mmcpeck

This problem has been annoying me for a year and a half, since I've had this truck. '92 Pickup, 5spd, 3VZE, 104K. I bought it with 97K. It's done this ever since I've had it.

The truck is almost perfect, except for this starting problem. Runs perfect, idles perfect, actually has pretty decent power despite what is said about the 3VZE.

The truck starts perfect when it's cold in the morning, starts EXACTLY the same EVERY morning, 2 cranks and fires over, or has sat long enough to cool down to a certain temp.. When it's at NOT and is shut off, it starts up again perfectly, as long as it only sits for like 5-10 minutes, like running into 7-11. But once it's shut off and sits for anything longer than 10 or so minutes, it is a pain to start, like when I shut it off at work and it sits for 3 or 4 hours, it sucks to start it.

When I turn the key it cranks and cranks and cranks and cranks, and then maybe it will stumble over, but usually it won't and I'll stop cranking, then as soon as I crank again seconds later, it fires right up and runs and idles perfectly. It drives me nuts, and I cannot figure out what the hell is causing it to do this, but it's obviously temp related.

I have changed plugs, wires, cap and rotor. Timing is dead on, and I have even advanced it to 12* and it didn't help anything. I cleaned the TB completely, and have Sea Foamed it twice. I would think about the Cold Start Injector, but it starts great when cold.

I really have no idea what else to look at. If it did this everytime I started it, no matter the temp, there might be some other things to look at, but the fact that it starts perfect ice cold and fully hot confuses me.

Anybody ever seen this, or know what would cause it? I've posted about this before, but still can't figure it out and the longer it goes on the more it makes me nuts!! Somebody must have seen this with the 3VZE before.

Thanks.

scope103

And doesn't start when it's "not" cold?

There are a million causes of what you describe, but it sure sounds like it might be flooding when warm. And a possible cause is a cold start injector that doesn't know when it is "not" cold.

A really quick check is to disconnect the electrical connector to the cold start injector to see what happens. If that clears it up (or moves your hard starting from when-warm to when-cold), you've got the system to look at.

shaeff

Another thing to check- does your truck have an operational fuel pressure regulator VSV?

mmcpeck

Good point scope. I had read about the cold start injector time switch, so I was thinking that maybe that switch was running the csi while it was warm. I'll check that out.

shaeff....what is a VSV?

mmcpeck

C'mon mods! I didn't name this thread anything to do with hot starting because I don't have a hot starting issue. My post clearly states that my issue is not with hot starting and that hot starting is completely fine.

I suspect I will receive no more answers to this question beside some smart ass telling me to use the Search function. Thanks for changing that.

mmcpeck

Huge surprise, no more answers or help after the all mighty mods felt the need to change the title of my post to something that is not my issue.

Thanks for the useless job you do moderators.

TNRabbit

Did you remove the Cold Start Injector wire when it is "warm but not hot" to check? Or it's possible as you said it's not recognizing the engine as cool enough to switch it on after a couple of hours. There is a sensor (PM sent).



IIRC, VSV is Vacuum Switched Valve.

shaeff

Yes, VSV is vacuum switching valve. It's basically a small solenoid that, if I'm remembering this correctly, will switch open and allow air from the atmosphere to be used as a source for the fuel pressure regulator when the motor is warm, thus allowing for easier starts.

Try this next time you have trouble starting. Find your fuel pressure regulator and disconnect the vacuum line going to it. Try starting the truck. If it starts easily, you've narrowed the problem down. Make sure you plug the vacuum line back in, though.

mmcpeck

Will try. How would atmospheric air pressure control the fuel pressure regulator, and make it easier to start? Sounds interesting, never heard of that. Man the things they think come up with. Wouldn't that have to be calibrated to whatever location the truck happened to be in? I would think that would work differently at different elevations. I'm at sea level, so atmospheric pressure is completely different from say in the mountains....or am I thinking wrong?

Anyway, thanks for the help. I will give that a shot.

mattches

The VSV for the fuel pressure regulator applies vacuum to the regulator at times of high vacuum, like decellerating (sp?). This opens the regulator and allows fuel to flow back into the tank, thus reliving excess fuel pressure. It might be your problem. But I would guess that it is not.

I would think that it is your temperature sensor. It is what tells the computer what the fuel mix should be at a given temp. If this sensor is going bad, it can provide the wrong signal to the computer, particularly when the truck has sat for a while and is hot, but not at normal operating temp. The cold start injector time switch will not activate at all if the engine is warm, hence why it is not a dynamic resistant sensor. Temp sensor is $30 at Napa. But you have to remove the plenum to get to it.

http://personal.utulsa.edu/~nathan-b...98engineco.pdf

shaeff

That's incorrect, I don't agree with that at all.

When the VSV is powered, it allows atmospheric pressure to the fuel pressure regulator at startup. This allows higher fuel pressure at start up to aid in faster hot starts and decrease the chances of vapor locking the system.

When vacuum is applied to fuel pressure regulator, it DECREASES fuel pressure, which is why the VSV is there in the first place, for hot starts to increase pressure.

