Trouble starting in 17*f weather
 

ive been having trouble with my 81 300sd lately, but only when cold out. its never seen the snow before so ive never had any trouble getting it started before, but the first trip to cold weather i killed the battery trying to start it. i gave it two glows before starting, waiting until the relay clicked off both times. i checked the glow plugs at the big connector behind the driver headlight. they were all around .8 ohms. i brought the battery inside and charged it, then just cranked maybe 3 or 4 times and while i was cranking, my friend unscrewed the oil fill cap on the valve cover, and right when he unscrewed it the engine started. this was about a week and a half ago, i thought it was a coincidence until tonight when the same exact thing happened.

it decided to snow yesterday, so today its freezing out and i try starting the car, figuring it would work fine because its been nicer out the past couple weeks.. killed the battery AGAIN! this time i pulled the glow plugs and replaced a couple.. noticed the first one had a loose connection to the wire harness. (maybe thats why my car's been stumbling a little bit for the first few minutes after it starts up??) i ended up getting the size 49 battery because i realized the one i had in there was the wrong size. it just died too quickly after trying to crank and glow only a couple times. so i put the new one in and cranked for a good 5-10 seconds, after doing two glow cycles. tried again. and again. then same thing- my friend unscrewed the oil cap thinking it would work again and it did.

just a side note- ive done a valve adjustment within the past 100 miles and i ran diesel purge through the engine, about 2000 miles ago. when it ran through it came out clear and didnt seem to have any affect on the running of the engine. the shut off valve at the back of the ip was replaced about a month ago, in case you were thinking somehow it was keeping the engine from starting. and im pretty sure it isnt air in the lines, i pumped the primer pump and could hear the overflow coming back out the ip, i just wanted to make sure the fuel wasnt frozen soild!

i don't think i have excessive blowby; the oil cap will just rattle on the valve cover when its unscrewed, it doesnt fly off.

anyone have any insight as to why unscrewing the cap helped the engine to start? i know there must be something else wrong, because today (before the battery died) i tried unscrewing the cap before cranking it, thinking, "just in case i can't get it started, this is what worked last time". maybe my glow plugs are all bad?? maybe its the excessive cranking that heats up the engine enough to get it started? and somehow pressure is building up in the valve cover, keeping it from starting? i dont know..

I would check timing chain stretch. No idea why taking off the oil cap would change anything.
Probably before that though, I would check the glow plugs in their sockets. Sure it involved removing the injector lines and injectors, and replacing the heat shields, but you can watch the glow plugs burn. Physically seeing something work is a better test for me. Might be more involved, but for me it's piece of mind, and I'm simple like that.

To check glow plugs I unscrew the wires off the plugs.Then check with ohm meter for continuity.
If they are Bosch Duratherm or Monarks just replaced the ones that are bad.Warning Autolites will break apart.Oh yeah touch ohm meter to engine ground and the center of glow plug.
Two alot of glow plugs can test good but when taken out,and using jumper cables to see if they light,they don't work.

Firstly, three separate incidents of removing the cap and starting cannot be ignored, if factual.

If...........and this is a big if............crankcase pressure can build sufficiently during cranking to pressurize the crankcase, the shutoff valve will partially close making starting very difficult. However, the only possibility for this to occur is if the breather tube on the top of the valve cover is completely obstructed. This tube extends to the air cleaner and provided crankcase ventilation for the engine.

Check for any obstruction in this tube and eliminate it. Report back with results.

the only thing I can think of with the cap is you may have a frozen oil separator. the hose that is on top of your valve cover goes to the oil separator in the bottom of your air cleaner. if water is collecting in it, you would freeze up in cold weather, and it would pressurize your motor and force the fuel shutoff to keep the car from starting. you could also have gunk in the tray in the top of your valve/cam cover and it could be blocking gasses from escaping.

Brian, like minds think alike...

