monkie Posted November 4, 2016 Share Posted November 4, 2016 That's odd. It is such a simple circuit. So you have 12v at the switch then. Wire the switch up, then disconnect the brown/red feed wire from the glow plugs and get the volt meter on it. Maybe you need to wire up a new feed wire from the ignition switch? Quote Link to comment Share on other sites More sharing options...
sheathy Posted November 5, 2016 Author Share Posted November 5, 2016 Wire is fine, switch is fine. I'm confused. Quote Link to comment Share on other sites More sharing options...
Kevm Posted November 5, 2016 Share Posted November 5, 2016 just been out and checked mine (2.5na) with the meter positve clipped to the first plug (rearmost) and the negative to earth I have about 8.5v initially then it rapidly rises to 10v. If I disconnect the wire from the plug and repeat I have a healthy 12.5 volts. The resistance (through all the plugs in parallel) is about 5.0 on the 200ohm setting. If you have the 12.5 (ish) volts at the wire when you turn the switch to heat and you can measure a small resistance through the plugs then it should work. Quote Link to comment Share on other sites More sharing options...
Kevm Posted November 5, 2016 Share Posted November 5, 2016 Sheathy, While I had wires disconnected I thought I would do a full check of the plugs and found one loose - tightened now, thanks for making me check The resistance through individual plugs is about 1.2ohm which according to a quick google is good - yours should be the same. Also when the wire that feeds the power to the back plug is disconnected and floating in mid air the light will still illuminate when the key is turned, so the liight is just a dumb tee off the power lead and has no idea if the plugs are working or not. Quote Link to comment Share on other sites More sharing options...
monkie Posted November 5, 2016 Share Posted November 5, 2016 The problem has got to be further up then. Take off the yellow/black feed wire to each plug and carefully check it to make sure it is okay and the terminals are clean. Then take each plug out and give it a resistance check as above. I also think you can't beat visually checking to see if a glowplug glows hot at the tip within about 7 seconds when energised. Test each plug individually by connecting it to the brown/red feed wire and hold it against the cylinder head with a pair of pliars while someone turns the key to energise the plug. Just be careful not to accidentally earth the feed wire when it is live! If you need a new plug, renew the lot. I've always found Beru to be good. The ones you need are Beru GV602. Hope that gets is sorted for you. Quote Link to comment Share on other sites More sharing options...
Peaklander Posted November 5, 2016 Share Posted November 5, 2016 You shouldn't need to remove the plugs to check resistance. Disconnect the feed from the end and check resistance of each one, measured between the end that takes the connector and the earth of the cylinder head or block. If you do decide to take them out and put a live directly across them each as described, if they work, you will see as they glow very clearly and also remain hot for quite a while afterwards. Otherwise, with all wiring in place, clamp the red/positive of the voltmeter onto the connection at the first plug, clamp the black/negative to a good metal point on the engine and position the meter somewhere where you can watch it as you turn the key to "heat". That's when you should see ~12 volts if your connections are all sound. If it isn't, then there's a high resistance along the circuit. Quote Link to comment Share on other sites More sharing options...
sheathy Posted November 7, 2016 Author Share Posted November 7, 2016 OK, update. I checked the voltage in the way peak lander described but I have 24v at each glow plug... how is this possible? Quote Link to comment Share on other sites More sharing options...
Peaklander Posted November 7, 2016 Share Posted November 7, 2016 (edited) Yes a bit strange. Is it really 24v? What voltage do you measure directly across the battery? Edited November 7, 2016 by Peaklander Quote Link to comment Share on other sites More sharing options...
sheathy Posted November 7, 2016 Author Share Posted November 7, 2016 12v on the battery. How is that possible? Quote Link to comment Share on other sites More sharing options...
Peaklander Posted November 8, 2016 Share Posted November 8, 2016 I'm confused too ? (It's not 2.4 is it?). I don't suppose you have another battery anywhere on the vehicle do you? Quote Link to comment Share on other sites More sharing options...
monkie Posted November 8, 2016 Share Posted November 8, 2016 I've no idea how you have a reading of 24volts on the glow plugs. Have you taken them out for a visual check to see if they glow at the tips? I think that is the best way to check them. Quote Link to comment Share on other sites More sharing options...
sheathy Posted November 8, 2016 Author Share Posted November 8, 2016 Haven't done the visual check yet but will today. Only reason I haven't yet is that the Haynes says you need a new seal when you refit the plug and I don't have these. Is it really necessary? Also, probably a stupid question, but it couldn't have anything to do with it having the 24v circuit in previously? I removed the alternator and batteries for the 24v circuit so not sure how it could be effecting it but still. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted November 8, 2016 Share Posted November 8, 2016 A photo of the engine bay will help here massively, to identify positively whether you have a 24V system still How many batteries are installed on the truck now? I'm not 100% clear on the later radio trucks, did they run separate 12V/24V systems, or was the whole truck 24V like the old Lightweights? I re-read your first post, and it says '1995 2.5NA', which can only really be ex-military, as the rest of the world was on TDIs by then, so we need to establish what we are dealing with first, hence the picture If the truck is 24V, then only having 12V at the ignition switch points to earth problems, or supply problems, which shouldn't be too difficult to track down Quote Link to comment Share on other sites More sharing options...
monkie Posted November 8, 2016 Share Posted November 8, 2016 I think the seal the Haynes manual is refering to is something to do with a crank case ventilation pipe not the glow plugs them selves. Other than putting a bit of copper grease on them and tightening to the correct torque, there is nothing special about refitting the glow plugs as far as I am aware. I don't know much about the military 24v systems. I thought it was something to so with the raidos they had fitted and nothing to do with the engine electrics? I can't understand how you have 12v at the feed but 24v at a glow plug? Quote Link to comment Share on other sites More sharing options...
