No power to glow plugs

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mastersdave2

New Member
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86
Location
Birmingham
back again folks, ive sorted some major problems on my 300tdi now going through the niggley stuff, its a bitch to start when cold, ive just wired up a very basic tester, 2 crocodile clips to a light bulb, connected one clip to negative terminal and the other to the nut on top of the glow plug, put the bulb in the windscreen, and turned the ignition on, and guess what ... nothing, (i have tested the lamp works and its fine), im presuming the main suspect is the glow plug relay, where is it located? and am i presuming correct?



it is also a pain in the ass when its warm as well, if i turn it off whilst its warm it wont restart, like it has a flat battery, i have thought all along it is the starter motor, as i have had 3 batteries in the last 14 months, any clues?
 
The relay is fitted to a bracket at the rear of the engine bay fuse box area, starting when hot could be an electrical problem (earth connections) can't help with the rest as I know nothing about diesels.
 
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ok, cheers buddy, i have located it, it clicks once for around 15 seconds when i turn the ignition on, i can also feel it, after 15 seconds it clicks again, so im assume it has power and the timer is working, , i have just found a wiring diagram on google, i have tested the earth on the relay and it is fine, tested the output on the relay and nothing, can someone just confirm that the relay is fooked?
 
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The earth and the signal to the relay are working but does it have a permanent live feed? if it does then the relay is dead but if there is no live feed then activating the relay won't supply a voltage to the plugs.
 
So u checked the output voltage in the 15 seconds from switching on and timing out, the click is only an indicating the relay coil is operating not that the contacts are closing fully.

So as stated check there is an input voltage, u have confirmed there is an operating voltage, if u find there is an input voltage but no output from the relay the indeed the relay is faulty. Note the starter-relay shares the same fuse as the glow-plug relay so if the starter is ok then no probs with fuse.
 
also do you mean, cold as in the engine hasn't been used or -10C temps?

it should still start alright without glows from cold(not temp one ;) )

classify 'bitch', 5 secs of crank, 10 secs, multiple attempts 10secs etc?
 
mastersdave2 said:
cold as in left for 18-20 hours over night, and can take upto 30 seconds of turn over before it will go, usually i do this in 3 x 10 sec blasts
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i'd do the simple things first.

check you have a decent earth. take a jump lead and stick one end on the neg post of the battery, the other to the engine block. try and start it from cold or hot. if it fixes it then it's a bad earth.

check battery/charging system works:

pull out your multimeter (if you haven't got one, then you *need* one) and make a note of the battery volts. Leave it connected and start cranking.

make a note of the voltage when it's cranking.

once started.. you guessed it, make a note of the volts.

post the readings on here ;)

after that, i'd look to see if your fuel is leaking back over night, so all your cranking is priming.

get going with that lot
 
a tdi should start ok with no glows, there is a fuse in the glow side of the relay too, not sure where it is on a disco, but on the fender its under the bonnet, a 60A maxifuse.

mines got no glows atm, and starts in 5 secs, she was awkward the other day and took 10.
 
ok guys, feel im making progress now, just connected a jump lead to the neg terminal and the other end to block as suggested, it hasnt been started for 35 hrs so is stone dead cold, and it started in less than 3 seconds with a half dead battery, so it seems to me as suggested that there is an earth problem, how do i sort that out?
 
replace the old earth lead or add another ,on a landy you need chassis ,body and engine/transmission all earthing together and to battery ,anywhere suitable on engine or transmission would do
 
mastersdave2 said:
ok guys, feel im making progress now, just connected a jump lead to the neg terminal and the other end to block as suggested, it hasnt been started for 35 hrs so is stone dead cold, and it started in less than 3 seconds with a half dead battery, so it seems to me as suggested that there is an earth problem, how do i sort that out?
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follow the neg wire from your battery to the chassis. undo the bolt, clean all the rust away, refit bolt or use new.

look for another earth strap from the engine to chassis, do the same. if it's not there then add a nice big one.

keep an eye on your battery/alt though..it sounds like something mightn't be right.
 
after cleaning away rust, would copper grease be advised?

james i will put an additional earth lead in once i have some cash,

would this explain it being hard to restart when hot or is that another issue?

thanks guys
 
mastersdave2 said:
after cleaning away rust, would copper grease be advised?

james i will put an additional earth lead in once i have some cash,

would this explain it being hard to restart when hot or is that another issue?

thanks guys
Click to expand...

yeah i'd grease it all up or grease thread and paint over it. anything to prevent rust.

btw you can pick up earth straps for 3/4 quid, just check the length.

resistance can increase with heat, so maybe. you'll just have to try it to see :)
 
spot on guys, bad earth was the cause of my starting issues, not sure whether or not it has solved my hot restart issues, only time will tell,

i also did some more investigations into the none functioning glow plug relay, i found that there was no permanent live feed, on further investigation i found that the brown/orange cable from the battery to the relay was broken,

i have since repaired this, i rigged up a simple light tester between neg on battery and positive on glow plugs, put bulb in windscreen where i could see it, when i switch on ignition the glow plug light comes on as does my diy tester, when the glow plug light goes out my make shift tester does not and continues to illuminate, therefore it is still sending power to glow plugs even after the glow plug timer has gone out, i dont think this is right, but can someone confirm this? or is this how it is supposed to be?
 
mastersdave2 said:
spot on guys, bad earth was the cause of my starting issues, not sure whether or not it has solved my hot restart issues, only time will tell,

i also did some more investigations into the none functioning glow plug relay, i found that there was no permanent live feed, on further investigation i found that the brown/orange cable from the battery to the relay was broken,

i have since repaired this, i rigged up a simple light tester between neg on battery and positive on glow plugs, put bulb in windscreen where i could see it, when i switch on ignition the glow plug light comes on as does my diy tester, when the glow plug light goes out my make shift tester does not and continues to illuminate, therefore it is still sending power to glow plugs even after the glow plug timer has gone out, i dont think this is right, but can someone confirm this? or is this how it is supposed to be?
Click to expand...

are the glow plugs supposed to be powered even after the glow plug light has gone out on dash?
 
trax said:
i'd do the simple things first.

check battery/charging system works:

pull out your multimeter (if you haven't got one, then you *need* one) and make a note of the battery volts. Leave it connected and start cranking.

make a note of the voltage when it's cranking.

once started.. you guessed it, make a note of the volts.

post the readings on here ;)
Click to expand...


ok so prestarting i had a battery voltage of 12.2v

on cranking i had between 8.9-9.4v

once started it crept upto 14.3v

Advice?
 
What advice do u need? battery voltage will drop under a load, and that's any battery but cranking voltage is anywhere between 9.5 to 11.0 normally, so your battery may have little time left, that is depending how accurate you meter is. My expensive and certified Fluke is +- 2% in some of the ranges.

Try adding 2% on your numbers and things are not to bad. :)
 
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discool said:
What advice do u need? battery voltage will drop under a load, and that's any battery but cranking voltage is anywhere between 9.5 to 11.0 normally, so your battery may have little time left, that is depending how accurate you meter is. My expensive and certified Fluke is +- 2% in some of the ranges.

Try adding 2% on your numbers and things are not to bad. :)
Click to expand...

advice because this is the 3rd brand new battery (all different makes) i have had in the past 16 months, this latest one i have only had on for 3 months, i was asked to post readings here which is what i have done, i have sorted out the bad earth i had, and put the battery on charge over night, it is still mega slow turning over just about starts, i have a reasonable good voltage meter, my thoughts all along have been the starter motor, do these figures point towards that?
 
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