..........as always...........but I like the frozen block of water.......;)

I'd remove and check with direct 12 volts all the glow plugs to make sure they are glowing red hot and ream the holes. Reaming the holes in my SD reduced cold starting ability by about 7-10 degrees.
I'm a doubter on the pressurized crankcase. I don't think the crankcase could build enough pressure while cranking with the starter to push on the shut off diaphragm. If it was doing that, it would seem the engine would shut off after it was started and the oil cap replaced.
I think most of your problem is related to the smaller battery you were using. By the way, 10 seconds of cranking is not long in cold weather. MB says you should keep the engine cranking until it starts. I've done this for well over 30 seconds in cold weather. Typically one or two cylinders will start firing but you still need to keep the starter engaged to keep it running long enough for more to start firing. If you read the threads on here on cold starts, you'll learn that you only really get one attempt. Subsequent attempts, after the first, are very unlikely to get the engine started in cold weather. You can't think of starting a 617 in the cold the same way you think of starting a gasser. Glow twice, hit the starter and keep it engaged until its running.

cold checklist
 

Valves (done)
Cables (done)
Battery (done)
Synth oil (?)
Starter speed (listen to other 617 cars) is critical on a diesel
Procedure (as mentioned: glow. Press/release pedal to loosen rack (Dr Booth). Crank until running. )

Your name is biotour, so can I assume you are running biodiesel? Most B100 gels before 32F. Are you using B100?

Edit: I just noticed you listed you have a two-tank conversion in your sig. Are you running D2 in the main tank and veggie in the 2nd? Short purges of the veggie would cause cross contamination into the diesel tank. If you don't keep much D2 in your main tank the % of veggie in there could become high and thus gel at cooler temps.

Also I'm assuming you filled with D2 in a warm area where there is no blending done with pump diesel. Then you drove to a colder area (17F). 17F is about the low point for D2. Alone, D2 should be okay at that temp but if it is somewhat contaminated with veggie then the gel point becomes higher.

I would try adding some kerosene or anti-gel additivie to the main tank. Or at a minimum top off with blended diesel in the area you are now in if this is the case.

Ye ole' strip fuse.
 

12V at the glow plugs??

Jay.

would buying new fuel injection nozzles help the cold start issue? the engine in this car was from the junkyard and i have no idea what the current injectors are like. same with the glow plugs, but i never had an issue with them so i never thought they were bad until i moved to colorado!

i'll pull all 5 next time its warm out, and hook them all up to a battery to see which ones glow red. is there anything i can diy to make a glow plug reamer? or where would i buy one? thinking i'll also stop by harbor freight and get a compression tester just so i know what im dealing with. will also check crankcase breather tube. ill try blowing through it with the oil cap off and see if air comes out.

im running mobil 1 synthetic, i got 5 quarts of 15w40 and topped off the rest with 5w40 rotella synthetic from autozone. its been in there for about 2500 miles, and is my first time using synthetic. when would be a good time to change it? i was told this oil is good for at least 5000 miles.

i usually only have between 1/4 and 1/2 tank of diesel since i try to run mostly on veggie oil. i havent been using it as much because ive been doing a lot of short trips, but there is probably some veg in my diesel tank. ive filled up a few times here but i only put in a few gallons at a time.

The easiest/best starting point is the glow plugs. You can verify the resistance from the connector on the relay without removing them. They should read less than 1 ohm when they're cold. They will normally read infinity if they are dead.

If the injector(s) are bad you should also hear some injector knock, especially with a cod engine.

How does it run in warmer weather?

Not just cold. Elevation may also be an issue. Thinner air, lower compression. What's your elevation? When's the last time you replaced the air filter?

Fuel gelling then doesn't seem like an issue if you have put fuel in a few times in the new location and you aren't dumping tons of veggie in the main tank.

Once the glowplugs are in order, IMO oil weight makes the biggest difference in cold starts. I would run exclusively 5w40...actually I do. :P

And since you are running veggie you will want to run shorter oil change intervals than someone using the same oil running D2 since the veggie doesn't burn off in the oil like D2 does. I would think 5k on M1 or Amsoil would be the max for running veggie. If you are using dino I would probably stick with 3k. Rotella, probably somewheres inbetween.