OK, I have a 97 12v, 164k on it. As long as you plug it in, it starts ok, but if you do not plug it it, it flat out will not start !!

I had to get towed home yesterday cuz after 4 hrs of trying to start it, it just would not start.

Possible issues:

1) timing slipped (again)
2) low compression (burns oil bad)
3) grid heater may not be working, but it is only 1 1/2 yrs old
4) grid heater solenoids may not be working (replaced them with ford starter solenoids when the stock ones stuck on)
5) fuel pre-heater may not be working (it is 2 yrs old)
6) batteries are old and questionable, but will survive several starts before they start to slow down


what else ???

 

Need more specific info , start with the easy / common stuff 1st .
How cold are you talking about ?
Is the volt gauge dropping - showing that the grid heaters are pulling power ?
If not then look at fixing those 1st .
What about fuel , what do you know about your fuel in tank , level , winter mix , additives ?
How long since filter change ?
Drain some fuel into a glass jar , how does it look , let sit in at least 65*F room for an hour or 2 , look to see if there is anything but fuel in it .

 

That's where I'd start.
These Cummins can seem like they're cranking good enough to start but sometimes it seems like it takes the extra 1 rpm to finally get them to catch.

 

Yup, compression takes speed. The slower you crank the less compression heat you make and then it just won't fire. That additional heat you give the water with the block heater is giving just enough of a head start to compensate.

 

outside air was 28 deg

volt gauge seems to indicate heaters are working, but no temp change was discernible at the intake manifold

1/4 tank, PS and seafoam in it

last filter change 6-8 months ago, but truck hasn't been driven but maybe 15 times since then

I had a tow truck hooked up to it for over an hr, and when he was hooked up, the volt meter read 13.8-14 v, turned over pretty quick, but still would not fire

 

When you are trying to start it, are you giving it some throttle? And if so, does that help it?

At 28 degrees, these motors will start without the grid heaters if everything else is in good shape.

How does it run after you get it started? Do you see a lot of smoke of any color? Does it miss for a few seconds on startup?

Either you are not building enough heat in your cylinders or you have a fuel supply issue. The heat issue would be due to slow cranking or bad compression. A fuel issue could be an air leak or slipped timing or even a fuel shutoff solenoid that isn't always pulling up(have you checked it?).

 

Making sure you crack the throttle when you are starting makes mine fire right away. I always assumed it was due to some problem with my P7100, but with my new truck I got an owners manual, and sure as it is, the manual says give it 1/4 throttle while starting.


Past that, at 28 degrees you shouldn't need grid heaters, and you sure don't need the fuel heater.

 

I would also do a compression check since you said it burns oil bad.

Tobin

 

giving it throttle doesn't/didn't help

when it does start, it takes awhile to run on all cylinders, like > 2-3 minutes if you don't raise rpm

lots of smoke on startup

it also backfires sometimes when idling, even warm

injectors were checked and cleaned less than a year ago

P7100 was rebuilt about 1 1/2 yrs ago

 

The more we speak about it, it seems less like a fuel problem. Tobin may be onto something with the engine being a little sick.

 

Then I would do as the others have said, check timing and run a compression check.

At 28 degrees temperature, unless the timing has slipped quite a bit, it should fire right up.

 

Which way are you guys talking about the timing slipping? The timing in my 95 slipped, and was approximately 8* advanced, compared to the ~12.5* stock, and that truck fired up at -25 unplugged when my 97, at 17* timing, didn't start plugged in. It would start at 0 with a touch of the key. That truck had 210k miles, motor never been opened up. Less timing equals better starting.

Make sure the compression is good and that the motor is fresh, and check your fuel system.

 

I do not remember if you gave this info or not , what fuel pressure are you getting ?

 

28+ from idle on up

 

28 is idle pressure , 36 psi at 2,000 RPM no load is the rest of it .