black smoke / fuel lift pump?

[BLUE68FORD]

I have a 94 cummins in a 68 ford. I get a big puff of black smoke when I start. Then it all seems "clean" after the initial start. Runs great and starts easily enough.

I don't have the fuel heater connected which I thought may be the problem but I even get the smoke in the middle of the summer with temperatures in the 90's. Any ideas?

Also, (and probably unrelated) the truck starves for fuel if my tank gets below 1/3 to 1/2 tank. Fill it up and no problems. Is my fuel lift pump going bad or do I have a fuel tank problem?

Thanks for any help.

 

[argve]

The black smoke is normal. As for the starving for fuel when tank levels are lower I would also suspect the lift pump or a bad pickup tube. From my knowledge the pick up tubes are not a known source of problems but it's worth a look see.

 

[nevrenufhp]

Put some big injectors in it, then you'll see some REAL black smoke! I'd be suspecting the pickup in the tank, the lift pump on the 12valves rarely go bad(but still do). Any pictures you'd like to share? Always good to see a swap!

 

[BLUE68FORD]

my truck

here is my truck

 

[holtzer1]

looks right at home in there, like it was meant to be

 

[holtzer1]

oh...btw, another reason for smoke is the lack of an intercooler.

 

[Doggy Daddy]

Do you mean when you start the engine or when you start away from a stop? In either case I wouldn't sweat it too much since a bit of black smoke is normal. If it is really bad on acceleration from a stop there could be a misadjustment or a binding problem in the aneroid system. There is a diaphram on the injection pump connected to the intake manifold that won't allow the lever that regulates the fueling to travel full stroke when there is low boost. It has 3 adjustments that typically influence low boost smoke: 1 The whole cover (under which is the fuel or "cam" plate) moves fore and aft. I guess you could say this sets the range of aneroid control. 2 The "Star Wheel" sets the spring tension against the diaphram; it is under the round plug with an 8mm allen drive at the top of the cover. 3 No Load stop sets where the aneroid system starts to intercept the fuel lever. This one is frequently what does it to get a truck to pass an emission test. It is on the back side of the aneroid diaphram housing with a sheet metal cover over it (secured by a slot head screw and anti-tamper shear head bolt). It is possible that the aneroid has stuck in the "high boost" position and is not controlling the fuel lever.

It can be adjusted to not smoke and with a little trial and error it will still accelerate OK (that is the trickey part).

 

[Doggy Daddy]

oh...btw, another reason for smoke is the lack of an intercooler.

Well, no, the intercooler lowerers the EGT which allows more fuel to be added safely. Also, from a stop would be where the intercooler has no effect.