I am working on a 2001 Dodge Caravan Sport 3.3L Flex Fuel that will crank, has spark, has fuel at the rail, has compression on at least the front 3 cylinders (cannot easily reach the back three to test), but will not start or even attempt to fire. Even spraying starting fluid directly into the throttle body does not yield an attempt to fire.

Getting spark: Yes
Fuel pressure at Schrader Valve: Yes
Battery voltage: 12.55v
Cranks: Yes
Compression: Yes

I do not have an insulation piercing probe, so I have not been able to test the voltage to the camshaft position sensor while connected, but when disconnected from the sensor the voltage on the connector hot lead is 4.53 volts. I understand that this should be 8 volts, but I am not sure if I can even consider this test worthwhile since I was testing with the sensor disconnected.

The only code being thrown is the P0601, but this code has existed for the past 6 years.

The only other oddity that may or may not be important is that when I hook up my scan tool to the ODB-II port, the tool displays a Low Voltage warning.

I am seeking guidance on the best way to proceed with further diagnosing this issue to determine the root cause.

Thank you!

 

The P0601 code is an internal fault for the PCM. I would replace the PCM and remove all the spark plugs. The back ones could be fouled with fuel.

 

As mentioned, a PCM should be the first thing you should fix.

Allcomputerresources.com is repuatable. I believe Autozone carries Reman PCM now if you want to buy Locally for more convenience. But you HAVE to supply them your VIN number and give your old PCM back to them.

 

Thanks for the replies, guys. I appreciate the recommendation on the reputable resource for PCM replacement. I may go ahead and replace the PCM, but since it's been throwing that code for the past 112,000 miles with no noticeable adverse impact, I am not sure that's the root cause of the situation.

I had somewhat of an accidental breakthrough tonight, but I don't know what it means yet.

While testing for spark tonight, I pulled the fuel pump relay so as not to soak the plugs with fuel while testing. With the fuel pump relay removed, the van started right now and ran perfectly for about 5 seconds. I assume it was burning whatever fuel was left in the rail. I then put the fuel pump relay back in and cranked. I still got spark, but the engine wouldn't fire. I then removed the relay again, cranked for about 3 seconds and it fired right up and ran again for about 5 seconds. I repeated the whole process one more time and got the same results.

Any ideas as to why this gal will fire up when the fuel pump relay is removed, but as soon as I put the relay back in she won't even try to fire?

Thanks!

Jason

 

The fuel injectors maybe on and filling the cylinders with fuel. Also took a look where the fuel injection harness is going. If its on the rear cylinder head. Open the harness and see if the wires are shorted together.

 

@master tech - Thanks for the suggestion. I will check that tonight when I get home. That would jive with what my gut is telling me. The relay removal leads me to think I've got an electrical problem. I was thinking that it might be a short that was causing the timing to get thrown off (could something in that fuel pump circuit be impacting the cam or crank sensor???), but I can see your theory having merit, too.

It is plausible that the injectors are all dumping fuel and with the pump off, it's not throwing enough fuel to flood out the cylinders, but is giving enough for it to startup and run.

I'll report more tonight when I have a chance to tear into it more. I assume I'll have to remove that upper intake to get to that wiring harness to see it?

Thanks!

Jason

 

Because the injectors drivers are hung and flooding it. My money is on the injector harness. Even if, the PCM is probably toast at this point...the injector drivers anyway. Keep in mind the MAP sensor wires are in that loom too. Often times those symptoms get in the mix as well.

 

@tntech - I'll check that injector harness tonight and report back. I don't have the vehicle in front of me, but am I correct in assuming that I'll have to pull the intake manifold to get access to that wire cluster?

Thanks!

Jason

 

No, the problem area will be at the back end of the rear head. I move the power steering reservoir out of the way to get to it.... and the vacuum hoses.

 

I've checked the wires by pulling the vacuum tubes aside and unbolting the power steering reservoir. I cut back the insulation around the bundle of wires and they're all in good shape.

Running on the other proposed theory that too much fuel is being dumped in the cylinders, I started the van up with the fuel pump relay removed and then quickly installed the relay. The van kept running, but was spewing the telltale white smoke that would indicate unburned fuel.

I did confirm that I have just over 50PSI fuel pressure.

Someone else had suggested an that an upstream O2 sensor has gone bad is fooling the PCM into thinking I am running E-85 and that's why it is dumping so much fuel into the cylinders.

Jason