More fine tuning

I’ve been thinking a lot about tuning the engine, and specifically, why it suddenly seems to run pretty poorly as of this past Wednesday.  I had let the injection pump soak with acetone again for a while, which didn’t seem to do much.  The engine was difficult to start, then would stall after it warmed up.  The idle was low and adjustment of the idle speed didn’t do much.

Out of concern for the problems it can cause, I first took apart the cold start valve.  Taking it apart was quite easy… just two screws hold the solenoid to it, and three bolts remove it from the manifold.  I confirmed that it wasn’t leaking fuel and the needle inside moved freely. I also confirmed that its a very good idea to replace its seals.  They were in very bad shape.  The small seal (A 001 997 75 40) is very expensive for a little o-ring, list price is $22.50.  The larger seal (A 002 997 52 45) is a value at only $3.  This is well worth the peace of mind.

Next started looking toward the thermostat on the injection pump used for warm-up.  It was clear that it didn’t work correctly since some air was being pulled through the little filter after the engine was warmed up.  I installed a new thermostat (A 001 203 95 75) and experimented with adding shims below it and it didn’t make any real difference in how the engine ran.

After thinking about it, the problem was quite obvious:  ignition timing.  When I removed the distributor to fiddle with the injection pump rack, I only eyeballed its position.  It turns out that it was WAY off.  I set it correctly and the difference in the way the engine ran was quite remarkable.

I ended up adding about 0.5mm of shims under the injection pump thermostat and it seems to work well now.  When running at operating temperature, no air is pulled into the warm-up system.  The idle speed adjustment screw works correctly and the engine idles smoothly at 800rpm now.  Throttle response is also much better.

To celebrate, I took the car on another trip around the parking lot:

As you can see, the car runs very nicely now.  There is no hesitation and it seems to have very nice power.

After this drive, I changed the oil.  It had already started to turn dark and I was worried it might be diluted with gas.  I also noticed that one of the front air bags began leaking, moving this job way up on the the list of things to do.

Turning the engine, and other work

I spent about two hours working on the car today, mostly taking care of little things.  I replaced the heater hose eaten by mice, changed the oil and filter, and managed to get the battery cable off the positive post of the 1983 battery finally.  The oil was quite clean, almost red in color.  The bottom of the oil filter housing had some sludge, but I couldn’t feel much of anything with my finger in the bottom of the oil pan.  I was happy to see the filter was a nice German made one:

But the most important task of today was turning the engine:

Very exciting video, I know.  But it turned very easily.  I had already changed the oil, and poured a bit in each cylinder, on each cam lobe, the rockers, and around the chain tensioner.  This is very encouraging!

I then moved onto the interior and started to repair the wiring which was chewed by mice.  It wasn’t quite a bad as I thought.  Head light switch had 4 wires with the insulation chewed a bit, and about the same with the fuse box.  The two wires running to the switch inside the air suspension height adjustment box were the worst and will need to be cut back and replaced.  Lowering the fuse box down for inspection turned out to be a bit more of a project than I expected:  The B pillar cover, threshold plate, air suspension and hood release assembly, and the carpet in the foot well had to be removed to access the two bolts securing the fuse panel.  But it was worth the effort and piece of mind to know there is nothing that is at risk of burning or catching fire.

And finally, I took a closer look at the shifter bushings I need.  My parts guy gave me two to try, but I don’t think they’re right.  I can’t quite understand what holds the bushing and linkage to the shift lever.  There is no place for a clip of any kind, and the EPC doesn’t show anything.  Anyone have any ideas?  You can see the stub the linkage hangs on here:

I’ve been thinking about buying some short jack stands to support the car so I could climb under it.  Today I used a solution the worked very well, and seems more secure.  I took the cut 2x10s I had ready when we picked up the car and stacked them under the frame rail on each side of the front of the car.  When the car’s suspension is pumped it, the boards fit under without the need for a jack.  After the car sinks down a bit, it sits on the boards.  Removing them is easy, just connect the compressor and raise up the car.  I’ll have to cut more boards for the rear of the car when it comes time to drop the fuel tank.