engine start

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searover2

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Hi, all wonder if anyone can throw light on this .... bmc thornycroft 1.5 runs great, starts ok, untill yesterday hard to start. Dont know why never been a problem before, although i noticed on start up engine ran roughf for a couple of mins, then ran great, could it possibly be injectors need reconditioning, as maybe not spraying rite, or am i on the wrong track, any diesel heads out htere who can steer me in rite direction thanks in advance........
 
Hi yes there are heater plugs, but tested them and they are ok, all glow well, no crank case compresion, so ive been told , now when starts it runs a little rough fer a few seconds then runs smooth. batteries are good and starter motor turns fast thats ok , only had problem for the first time yesterday,and the engine hasnt been started for a while though.
 
Dirty fuel perhaps? When was the last time you filled up / changed the filters? Might be an idea to stick a couple of new filters on and bleed...
 
Air in the fuel- the beginnings of a fuel leak somewhere close to the injection pump,
or it may be the first symptoms of wear in the first stage of the injection pump.
 
check the heater plugs for carbon build up on the head this can build up and if there is insuficient clearance you are tring to head the head rather than the air in the space it can be cleared using the correct size drill bit
 
During the time it's running rough, crack as many of the injectors as possible, to see if any of them make NO difference. That will highlight the fault area. The fact that it "recovers" could indicate some air in the pipework related to THAT injector, rather than a faulty injector.
Or maybe the injector pump needs an ovehaul (God forbid!).
Good luck.
 
Provided that you have not adjusted, maintained or otherwise interfered with the engine, you are looking for something that was working fine when last run but now isn't. This effectively rules out most of the things that deteriorate slowly over time, such as injector pump, injectors, compression, timing, etc.

The two things that influence starting the most are air and fuel. Air in the fuel will cause all sorts of starting and running problems, so check for that, i.e. gaskets on fuel filter suddenly leaking, hoses slipped, dirt blocking fuel pipes, etc. Condition of filter good? Look at air filter also. Cracking each injector fuel supply in turn is good advice - this identifies whether there is a problem with one cylinder.

You say you have checked glow plugs so I don't include them.

The other things that can happen if the engine has been standing for a while, especially if only run briefly each time over winter, is gumming of piston rings or maybe some carbon under valves. Best way to treat this is probably a flat-out run for an hour or so, then progressive power reduction.

Finally, in this weather, battery condition is important, especially if it hasn't been run for a while. 30 seconds of glow plug can knock the available cranking power well down on an already marginal battery, so make sure it is fully charged.
 
30 seconds? Seems likes a long time to me.

On previous boat with the same engine as OP, I think the manual said 20seconds when cold.

On current boat (different engine) I can get away with less than 10seconds, in fact yesterday I forgot altogether and she started after about 2 seconds of cranking.
 
If he's tried to start it a few times then he has almost certainly glow-plugged at least twice, maybe five, ten?? who knows? My Audi A4 glowplug light is on for about 7 seconds and my Ducato probably even less than that.
 
Had this problem on my 1.8 BMC 2 weeks ago. Found it to be one of the relays controlling the heater plugs not operating. Lucas SRB501 type. New one obtained from local motor factors for a few quid. Starts straight away now, well after 5s heating. Hope this helps.
 
Vyv
I suspect that the reason the thing is running rough for a few secs is that it is flipping cold at the mo, as you said, if it was running ok before then nothing should be wrong, my guess perhaps a solenoid not getting the juice to the plugs or could be a valve has been half open over the winter and got a bit pitted or a bit of carbon on the seat? happened on my vp2030
stu
 
Hi, thanks for replies. I have with your help found the problem, there are two plugs broken off 2 and 4 at the tip. lovely now as i type the head is is on its way off, so ill recondition the whole head while off,stem seals ,grind valves in decarban, etc. Now you expets is it worth having head skimmed as well or not ......?
 
Skim - Not in my opinion. If it's not broken don't fix it. You haven't been overheating and twisted it so leave it alone.
Do you mean heater plugs or injector tips that are broken?
Does the head really need to come off?
 
I seem to have it in mind from old cars that the way of checking whether a head needs skimemd is to lay it on a flat piece of glass and check whether its possible to get a feeler guage under any of the corners. But like other posters, I don't see any reason why the head would need skimmed.

I guess you're having to remove the head to get the broken remains of the heater plugs out the cylinders?

Chris
 
HI all, thanks for the interest, yes its the heater plugs that have broken tips i think that i read somewhere that you can drill out without taking the head off, but wouldnt like to do that ,im not an engineer.unless of course it is common to drill out if i can find someone local to do it .......regards
 
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