Not as fired up as she used to be.

[Gleno]

Evening all,

Not been in the forum for a while, goes to show the veg burning 2.7 LWB Maverick has been running well!

However, I've recently been experiencing a need to turn it over for quite a while before it fires. Although the glow plugs checked out ok, from looking at the archive I'm having my doubts. They were changed as part of the Elsbet veg oil conversion back in 2007, so shouldn't be dead. Once running it seems ok, if maybe a little unwilling to pull a gear as well below 1500 rpm as it did (but that might be just me being paranoid).

Obviously with running veg oil I was initially worried that the injectors were getting blocked, but after some injector cleaner, there doesn't appear to be any change in the starting (and she's not overly smokey when given a boot). But I'm currently just on diesel to give it an easy time.

I've done a search and a couple of suspects are fuel shut-off solenoid and the TDC sensor - any ideas?

Many thanks,
Glenn

 

[makeitfit]

I run mine on neat bio diesel and dont think the glow plugs last as long, or the ones I bought were reet cheap :augie
Sounds like them to me, have you actually taken them out for a quick look?
Mine were ok as in power there, but they were only stumps in reallity:doh I can only hope there's more heat on rapeseed :augie:nenau

 

[rayf3262]

I'd agree with Makeitfit, glow plugs....
how did they "check out ok" ?
Have you checked there is voltage on the plugs during the pre-heat phase?
If so, pull the plugs and do a visual check, if that appears ok connect each one to a 12V battery and check it does actually glow!

 

[lacroupade]

I am not arguing the diagnosis for a moment but I'd be interested to understand how these fuels could cause the glowplugs to burn away.

Firstly lets remember that Makeitfits bio is a totally different home-brewed kettle of fish to veg oil. Given the skanky chemicals that are used in the process, and which are almost impossible to remove unless the manufacturer is a major petroleum company (and Pete's supplier isn't) I can understand some kind of chemical reaction going on, because I'm not aware that bio burns any hotter than diesel, so it can surely only be a chemical reaction of some sort in his case.....I mean apart from the first 5-10 minutes when they are heated, the glowplugs are just inert lumps of metal in the cylinder head.....

Its my belief that veg oil burns at a slightly lower temperature than diesel (but I could be wrong, there are some tables somewhere that I can't be arsed to look for....).

So the questions before the forum, given that this HAS to be either chemical or temperature related (if indeed Glenos plugs turn out to be worn away) are:

1. What are the relative burn temperatures of home-brew bio versus veg oil versus normal diesel.

2. What are the chemical reaction possibilities of the three fuels? (I suspect it has to be home-brew bio the worst culprit and diesel/veg oil lower down the scale and on a par with each other....).

 

[makeitfit]

Please sir , me sir, sir , sir..................
I may also have skewed the brew by adding my favourite stuff of the season :sly
LPG mmmmm POWER :naughty
Now that does make a bigger bang :augie
Analise that forum :lol

 

[rayf3262]

.I mean apart from the first 5-10 minutes when they are heated, the glowplugs are just inert lumps of metal in the cylinder head.....

Mine were/are all ceramic tipped.
When I pulled the originals out all but one of them had the ceramic tip completely missing! One of the four had about half of the ceramic tip left.
They were all non working too.
As far as I am aware this engine had only ever been run on regular diesel.

 

[Timbo_1975]

Glow plugs. Although perhaps all 4 are still working, they do loose their effectiveness as they age.

Does it start better if given acouple of cycles of glow-age?

 

[MudLifeCrisis]

Starter motor on the way out would have the same effect , might be worth checking


Brian

 

[lacroupade]

Mine were/are all ceramic tipped.
When I pulled the originals out all but one of them had the ceramic tip completely missing! One of the four had about half of the ceramic tip left.
They were all non working too.
As far as I am aware this engine had only ever been run on regular diesel.

Still find it odd how these work out.....my old automatic was up to around 210,000 miles last time I heard (with Extreme), left me with 180k miles and unless he did it afterwards, the plugs were never touched in all that time. Current truck has done 50k since purchased and again, unless they were done in that first 50k miles it already had on it (now at 100k) which I doubt very much, plugs were never touched.

All said I've done probably 350k miles in 5 trucks and never had plug problems, and thats with lots of veg oil use AND frequent additions of acetone....the only thing I can say with certainty is that every one of them has been soundly thrashed....?

Forgot to mention for the OPs benefit....as I'm sure he knows, when temperatures drop, starting with veg oil in, especially at high concentrations, is a VERY lumpy business......I usually keep the key in the ON position a few seconds after the glowplug light goes out before actually starting it, which helps a lot.

 

[4wheel]

Don't forget the Glow Plug relay behind the battery.Check the plugs out on a 12v battery or with a tester before you replace them.Could be the relay if the plugs are ok.

 

[rayf3262]

Still find it odd how these work out......

