Fuel Starvation

[Springwhit]

HAve followed fule starvation thread and cannot solve my problem. My late model A4 idles smoothly. Put it in forward and after 3-5 minutes it appears to run out of gas. IT will crank right back and run, it will continue to run if you take it out of gear before it quits.

I have replaced fuel lines, filters, added water seperator, put on a new carb, new fuel pump, made sure the vent tube is clear and the pick up tube is clear and removed the siphon valve.

I am hopelessly lost now.

Thaks - Whit

[Bob Grenier]

Whit...This may not be fuel related at all...I had similar symptoms on my A-4 and it turned out to be a blockage in the exhaust...Would run fine in neutral but would die when I put it under load…This may or may not be your problem…I remember I also thought fuel at first...If you have vacuum gauge you can check this out. I find a vacuum gauge to be a really good tool for diagnosing the A-4 ( cheap too )

Bob

[Don Moyer]

Whit,

There's an article posted in the Tech Tip section of our web site entitled "Fuel related shutdowns" which may address your situation. Here's the link (http://www.moyermarine.com/shutdowns.htm).

I would particularly endorse the suggestion that comes rather late in the article, to install a small rubber priming bulb ahead of everything else in your fuel supply system.

If, after exploring everything in that Tech Tip and insuring that you have a continuous flow of fuel to your new carburetor, it may be time to reconsider your assumption that your shutdowns are fuel-related.

Regards,

Don

[Don Moyer]

Bob,

Good observation! I would only add one thing to your suggestion for Whit, which is to remove one of the spark plug leads and try to accelerate the engine again. If the engine runs better on any three cylinders than it does on all four, a severe blockage in the exhaust would be indicated.

Don

[Springwhit]

Don and Bob: Question - If the exhaust was clogged or otherwise restricted would the water flow coming out the stern be restricted? I replaced the muffler and hose in this orderal as well (bought the new stainless muffler). The water flow is as strong as ever and the engine temp is normal.


Thanks - Whit

[Don Moyer]

Whit,

Other than noting whether or not water is "batching" out of the exhaust at cruising RPM, a change (or absence of a change) in water flow is not usually the most reliable way to predict exhaust back pressure problems. This is partially due to the fact that we're usually talking about rather low pressures becoming a problem. Remember that the Atomic 4 likes a very low back pressure (in the range of 1 to 1-1/2 psi) which means that pressures in the range of 2 to 4 psi can cause problems with the engine, but not necessarily be noted as a water discharge issue.

Having said all that, I'm still thinking your problem is more likely in the long wiring harness with the three old quick disconnects.

Don

[Springwhit]

Don: I hope I'm not beng a pest -and not to question the Master, but... How would the wiring harness affect a symptomm so much like fuel stavation - wouldn't the engine just quit, like an electrical shut off? PLus, by the way, he priming bulb will pump up firm, but lose its firmness, even tho' my in-line filter, which I can see through, is full of gas. The primmg bulb is between the gass tank and the filter.

I'll definitely check the harness

Thaks

Whit

[Don Moyer]

Whit,

The term "Master" hardly applies to someone who makes as many mistakes as I do.

The big problem of course is that when troubleshooting over the phone or via email, a tremendous burden is placed on our combined ability to communicate completely and accurately. One of the mistakes I frequently make on my end is to engage in long troubleshooting exercises within a particular system of the engine (say ignition), only to learn that the problem was really within the fuel system all along - or vice versa. When this happens, it sort of feels like you're trying to play tennis on a football field.

My best guess remains that your problem is most likely within your fuel system, but having spent a lot of time on the football field and not making much yardage, I'm a little distracted by something on the tennis court next door, namely that you have a Catalina 30 with an original wiring harness. Since these harnesses (especially the middle quick disconnects under the cabin sole) are a known cause of shutdowns and other unreliability issues, it seems like a good idea to check yours out, if only to catch our breath before getting back into the fuel system.

Regards,

Don

[Don Moyer]

Whit,

I forgot to mention in my last message that the priming bulb will normally appear less than inflated during normal operation. The one on my own boat looks sort of like a raisin as I'm motoring along.

Don

[Springwhit]

OK - don thanks and glad to know the bulb doesn't need o firm all the time. With Mothers day this weekend it will be another week before I can attack it. I'll be sure to let you now what happens.

Whit