Wierd Smoking Problem

[vol96]

I've been scratching my head trying to figure out what could be wrong with my 73e mfi motor.

When I start the car it behaves fine. Driving around it behaves fine until I take the whip to it. Once I accelerate hard it starts to smoke badly from the tail pipe and continues under both accel and decel. If I turn it off for a few minutes, upon restart it doesnt smoke, idles fine and runs fine until I accelerate hard, then the smoking starts again. It also clears up if I let it idle for a few minutes.

The engine was rebuilt about 20k ago. The car has been in storage for about a year. It has new dist cap and rotor. It had new plugs until 5 days ago. I couldnt get it to run with the new plugs, I think they kept fouling. When I put in older plugs (with wider gaps) it runs good and idles good......except for this smoking problem.

It has over 100k on original pump with no rebuild so it runs very rich. Plugs have lots of fluffy carbon build up even tho they still fire OK.

Compression is 130 in all cylinders.

Any ideas/suggestions of a tuning nature? I dont want to rebuild the pump at this time or go to carbs. I have MFI tuning tools.

[dickster]

my only experience with smoke on hard acceleration was due to worn rings, but i would start by getting your mixture sorted. if they are sooty black they won't run fine for long. and it won't be doing your engine any good.

[Bones]

Like Dickster says get the mixture right first the smoke might be black smoke (rich mixture) hard to tell when looking in the rear view mirror. If not that and it's onlt happening under high load then the oil is being 'sucked' into the combustion chamber probably from the crank past the rings. Seems more like a rich mixture at this point though.

[vol96]

Dont know if this means anything but when I remove oil tank cap I dont feel any blow by. Hopefully this means rings are probably OK...which puts us back to the MFI pump and/or adj of same.

Thanks for the input guys. I'll attack fuel mixture adjustment then report back.

In the mean time any more ideas are welcome.

[Early_S_Man]

vol,

Have you downloaded, printed, and read all of the MFI documents at the following Pelican page, including the Q & A after the set of links to specific documents?

http://www.pelicanparts.com/techarticles/911_MFI/TipMFI.htm

Your description of running rich, then returning to normal after a brief cool down ... leads me to think that something is sticking in the regulator or thermostat on the MFI pump. That suggests that one or both of the following procedures could help the situation:

1. Pump Degumming -- Remove pump from engine and clean everything external with either sprayed or brushed-on Berryman's B-12 Chemtool. After external cleaning, remove both oil fittings on the right side of the pump and drain by turning the pump on it's right side over a metal pan with the rear elevated approx. 1/4" ... until all oil has drained from the sump. Turn pump over where oil fitting holes are upwards and fill the sump with liquid B-12 Chemtool. Cover both oil fitting holes with thumbs and shake vigorously for a couple of minutes. Tape over oil fitting holes with duct tape and let pump sit for 4-6 hours. Drain al B-12 Chemtool from pump, then refill with B-12, repeat shaking , and let sit fr another 4-6 hours. Allow pump to 'dry out' for 24 hours, covered by an inverted metal pan to protect from dust, dirt or insects. Pump should now be in a 'degummed' state.

2. Thermostat Cleaning -- Digital pictures taken during disassembly could be VERY useful!

Remove thermostat assembly from pump after reading the separate article about cleaning thermostat, and also the 'Blue Book' ... Check, Measure, Adjust document. Disassemble and clean the thermostat with B-12 Chemtool and check for corrosion inside thermostat housing, and sand or use Scotchbrite until finish is smooth to the touch over the entire cylindrical surface. Clean housing again thoroughly with B-12 and dry inside bore with paper towels. Reassemble thermostat, paying attention to proper orientation and organization/order of parts. Reassemble thermostat to pump housing.

3. Pump and Injector Testing -- Refill pump sump with the same grade motor oil normally used in engine. Attach short 7 mm ID fuel hose to one of the supply or return banjo fittings that has been loosened, rotated upwards, and retightened. Insert Coleman Filter/Funnel [available at most sporting goods departments of a major store such as Target or Wal-Mart] into short fuel hose ... and fill plenum until overflowing with Mystery Marvel Oil. Remove injectors and supply pipes from engine ... and attach to pump in the normal firing order. Place the assembled pump & injector assembly [what I call the 'Butterfly' configuration] inside a large metal or plastic tub lined with old newsprint. Rotate cogged belt drive pulley until all injectors are spraying evenly, then examine all injectors for proper conical spray pattern while turning pulley. If any injectors have an uneven pattern, you can clean them in an ultrasonic cleaner, preferably one with heater and timer -- with B-12 Chemtool overnight, or for 12-14 hours.

Good luck!