Cold "Luv" Machine question

[GreeCguy]

Good evening all out there in Bitog land.

A question about the soon to be world famous "Luv" machine.

"Luv" machine is a 1986 Chevy Astro Van, 4.3 V-6 throttle body injection used as family farm mule.

Yesterday I used the "Luv" machine to haul firewood. I was surprised that the ole gal was a little hard to start and required a warm up time before we could go to work. This happened on several occasions during the day, (like when she sat for an hour or more while I did other work that didn't require her assistance). Once she was warm, she would go anywhere and haul with a will. But when she was cold, she would sputter and would hardly pull herself along. It reminded me of years ago when cars had carbs and you had to let them warm up before tooling down the highway.

My question is this, what "device," (for lack of a better word) is on more modern cars that regulates fuel flow during cold weather. I guess my mind is trying to wrap around the idea of what replaced the choke on a carb when the automobile industry moved from carbs to various kinds of fuel injection? I'm thinking on the ole "Luv" machine, whatever is suppose to happen during cold morning start ups is not happening or happening poorly and I'm wondering what is or isn't happening.

I am,

Confused about sputtering Luv in the cold.

 

[yonyon]

I guess the equivalent to a choke would be the coolant temperature sensor. It's just a thermistor in a brass housing screwed into a water jacket. The ECM gets a temperature out of that and according to the program on the memcal chip it gets to run rich until it warms up enough to use oxygen sensor feedback. I'm not saying that's what your problem is, just that's the closest thing you have to a choke.

You can check the ECT with an ohmmeter if you have a good idea what the temperature should be. 32°F should be around 9500 ohms. Colder is higher resistance so 100k ohms (or unplugged) is -40°F. 50°F would be maybe 5500 ohms, 70°F is about 3500 ohms and so on.

There's that and the closed loop timer. The closed loop timer isn't even a physical thing, just a number in the ECMs memory. The ECM runs in open loop mode (ignoring the oxygen sensor) until the timer counts down.

 

[JHZR2]

This vehicle that does not have an alternator and is running off of a cycled (and questionable) battery???!?

I wouldnt think of digging into sputtering until you had the electrical ducks in a row.

 

[Astro14]

Originally Posted By: yonyon
I guess the equivalent to a choke would be the coolant temperature sensor. It's just a thermistor in a brass housing screwed into a water jacket. The ECM gets a temperature out of that and according to the program on the memcal chip it gets to run rich until it warms up enough to use oxygen sensor feedback. I'm not saying that's what your problem is, just that's the closest thing you have to a choke.

You can check the ECT with an ohmmeter if you have a good idea what the temperature should be. 32°F should be around 9500 ohms. Colder is higher resistance so 100k ohms (or unplugged) is -40°F. 50°F would be maybe 5500 ohms, 70°F is about 3500 ohms and so on.

There's that and the closed loop timer. The closed loop timer isn't even a physical thing, just a number in the ECMs memory. The ECM runs in open loop mode (ignoring the oxygen sensor) until the timer counts down.



That would be my guess too...FI doesn't know the engine is cold, so it isn't metering fuel correctly....

 

[Corvette Owner]

Is your Luv Machine licensed to drive on streets or just a farm vehicle?

 

[UNC017]

Originally Posted By: yonyon
I guess the equivalent to a choke would be the coolant temperature sensor. It's just a thermistor in a brass housing screwed into a water jacket.



+1, since that vehicle is probably too old to have an inlet air temperature sensor.

Another (less likely) possibility is that the fuel pump isn't generating enough pressure to give enough enrichment when cold. If this is truly a mule vehicle that never sees highway use, you might never notice that until the temp drops.

 

[GreeCguy]

Originally Posted By: Corvette Owner
Is your Luv Machine licensed to drive on streets or just a farm vehicle?


The last time the "Luv" machine was actually driven on the road was ten years ago. In truth, I think it would go down the road, but I would be somewhat afraid to take it over 10 mph as the brakes aren't too good anymore.

 

[GreeCguy]

Originally Posted By: JHZR2
This vehicle that does not have an alternator and is running off of a cycled (and questionable) battery???!?

I wouldnt think of digging into sputtering until you had the electrical ducks in a row.


Per advice offered on another post, I sprung for a brand new deep cycle battery, (it was the quickest and easiest thing to do given the amount of work I had in front of me).

What amazed me was I drove all day and all night on that battery without having to charge it one time. By the morning however, you could tell it was running down as it was starting a little slower. Even so, the battery preformed like a champ and I was very happy with it.

As far as the motor running, once it warmed up, (about five minutes), it would run fine, but before it warmed up it would cough and sputter and hardly pull itself. One time, I even parked it by one of the fires, (with the front end right next to the fire). But then I grew concerned it might catch on fire as there were a few gusts of wind that made sparks fly in abundance right up into the van. I was watching and thinking, "my gas tank is a five gallon bucket that's full of gas." Then I remembered the old song I learned in Sunday School, "It only takes a spark, to get a fire going . . ."