I haven't experienced this issue, but the only thing that rings a bell, from posts here, would be a problem with the immobilizer. Do you have the immobilizer system (not all Siennas did), the RS3200 option, or an aftermarket alarm?

 

Thanks for your message. There is no after market alarm and I will check if there is an immobilizer system tonight.

 

There is an immobilizer system and it looks to work OK, red light turn off when we get the key in the cylinder

 

Unfortunately, you might have erased the codes that lit the Check Engine Light by disconnecting the battery. Now that the car won't start, it won't reset the codes. You are caught in a Catch-22 situation. So you have to debug it the "old-fashioned" way. It is probably not the immobilizer if the car is "trying to start." That, to me, indicates you were getting partial ignition. You would get none if the immobilizer were blocking ignition. So I think you are down to determining whether the problem is spark or fuel. You can "rent" a fuel pressure tester for free from Autozone or O'Reilly's. They refund your deposit when you return it...so it's free. My fuel pump died on my Grand Prix. A fuel pressure check confirmed the problem was fuel pressure. It would die after running for a few minutes. The fuel pressure slowly ebbed away until it died. Now your Sienna isn't running at all. The fuel pump could have failed more catastrophically.
You can check for spark fairly easily by removing one of the 3 front spark plugs and seeing if it is firing when you crank the starter. All 3 front plugs would be easy to check. The back 3 are not so easy.(understatement)

Other things to possibly check?
Make sure the throttle body and Idle Control Valve are clean.
Look for any disconnected/cracked/broken vacuum lines

 

Thanks Robert, agree we are down to Spark or Fuel ...for now.
Fuel fuse and relays and OK under the hood but the pump does not make any sound when you open the gas cap. I dropped the gas tank, extarcted the pump, tested it and it does work. I will replace it anyway with a new one and I need to check if there is electricity at the gas pump connector. It may be a wiring or ground issue as well as we have a lot of salt in NJ and the gas tank fittings and nuts are very corroded. I will get everything cleaned up, back in place and will rent a fuel tester and test sparks. Agree that accessing the 3 back sparks is a pain to say the less.
Alain

 

Check out the crank position sensor. There are resistance checks that can be done.

 

That's a good idea...
Also, possibly the cam position sensors.
I have never messed with either personally.

 

Sienna 2001 stats but rumble. Codes 0172, 0300, 1346

Hi Toyota Nation
It is restarting and I managed to get codes!
I installed a new fuel pump, change IAC and throttle sensor, carefully cledaned up the two throttle bodies, and checked carefully for any cracked line for vacum.
To be on the safe side I changed the 6 plugs, changed manifold and throttle gaskets and gave a new try.
Engine started this time but is very hesitating and rumbling.
After 2 minutes of warming up the VSC, Trac Off and Engine lights turned on.
I connected an OBDII code reader and the following came out:
P0300 Random Multiple Cylinder Misfire detected
P0172 System too rich bank 1
P1346 Manufacturer Control
I suspect a problem with the Engine Controle Module.
Thoughts? Suggestions

 

P1346 points to the camshaft position sensor. Had you had work done on the van at any point? Timing belt?

 

Timing belt was changed 20,000 miles ago.