Engine Throttle Control Fault

[Streetcar]

Hello, I have an intermittent failure on the single lever throttle control for a volve penta engine.

Very occasionally when I put the engine into gear, it clunks in but will not then rev up as I move the throttle forward or back. 5 mins later it works just fine. Not hit the dock yet, but its going to happen.

Haven't been able to re-create the problem under test conditions as it is so intermittent. I've done visual checks at both ends and all seems to function OK. Anyone have any ideas or experience of a similar issue?

[GordMay]

Greetings and welcome aboard the CF, Streetcar.

Are you certain that the cable jacket clamps are absolutely tight??

[Streetcar]

Thanks. Yes I checked the cable ends are properly secured. I can't see any problems with the cables or external mechanisms at each end.

[daddle]

The trick with diesel injector governor pumps is that the fuel control cable is not connected to anything solid inside the pump. Just a spring. So if something is sticky inside moving the control may not do anything. Might need to pull off the pump (difficult).

Test: Disconnect the fuel control cable at the engine and see if you can recreate the problem moving the fuel lever on the engine manually.

[Streetcar]

Thanks, I've been trying to figure out what could be a problem in the injection pump end. I'll disconnect and try it out. One other piece of info - the problem only occurs when the engine has been running for some time.

[MikeTurner]

We had a similar problem with the single level engine control on our Perkins 4.108, in the shifter linkage - sometimes it worked fine, sometimes shifting seemed to hang up. I couldn't find anything that looked wrong in the shifter, cables or linkages. Finally the transmission stuck in forward, no neutral or reverse.

Turned out the cable had corroded internally - the cables consist of a vinyl outer case, a hollow twisted cable, and a solid core that is the actual moving part. The twisted cable had corroded thru and was hanging up the core. It only became apparent once the corrosion finally burst thru the outer vinyl case. The cable ran under the engine heat exchanger, where engine vibrations had worn a small hole in the vinyl cover allowing seawater to penetrate into the twisted cable. The cable was right beneath the pencil zinc, so every time anyone checked or replaced the zinc, the cable got a saltwater bath and some saltwater entered the cable, leading to the corrosion and eventual failure.

So, if you check the pump and follow the other suggestions above and you still haven't found the fault, you might disconnect the engine end of the throttle cable and see if the internal core runs freely when you advance the throttle lever - if it seems to hang up, the cable may be suspect.

[Streetcar]

Thanks again, for more useful suggestions. I had a similar problem with cable-in-conduit steering a few years ago which almost put me on a reef.

This [engine throttle] cable is only a few years old, but your fault is still possible. The odd thing is that (when the problem occurs) the throttle lever moves freely with no indication of any binding in the cable or mechanism - just the revs do not respond.

I have a longish passage tomorrow and with little wind will probably use engine, so hopefully it'll foul up on me and I'll get a chance to trace these suggestions.

[stillbuilding]

Same problem but I hit the dock. Go only as fast as you have to in order to retain steering! My cable/lever control was worn and the cable corroded.

[Streetcar]

So far, I've been able to drive into dock slow.

Problem has not reappeared for a week or so despite continual use on passage down atlantic Spain/Portugal.

I've checked everything I can, so I am getting to the point of just ripping it all out and replacing with new... and then hopiung its not the injection pump...

[daddle]

A few hundred dollars will get the injection pump cleaned and rebuilt. Or maybe the governor flyweights that are stuck. It's complicated inside there.

[osirissail]

Before spending a bundle on an injection pump take out the whole cable and inspect it. It is common that the internal wire breaks or that the outer casing/cover breaks. Also check and observe the shifting action at the engine while somebody is moving the throtte/shifter. It is also common for mounting brackets to come loose.
- - It is much cheaper to replace the cable than an injection pump. Also we wary, cables come in 3 grades of quality. Don't buy the cheaper version.

[Streetcar]

OK, so I have now renewed everything between the throttle lever on the engine and the handle in the cockpit. That is: cables (both gear and throttle) and cockpit control mechanism).

Guess what? It did it again. Once again I was lucky and managed to stop the boat in time. Not easy at 21 tonnes.

Now the only theories I am left with are:

1 Maxprop sticking with blades fore/aft and the resistance (due to trying to 'paddle') being too great for the engine to rev up, once in gear.

2 Something sticking in the injection pump

A very reliable source has told me that the first of these is the most likely. Anyone had any experience of this?

[Florida Mike]

Two things you might try, first check your single lever mechanism. The second thing you can do to eliminate whether it's the injector pump or something else is to rig a second way to throttle up the engine. Depending on if it is a push or pull type of system. It is a pull type back it off and put some kind of a small chain or flexible cable. If it is push it becomes a lot harder. Another thing you might try is to rig some sort of a string so that you can tell that the throttle lever on the side of the engine is actually moving when it malfunctions on your. I realize putting the string will be complicated to get it out and around where you can see it but that will eliminate mechanical failure of the throttle mechanism.

You should be able to tell by the sound of the engine if You’re Maxprop, is sticking with blades fore/aft. ( If the Maxprop is sticking in the engine should be laboring.) Just my thoughts, Mike.

[DeepFrz]

Yeah, I think the injection pump sticking is likely. There was just a thread about that a week or three ago. The person sent his pump out for service and the mechanic said it was pristine inside, no known cause for the sticking, but it was. (in his case the injection pumps themselves were sticking and he had to tap them back down in order to get the pump working again) The Ultra low Sulfur fuel doesn't have much lubrication qualities left in it so maybe an additive with lubrication properties might help?

[Florida Mike]

I used to cycle oil, in my case from Wally World. It seems to make my truck engine run quieter and is designed to burn. I try to run 1 ounce per gallon although many others are only running half ounce per gallon. Which brings up another thought one of the things that happens here when we use Byo - diesel, is it seems to clean the fuel system out. I wonder if you could use a 6 gallon fuel time fill it with biofuel and run it through the engine to clean the injector pump injector’s? Another two cents worth, Mike.