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Glow Plug current draw


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I have a suspicion that the glow plugs in my engine are not working so I will be trying to test them tomorrow. I will not be going too far with the testing as the engine is still under warranty, but I want to know there is an issue before calling the builder out.

 

The engine is a canaline 42 and the glow plugs are E6301-65512 type (cannot find that using google). My understanding is that they should be pulling a fair amperage when active (i.e. the glowplug light showing on the control panel), somewhere in the mid tens of amps, e.g. 40 ish. Is this correct?

 

I have had a quick look and cannot see an inline fuse on the circuit, the generic wiring diagrams I have seen don't show one either. Should there be one? If so I'll take a better look tomorrow as the weather will be a whole lot better than today.

 

Anything else I should be aware of to easily and quickly test? Like I say I don't want to remove them and test individually as the engine is still under warranty.

 

The reason I'm asking is the engine is getting harder to start, today it took three spins before firing and that was followed by a large cloud of white smoke which went after a few moments. Ran a bit rough initially too which I seem to recall is another indication the glow plugs may not be working.

 

I will also check the starter battery resting voltage tomorrow too, I know the starter battery alternator is working (or it was a week or two back) as I have checked that with a meter (only for voltage which was 14.6v).

 

TIA,

Paul.

 

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Just now, Tonka said:

Do the glowplugs work automatically or do you have to manually select them by turning the key the other way or something 

Manually select them by turning the key

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Just now, ditchcrawler said:

Measuring the starter battery voltage while some one turns the switch to heat should give an indication if they are working at all

Thanks Brian I will try that too.

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Maybe 40A is a bit on the high side, but a few 10s of amps anyway. There will be a fuse somewhere, maybe not one specifically for the glow plugs but for the entire engine electrical system. How long are you holding the key to glowplug? Read the manual but usually it is around 5 to 10 seconds. If you have held it for much longer, you may have burnt out the glow plugs. Or if much shorter, not long enough to heat.

All that said, our Beta 43 which is now about 10 years and 4000hrs old, starts in winter without the use of the glow plugs. It takes perhaps an extra second to fire (ie 2 seconds instead of 1) and there is a bit of smoke, but it still starts easily without glow plugs. Not sure about the Canaline but I would wonder if there wasn't a different problem affecting starting.

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I'd have thought each glow plug would draw about 10A. How many cylinders are there? Multiply this by 10A to get the total current a working set will draw. 

 

Then get yourself a DC clamp meter and measure the current to see. OR, disconnect the wires and use a DMM to measure the resistance of each glow plug, to see if any has gone open circuit. I'd expect a resistance in each of about 1 Ohm. 

 

Edit to add: 

I happen to have about my person a brand new glow plug for my Mercedes van (don't ask why!) I just measured the resistance and it is 0.9 Ohms. 

Edited by MtB
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8 hours ago, MtB said:

happen to have about my person a brand new glow plug for my Mercedes van (don't ask why!) I just measured the resistance and it is 0.9 Ohms. 

 

Yes, but it probably has a positive temperature coefficient so that would go up as it heated. I would expect four modern glow plugs to draw over 100 amps cold quickly dropping to around 50 amps but it varies a bit.

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1 hour ago, Tony Brooks said:

 

Yes, but it probably has a positive temperature coefficient so that would go up as it heated. I would expect four modern glow plugs to draw over 100 amps cold quickly dropping to around 50 amps but it varies a bit.

And with that current you should see the battery voltage dip a little bit

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More likely to be a wiring fault than all 4 plugs gone O/C.  From memory, 42A draw for all 4 after about one second.

The open uninsulated bus bar connecting them on a Beta 43 engine is very susceptible to getting shorted to the head by dropped nuts and bolts. The connections then burn off.

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7 minutes ago, Tracy D'arth said:

More likely to be a wiring fault than all 4 plugs gone O/C.  From memory, 42A draw for all 4 after about one second.

The open uninsulated bus bar connecting them on a Beta 43 engine is very susceptible to getting shorted to the head by dropped nuts and bolts. The connections then burn off.

 

Would there not be a fuse to protect the wiring, which might have blown had a dropped engine component shorted it? 

 

 

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A lot depends on the impedance ( resistance ) of the cables limiting the current till the weakest point goes flutt.

I had a battery bank in a telephone exchange go into melt down when a battery rack collapsed due to acid leakage that no one discovered. The lead posts on the batteries proved to be the weak link, they burnt off and left lead puddles on the quarry tiled floor. The wiring mostly survived. Bearing in mind that some of these banks used tons of batteries and rectifiers of around 1200A capacity and its surprising that the whole lot didn't set on fire.

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22 minutes ago, Tracy D'arth said:

Often, not, unfortunately.

The standard Beta 43 wiring harness has a 40A fuse in the supply from the battery, wiring is 2.5mm^2. The supply for the glow plugs comes directly from the ignition switch, there is no relay or anything. I would be fairly sure that the fuse would blow with a dead short across a 40A fuse and 2.5mm^2 wiring.

