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John Hilley · 01-04-2011, 07:37 PM

Had to start the motor home this morning at about 10 degrees below zero. It spun over fast, but wouldn't fire. I noticed on the Scan Gauge II that the voltage dropped to 8 volts during starting. I used the house battery momentary boost, the voltage stayed over 12 volts and it fired instantly. I think with the ignition it has, it needs near full voltage to fire.

bdpreece · 01-04-2011, 09:47 PM

At 10 degrees below zero I am surprise anything would fire up. My only advise is go South and soon while it is still running.

KC1BUD · 01-05-2011, 02:03 PM

I am no help, Mine sits in a un-insulated un-heated barn for the winter, it won't be out until around April. The barn is locked for the winter.

LVJ58 · 01-05-2011, 02:08 PM

John, the reason it wouldn't start the first time is that the PCM (powertrain control module) often referred to as the engine computer requires 12v to function properly, i.e. activate the fuel pump, injectors, coil over plugs, etc.

tderonne · 01-05-2011, 02:32 PM

It probably didn't start because you had summer fuel in the tank. It should start down to about -40 without a boost with winter fuel. It's normal for the voltage to drop during crank, no big deal.

Midniteoyl · 01-05-2011, 03:46 PM

The injectors need close to 12v..

mpaton · 01-05-2011, 06:09 PM

Quote:

Originally Posted by Midniteoyl

The injectors need close to 12v..

Not exactly. They only need it to deliver an accurate amount of fuel.

Which is why the injection pulse width is compensated for voltage from about 6v to about 15v

pkunk1 · 01-05-2011, 08:19 PM

Quote:

Originally Posted by John Hilley

Had to start the motor home this morning at about 10 degrees below zero. It spun over fast, but wouldn't fire. I noticed on the Scan Gauge II that the voltage dropped to 8 volts during starting. I used the house battery momentary boost, the voltage stayed over 12 volts and it fired instantly. I think with the ignition it has, it needs near full voltage to fire.

Get a bigger/better start battery-mine starts nicely at -15°.

Scangauge never below low 12's

Although last winter when it was somewhat below that at 0830 as we were getting ready to head out, the engine ran real rough and belched some black smoke for a bit when first started. It was making such wierd noises I didn't pay any attention to the Scangauge

Jagtech · 01-05-2011, 08:22 PM

Um, did you have the choke on ??

I think LVJ58 is right, it need's something close to 12 volts for all the systems to function properly. At that temperature, you'll want to warm everything up really well before shutting it down again.

subford · 01-08-2011, 06:54 AM

Only use a 9V DC battery when testing a fuel injector. If you use 12V you will burn it up as you can not get on it and back off fast enough when testing.

The Computer is very fast and does not put 12 Volts on it very long.

gasser 38 · 01-12-2011, 10:40 AM

at -10 if your chassis battery is not 100% or is not the correct CCA I believe they are 750 you may have trouble and you say spinning fast but was it faster with the boost? Obviously if it started with the boost your problem was low voltage

John Hilley · 01-12-2011, 06:20 PM

Quote:

Originally Posted by gasser 38

at -10 if your chassis battery is not 100% or is not the correct CCA I believe they are 750 you may have trouble and you say spinning fast but was it faster with the boost? Obviously if it started with the boost your problem was low voltage

No it didn't spin perceptibly faster with the boost. The problem was the low voltage. I wouldn't have noticed and tried the boost if I didn't have the Scan Gauge II. I will probably add a block heater next summer. We are safely in Arizona now, so don't have to worry for another year.

Big Bear Local · 01-12-2011, 07:51 PM

Quote:

Originally Posted by John Hilley

No it didn't spin perceptibly faster with the boost. The problem was the low voltage. I wouldn't have noticed and tried the boost if I didn't have the Scan Gauge II. I will probably add a block heater next summer. We are safely in Arizona now, so don't have to worry for another year.

I lived in North Dakota, we had block heaters in all our vehicles. They would start with out them even at 22 below but you took the chance of throwing a rod because the oil would not flow.

johnsonjm209 · 01-13-2011, 07:41 AM

In the past I would go south just after Christmas and battery was no problem. 2 years ago we didn't go and I yanked them all out and put them on a charger in the cellar. Last year it was colder in Fl. that it was it Ct., so no problem.
This year when I put an ampmeter on the battery, I found out that the inverter does not charge my chassis battery. The battery was reading 11+ amp. I yanked it off three days ago and put it on a slow (2Amp) charge. After 32 hours it is now up to 12.5 amps and it will stay in the cellar until about a week before I leave in February.
But, the battery is 7-8 years old and I will have to monitor it. The fluids were kept up fine.
It better start next month or it get replaced!

Joe from Ct.