A4 Frustration - one of those days

[joe_db]

I needed to be someplace 18 miles up the river yesterday. The engine, which has really been close to trouble free, decided it was not going to play nice. It was missing pretty badly, it almost sounded like someone was jiggling the ignition switch at times.

I did the MMO routine to make sure it wasn't a sticking valve, no change. Voltage at the coil is good and steady. Pulling plug wires showed it was not just one cylinder. Fuel pressure is steady as a rock on about 4.8 PSI and fuel vacuum is 0.
The symptoms actually resembles a bad condenser, so I decided to take a look and went right down the old-engine rabbit hole. For some reason one distributor cap screw was stripped and NOT coming loose. I had to remove the distributor now to get it off So whatever the actual issue is, now I have another one too
The condenser ended up testing fine with my meter to make the day even better. Some google-fu shows that a real condenser test requires 300 volts or more, so it might possibly be bad and show OK on a multi-meter. Since I have it all apart anyway I decided to replace the points and condenser and the cap too with one I can get on and off. Before knocking off for the day I set the engine to #1 TDC, so this morning's task is putting the distributor back on and timing the engine.
With my luck it is going to turn out to be something totally different My one saving grace here is I had no idea the cap wasn't coming off easily, this is a lot easier to deal with at the dock than out in rough seas someplace.

[zellerj]

I have a question about fuel pressure. If there was crud in the carburetor bowl periodically blocking the jet, would a fuel pressure gauge hold steady at a good pressure? OR would the pressure gauge fluctuate?

[joe_db]

I have a question about fuel pressure. If there was crud in the carburetor bowl periodically blocking the jet, would a fuel pressure gauge hold steady at a good pressure? OR would the pressure gauge fluctuate?

No it will not, the gauge will hold steady. I would suggest cleaning the carb out and adding a polishing filter to keep any crud out going forward.

[joe_db]

Update - the engine is running fine after I put it all back together. My issue now is timing.
My initial timing is right on at 0 degrees at idle. At high RPMs the timing seems jumpy, the pin holds steady in the strobe, then jumps back a bit, and then back to normal. Also it seems to be around 12 degrees, which I think is less than ideal. I am not sure what is going on here, electrical issue, fly weights sticking and unsticking, or ?????
Another thing is maybe the timing light trigger is too sensitive and is grabbing a pulse from another plug every now and again.
I might post a video if I can capture it.

FYI - If you need ignition parts right this second and not in the mail, ask for stuff for a 74 Chevy Vega

[JOHN COOKSON]

ideal. I am not sure what is going on here, electrical issue, fly weights sticking and unsticking, or ?????
stuff for a 74 Chevy Vega

I would definitely check the advance especially if it has been a while since you serviced it.
Been down this road myself............

ex TRUE GRIT

[sastanley]

Ugh, sorry Joe...I definitely had trouble when the weights were sticky...however, mine would not even run with the throttle down when I later learned the advance weights were stuck..Fortunately, I had a couple old school Harley guys cruising on another boat and we solved the issue on the dock later. Anyway, I probably wore out the clutch plates a bit that day since she would only run at 2,000 RPM, but I told the dockmaster in Cambridge, I was having a bit of trouble and I was coming in hot and please do not be alarmed. We docked without smashing into anything, cleaned the dizzy & weights and no problem the next day.

My buddy Spencer with a questionable condensor could not even get the motor to run..a $10 part and it ran great when we replaced it..I would have extras on hand in my world if I did not have electronic ignition.

Timing: Depending on your motor, in the Cat 30 world, putting the timing mark on the accessory drive, which we have great access to, has been a fabulous upgrade in timing checks, thanks to innovations by Neil and Thatch. I can dial that sucker in no problem. You could easily set the 17° number on the flywheel cover too, with a protractor and a level.

[joe_db]

My strobe can dial in advance, so the actual timing setting is not an issue. What I am wondering is if I am getting around 12-14 degrees instead of 18, will setting the timing at cruise RPM to 18 give me 2-4 degrees advanced at idle when it should be zero?
Here is the video at cruise:

http://www.dellabarba.com/sailing/a4/timing.mp4

In this video the strobe is set to zero degrees, so the mark is not straight up at cruise. You can see it jump every so often, I am not sure if this is a problem with the strobe or the engine or what The engine seems to run fine now, somewhere in the new coil, cap, rotor, plugs, points, and condenser the problem was eliminated. I know shotgun repairs are not always the best idea, but I had it all apart anyway and I didn't want to come back and do it again.
One of these days I am going to get around to my EI dual coil plan, I still have the coil combiner sitting around waiting to be used.

[joe_db]

Somewhere in all those repairs I did something good, I was out just now and full throttle was 6.7 knots at 2500 RPM That is an improvement!!!!