1996 Toyota 4runner Limited
3.4L V6 (5vzfe) w/ auto tranny
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Piston looked pretty bad so I replaced my engine with a low mileage engine from Remanns.
Hooked everything up except radiator & fan. Put fresh oil in.
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PROBLEM:
The vehicle will crank but won't start. No codes. And when I say crank, I mean the starter makes a good solid connection with the flywheel and the engine happily spins around, but the ignition & EFI system never take over.
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WHAT I HAVE DONE:
I have tested the resistance on the crankshaft position & camshaft position sensor, the coil packs (weird design where there are only three and two cylinders "share" one pack), and the ground points around the engine bay.
I removed the connector for one of the coil packs and one of the fuel injectors. Here is where it gets weird. The voltage at both connectors is somewhere between 1 - 2V when it spikes for that/those cylinder(s). So the ECU is trying to make stuff happen, but the voltage is just not enough. I actually couldn't find the necessary voltage required to run the fuel injectors or the ignition coils, but I assume 1 - 2V is not enough.
I also removed the engine ground wire and the connectors to the ECU. After doing that, the engine was still somehow grounded. I'm wondering if maybe there is a crappy ground somewhere there shouldn't be. It's my understanding that all mounts are insulated and that the engine shouldn't be grounded unless I deliberately ground it somewhere.
According to the wiring diagram when you start the car, all of the ignition components receive + and as the system cycles cylinders, it grounds and ungrounds the various components causing them to fire. I jumped the main brown grounding wire with the specific ground wire for the first coil pack and then attached my multimeter to the negative on the coil pack connector and the other end to B+. When I did that it got the full 12.6 volts (about 10.6 if starter is going). So the super low voltage drop seems to only happen under load.
Putting everything back except the one coil pack connector, and removing jumper wire, if I attach my multimeter to the negative on the battery and the positive on the ignition coil connector, when I start the truck it reads a 10.6, which is the healthy voltage under starter load. Remember, the ignition system works by making everything hot, and alternating ground connections. So basically the connector would've been supplying a constant 10.6 since its the ground that alternates and I had the ground straight wired into the battery.
If I do the inverse and attach one end of the multimeter to the battery positive and the other end to the ground it alternates off and on as it cycles through the cylinders, since supplying + manually is similar to what the car does anyway. BUT it gets the funky low voltage that won't spark the plugs, 1 - 2V.
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Basically I'm completely at a loss because nothing is consistent enough to lead me in the right direction. I'm thinking its a ground problem, but I don't know for sure.
The Power side of the ignition coils and fuel injectors are pretty simple circuits.
Here's the wiring for the ignition coils. I highlighted the circuit Red for Power and Green for the Ground switching signal.
1996-2002 Toyota 4Runner
Starting at the lower left of the diagram, Power comes from the Battery, through the 30 amp AM2 fuse, to the AM2 (terminal 7) on the Ignition Switch. When the Switch is turned to Start or Run Power comes out of the Ignition Switch at the IG2 (terminal 6) and goes to the Power Side of the Ignition Coils and the B+ terminal of the Igniter.
So it should be pretty easy to go through the circuit, starting at the battery and determine where you're losing battery voltage in the circuit between the Battery and the Ignition Coils.
The Fuel Injector circuit is wired like this. Again, I highlighted Red for Power and Green for the Ground Signal.
And here the Power side of the Fuel Injectors circuit is very similar to the Power side of the Ignition Coils circuit.
Power comes directly from the Battery, through the 30 amp AM2 fuse to the AM2 (terminal 7) on the Ignition Switch.
When the Switch is turned to Start or Run Power comes out of the Ignition Switch at the IG2 (terminal 6) and goes to the Power Side of the Fuel Injectors.
So, start at the AM2 Fuse. Are you getting battery voltage on both sides of that fuse?
If so, go up to the AM2 (terminal 7) of the Ignition Switch. Are you getting Battery Voltage there?
If so, Switch the Key to Run and Start. Are you getting Battery Voltage on the IG2 (terminal 6) on the Ignition Switch in both of those positions?
If so, inspect the wiring and connectors between the Ignition Switch and the Ignition Coils and Fuel Injectors
Seems like the igniter is getting full voltage. Maybe the internal transistors or mosfets are not opening all the way and so the coils are not getting the full voltage? It's pretty much the last stop before the ignition coils. And if I manually jump the ground rather than let the igniter do the work, I get the full voltage. Something tells me that it's not that simple because I'm also getting low voltage on the fuel injectors, but I have to do something, so I'll go ahead and order an igniter and see if there is any improvement.
I have never seen an engine block that was not separately grounded in addition to the various mounting connections.