To be honest I knew my glow plugs where gone for a long while, but chose to nothing about it as with the ZD30 DI engine it has to be ~ -10C or below before starting without glow plugs is a little hit & miss.
I seem to recall Timbo saying that on some of the BMW's do not switch them on until below -7C!
But the 2.7 being indirect injection will rely much more heavily on glow plug pre-heating to get the fires burning.

 

[lacroupade]

To be honest I knew my glow plugs where gone for a long while, but chose to nothing about it as with the ZD30 DI engine it has to be ~ -10C or below before starting without glow plugs is a little hit & miss.
I seem to recall Timbo saying that on some of the BMW's do not switch them on until below -7C!
But the 2.7 being indirect injection will rely much more heavily on glow plug pre-heating to get the fires burning.

How does one start without glowplugs then? Or do you just mean ones that are acting up.....

 

[rayf3262]

How does one start without glowplugs then? Or do you just mean ones that are acting up.....

Yup, all four glow plugs were totally shot for sure, probably before I owned the vehicle!

A direct injection diesel will usually happily start without fuss or drama at anything broadly around 0 deg C or even lower, I only really started to notice a reluctance to start first time, at around -12~-15 deg C.
I believe the fuel is injected at some 3~4 times the pressure of and IDi engine, so that will have a significant heating effect on the fuel in itself, further aiding starting.

Typically, indirect injection will have the glow plugs in the pre-chamber while direct injection the glow plugs are in the combustion chamber.

 

[Gleno]

Thanks to all for the useful comments.

As I'm in darkest Devon at the moment I'll have to wait till I get home before doing too much in-depth investigation. However, doing a few cycles of the glow-plugs doesn't seem to make any difference (ie wait for light-out, switch off ignition and switch on again). Also, with a warm engine, when the light naturally goes out earlier, the same problem occurs. I find it helps to have some throttle whilst turning it over.

It's worth saying that (at the moment) the battery is turning it over well. It almost feels a bit like when (in my youth) I would flood the Mini and it needed to clear it's throat (so to speak) before firing.

I may take a punt at the glow plugs and see how we get on.

Thanks again for your time.:bow

Glenn

 

[BIGSEAN]

The last thing you should do on starting is give it any throttle.as you have stated yourselfit feels like its flooding,probably because it is

 

[leafy1]

To be honest I knew my glow plugs where gone for a long while, but chose to nothing about it as with the ZD30 DI engine it has to be ~ -10C or below before starting without glow plugs is a little hit & miss.
I seem to recall Timbo saying that on some of the BMW's do not switch them on until below -7C!
But the 2.7 being indirect injection will rely much more heavily on glow plug pre-heating to get the fires burning.

My Saab will need to get down to about 5c before the glowplugs work

 

[lacroupade]

My Saab will need to get down to about 5c before the glowplugs work

Stupid question, but how do you know....does the GP light not illuminate or something? Can't say I've ever seen the T2 light NOT come on but that isn't to say other vehicles don't work differently....:nenau

From digging it seems some vehicles do rely on a pre-combustion chamber (mentioned above) which I assume pre-heats the diesel or something?

 

[geoffdown]

Stupid question, but how do you know....does the GP light not illuminate or something? Can't say I've ever seen the T2 light NOT come on but that isn't to say other vehicles don't work differently....:nenau

From digging it seems some vehicles do rely on a pre-combustion chamber (mentioned above) which I assume pre-heats the diesel or something?

That's idi

 

[Timbo_1975]

My Saab will need to get down to about 5c before the glowplugs work

With direct injection common rail being the norm now, injection pressures are simply mind boggling (2200bar = 32,000psi !!) at full load for some systems.

At cranking they will generate at least 400 bar (5800psi) and injector nozzle holes are smaller than a single water molecule in some cases.

Thus droplet size is soooo ridiculously tiny that even with a 16:1 compression ratio there is enough heat created at cold start to make fire without needing glowplugs down to below freezing.

Such systems also use up to 5 injection events per cycle.

Remmeber a 2.7 has a 22:1 cr and needs a good preheat at sub-zero temps...

Another (un)interesting fact is that some engines with a particulate filter utilise the glow plugs *at operating temperature* to ignite the additional fuel when it is injected on the exhaust stroke during DPF regeneration.

 

[lacroupade]

With direct injection common rail being the norm now, injection pressures are simply mind boggling (2200bar = 32,000psi !!) at full load for some systems.

At cranking they will generate at least 400 bar (5800psi) and injector nozzle holes are smaller than a single water molecule in some cases.

Thus droplet size is soooo ridiculously tiny that even with a 16:1 compression ratio there is enough heat created at cold start to make fire without needing glowplugs down to below freezing.

Such systems also use up to 5 injection events per cycle.

Remmeber a 2.7 has a 22:1 cr and needs a good preheat at sub-zero temps...

Another (un)interesting fact is that some engines with a particulate filter utilise the glow plugs *at operating temperature* to ignite the additional fuel when it is injected on the exhaust stroke during DPF regeneration.

NO such thing as an uninteresting fact LOL:thumb2