A4 engine dies when transmission engaged.

[mikemoyer]

I have a 1979 Pearson 32 with an Atomic 4 engine. On a recent trip we motored for about 30 minutes when we started losing power and the engine died. It seemed like it had run out of gas, but that wasn't the case, the gauge read 3/4 a tank of gas. The engine started back up and ran normally. We engaged the transmission and it ran fine for another 10-20 minutes before losing power and dying again. We disengaged the transmission and started the engine back up. After engaging the transmission again it ran for another 10 minutes. Each time we did this it ran for shorter and shorter amounts of time after engaging the transmission.

I didn't have any lines go missing so it's probably not a wrapped propeller. The appears to start and idle okay (it's turned up a little too high). While the engine does occasionally cut off when moving, it's usually at low speeds, I can't remember it ever cutting off at higher speeds.

I looked at the engine cutoff video from Moyer Marine. The weird thing is that this happens only when the propeller is engaged.

Thoughts?

[JOHN COOKSON]

A dying coil will exhibit these symptoms. Do you have an EI?

After the next shutdown check for spark by pulling the big wire out of the center of the distributor cap and hold it close to the engine to ground while turning the engine with the starter.

ex TRUE GRIT

[mikemoyer]

Propeller engaged

Will the coil problem be exacerbated when the propeller is engaged?

[TimBSmith]

My first thought when reading was coil as well HOWEVER

As a relative newbie passing my 1 year anniversary I know to start at the beginning for each spark, fuel, compression. Some threads start with guess-work and for me the best ones seem to stay evidence and end-to-end focused.

Prop and coil. Not really for the sake of this diagnostic and easy test to tell. Fouled propeller. Let's think through together. If your engine is in gear and prop fouled the coil will keep firing spark until distributor stops. Distributor may stop from power train stall from fouled prop. However, does the engine still stall in neutral, when the power train is disengaged? Start and stay in neutral. That is a good diagnostic test. I suspect it stalls both in and out of gear. Coil delivers spark as long as functioning distributor spins with ignition "on" the coil is potentially working. So you MAY be getting a log curve failure, progressively fewer distributor spins per coil failure. The power train MAY be binding up and causing a stall. You have said it happens at lower RPM not higher RPM this MAY indicate timing, idle, distributor. HOWEVER, let's not guess about anything. I am too simple minded to guess.

I rely heavily on the manuals from Moyer, this site. Here is what I have learned.

IMPORTANT Did you change, remove, adjust, tinker, wiggle or jiggle anything before these symptoms started? Have you resolved these symptoms before?

1) Check spark and distribution of spark.
Here is our host taking us through coil check

https://youtu.be/IlmvMWf_1o8

I use meter and I have EI with ballast.

2) Use a spark plug tester (my preference) or common plug to block tests to check plug spark for every cylinder. Make sure that nothing is done to change plug firing order in this process, make sure all distributor wires kept in order. I might re-gap plugs if I am going to pull-test them anyway.

3) If coil and spark check out, I would not dig into distributor at this point. And your problem is engine dying with progressively shorter run times not running rough so that gives me further hold on distributor function questions.

Fuel

1) Reconfirm fuel pump function.

2) Reconfirm fuel quality and check for water or crud in fuel fouling jets. Possibly run clean fuel from alternative source.

3) Reconfirm fuel filter function drain filter check bowl for water.

4) Take carb off and inspect jets and nozzle. Just to be sure.

Compression

Again. Your symptoms are not about the level of power our output. It is the failure to sustain engine combustion, keep engine running. You can check compression but I would like more information before that(and you have not mentioned loss of power).

Exhaust system backflow and pressure. This will come up but premature from my point of view. Checking pressure and blockage that creates back pressure and kills engine is less likely. Usually rough running symptoms not failure to maintain operation.

Oil pressure and pressure safety switch may come up but not helpful to me at this point.

I like to keep it simple and systematic. Good luck. Others more knowledgeable with build on this. Stay well.

[Dave Neptune]

Since she started right back up I doubt it is spark related as a coil can open up and quit when warm it does need a bit of time to cool and throw a spark. Does the spark look blue or yellowish?

I think you are developing a fuel delivery problem IE the fuel pump can keep up with idle but runs out under load. Check the fuel pressure at the carb. it may be fine at idle however under load it will show a drop in pressure. Could be as simple as a clogged filter reducing flow too.

Dave Neptune

[edwardc]

...I think you are developing a fuel delivery problem IE the fuel pump can keep up with idle but runs out under load. Check the fuel pressure at the carb. it may be fine at idle however under load it will show a drop in pressure. ...

Dave Neptune

Another possibility that can cause an “insufficient fuel” problem is the “stuck ball” failure in a Facet fuel pump. Easy to test for. Remove the bayonet bottom of the fuel pump (be prepared to catch the small amount of gas), exposing the bottom of the check valve ball. Press gently with a fingertip. It should operate smoothly. If it sticks, press harder. It should come free with a “click” and then operate smoothly.

Unfortunately, this fix is only temporary. It will stick again, usually at the most inopportune time! The only permanent fix is a new pump.