on the old pump, sometimes I couldntl blow though it, other times the check valve would make a buzzing sound and would let air past. I drove around over the weekend with the fuel pressure guage on, and it holds 43psi for better than an hour. Starts right up, even hot.