Author: jarle

The exhaust had started to wheeze and even leak a little recently, resulting in unpleasant noxious fumes in the cabin. It was especially problematic with the windows down, and with as much beautiful warm sunny weather we have here, a lot of driving is done with the windows rolled down…

A quick inspection revealed that the PO had connected the headers to the exhaust pipes without any gasket or clamp, and it was surprising it didn’t make more noise than it did.

2 olive gaskets and exhaust clamps later and the beast is purring like a 2 tonne kitten, not a whiff of exhaust to be had in the cabin anymore.

Nice. Ready for the next problem!

Tried out some different things with a mechanic friend today and got the speedometer to work. We kept checking each part of the puzzle, and found that the angle on the impulse generator was causing the problems with the speedometer not working. Connecting the generator directly to the output of the gear on the transmission resulted in the speedo working, but showing too low a speed. Inspecting the angle, it doesn’t appear to offer any change to the rotational speed hitting the generator module, leading us to suspect a problem with the generator itself.

So now I need to find a replacement generator and angle and see of everything works after swapping in a new unit.

My new odometer gear arrived today, courtesy of Palo Alto Speedo in California. The old one had crumbled into tiny pieces, I have no idea when. The speedometer hadn’t been working since I received the car, and I’ve been trying to do what I can to fix it.

When I overhauled the transmission, I also dismantled and checked the speedometer pulse generator and reduction gear, it’s a small assembly that takes the mechanical rotation of the speedometer from the transmission’s output shaft and uses it to run a tiny generator, not unlike those found on bikes in days gone by. This sends an electrical signal to the instrument cluster and speedometer. I had hoped that by  repairing it (there was a drive bar that was worn and too short) my speedometer would work again, but no such luck.

While speaking with several knowledgable people in the US about this, I learned that there are no standards whatsoever as far as speedometers and the impulse generators go. Some send out square waves, other sine, some are very low level, other high, and there are a variety of impulse per mile versions. Every car maker had their own system, especially when electronic instruments were just becoming common, i.e. in the early 80’s.

I did run it with a drill and measure the output, I neglected to note it but seem to recall it being approximately 0.5v DC.

Installing the odometer gear was easy, regardless of the problems with the speedometer. The new gear is also soft, but much less than the disintegrated and discolored original. I’m told they’re made like that so that they don’t make any noise, I don’t know if that’s true. The instruments in the Quattroporte are made by VDO and are the same as those used in contemporary Porsches. The electronic input board is Jaeger, the aforementioned gear reduction and pulse generator unit is Arthur Allen (unfortunately they’ve recently closed down, and are no more).

VDO USA recommended that I talk with Nichols Speedometer in North Carolina for help troubleshooting the speedo. “Chuck”, a wonderfully experienced gentleman with a southern drawl on the phone had a few tips. I applied 12v DC to the two wires connecting to the actual speedo coil, and the needle jumped to the far end, indicating at least that part is working. Touching 12v DC to the same colored wires on the PCB didn’t result in anything, however.

When I started her up after months in a rented garage to rebuild the transmission, it was like music to my ears. A minor setback with a recalcitrant starter motor aside, she started up willingly on the very first attempt, no coaxing was needed.

It’s hard to describe the throaty growl the Maserati tipo 107 creates, it’s got a great low rumble with an urgency to it at idle, with increasing midrange bark as the revs increase. It’s one of Maserati’s longest running engine series. You can read a little bit more about it here: http://www.maserati-alfieri.co.uk/menotti12.htm

Getting the car back on the road was great, and the engine sounded smooooth as could be when I rolled out of the garage a few months ago. She’s been running great since, up until about a week ago, when things started getting rough.

I haven’t done anything at all to the car or motor (well, I removed the rear seats in order to clean and provide better access to the rear parcel shelf, of which I’m trying to restore the leather covering), and am at a loss to understand why it’s running so poorly.

It usually idles ok, but at lower than normal revs (4-600 instead of 8-900). Today it actually died while idling, which is new. While out on a trip yesterday it would sputter and die when accelerating from a standstill, but would idle fine. If I managed to coax it past the stumbling, it would accelerate fine, and seemed smoother the higher I rev’ed the engine. The problem seemed to lessen after driving for 30 minutes or more on the highway (I always warm up the car – water & oil temp to at least 50C – before driving, what I’m describing happens after the car is warmed up), although today accelerating from a standstill seemed to work ok. The engine was running rough all along today, at slow or highway speeds.

Another symptom is backfiring – with occasional flames coming out the exhaust (as entertaining to passerby’s as it is disconcerting to me), at all speeds, but especially prominent when decelerating.

Pondering the cause and possible solution, several lines of thought emerge.

1. Perhaps something is clogging the fuel line, or the carburetor jets are dirty? I found the fuel pressure gauge had stopped working two days ago, and removed it and replaced it with a plug. I had used Teflon tape on the threads, bits of which seemed to be disintigrating. Finally I pulled it out, cleaned up the threads and used Locktite white thread sealant (e.g. Stag) on it. Maybe some bits ended up in the carbs?

2. Vacuum leak somewhere? Seems to be a common cause of backfiring and acceleration problems. Not sure if it’s mine, though, and even less sure as to where to begin looking.

3. Exhaust leak? I’ve noticed a faint whiff of exhaust in the car on occasion, especially when the windows are rolled down. Due to the missing grommet and bushing around the steering column through the firewall, i’ve previously thought that the open windows create a vacuum that sucks in fumes from the engine bay while driving, but lately I’m not so sure, and suspect there may be a leak between the headers and exhaust underneath the car.

4. Condensation in the distributor? The weather has been wildly (and typically) unpredictable, changing from sunny almost warm days to hail and prodigious downpours only a few degrees above freezing.

Today I checked all fuel input filters on the carburetors, hoping to find scads of miniature teflon spaghetti remains clogging them up, but was disappointed (and a little bit relieved) to find them clean and clear. So barring some larger debris in the fuel line between the fuel filter and carburetors (where the pressure gauge was installed), I can cross suspect number 1 off the list.

I recall that when I got the car, it was running a bit rough initially as well. It turned out to be the battery.  When I replaced it, the car ran perfectly and has since. Since the battery is only a year old (and a high output AGM type), and measures ok, it’s not the problem.

Next up will be to spray the distributor cap with moisture repellant and see that everything inside looks ok.

Since the PO (previous owner) had the heads, manifolds, and carbs all cleaned, refaced, rebuilt and tuned (and it has run perfectly before), I’ve ruled out carburetor adjustment for the time being, choosing instead to focus on the points listed above.