Isuzu 33 starting probs update.

[Frankieboy]

Right, as a follow up to the previous post, the basic symptons are:

Engine starts but when started it struggles to tick over (chugs quite a bit). I then turn the ignition from position I to 0 and then it picks up to normal and then I put the ignition back to I, and it is now running fine.

This leads me to believe that it is probably not a dirt / air in fuel problem.

The stop solenoid is seperately wired to a button which you press to switch the engine off, and this seems to work fine. The manual engine stop seems to work fine too.

What I cant work out is what is turning the ignition back to 0 then back to 1 actually doing (i.e. activating or deactivating that would be causeing the engine to struggle). I presume it turns off the alternator / battery supply but I'm not necessarily sure if that would have had any influence on engine tickover.

Any suggestions?

[Sir Nibble]

What if anything, happens if when the engine is "chugging a bit" you blip the throttle and then let it return to idle?

[Frankieboy]

What if anything, happens if when the engine is "chugging a bit" you blip the throttle and then let it return to idle?

 

Until the ignition is turned off then back on, nothing happens. If I increase the throttle before that, nothing happens. Once the ignition is switched off then back on, it seems to then run as per normal.

I ran the engine yesterday, and later in the day I started it again when it was still warm and it started as per normal, without having to do the ignition off then on thing.

This leads me to believe its something that only occurs when the engine is cold.

[Sir Nibble]

OK, a little thinking out loud. Alternator, yes it can be a HELL of a load. Now I am thinking of the alternator field fully energised and the engine struggling at full fuel below even correct idle speed lugging at this load. Honest, an alternator is a big load under the wrong conditions. Turn off ignition and alternator de energises, some do, some don't; for the sake of argument let's say yours does. Relieved of load the engine gains it's correct idling speed and smooths out. Re engaging the ignition and alternator you now have an engine running in a condition able to take the load better, you also have a less highly energised field due to the alternators higher speed. All theory, but when a fault has no obvious cause it's time to look at the obscure.

Slacken the belt right off and try again, if the engine goes to a sensible speed and the belt screams; there is your problem.

[Frankieboy]

OK, a little thinking out loud. Alternator, yes it can be a HELL of a load. Now I am thinking of the alternator field fully energised and the engine struggling at full fuel below even correct idle speed lugging at this load. Honest, an alternator is a big load under the wrong conditions. Turn off ignition and alternator de energises, some do, some don't; for the sake of argument let's say yours does. Relieved of load the engine gains it's correct idling speed and smooths out. Re engaging the ignition and alternator you now have an engine running in a condition able to take the load better, you also have a less highly energised field due to the alternators higher speed. All theory, but when a fault has no obvious cause it's time to look at the obscure.

Slacken the belt right off and try again, if the engine goes to a sensible speed and the belt screams; there is your problem.

 

 

Its nice to hear someone thinking along the same lines I was. Only question is, which alternator? I would intially try slackening the belts on the 110amp (leisure) alternator as Im not sure the leisure batteries are necessarily charging as much as they should (newish batteries so no prob there).

Engine starter battery seems to charge fine.

[Sir Nibble]

Its nice to hear someone thinking along the same lines I was. Only question is, which alternator? I would intially try slackening the belts on the 110amp (leisure) alternator as Im not sure the leisure batteries are necessarily charging as much as they should (newish batteries so no prob there).

Engine starter battery seems to charge fine.

Without actually seeing the job it's difficult to venture a definate opinion. I would try both, that way you can determine either it's not that (bugger! think again) or reduce the job to just which alternator and tighten one set of belts to find out. I would suspect the 110A domestic as most engine battery alternators are too small to have this sort of effect.

[nb Innisfree]

We have a large alternator for domestics and when we used to start up engine it would struggle at tickover so I always used some throttle beforehand. A while ago our alt stopped self exciting so I fitted a manual exciter button and an unexpected bonus is engine starting and going straight to tickover.

[Serendipity]

Alternator, yes it can be a HELL of a load. Now I am thinking of the alternator field fully energised and the engine struggling at full fuel below even correct idle speed lugging at this load.

 

As an aside, can an alternator energise and present a load whilst cranking?

[Sir Nibble]

As an aside, can an alternator energise and present a load whilst cranking?

