Could 5W-40 cause some smoking at startup? - Diesel Forum

dirtyb15 · 12-23-2012, 09:05 PM

Hi all, over the last couple of weeks my truck has started to smoke pretty heavy at startup. (20-50 degrees out over the last two weeks.) I had 3 glow plugs out on the passenger side, so i replaced all 4 of those. The driver side all tested okay. I also checked the relay and it is fine. The truck starts up very easy it just smokes heavy enough to annoy the neighbors im sure. The smoke does have a blue tint to it so thought maybe it was oil related, but also smells like fuel.

Anyways, it occurred to me that it started smoking at start up soon after my last oil change. I ended up going with rotella synthetic 5w-40. The motor has 314,000 miles, maybe the thin oil is just making its way though when the 15w-40 was not? Anyone else ever experience smoking after switching to a lighter weight oil? I also noticed a few small oil spots on the driveway and it never leaked before the oil change. Maybe i should switch back to the heavier oil.

**bugman** · 12-23-2012, 09:11 PM

How long have you had your truck or how many winters.

It sounds normal to me during the winter months when it is cold.

dirtyb15 · 12-24-2012, 09:36 AM

Ive had it a little more than a month now, this is the first winter. So sounds normal to you? If i start it after sitting 8 hours or more, i get a pretty good cloud for about 15 secs, then it dies down to a steady stream. Does not clear up till i start driving, then its gone the rest of the day. Runs great, tons of power. If this is common guess i wont worry about it.
thanks!

dirtyb15 · 12-24-2012, 11:22 AM

Well, now i am stumped. I had the truck plugged in over night and today when i went to start it had no smoke at start up. I put a meter on the relay and i am only getting about a .6 volt drop over the terminals so pretty sure the relay is not the problem. The 4 passenger side glow plugs are brand new and i ohmed all the connectors on the valve cover after installing them and they all checked out fine. I did not replaced the driver side glow plugs because none of them tested open. Is it possible that a glow plug could be bad even if it is not open? (I always thought they were either good or bad.).

**bugman** · 12-24-2012, 11:29 AM

The glow plugs should be tested with a volt/ohm meter. The reading for a good plug is between 0.6 and 2 ohms, outside of those readings they are bad. The relay should have less than 0.3 volts difference between the two large lugs when it is energized.

artificer · 12-24-2012, 01:21 PM

Another possibility is bad injector o-rings. My truck is doing the same as yours. I plan on installing new glow plugs and new o-rings. At 314k, the injectors may need to be rebuilt, but others will have to confirm that.

Michael

madpogue · 12-26-2012, 12:41 AM

Quote:

Originally Posted by dirtyb15

I put a meter on the relay and i am only getting about a .6 volt drop over the terminals so pretty sure the relay is not the problem.

Relay fail. Voltage drop should be no more than 0.3V. Another way to test it - on one of those "cold" days, run a jumper cable directly from one of the battery positives to the "downstream" big terminal on the relay for 10-15 seconds. Then start it up and see if it smokes any less.

Snowtow · 12-26-2012, 10:51 AM

Blue smoke at cold temps is perfectly normal. It's an indicator of an incomplete burn of fuel. Your engine is cold enough that this is going to happen as temps drop. Plugging it in and getting no smoke just proves the point. Glow plugs can only heat up so much.

Jcart · 12-26-2012, 02:34 PM

Sounds normal to me given number of miles. When you need to replace your Glow plug relay get a Stancor one, significantly better then a stock one.

jrc

Phil A. Bowl · 12-26-2012, 09:46 PM

My truck does the same. I chocked it up to a few bad injectors.

Stan96 · 12-27-2012, 10:22 PM

Same here, when it's cold, you get a big cloud of blue smoke for a bit, no big deal

dirtyb15 · 12-27-2012, 10:33 PM

Okay, thanks all for the replies. Sounds like it is nothing i need to be terribly concerned about.

madpogue · 12-28-2012, 01:20 AM

Quote:

Originally Posted by dirtyb15

Okay, thanks all for the replies. Sounds like it is nothing i need to be terribly concerned about.

You still have a weak GPR, if the voltage drop is 0.6 volts. Replacement will probably reduce the start-up smoke considerably.

dirtyb15 · 12-28-2012, 08:43 AM

I have a new one on order. Im going to go ahead and do the driver side glow plugs as well since i already bought them. Ill let you know if the smoke dies down after the new GPR.