Voltage drop while starting - fouling plugs

[JohnJL]

I've had intermittent problems starting my race car, especially when cold.

Today I tried starting her after sitting for a few weeks. When it wouldnt start, I checked the plugs and they were indeed soaked with gas. I removed them all and cleaned/dried them. Also turned the motor over a few times with the plugs out to clear out any gas/oil that might have pooled.

I then hooked up the ECU and logged it while cranking a few more times. I can see the voltage drops to ~9v while cranking.

The battery is new and fully charged (Odyssey 925) and hooked up to a "smart charger" designed to be plugged in and has a "start assist" 75amp boost function for starting cars.

I expect a voltage drop as it is 5 degrees Celcius outside and the starter (a high-torque unit) is turning over both the motor and the supercharger.

I suspect the battery and charger are giving enough current to turn over the motor but that the plugs are not arcing and getting immediately flooded/fouled.

I had this problem before and only fixed it with a fresh set of plugs and when the morning had warmed up (i missed the morning track session.)

Is it possible/advisable to get the voltage up during cranking by running another battery in parallel to the new Odyssey? I have a new Optima yellow-top, would it damage the batteries to hook them up in parallel and try starting?

Thanks
John

[911pcars]

Originally Posted by JohnJL

I've had intermittent problems starting my race car, especially when cold.

Today I tried starting her after sitting for a few weeks. When it wouldnt start, I checked the plugs and they were indeed soaked with gas. I removed them all and cleaned/dried them. Also turned the motor over a few times with the plugs out to clear out any gas/oil that might have pooled.

I then hooked up the ECU and logged it while cranking a few more times. I can see the voltage drops to ~9v while cranking.

The battery is new and fully charged (Odyssey 925) and hooked up to a "smart charger" designed to be plugged in and has a "start assist" 75amp boost function for starting cars.

I expect a voltage drop as it is 5 degrees Celcius outside and the starter (a high-torque unit) is turning over both the motor and the supercharger.

I suspect the battery and charger are giving enough current to turn over the motor but that the plugs are not arcing and getting immediately flooded/fouled.

I had this problem before and only fixed it with a fresh set of plugs and when the morning had warmed up (i missed the morning track session.)

Is it possible/advisable to get the voltage up during cranking by running another battery in parallel to the new Odyssey? I have a new Optima yellow-top, would it damage the batteries to hook them up in parallel and try starting?

Thanks
John

Sounds like the spark you have is borderline; unable to ignite a used plug; only able to ignite a new spark plug. Check the quality of the spark. It should jump a sizeable gap and do it with a fairly audible snap.

Voltage drop to 9 V while cranking is quite normal and should be sufficient to light the ignition system. Two batteries connected in parallel won't hurt the system, but will only provide more cranking capacity. The system voltage remains the same. Voltage and current requirement is determined by the needs of the particular load. Don't try to increase system voltage. It could damage sensitive electronic circuits.

Sherwood

[T77911S]

9volts seems low. someone did a test on the minimum voltage a CSV would fire for a CIS car, but i have not seen anything on any others. even though your plugs are wet, depending on how long you cranked it, that could just be from the injestors.

i would check and CLEAN all major connections. inlcuding the grounds. when you have hi current, it does not take much resistance to create a large voltage drop. .1 ohms can make a big difference. how is the ground from the engine to the body?

you can do batteries in parallel, that will increase the available current, but may just be a bandaide to another problem.

any chanace you have some injectors leaking? what about any air leaks? perhaps pull the plugs after a week of sitting. just curious, what heat range plugs are they?