Fuel problems?

[Peregrine]

My A4 has been sitting for a while, but has always been reliable. Now when I start it, it runs well for about 15-20 seconds, then stalls, but fires again just before it completely quits. In other words, the engine runs, stalls, surges again for another 15-20 secs, stalls, surges, etc.....

When it is running, it runs smooth. Do you think this is some kind of fuel contamination problem or some strange electrical/ignition problem? Or something else?

Larry

[Don Moyer]

Larry,

The regularity and consistency of your symptoms seem to me to be more easily explained by something going on within your ignition system than the fuel supply. Fuel supply problems can also cause an engine to falter and stop, but I can't conceive of a method (even if I tried to duplicate your
symptoms) that would be so consistently repetitive (almost rhythmically).

We also have to account for the fact that the problem developed after a long lay-up.

One of the things that frequently happens while an engine sits for an extended period is that a thin layer of corrosion grows over the surface of the points. Usually this condition will simply prevent the engine from starting, but other times it will cause rough running as the points make contact sporadically. It may be a bit of a stretch, but I can see a potential sequence where the points will work for a few seconds, then fail to make contact as the heat of resistance builds within the corroded zone, cool off and work again, etc., etc.

In short, I'd clean off the points before doing anything more complicated.

Don

[Peregrine]

Don,

I have the electronic ignition installed. I have been using it for a few years now with no problems. This gets a little more complicated for me. Could this be causing the intermittent engine cutouts? If so, what should I check?

Larry

[Don Moyer]

Larry,

Having an Ignitor installed causes me to look back to the fuel system. There is one fuel issue that could easily explain your symptoms, which is that the fuse between the coil and oil safety switch could have failed. With the fuse failed, the fuel pump will run only while you're actually cranking the starter. A fuse failure doesn't really fit the profile of something that usually happens while an engine is just sitting idle, nor of course, if you have a mechanical fuel pump.

Don