sheathy Posted November 8, 2016 Author Share Posted November 8, 2016 Apologies for the lack of clarity. It is indeed an ex mod ffr. It had both 12v and 24v systems but now only has 12v alternator and 12v battery. Has been working perfectly well as well which is worth mentioning- no changes in terms of battery of wiring were made immediately prior to the glowplugs not working. Haven't got a pic of the engine bay to hand but can get one later. Quote Link to comment Share on other sites More sharing options...
sheathy Posted November 8, 2016 Author Share Posted November 8, 2016 Further update. Just taken out and checked all 4 plugs, all work and heat up to red hot quickly. However when put back in to place and left to heat for 30secs+ they aren't even feeling slightly warm when I stick my finger in right on the nut. With regards to the voltage I tested the battery again and the voltmeter is saying 25 now so it must be down to a dodgy voltmeter (that's what you get for buying a 13euro one on amazon). I'm getting 23 from each plug when tested with the voltmeter so at least they are all consistent. No closer to working out what is going on though. Quote Link to comment Share on other sites More sharing options...
western Posted November 8, 2016 Share Posted November 8, 2016 you won't feel the heat when glowplug is working & fitted to the engine, as the heating section is buried in the cylinder head. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted November 8, 2016 Share Posted November 8, 2016 I'm still perplexed by the 25V reading, even the cheapest normally read OK, I tend to use the disposable £5 ones from el-cheapo-mart. Might be worth picking one up and double-checking? I assume you have it on the right range Quote Link to comment Share on other sites More sharing options...
monkie Posted November 8, 2016 Share Posted November 8, 2016 Having a recap of what we know at this point: When the plugs were working okay you activated them as we all think you do by just holding the ignition key while the light comes on to indicate pre-heating then you start the engine The warning lamp bulb is working if you put a 12v supply to it You have a 12v battery and 12v alternator fitted You get 12v supply straight from the positive terminal of the battery (via the starter motor) to the ignition switch You've replaced the switch and get 12v at the switch terminal were the feed to the glow plugs connect when the switch is held in the pre-heating postion When you connect the feed wire on the switch you get 12v on the other end of the feed wire when the switch is held in the pre-heat position One of those 6 points must not be correct or the plugs would work as far as I can understand. As I said in an earlier post the glowplug circuit on these engines is very simple. However I don't know if the military Land Rovers added in a relay from the ignition switch. I think it would be a good idea to use your multimeter in continuity mode to check that the glow plug feed wire from the switch goes straight to the glow plugs. Quote Link to comment Share on other sites More sharing options...
Kevm Posted November 8, 2016 Share Posted November 8, 2016 I think you need to do what Monkie says above, if you only have one battery how are you reading 24v? Can you go through that list and let us know what readings you get at steps 4,5 and 6? Quote Link to comment Share on other sites More sharing options...
sheathy Posted November 9, 2016 Author Share Posted November 9, 2016 OK. Either the voltmeter is wrong or I'm doing something wrong with it. It's reading 24/25 on the battery so baring that in mind in response to Monkies points: 1-correct 2-correct 3-correct 4-24v 5-23v 6-23v Today I was playing again, let the plugs heat for a minute or so tried to turn over- does turn over but wont start- before driving to Geneva from the UK it would would start instantly on the first turn after plugs were heated for 20 seconds. Maybe it's a deeper issue? Quote Link to comment Share on other sites More sharing options...
monkie Posted November 9, 2016 Share Posted November 9, 2016 Right it all seems to go wrong at point 4. I can't understand at all where that 24 volt reading is coming from given you apparently have x1 12v battery installed. Can you confirm the following: 1- You have just one battery 2- That battery gives you 12v across the terminals 3- You get 12v at the main terminal on the starter motor solenoid (from there it should go straight to the ignition switch via a thick brown wire) Quote Link to comment Share on other sites More sharing options...
Peaklander Posted November 9, 2016 Share Posted November 9, 2016 As above ^^^^ and perhaps you could post a pic of the voltmeter set-up and connected across the battery terminals. It's so hard to understand what's going on without seeing the evidence. Please don't take that the wrong way - there must be an explanation. Quote Link to comment Share on other sites More sharing options...
Kevm Posted November 9, 2016 Share Posted November 9, 2016 Sheathy, If you only have one battery then your meter must be doubling up the reading for some reason, still you do seem to have power going to your glowplugs which is good. When you crank it over do you get any smoke from the exhaust? You should not have to heat for a minute, 10sec should be plenty. Can you set your meter to read ohms, disconnect the glowplug wires and individually check the resistance on each plug - it should be about 1.2ohm. If you can confirm the glowplugs are all good then the problem is elsewhere. Quote Link to comment Share on other sites More sharing options...
sheathy Posted November 9, 2016 Author Share Posted November 9, 2016 Thanks for the replies Monkie, to clear up the confusion the voltmeter is obviously doubling up for some reason- no idea why but it's giving me 24v at the battery too. Peaklander- the voltmeter is set up as per the instructions but it's obviously doubling up the voltage somehow- no idea how. Can send a pic tomorrow but I don't think that's the issue. Kevm- Indeed, power is getting to the plugs, all of them, and it's pretty much the same voltage as I'm reading at the battery. Will test the resistance tomorrow but as I said all the plugs glowed red in 10 secs or so when removed and tested so they are all working. No smoke when turning over but white smoke when/if I can eventually get her to fire up- I assumed this was due to insufficient heating as when I first got the truck I didn't know about the glow plugs needing to be held on before start so I had trouble and lots of smoke when starting her in those days. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.