Certainly. It is remarkable how much of a load too. Fully energising the field on the bench actually makes it tough to turn by hand.

[Pretty Funked Up]

with engine running on mine.....

 

Key position 0 = full charge going to starter battery.

Key position 1 = charge spread across starter and leisure batteries.

 

not sure if yours will be the same, but thats the difference in key positions on mine.

I'd hazard a guess its a loose connection in the wiring.

[blackrose]

Er, I'm not sure if I've read this correctly, or if anyones already mentioned it, but the ignition shoud never be switched off (back to the zero position) while the engine is running - at least not on my Izusu 55 - as it risks wrecking the alternator.

Edited January 22, 2010 by blackrose

[tony collins]

Er, I'm not sure if I've read this correctly, or if anyones already mentioned it, but the ignition shoud never be switched off (the zero position) while the engine is running (at least not on my Izusu 55), as it risks wrecking the alternator.

 

I second that!

 

Tony

[Pretty Funked Up]

it depends on your setup.

 

the safest thing to say is never go to position 0 with engine running

 

For me though and many others its ok as there is still a battery connected to alternator in position 0.

[Keeping Up]

Er, I'm not sure if I've read this correctly, or if anyones already mentioned it, but the ignition shoud never be switched off (back to the zero position) while the engine is running - at least not on my Izusu 55 - as it risks wrecking the alternator.

I don't believe that there is any risk of damaging your alternator in this way.

[nb Innisfree]

I don't believe that there is any risk of damaging your alternator in this way.

 

I have inadvertently turned off master switch or ignition several times with no ill effects.

 

Edited to add: We have Lister Petter but principle is the same, depends on alternator fitted I guess whether damage will be done.

Edited January 22, 2010 by nb Innisfree

[Keeping Up]

I have inadvertently turned off master switch or ignition several times with no ill effects.

 

Edited to add: We have Lister Petter but principle is the same, depends on alternator fitted I guess whether damage will be done.

Turning off the master switch could definitely cause damage if one switch serves both batteries. But turning off the ignition switch merely removes the external excitation from the field coils, which is not going to do any damage.

[Sir Nibble]

Most likely the only ignition supply to the alternator is either simply an enable signal intended to tell the regulator to switch on, or a sense lead. Once upon a time loss of voltage at the sense lead would cause the regulator to say "how flat!?" and charge like crazy. More recently (last 30 years or so!) loss of this sensing input either drives the regulator to a default voltage referenced at B+, or more simply shuts it down.

[ditchcrawler]

I don't believe that there is any risk of damaging your alternator in this way.

I agree with that,all it does is take the supply off the field. the output is still connected to the batteries.

I don't have any connection at all to my domestic alternator, so its like the switch being turned off all the time.

[Guest]

OK, a little thinking out loud. Alternator, yes it can be a HELL of a load. Now I am thinking of the alternator field fully energised and the engine struggling at full fuel below even correct idle speed lugging at this load. Honest, an alternator is a big load under the wrong conditions. Turn off ignition and alternator de energises, some do, some don't; for the sake of argument let's say yours does. Relieved of load the engine gains it's correct idling speed and smooths out. Re engaging the ignition and alternator you now have an engine running in a condition able to take the load better, you also have a less highly energised field due to the alternators higher speed. All theory, but when a fault has no obvious cause it's time to look at the obscure.

Slacken the belt right off and try again, if the engine goes to a sensible speed and the belt screams; there is your problem.

I have had a similar experience. My split relay has a 10 second delay (various people scoffed the idea on here) which allows the engine to settle down and run evenly by the time the alternator connects to the domestic bank. It works a treat.

 

Edited cos I can't tipe or spell proper.

Edited January 24, 2010 by Guest

[Frankieboy]

Right, heres the general outcome.

I was haphazard and did a few things together so can't say for certain what the problem was.

I drained the fuel pipes and filters and refed them (in case of any water/dirt).

I took out the injector piping and blew through it all to clear out any dirt.

I also removed temporarily the aux alternator.

Engine started and seems to be running fine.

I have since put the alternator back on and the engine still seems to be running fine touch wood.

Overall hypoithesis: dirt / water in fuel system or alternator was being moody.

Thanks to everyone for their help, its nice to have it back up and running.

Thanks again

Frank