I have a diesel car with the Citroen/Peugeot DW8 engine that has become reluctant to start, especially on cold mornings. It runs OK once started.
My initial thought was duff glow plugs. However, if I cycle the ignition 5 or 6 times all 4 glowplugs are warm to the touch so they are all obviously heating OK.
I'd assumed that glow plugs would fail open circuit and thus not heat. Is there a failure mode of glow plugs that I'm not aware of where they heat but don't ignite the diesel? Do they get dirty/coked up?
(I haven't removed any of them yet as they are difficult to get to)
Checked it with a test lamp. Glow plugs are energised for ~ 30 seconds before cutting out. Glow plug lamp however, cuts out after 1.5 seconds.
However, start the engine and the glow plugs are also energised while the engine is running. I haven't checked if they cut out once the engine is up to operating temperature.
Is this a function to improve cold running or is it a fault?
that is correct, your figures are just as they should be.
First check is battery condition, as this is the weather that finishes off a battery, it might work in the warm, but cold and damp mean you need a really good battery in a diesel.
Next step: remove and energise each glow plug, any that don't glow in a second or two are U.S.
Assuming the above are right then next would be air leaks somewhere in the fuel system.
Some engines are quite critical on cold start advance, but that is hard to check.
After that ?? worn out engine, failed injectors, you name it.
I've got a late XUD9 in my 306, it runs the glowplugs at low revs for a while after startup, there's a switch activated by the lower reaches of throttle travel mounted on top of the injection pump. I suspect it's perfectly normal behaviour for yours too, probably something to do with emissions regulation.
I have a diesel Fiesta. About 100k miles ago I took it in to my local indy garage and moaned about the poor starting on a cold morning. The advice he gave me has served me well.
Turn the ignition key and the glow plug light will light up. The light will then go out after about 4 seconds. Wait until you here a tick from the HT circuit (about 12-15 secs) and then immediately turn the ignition key the remainder. I can only hear the tick if the demister and radio are off.
My Berlingo van had the same problem. (Possibly the same engine as yours) I bought a set of replacement glow plugs but discovered I'd got the wrong ones. While the van was in the garage I decided to change the oil & filter, and planned to swap the plugs the next day. That night was very frosty but the van rattled into life almost instantly, with the old plugs still in.
The old oil was so thick and sticky in the cold weather the starter motor couldn't spin the engine fast enough to start.
I think a lot of engines just mindlessly heat the glowplugs for about 30 seconds regardless of whether the engine's running or not.
Yeah. Get a multimeter (why doesn't everybody have one?!?! fiver from Maplins. In any sane world birth would consist of baby pops out, placenta pops out, then multimeter pops out). Check voltage between the glowplug busbar and the engine body while the plugs are energised. Should be 9-10Vish really. If the engine's turning over as it should then battery itself is probably fine.
Or if removing the plugs is a bastard, put the multimeter on the high-current range and plug settings, disconnect the busbar, and connect the meter between battery +ve and glowplug tip in turn. Each should register several amps and they should be more or less the same. Expect the current to drop off a bit as the plug heats up.
Be careful in measuring current like this 'cos if you get it wrong you'll blow the high-current-range fuse in the meter.
Is the DW8 not the engine code for the HDI engines?
If it is, glow plugs shouldn't make that much difference to cold starting as it's a direct injection engine. I'd still check the glow plugs by doing a current test on each glow plug, and also making sure the starter is spinning the engine as quick as it should. But on a DI common rail engine, there is a strong chance it's a sticky injector causing the poor starting.
Injection timing is critical when the engine gets cold and if it has changed because of a worn (stretched) belt then you could well experience these problems. Heat the plugs up two or three times before starting and then start as the glow plugs switch on, that'll give maximum glow plug heating time as the engine runs it's first few hundred revs. It is advisable to have the belts, injection and cam changed, especially if you haven't had this done for 20 or 30 thousand miles or 5 or 6 years.
True but as you crank the engine their charge is reduced.
If you double work them you have them at a real good glow and the reduced current to them under cranking the engine serves to reduce their heat to what they would be at, and less time is needed to reheat them to that temp again when your motor has started.
Just the same as if you'd left them on for the same period of time assuming the glowplug relay hasn't de-energised.
Agreed (marginally) although by design the glowplugs should be able to start combustion following heating, even during the period of reduced voltage during cranking. But this is irrelevant. The glowplugs get to the same heat (to all intents and purposes) just prior to cranking regardless of how many times you on-off the ignition key.
Just the same as if you'd left them on for the same period of time assuming the glowplug relay hasn't de-energised.
Unless the glowplug relay is de-energising stupidly early, all this on-off-the-glowplugs a few times is just a ritual people go through, it doesn't achieve any more than putting a bone through your nose and waving a few sacred herbs over the engine. Unless you are going to argue for the cleaning effect of cycling the glowplug relay contacts?!?!
OOO okay, the charge is flowing for longer. All those coulombs for a certain definitive time. Mr Ohm'll explainit I can't be arsed.
No, now you try to tell me you couldn't melt them if you fed them form the battery for an hour...
I never done it but I believe I could.
Cleaning effect?
The glow plugs heat for longer, more heat dissipates into the walls and the gases in the combustion chamber and other parts of the bores, there is more heat supplied therefore more heat exists when the ignition is fired.
Vim, wear a condom, it's a soporiphic, jsut an adjunct, it has no real effect. Like the heat if you rub your willy for longer doesn't make your willy warmer nor your belly go tickly.
Energy can neither be made nor destroyed.
There is a continuum.
When you rub your willy you lose calories in both the arm motion and in making your willy warm, aint that fantastic??
Q1=Q2=Q3 ignoring losses
m1v1^2/2=m2v2^2/2 ignoring losses.
As time goes by the fundamental things in life apply, and they apply time after time.
If a current of 3 amps flows for ten seconds we have a charge of 3x10=30 coulombs passed.
These coulombs of electrical charge make the heat. Nothing else does. Or does it?
A coulomb is, basically, a number of electrons.
Hence when you charge your battery with amperes, the amperes collect. Smae thing in the heater plug, the amperes pass nto the plug and charge the cylinder with the charge they recieve.
Question is, whena bullet is flying after it's charge fires it, is it amping before it hits the target?
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