2 hours ago, Tony Brooks said:

 

Yes, but it probably has a positive temperature coefficient so that would go up as it heated. I would expect four modern glow plugs to draw over 100 amps cold quickly dropping to around 50 amps but it varies a bit.

As per above, the Beta 43 has a 40A fuse that takes all engine related current including the glow plugs  (except the actual starter motor). The glow plugs are supplied via 2.5mm^2 wiring. So I would doubt that the glow plugs would take 100A even for a short time.

Edited by nicknorman
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I had a similar experience with a new Canaline 38 a few years ago. The starting was fine when I got the boat in the summer but as it progressed into winter this poor starting became evident.

 

Reading up a bit (I believe searching on here) I found other reports of poor starting of Canaline 38 and 42s. The suggestion being of voltage drop depending on length of wiring between control panel and engine.

 

I approached Canaline directly and they sent an engineer out (Chris Jones from Stoke on Trent I think it was) who added a relay so that the glow plugs were supplied directly from the starter motor feed triggered by the feed from the ignition switch. He also checked the timing and adjusted it slightly. I had no problems following this in any weather.

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All useful info, ta.

 

I have a dc clamp meter (does ac too). Just checked voltage drop and there is none. Clamped onto various points onto +ve feed and saw a very small current appx 1.8A, when ignition in the ON position, when switching to glow plug, no change.

 

Tested voltage at the battery, 13.2v rested, tested voltage at the first glow plug terminal and it was 0. Traced the feed wire back and found a relay, a 12v 70A job. Getting o volts from the output from the relay when switched to glow plug position. Tested the input +ve and that was showing 12.8v when in the glow plug position.

 

I think this means the relay is shot, but happy to be corrected. If so I will swap it out.

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8 minutes ago, PCSB said:

All useful info, ta.

 

I have a dc clamp meter (does ac too). Just checked voltage drop and there is none. Clamped onto various points onto +ve feed and saw a very small current appx 1.8A, when ignition in the ON position, when switching to glow plug, no change.

 

Tested voltage at the battery, 13.2v rested, tested voltage at the first glow plug terminal and it was 0. Traced the feed wire back and found a relay, a 12v 70A job. Getting o volts from the output from the relay when switched to glow plug position. Tested the input +ve and that was showing 12.8v when in the glow plug position.

 

I think this means the relay is shot, but happy to be corrected. If so I will swap it out.

 

Probably, but if you link the relay power connections (30 & 87) it will bypass the contacts, in fact a a big spark as you make that connection will more or less tell you the relay is at fault.

  • Greenie 1
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39 minutes ago, Tony Brooks said:

 

Probably, but if you link the relay power connections (30 & 87) it will bypass the contacts, in fact a a big spark as you make that connection will more or less tell you the relay is at fault.

I've just put the meter on the brown feed (conn. 30) and it shows 13.1v. Also checked the earth on connection 86 and that is good. When switching to glow plug there is a very, very faint click and it should be a good thunk as it engages. Have spoken with the builder (it is still under warranty) and he agrees that the relay is shot. He has a spare in the office and is not too far away but we may get one locally. We are in Ellesmere at the moment so there are far worse places to be "stuck" - not that we really are but ... 

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86 is normally either the feed or the negative for the coil. 85 is the other one, so if you have 86 to negative you should find battery voltage on 85 when you energise the glow plugs.  30 is the positive feed for the contacts, and 87 the normally open other part of the contact circuit. I would still bridge 30 and  87 to prove the relay is faulty and not something else but not do mush more as it is still under warrantee.

 

Battery voltage on 30 is no proof it is not a wiring fault (excess resistance) unless the glow pugs are being powered. Golden rule - never take an off load voltage to be significant, they  too easily confuse.

 

If you decide to source one locally be wary although they may look the same many readily available relays are only rated at a round 10 amps and you need at leats a 40 amp one. Both Bizzard and myself would prefer to use a starter solenoid for that duty because of the current. but you can't go messing with a new installation.

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10 minutes ago, Tony Brooks said:

86 is normally either the feed or the negative for the coil. 85 is the other one, so if you have 86 to negative you should find battery voltage on 85 when you energise the glow plugs.  30 is the positive feed for the contacts, and 87 the normally open other part of the contact circuit. I would still bridge 30 and  87 to prove the relay is faulty and not something else but not do mush more as it is still under warrantee.

 

Battery voltage on 30 is no proof it is not a wiring fault (excess resistance) unless the glow pugs are being powered. Golden rule - never take an off load voltage to be significant, they  too easily confuse.

 

If you decide to source one locally be wary although they may look the same many readily available relays are only rated at a round 10 amps and you need at leats a 40 amp one. Both Bizzard and myself would prefer to use a starter solenoid for that duty because of the current. but you can't go messing with a new installation.

The engineer from the builders is sorting a replacement. They use a 70Amp relay. To be clear, I did switch to the glow plug position and there was no change in voltage. As it is still warranted I'll let the engineer deal with it now, but it is a very simple job to swap over.

 

 

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