Engine dies every few minutes

[david rj]

Hello-

I have been reading through the fuel related shutdown posts and I think that is what I have been experiencing. I am quite new to the A4 so I thought I would share my particular situation to see if any one can confirm the issue or pass on any helpful tips.

My A4 is very clean well maintained and starts perfectly with no issues. It has an electric fuel pump and a standard marine filter between tank and engine.

Until recently it was running and idling perfectly. However, now upon running the engine for several minutes (3-6) at average idle it cuts out. After it cuts it is almost immediately re-start-able but dies again after another short while. These start-die-start steps seem indefinitely repeatable. If I have the engine running w/ an above average idle (i.e. slightly revved) it doesn't die but rather wavers briefly (i.e. rpms dip and sounds as if it is about to die but doesn't) with approximately the same intervals.

I am assuming this is a fuel starvation related issue but not sure of which variety. Presently I assume the issue to be either a faulty/failed fuel pump or an issue w/ air in the gas line. Based on these symptoms can any one offer any more specific tips or insights?

Many thanks in advance.

[jhwelch]

I bet if you put it in gear and run at around 1,800 rpm it dies within
20 seconds. This has happened to me a lot in the past; the needle
valve in the carb gets stuck in a partly open position so not enough
gas is getting through.

If you can hear your electric fuel pump ticking over (or even better,
if you disconnect the hose from the carb and fuel runs out at
a reasonable rate) then you know it's not the pump.

You can try tapping on the float area of the carb to see if that
will get the needle valve to drop. Or you can take the carb off
and open it up (which is probably a good thing to do every now
and then to clean it of gunk and bits of grit).

-jonathan

[Don Moyer]

David,

I find your symptoms quite interesting, and I think you're correct to suspect some sort of fuel supply issue, though at the moment I can't think of a likely scenario to explain the regular and predictable interruption of fuel pressure every 3 to 6 minutes.

The fact that the idle system shuts down, and the high speed system does not, is rather easy to explain by the fact that the idle system is much more fickle than the high speed system and (particularly if the idle mixture is set a bit on the lean side) is always prone to shutting down anytime any anomaly occurs in the fuel supply system.

Until we can come up with a specific issue in the supply system, you might try to set the idle mixture a bit richer (clockwise a half-turn or so) to see if the engine at least will keep running at idle. It would also be useful to know if the engine exhibits these symptoms under load at your favorite cruising RPM.

Don

[david rj]

thanks for info.

i was looking through the various documents i acquired with the boat and turns out this is a Moyer Marine late model direct drive exchange engine from mid 2005. i was wondering why it was still looking so good! really, the engine starts easily and runs nicely it is just this intermittent stalling that is the issue.

my approach to assessing the issue will be as follows (please let me know if there is something else i should look into):
-check primary filter for water/debris/flow
-check electric fuel pump for good flow, and good wiring
-check secondary filter
-quick check of carb needle valve as noted by jhwelch
-check tank-side fuel intake and fuel tank debris

if all these components are functioning correctly and the problem persists then i am assuming the next step would be a more invasive cleaning of the carb(?).

let me know if this sounds reasonable or if there is any other easy steps i can take.

thanks.
-david

[Don Moyer]

David,

The corrective actions you're planning are all reasonable, assuming the engine is shutting down due to a fuel starvation issue.

I'm attaching a short checklist for you to go through if possible, the next time the engine stops, which should help you to pin down the general reason the engine is stopping: i.e., fuel, ignition, or compression.

Regards,

Don

[david rj]

thanks again for the info and tips. seems i have been able to sort things out!

after looking into the gas line and fillters for proper flow i checked the small inline automotive fuse connected to the fuel pump. turns out the 10 amp fuse was burnt. upon replacing this fuse with a 20amp all was well again. any potential issues w/ using a 20amp fuse in that location?

i had initially ruled out the fuse as the engine did start and ran for some time prior to stalling. i figured if the pump was not functioning that there would be no fuel and no starting.

checking the filters and fuel lines wasn't in vain as i emptied some sediment from the racor filter and repaired a potentially serious crack in the fuel line. i am sure you will be relived as i to know that all things are once again in working order!

thanks again!
-david