Uneven running deisel engine

[Guest]

I have a 20HP Beta engine which starts first time from either battery one or two.

When I switch the isolator to 'both' after starting the engine runs unevenly for a short time then settles to a steady beat. Swiching back to one or two immediately smooths out the running.

Is this normal?

Any thoughts appreciated.

Norman

 

[Guest]

I'm guessing that switching to two batteries demands a higher load from your alternator, and thus from your engine. The same happens in older cars when you switch the airconditioning on. Sounds pretty normal to me, but as I said, it is a guess - other people probably have other views!

 

[Guest]

I think its a good guess

Particularly so if the poster is the same Norman as the string below asking about batteries losing charge.

As to the batteries the probability is that there is no major leakage. The be sure you could beg borrow or steal an ammeter and put that in circuit with everything switched off.

If ou do have an unauthorised leakage of current I wish you luck 'cos it can be a ***** to trace.

 

[Guest]

It rather depends by what the 'uneven running' you are reporting actually is.

Diesels do not need electricity to run, so the batteries can have no direct effect on the running of the engine. Varying alternator loads can cause a noticeable drop in engine speed at tickover, but will not cause irregular firing.

I would be looking for problems either in the stop solenoid on the injector pump, or to see if there is an electrically controlled cold start mechanism. An elctric cold start mech coming back on while running may well cause misfires, black smoke etc, while a voltage change may upset a faulty stop solenoid and cause it to flutter - you would probably notice an erratic clicking noise from it, if it was doing this, accompanied by an erratic misfire as it switches on and off. A faulty electric cold start plunger is more difficult to diagnose, and you may need help with that one (or try substituting it with one that is known to be good). First off, try disconnecting it while the engine is running, then reconnecting it, to see if you can reproduce the fault.

But no, it is not normal for a diesel to falter on battery changeover, and you do need to find out what is going on. Otherwise one day (and a certain law will ensure its the worst possible moment) you may HAVE to track it down to get going again!

 

[Guest]

I think he needs to clean his spark plugs (giggle)

 

[Guest]

You may laugh, but I once worked on a pleasure boat out of Saint Ives, that had a 44hp petrol/diesel Kelvin. It had to be started on petrol (poured into an open trough on top), and once slightly warmed up, changed over to diesel and the petrol side magneto!! earthed. Usually with a shock to the operator.

 

[Guest]

told ya so lol

*

 

[Guest]

Ah, but we are talking about a REAL engine here - not a geriatric museum piece that runs on creosote and cowpats, needing 25 minutes with a blow torch to start it!

 

[Guest]

Thanks to all for replies.

I think the extra load on the alternator sounds very likely as the engine runs sweetly otherwise and always starts first time.