Hemi swap 6.1L Turnover, Pause Start Issue

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69SixOneDart

69SixOneDart

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This is a crank, pause, crank, pause issue that is happening on a late 60’s A-Body Mopar resto-mod with a 2010 6.1L Hemi swap.
Link to video:


Anybody know what could be causing this? The ignition key is being held fully in start position until motor starts. And also does it during WOT-n-release for oil pressure prime. Motor has the 5.7L truck starter for mate up to 545RFE auto trans. We are suspicious of faulty starter or possibly a bad ground, but have found no evidence of either.
The motor and stage 2 flash PCM were brand new at install back in 2012-ish. But the vehicle only has about 400 miles on it since the build. It did a bit of sitting in a clean, dry garage over the years, and started this cranking issue in the last couple of months after installing a brand new battery (which we’ve verified is not faulty).
Below are the OBD-2 codes it is throwing up, many of which we presume are not related to this cranking issue and have existed since the build. Any input you have on those codes would likely help too, but we are taking things one step at a time by starting with this cranking issue first.

Thanks!

P0499 Evaporative Emission System Vent Valve Control Circuit High
P0480 Cooling Fan 1 Control Circuit Malfunction
P0443 Evaporative Emission Control System Purge Control Valve Circuit
P0073 Ambient Air Temperature Sensor Circuit High Input
P0463 Fuel Level Sensor Circuit High Input
P0038 HO2S Heater Control Circuit High (Bank 1 Sensor 2)
P0058 HO2S Heater Control Circuit High (Bank 2 Sensor 2)
P0700 Transmission Control System Malfunction
P0734 Gear 4 Incorrect ratio
 
Sounds like a blown fuse that supplies power to those circuits. Locate the blown fuse/ replace it/ if it pops again, unplug the o2 sensors/ replace the fuse again, if it doesn't pop, plug in 1 sensor at a time until the fuse pops, I have found the heater in a o2 sensor can short to ground just because. Or you may need to unplug the transmission connector or any item on that fused circuit. Do you have a schematic?
 
jpl572103 said:
Sounds like a blown fuse that supplies power to those circuits. Locate the blown fuse/ replace it/ if it pops again, unplug the o2 sensors/ replace the fuse again, if it doesn't pop, plug in 1 sensor at a time until the fuse pops, I have found the heater in a o2 sensor can short to ground just because. Or you may need to unplug the transmission connector or any item on that fused circuit. Do you have a schematic?
Click to expand...

How could it be a blown fuse? If the fuse blows, there would be no power at all. His is losing connection and then regaining it. Just asking to understand.

I would pull the starter and bench test it's operation (see if you can duplicate). Maybe a faulty ignition switch?
 
1...Are you sure faulty spark timing is not kicking the starter? Disable the ignition and crank it to see

2...If not I would Make up a lead so you can jumper power direct to the start solenoid. This will bypass all harness wiring and quickly get this down to the starter, cables, battery.

3...Even if you have to borrow, if necessary, clip voltmeters to various points in the battery / starter system so you can monitor what is happening. Frankly, for something like this an analog meter might be better, as you can quickly see by needle movement what is going on.

Start with a meter right at the starter big stud and ground. If that shows a big drop in the problem, leave one lead on the stud, move the other to the battery clamp or post. If this is a rear mount battery, get "any" wire, no 20 or larger to use as an extension. I have even "hacked" extension cords. You can hack a cheap lamp extension cord in half to get bare ends, then extend them with a longer cord That way, you can hook to a trunk mount battery and have your meter(s) up front while you are jumpering starter etc.
 
I was focusing on the list of codes that he listed. The computer will spit out high circuit codes, if the low reference doesn't change. IF it were on only 1 item, I would focus on that 1 item, but he listed many items with a high circuit code. Again it's normal diagnosing to check power's,grounds, etc. So it could be something else like an IGN switch causing these issues. Usually when a power source is missing, blown fuse,circuit(wire) has been cut, or connector unplugged, a high voltage code will set because the computer is looking for a change on the reference signal(wire) which is already high and doesn't change unless there is a fused source voltage on the other end and some type of component such as an O2 sensor, fuel level sensor, etc. that uses the available source voltage and sends a signal on the reference signal circuit back to computer that is monitoring the sensors. Sounds confusing. Sounds wrong to say "high" when a fuse is blown, but that's the way GM did it.
 
P0499 Evaporative Emission System Vent Valve Control Circuit High
P0480 Cooling Fan 1 Control Circuit Malfunction
P0443 Evaporative Emission Control System Purge Control Valve Circuit
P0073 Ambient Air Temperature Sensor Circuit High Input
P0463 Fuel Level Sensor Circuit High Input
P0038 HO2S Heater Control Circuit High (Bank 1 Sensor 2)
P0058 HO2S Heater Control Circuit High (Bank 2 Sensor 2)
 
Posting more codes does not answer my question. I am asking you "what is" a "high circuit code?"

All of those you posted?? Could even be because this is a modified installation. AKA why would this swap have an emissions sensor for the possibly nonexistent evap system?
 
I agree, on his modified install he probably didn't install some of those components. So here's an example of a high circuit code issue. Let's use the P0449. There are 2 wires(circuits) coming from the PCM to the Vent valve. 1 of those wires has either(5 or 12 volts) don't know without a schematic. And the other wire is the ground that actually does the switching on/off as it's applied by the PCM. That vent valve has voltage on it all the time when the engine is on, and the PCM expects to see that 5v or 12v voltage go low or drop when the vent valve is turned on once the ground is supplied, but the voltage never changes and stays high, because the vent valve probably is missing, thus "high voltage circuit code".
 
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