Ralphthe4runner

Last week my 4runner sputtered all the way to a no start on the side of the road. While waiting on my friend to trailer tow me off the road, I jumped Fp to B+ and got nothing in terms of fuel pump response, so I suspected fuel pump (I also did it in the quiet of my shop just to make sure). I suspect the FP as well because last two fill ups I ran it til the gas light came on, although it never died on me either time. So I ordered a denso pump changed it out, did the manual fuel pump test and the fuel pump whined liked new as it should.

I fiddled with the TPS in seeing if that was the reason for my no start while on the side of the road as well, so I naturally took the TB off and made sure it was positioned correctly and in spec. That checked out too.

All was good, after a couple of cranks (I assumed to prime the fuel line) he started right up and sounded really good. I forgot that my timing light was in the house so I walked about 30 seconds total while he ran and I came back and I hear it idling really low and it died. Wouldnt start again after trying the distributor in a couple positions.

I manually jumped the fuel pump again just to make sure it was still good and it worked. I then turned the key on and pushed the VAFM trap door and the fuel pump kicked on which it did as well.

So after a great initial start up and subsequently dying what simple thing am I missing here? Thanks in advance for any help.

scope103

Could you have dislodged a bunch of schmutz, that is now clogging the fuel filter? The quick test for that is to remove the fuel return line from the FPR, and replace it with a clear vinyl line (6mm,1/4") to a suitable container. Start the fuel pump with your jumper. I get about 1/2 liter / min (there is no spec).

If your fuel flow is significantly lower, I'd replace the fuel filter. Replacing the fuel filter on the 3zve is indescribably fun. https://www.yotatech.com/forums/f116...ctures-218962/

If you have enough flow out of the return line, there is still the possibility that crap is clogging the tiny filters in the injectors. Testing for that would be more involved (remove the plenum, put blotter paper down the runners to sit under the injectors, run the pump, use 12v to pulse the injectors). I would not expect crap to take out all 6 injectors at once, but who knows?

Ralphthe4runner

Well I wasn't able to do some testing until this morning and I tried firing it up again and it did the same thing: started up fine, idled great for about 5 minutes. Then it started to sputter. It would sporadically get to like 500rpm and get back up to regular idle. After about 3 minutes of that pattern it dies. And once again it won't start again. So I think it does rule out trash in the filters.

scope103

Why?

While a little more involved, you can plumb in a fuel pressure gauge to watch as it dies. If the fuel pressure stays up, I would say the problem is not in the pump or fuel filter. It doesn't tell you anything about the injector filters, but that's a low-probability cause.

Ralphthe4runner

It was the fuel pressure regulator

​​​​I did some more thread searching and took the return hose off and manually jumped the pump and fuel poured out.

But to answer your question, I assumed it wasnt trash in the line because I thought if something is clogged and has no way to flush it wouldnt allow for smooth starting and running then sputtering to a stall on a consistent basis. Might have been bad reasoning but my conclusion non the less.

Thanks much
@scope103

scope103

sometimes "trash" will move away from the stopping point, allowing flow for a few minutes/seconds until the trash is picked up in the flow and clogs the stopping point. Then, with no pressure/flow, the trash settles back down. More likely with something like the in-tank fuel filter ("sock"), but hard to rule out anywhere.

How do you know it was the FPR? Replace it and now it works?

Ralphthe4runner

As I said in the previous post, I took the return line off manually ran the pump and fuel poured out continuously.

scope103

That's what it's supposed to do (as I said, you should get about 1/2 liter/min with the fuel pump on and the engine off.)

We have a "return-style" or "Bypass-style" regulator https://help.summitracing.com/app/an...e-regulator%3F . Why did you think there was a return line?

Ralphthe4runner

I misunderstood the method of testing of the regulator @scope103 I thought you were saying if the fuel comes out then its not regulating enough not allowing enough pressure build up. So Im back to square 1 or 2 or 3 or whatever cause I know I'm getting a steady amount of fuel at the rails judging by my FPR.

Ill be removing the plenum to check my injectors today.

scope103

How do you plan to check the injectors? You CAN slip some blotter paper strips (blotter paper? What the heck is that? I had to use regular typing paper. https://www.yotatech.com/forums/f116.../#post52330847) down the runners in the lower intake manifold to sit under each injector, then apply 12v to each with the rail pressurized. Before you energize the injector, let it sit at pressure for a few minutes to check for leaking injectors.

The "return line" test doesn't tell you that you have the correct pressure on the rail, only that the pump is putting out enough flow to get the FPR into bypass. So it tests a lot of things, but not everything. The next step could be a fuel pressure gauge. A little more involved (and you have to get the tool and adaptors). If, instead, you direct test the injectors and get a fine spray, you probably have enough pressure.