I have a 89 F-250 with a 351w. When I go to start the engine it blows a little black smoke out the exhaust. Is it cause of old oil? I recently bought this truck and I use it around a farm. I dont know the miles because the dash cluster dose not work. It will only show the RPMs. Anything similar happen to anyone else?

 

I would guess it's from unburned fuel during the startup process. I wouldn't worry about it.

 

Is the check engine light on? How does it run?

 

Black smoke is unburned fuel, most likely you have an injector leaking down while the truck is sitting.

 

X2 on this..

 

Yep that's where I was heading.

 

It runs fine. It has trouble starting due to solenoid/relay or starter issues. But yes the check engine light is on. The wiring is a mess under the hood, but im really not concerned about that. Ultimately i have other plans for the 351. I was just curious if black smoke was particularly bad for the engine.

 

It dose run fine. Check engine light is on but thats because the wiring under the hood is a nightmare. Also because it was originally an automatic C6. Now it is a 5 speed ZF S5-42.

 

It's not great for it, if there's an injector leaking down that means that it's also washing away the oil that lubes the rings.

 

On most Fords checking fuel pressure is as simple as checking tire pressure. Screw on a gauge start it up turn it off & see if the pressure holds steady. If it does'nt something is leaking

 

You can also do a hard downshift engine brake test. If you downshift to ~3000 rpm and let the engine slow you down there should be no fuel injecting, so if it stumbles and pops and is not smooth, you have a leaking injector. In a downshift, it should be smooth as though the key was off.

 

Ok, thanks. This has been helpful. Curious question. How do I show my vehicles and specs under each post?

 

You add it to your signature in the user control panel.

 

The PCM doesn't control a C6 and wouldn't know you now have a 5 speed.

What codes are in the system?