Engine starting problem

Sea_Lark

Sea_Lark

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I fitted a new inboard diesel engine at the beginning of last season and all last season it was absolutely faultless. This season, whenever I start it from cold, the same problem occurs. The engine starts fine, but then after a few seconds the power drops and quite quickly the engine cuts out completely. I then restart it and the engine runs perfectly and will later restart normally so long as its still warm.

Not a big problem, but can anyone tell me what's wrong? It seems like fuel starvation or an air lock, but then why only on the first start from cold?
 
Sounds to me that you have air in the diesel supply line, which makes its way to the engine injector pump once the engine starts to run. Did you change the primary filter, or indeed a secondary one in the supply line? Did you purge the lines of air?
 
Once it has stopped, and you have re-started it, does it run every bit as well as it did when new....i.e. no smoke, full power, good revs?
 
No, not a battery power problem. The problem is there even when the battery is fully charged from shore power, if the engine is cold.
 
Yes to all, although maybe I haven't purged thoroughly. But then why only on the first start from cold. If there is air in the system surely it would cause a problem all the time?
 
Yes, it runs absolutely fine. There is white smoke initially on cold starting in cold weather, but that has always been the case and very soon clears.
 
[ QUOTE ]
Yes, it runs absolutely fine. There is white smoke initially on cold starting in cold weather, but that has always been the case and very soon clears.

[/ QUOTE ]The white smoke is unburnt fuel. Have you checked the glowplug, if fitted, or the procedure for cold start? Some engines have a pre-heat stage and others have a rich-start button. Are you following the instructions?
 
You are undoubtedly on the right track here. Its air in the fuel line. What is most likely is a small air leak somewhere in the system which lets air in when the engine is idle. a likely culprit is the filters. Replacing a filter with an old seal or not bedding the new one in properly can do this. The air is cleared on start up and then the engine runs OK. Leave it idle for a while and more air gets in. Check all seals and unions, but please if you have a CAV or Lucas prefilter DONT DO THE BOLT UP TOO TIGHT!!! What happens then is the body distorts and the seal wont seat properly. Only remedy then is throw it away........ /forums/images/graemlins/wink.gif
 
Totally agree with boatmike, mine is also a bitch to start after a couple of days, cranking for ever and it isn't pre-heater plugs either. One of these days I'll get around to bleeding it, somewhere I have a very small air leak, never found it, and usually get prompted to purge when the thing suddenly starts revving itself up indicating too much air in my rotary pump. If I don't then purge it eventually it revs up and dies somewhere embarrassing. I'm too lazy to purge it until it starts revving itself up, that's the sign on my Thorneycroft, and mine is a right cow to purge which is why I leave it untill the last possible minute.

Yours is almost certainly some air in the injector pump somewhere, you'll have to bleed it out and also look for the culprit joint that's letting it in. Best of luck, some air leaks are a bugger to find especially if very small like the one in mine!
 
With such a new engine (what make is it?) the first port of call is the manufacturer if you have done all the right things. Year old engines should not give starting problems.
 
As other have suggested it is likely a leak in the suction side of the pump. However I had a similar problem on mine where the fuel return line to the tank was blocked. The engine would start fine, but as the pressure built up in the return line the pump was unable to deliver full flow to the engine and the enegine would lack power then stop. Leave it for a few minutes and it would start again, then slow and stop.

Some fool had installed the fuel cut out in the return, not the feed line! Not me, I was the fool who knocked the cut off and blocked the return line. /forums/images/graemlins/blush.gif
 
Thanks all for your help. I was at a loss to think what could cause the problem only on first start, but the theory of a small air leak that only causes a problem over a long idle period does seem logical. Now comes the difficult part, finding it, but at least its only a minor annoyance at the moment, not a big problem.
 
Having said that it was an air problem, and I think now most agree, you can start with a shaving brush and a cup of fairy liquid, by checking all the pipework joints. By foaming the liquid and putting onto each joint, you can often see as the system sucks the air in, merely by movement of the bubbles. If that shows up nothing I would still go for the filters, and their respective sealing rings.
My Perkins 4108, would always start from cold, but if run for an hour or so, allowed to cool down, and then restart, would be very hard to start. Turned out to be a bad banjo connection which was leaking air... Good luck
 
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