There is ALWAYS fuel going back through the return line. The fuel pressure regulator's VSV should only be energized at hot start up.

Edit: before someone asks me to back up my statement, read page 9:
http://www.autoshop101.com/forms/h22.pdf

mattches

Okay, I stand corrected. You have it there in B&W. I learned something. I still don't think it is the problem, but it could be. Definitely would not hurt to check.

shaeff

Right on dude. MKIII Supras have the same type of issue, and it's commonly caused by the exact same type of VSV. It's easy to check, so why not, right? If it's not the problem, then we've eliminated one variable. If it is the problem, then even better!

The vacuum line on the fuel pressure regulator is there to reference manifold vacuum in order to adjust fuel pressure for different engine loads. As engine load increases (throttle angle gets higher), the vacuum in the motor decreases (gets closer to atmospheric pressure). The closer the FPR vac line gets to atmospheric pressure, the more fuel pressure it keeps because under load you're using more fuel.

If you had a fuel pressure gauge hooked up to your fuel rail, you'd see fuel pressure rise when you floor it, and decrease when you let off (engine goes in to vacuum). It'll decrease during vacuum because there's no demand for fuel, and many EFI vehicles shut off the injectors under deceleration until a certain RPM is reached (on the low side).

I always chuckled to myself when I see people put their vehicles in neutral on long downhill coasts "to save gas". You'll be saving more gas if you just let the vehicle decelerate down the hill because the injectors are shut off so no fuel at all is entering the combustion chambers. When they're putting it in neutral and coasting down the hill, they're using fuel to idle.

If anyone is interested, those autoshop101.com links have lots of Toyota EFI tech articles direct from the manufacturer. They're a great read and give lots of insight as to how many different applications function.

mmcpeck

Wow, all really interesting. I didn't know the FPR used atmospheric pressure to increase pressure. Also didn't know that injectors shut off under deceleration.

I'll post back when I check all these things out. Hopefully tomorrow, weekend was too busy.

Thanks.

scope103

I don't think that's quite what you meant to say. The fuel pressure regulator is designed to keep the pressure ACROSS the injectors constant. As you open the the throttle, the vacuum drops (pressure increases), so to keep the pressure across the injectors constant the fuel pressure is increased by the same amount. Why? So the amount of fuel delivered can be controlled just by changing the injector open-duration. 4.8ms open (for instance) always delivers the same amount of fuel. Regardless of throttle position, etc.

So if you watch a fuel pressure gauge, it is basically a manifold pressure gauge (because the fuel pressure just follows the manifold pressure), and goes up and down with engine vacuum (which is closely, but not absolutely, tied to throttle position).

So the pressure across the injectors is constant.

Almost all the time; the 22re has a feature where it changes the vacuum slightly on the fuel pressure regulator to raise the pressure across the injectors when cold. The 3VZE, instead, uses a cold-start injector to throw a little extra fuel into the upper intake manifold (plenum).

Engine load cannot be directly measured by manifold vacuum, so the ECM measures it other ways and adjusts the fuel delivery by changing the open-time on the injectors. It can do that because fuel-flow is directly proportional to open-time.

And I agree that www.autoshop101.com is excellent reading. Particularly because it is Toyota-centric.

Blair27

i have a 3.0 in my truck and it literally does the same thing... its really stupid and annoying but i dont bother to mess with it because it will still start up fine after i crank, let go, then crank again.

i thought it was just bad plugs or something when i first got the truck and eventually i put all new plugs in and it made no difference so its definitely something more technical lol

shaeff

You're right. I got ahead of myself and explained it a bit off. Thanks for catching and correcting me!

However, are you implying that the 22re doesn't have a CSI? My 22re pickup has a CSI in the upper intake plenum. Perhaps I'm just misunderstanding you.

Anyway, thanks again. I always look forward to your posts.

JR

Had the same problem with girlfriends 3.0l pickup, I checked everything I could think of. However the problem has gone away. I suspect the cold start injector was dirty and through the use of fuel injector cleaner has cleaned up. Fuel was leaking after turned off or allowing fuel to bypass on hot start up. Only way to tell if this is happening is monitor fuel pressure or even better remove injector and see if it is leaking when off or on hot start up. If leaking on hot start up unhook electrical wires and repeat hot start up, still leaks injector issue, no fuel bad information from computer or sensor.

Use to drive the girlfriend crazy.

mmcpeck

Alright so I disconnected the vacuum line from the fuel pressure regulator and it made no difference in starting. Then I disconnected the electrical connector from the Cold Start Injector and it starts exactly the same, perfect when cold or hot, like crap when "warm". Disconnecting the CSI made no difference at all. It's like the CSI has basically been doing nothing. WHat is the point of the CSI, if the engine starts perfect with it disconnected??

Oh also, I of course lost the clip that holds the electrical connector onto the CSI, didn't even feel it drop, it seemed like it just disappeared into thin air. I was being careful with it and the next thing I know it was gone. I guess I gotta hit up the junk for one of those huh?

mmcpeck

Bump ^^