Cold Start Smoking Briefly while backing up only

[Old-Red]

1986 F-250 XLT 6.9L Navistar 355,000 miles (approx) dual fuel filters

My parking area over the last 20 years has been on a 10% down grade driveway. I park front end down because if I park rear facing house, it is harder to start, but easy to start when pointing downhill in my driveway.. My assumption has always been that an air bubble is forming in the fuel lines of the fuel filters. So I have always parked front facing downhill.

Recently I have noticed that occasionally once warmed up with block heater, as I back out uphill, it appears that white smoke blows out, until I reach a level plane. Then never while driving. In fact once I start it white smoke is not emitted, only the short 18' distance while backing up the drive. And not every time.

Any ideas? Or could there be water in the fuel filters?

 

[Fredrickson]

How old are the injectors?

 

[Old-Red]

Replaced in 2006 but please explain why it only does this only occasionally and only while backing up the 18' distance of my uphill driveway, has to do with injectors, so I can understand. This never happens under any other driving condition

 

[rreegg]

Replaced in 2006 but please explain why it only does this only occasionally and only while backing up the 18' distance of my uphill driveway, has to do with injectors, so I can understand. This never happens under any other driving condition

I’m not sure but my initial assumption would be along the lines of backing up making the smoke more likely to pass by the front of the cab. Perhaps you can try to establish a baseline with a camera or something to see what happens when you don’t back up.

In both my 7.3 and 1.9 I notice sporadic white smoke on startup and there are so many variables.

Wish I could be more helpful but at least it doesn’t seem like a problem?

 

[Old-Red]

I can see it as I am looking in rear view mirrors to prevent a collision with a passing car. But I don't see it as it is passing my cab as it dissipates quickly like water vapor/steam

 

[Black dawg]

Is it using any coolant?

Most likely just slightly retarded timing or a slightly leaky injector. Little more engine heat covers it up.

 

[Old-Red]

Retarded timing. Huh, why then would it never smoke when going forward after a cold start? It doesn't even smoke when I start it, only when I back up that 18' run uphill to the road. I'm trying to learn here, but if the suggestion isn't explained I'm going to question it every time so I go away with a fix hopefully

Thanks Black dawg

 

[Black dawg]

Everything is just speculation at this point, but cylinder heat can come up quite a bit with some load. Timing typically retards slightly with throttle position....why it might not smoke while idling.

Does the cold advance work?

 

[Black dawg]

I bet if you start it cold and slowly increase the rpm to 2k it will begin to smoke and run rough.

 

[Old-Red]

Been away from desktop computer, so I'll give that a try this morning and thanks

 

[Old-Red]

Tried raving to what I considered 2000 rpm and no smoke this morning

 

[Black dawg]

Does the cold advance work?

 

[Old-Red]

Black dawg, I do not know what cold start does, or means

 

[IDIBRONCO]

Black dawg, I do not know what cold start does, or means

It advances the idle speed and timing until the coolant temperature reaches about 120*.

 

[Old-Red]

I see. So yes that is working well as once it warms up after starting, it idles higher, then drops down. Don't know the rpm as I don't have a tach, but sounds like 1000 maybe? But I never drive it until that drop down occurs, summer or winter.