Engine Surge Under Load

[david horowitz]

For a number of reasons my coach has sat for nearly a year, being run periodically to exercise the engine. I realize there is much more I should have
done to better prepare the coach to sit for a long while such as fuel treatment, etc. Now the coach is getting back into action and upon starting
yesterday I let the coach idle for a good while. Then, when underway for a brief while found that the engine was surging while under load.. under
way. Stopped, at idle, the engine just purrs without surge. What has likely happened? And what are the most efficient steps I can take to resolve
the issue. Thank you in advance for your input. Dave
--
David del Rio - 75 Avion - Raymond, CA

 

[Ken B]

The first things that come to mind are:

1. Dirty gas filter(S)
2. Winter blend gasoline

There are lot of other things it could possibly be.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[Jim Hupy]

I'm thinking that the mice have been chewing on your vacuum hoses,
particularly the vacuum advance hose. You might pull the distributor cap
and make sure that your mechanical advance weights are not frozen up due to
long inactivity.
Plugged fuel filters are a distinct possibility as well as bad gas.
Jim Hupy
Salem, OR
78 GMC Royale 403

> The first things that come to mind are:
>
> 1. Dirty gas filter(S)
> 2. Winter blend gasoline
>
> There are lot of other things it could possibly be.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
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[Matt Colie]

> For a number of reasons my coach has sat for nearly a year, being run periodically to exercise the engine. I realize there is much more I should
> have done to better prepare the coach to sit for a long while such as fuel treatment, etc. Now the coach is getting back into action and upon
> starting yesterday I let the coach idle for a good while. Then, when underway for a brief while found that the engine was surging while under
> load.. under way. Stopped, at idle, the engine just purrs without surge. What has likely happened? And what are the most efficient steps I can
> take to resolve the issue. Thank you in advance for your input. Dave

David,

I am glad that you are getting back to your coach.

You should know that there is nothing good that happens when an engine is run at idle.
When you write "exercise", did it move? If not, that could be part of your problem.
As Ken and Jim both wrote, there are things you should check out first.

You wrote "Surging under load", was this at a constant throttle position? Or was the power not regular with the throttle position?
If it is the former, then there is a good chance that it is fuel condition or minor carburetor fouling. Run the current fuel down and load new and
some fuel system cleaner. That may be enough.

If it is the later, then there is a better chance that the carburetor will have to be disassembled and cleaned.

If you idled the engine excessively, it may have carbon accumulated in the cylinders. The easiest cure for this is to take her out and run her a good
ways as highways speeds. And, that is a good way to get the new fuel into the system too.

Did you notice that a lot of what ails her may be that she was not run? This is common and more so with older engines.

Matt

--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit

 

[david horowitz]

Gent's... Thank you one and all!

- Ken.. Yes, it's time to change the fuel filter(s) no matter what.

- James.. you might be spot on!!! We found mouse droppings under the hood where there were none before! I'm going to check the vacuum lines first!

- Matt.. I come from a boating background and have learned the hard way what happens when an RV or boat sits. The same thing happened to my 'engine'
over the winter. Following a failed back surgery I (and the coach) spent the past year not being moved... and I too am showing signs of failure by
neglect. Fortunately I'm somewhat back on track, and so have turned my attention to my beloved coach! She was only just moved a few hundred feet and
the surging was while slowly under way with a constant throttle pressure, while going up hill. Idle was smooth and at normal rpm's. I'm going to do
the items above, then load her up with fresh fuel and a cleaning/conditioning additive followed by exercising her on the road. Fingers crossed for a
simple fix!

--
David del Rio - 75 Avion - Raymond, CA