daleyboy

Just bought this 91 toyota sr5 4x4 with the 3vze engine . I put a new oil pump, water pump, timing belt, belt tensioner, etc,etc. When I first started it up after all this work, it ran fine, but only ran it for 5 minutes of so. Now when I try to start it, it will only run for a second or 2 and die. It starts really fast, but immediately dies. Though it might be the fuel pump, but don't want to keep throwing parts at it. Anybody have an idea what the problem could be.

scope103

Welcome to Yotatech. Practice using the "search" function.

"Starts and runs for a few seconds" is the classic sign of a COR-VAF problem. It is also the easiest problem to diagnose on the whole truck. Jumper FP to B+ in the diagnostic connector. If the truck starts and runs normally, you've identified the problem. Now, using your factory service manual (the one you used to replace all those parts) diagnose the VAF then the COR.

daleyboy

Put a jumper on fp and b+. Still doing the same thing unfortunately.

daleyboy

daleyboy

Is this the fuel pressure regulator in the picture? I took the small vacuum hose off it, no gas present. Took off the larger hose to it, gas in it.

DeathCougar

iTrader: (23)

Small line is a vacuum line, if you have fuel in that small line you have bigger problems.

Yes its the FPR. The larger line should have fuel in it. Probably not your problem though, try doing what Scope recommended.

daleyboy

I already tried jumping the fp to the b+. I took the cover off the air cleaner and the trap door thing was not stuck or anything and moved back and forth easily. I even opened it up some with a rag and tried to start it, no luck. It's not even starting today. It tries to run when you first start cranking it, but won't start. I loosened up the fuel line at the cold starting thing on the intake . Gas comes out when you turn on the key.

daleyboy

I just went out and messed with it some more. B+ terminal has 12+ volts. I shot a little gas in the throttle body, and it instantly fired up and ran awesome, for a few seconds. Could the fuel filter make it do this?

scope103

You shouldn't loosen the high pressure fuel lines (at the cold starting thing or elsewhere). Whenever you do that, you MUST replace the crush washers. Cheaper than dirt, but only available from the dealer.

Instead, remove the fuel return line from the Fuel Pressure regulator, and replace it with a 6mm (1/4") clear vinyl tube to a suitable container. Apply B+ to FP, and run for 30 seconds. You should get about 1/4 liter (1/2 liter/minute). If you don't get close to that, you may have a really dirty fuel filter, or a weak fuel pump. You can reinstall the fuel return line with just the included hose clamp, as this is a low-pressure line.

This doesn't directly check fuel pressure in the rail, but that's a more involved process.

daleyboy

Ok, yesterday I put in a new fuel filter, today a new fuel pump. It's a little better. It'll run for about 3 seconds everytime you start it. I ran the jumper wire from +B to fp, does the same thing with or without the jumper. I took the return line hose off at the fuel pressure regulator. No fuel coming out. The fuel pump is running back there. I'm a pretty fair mechanic, but I'm kinda stumped on this one. I took the line loose at the cold start injector and there is pressure there. There's got to be something plugged up somewhere

Gevo

SO, thus far it seems like a fuel problem. It is very odd that after a new fuel pump and filter it behaves differently but still doesn't work. I have a feeling that the problem presents itself in various ways at random and the fuel pump/filter didnt have that much to do with it. If that is the case, that means it's still related to fuel delivery. I would pull out the return hose and check the fuel flow again with the new filter and pump.

If there was no fuel before and there is now and still it isn't running, that is a whole different situation. But don't forget to jumper the terminals Scope mentioned to turn the pump on.

If there was no fuel before and there still is no fuel now, I would check the voltage at the pump with the terminals jumped. If the voltage doesn't quite make it to 12, then you have damaged wiring.

If you are jumping the terminals correctly the pump should come on and stay on.

daleyboy

The pump did come on and stay on when I put the jumper wire on, but I couldn't get fuel out the line on the fuel pressure regulator.

toiyodah4WD

How'd it run before you worked on it?

daleyboy

I bought it not running. When I shoot some gas in the throttle body, it runs real good and smooth

Gevo

Interesting. How could you tell that the pump was on then?

daleyboy

I could hear it. Like I said, took the line loose at the cold start fuel lnjector, and there was pressure there. But not at the end of the rail at the fuel pressure regulator. I even cracked the line at the fuel filter to see if there was pressure there

scope103

Your diagnostic skills are pretty good; you're running the right tests in the right order.

Let me just review to be sure I've got it right. The jumper makes no difference, you can hear the pump running with the jumper, and if you loosen the small line at the Cold Start Injector fuel sprays out. So that means you have SOME pressure in the fuel rail, at least as far as the connection to the CSI. The truck will run with fuel squirted directly in the throttle body (it should run very poorly if the air filter is completely disconnected, so I assume you had some way to squirt fuel without disconnecting the induction piping).

If you disconnect the fuel return line from the Fuel Pressure regulator, NO fuel comes out with the jumper and key-on.

If I have these clues correctly, that suggests there is SOME pressure in the rail, but not enough. The FPR works by "dumping" the fuel flow that is more than needed to reach the called-for fuel pressure. If it isn't "dumping" any fuel, the pressure isn't high enough.

Or, the FPR is bad, but that should mean the fuel pressure is much too high in the rail. So I suspect a weak fuel pump, or maybe a complete blockage of the fuel rail (much less likely; the CSI is plumbed out after injector #3 and #5, and there are two paths for fuel to get to the left rail). Which means you may need to take the next step and check the fuel pressure. To do that, you need a gauge, and a fitting to connect it. This gauge https://www.summitracing.com/parts/anm-cp7838 comes with the right fitting. Here's a picture of one installed:



(oh. DO check that your have the correct line as the fuel return line. The smaller (no clamp) hose to the FPR is a vacuum line, and if you get fuel out of that the FPR is leaking.)

daleyboy

I had a big syringe that I would squirts gas in the throttle body, and then connect the air filter lines back up and then start it. I was thinking this morning of something I might have missed. I'll check this morning and see how many volts I'm getting to that pump. That is a test I completely spaced. I'll post the results

daleyboy

Think I might have found something. I unplugged the fuel pump and put a volt meter on it. I put the jumper on +B and fp. When I turned the key on, I was getting 11.50 volts. When I started cranking it over I was getting 9.75 volts. Where am I losing that voltage.

Gevo

I think 11.5 v is probably what the weak wiring system is able to do and probably isn't an issue. During cranking it will always drop significantly, that's normal.