Ferrari Mailing List: Testarossa repairs

[Rick Lindsay (richardolindsay]

Hello Friends,

Quick update this morning: My-Ric's-Deep's-Ric's-etc's Testarossa is back running. You may remember this car and the fact that it has always had idle problems - and starter problems. The later is probably just excessive wear from restarting after stalls. Anyway, I bought this car ages ago with the upper half of the engine in cardboard boxes. After careful reassembly and retrofitting the K-Jetronic fuel injection, the car ran great...but it still suffered idle instability. Charles Perry also has an early Testarossa with precisely the same malady. Design problem?

While studying the workshop manual, I found no mention of idle problems. However, in the parts manual I discovered a part that neither my car nor Charles' car has installed. It is a pipe that connects the outputs of the Control Pressure Regulators (also called warmup regulators). This little pipe causes the control pressure - the back-pressure applied to the mixture regulating barrels in the fuel distributors - to be the same. Otherwise, the two fuel injections, one per bank, compete for control of the engine. Our cars don't have that pipe installed so any tiny imbalance in the induction triggers the competition. The end result is oscillations in idle speed. In fact, the problem is so severe that the engine often dies. That's inconvenient,  embarrassing and dangerous when it happens in traffic - especially when a wonky starter acts up! Just ask Matt Boyd!

So the answer to the malidy is to add the balance pipe and retune the induction, both air balance and fuel-air ratio. And that is the task at hand. Oh, and I also have a new starter! I'll have the old one rebuilt locally and keep it in reserve. It also fits my 308GTB and accessibility is becoming increasingly difficult (read: expensive).

A day ago I went to my storage facility and began the task of bringing the car home. The first step was to remove the air cleaner assembly. That alone is non-trivial. Once off I could reach the idle speed adjustments. I added a half turn to both banks and started the car. I had previously charged the battery since this wonky starter only engages with a fully topped up battery. The car started easily, as is usual with a K-Jetronic fed engine. From dead cold, it idled smoothly at about 1200rpm. As heat brought the tolerances into spec the idle speed increased to around 1600rpm. That's way too high BUT it was stable. The upstart of this is that I can now drive the car home to affect repairs. I have all the parts (as does Charles) and the instruments and gauges to do the tuning. I only need time and a little nice weather. Fortunately, this week affords both!

So this afternoon I'll bring the car home, give it a bath, then begin disassembly, updates, a starter-ectomy, then tuning. Photos and how-to words to follow, Charles.

-rick

Sent on a Sprint Samsung Galaxy S® 5