In France - Bongo not starting

[eoptio]

Hi

thanks for the info. I agree ref the need to identify the cause of the problem. I have measured the resistance of each plug yesterday and it was around 2.0 Ohm each, but will check again today and let you know.

K

[briwy]

I'm not sure if this has been suggested or you have tried it but how about disconnecting the supply to the glow plug rail and temporarily getting some hefty wire with a 30A fuse and connecting to the battery and see what happens.

If the fuse blows then it must surely point to either a short on the glow plug rail or faulty glow plugs

This should eliminate the wiring as the culprit.

One other thought, could the relay be dodgy, dirty contacts etc so causing higher resistance in the wiring circuit and pulling higher current.

[dave_aber]

Higher resistance will draw a lower current.

I= V/R

If you are consistently drawing over 30A and popping the fusible link, you must have a path for that additional current to ground.

All your plugs are 2Ω, so they will draw 6A each, 24A in total. The only way that the fusible link can be asked to pass more than 24A is if the voltage is much higher, or the overall resistance is lower.

Presumably, the battery voltage is between 12v and 13.8v?

At the top end of this scale, you are still talking about 26.8A.

A breakdown in the insulation on the main cable to the rail, or a breakdown inside the relay (full of water?) or something similar would give you this.

With all 4 plugs in situ and connected, have you measured the resistance from the rail to ground? If it's less than 0.5Ω then you have some additional path to ground. Try the same thing with the relay disconnected. Try again with the plugs all out of circuit as well - there should be no path to ground at all.

It's just a case of breaking the circuit down into logical blocks and eliminating known good elemenrts until you find the bad bit.

[eoptio]

Hi

update: replaced the temp wire/fuse holder with 8AWG wire and a maxi fuse holder. Using a 30A maxi fuse, car starts 1st time, fuse does not blow. Using a 20A maxi fuse, this blows instantly on turning the ignition key. Could that therefore point towards a dodgy fusible link being the initial problem, ie wiring ok? Next problem is that the glow plug light now continiously flashes, back to a search on the forum....

K

[eoptio]

the flashing glow plug light was related to the leissure battery being removed for charging, once I put that back in the flashing stopped (I read ref the no 1 fuse being related to the flasing glow plug light, this circuit is on the leisure battery in our van).

Out of curiousity I made up a wire with a normal 30A blade fuse in it (using a new fuse holder rated to 30A max), as soon as I turned the ignition the normal blade fuse blew again. I am guessing therefore there is an initial surge of power the 30A Maxi fuses can deal with but the normal 30A blade fuse does not deal with.

In any case thanks for your help all, this forum is great!

thanks

K

[jaylee]

Fuse 1 ties together a lot of weird stuff.... It also deals with the memory settings circuit for the radio too!

[Trouble at t'Mill]

Eoptio, what is a 'Maxi' fuse? Is it a 'slow-blow' type?

There is every possibility that there's nothing at all wrong with your wiring other than a high-resistance connection at the 'fusable-link' near the battery. When a connector becomes corroded (or slightly loose), it makes a less-than-perfect connection with only part of it still making some electrical contact. This is what's referred to as a 'high-resistance' connection (it's not really a 'high' resistance as such, just higher than the original effective 'zero'!), but it's still having the original load trying to squeeze through the smaller contact area, and that's why it usually heats up.

Perhaps the heat damage you found on your 'fusable link' was down to a poor connection which caused a localised heating up? Rather than it being down to the fusable link itself heating up as it would had there been a fault further down the line. Did the heat damage look as tho' it was towards one end (either close to the battery connection or at the wire connector at the other end) or was the whole fusable link 'evenly' heat-damaged?

I'm not at all surprised that a standard 30A fuse pops instantly; the initial load from the glow plugs must be way over 30A, so that fuse just thinks it's doing its job and committing hara-kiri for the sake of your wiring .

It would be good to get a reading from a clamp-meter on this supply wire as the ignition is turned on from cold. I'd hope it would show a very high initial draw (I dunno - 50, 60 amps? Probably even more in very cold weather) followed by a rapid fall (within a couple of seconds?) to below 30A and further fall over 10 to 20 seconds down to, ooh, around 10 amps, where it should remain until the relay goes 'click' and it shuts it off completely. These are ball-park figures, of course, but that sort of behaviour would suggest to me that all is actually ok and all you'd need is a new fusbale link and clean connections.

Fingers crossed that's all it is

[eoptio]

Hi

a maxi fuse is a big blade fuse, approx twice the size of a normal blade fuse, see http://en.wikipedia.org/wiki/Fuse_%28automotive%29 for example, searching a bit more on the web it seems that maxi fuses or the cartridge style fuses are used now instead of fusinble links (see for example http://www.littelfuse.com/data/en/Techn ... 98-001.pdf and http://www.autoshop101.com/forms/hweb1.pdf for some more info), that's as far as my knowledge on it goes....

The initial 'damage' I had was in the connector of the fusible link with the wire to the glowplug relay. This connector had literally molten together. So it may be the problem was the connector itself, perhaps damaged gradually over time. I have now cut the connector out. It all seems to work ok albeit the fuse holder wiring (8AWG) and the fuse itself seem to get quite hot, the fuse however does not blow. I might have another look trow

K

[Trouble at t'Mill]

Basically a 'normal' fuse then, although the 'Maxi' fuse does have a longer blow time (ooh-er, missus).

According to your second link, a 40A Maxi will take nearly a second to blow when loaded with a whopping 200A! That probably explains why the 30A one manages ok with your glow plugs; it probably only has to deal with 60-odd amps for a couple of seconds before the current falls comfortably within its handling capability. At least at this time of year .

Mind you, it will be stressed every time you turn her on (matron!) so don't expect it to last very long. I wouldn't be surprised if it failed pretty rapidly - and repeatedly - come winter time, with the much lower temps, much higher surge currents, and longer 'overload' times.

I have to say, tho', that the symptoms you've described sounds as tho' it was all down to merely a bad joint (cough). But, of course, it's worth being certain.

Do you have plans to fit a proper 'fusable link' like the original, or just see how it goes? A poster above - who described his 'temporary' fix - seemed to get a good year out of a 30A fuse like yours.

[g8dhe]

This article from NGK covers the 701J (Self Regulating Metal) type, the Current and temperature are shown in graph format under the "Glow Plug Types"
this shows 17 Amps peak and 5 Amps after 5 seconds hence why the fusible link rather than a normal fuse is used, its a very slow blow type of fuse so can handle the peak current and yet still blow if the current exceeds about 20 Amps for any length of time.

Looking at the graphs, it looks like you've got 2 different lots of data mixed up there Geoff, the "SRM" type 701J plugs show 17 amps peak, dropping to 10 amps by 10 seconds with a low of @7.5 amps after 60 seconds, which puts 4 x glowplugs at 30 amps draw at their lowest Not sure how much I trust a graph that measures voltage in (A) though

Your right, looked at the Yellow line rather than the Red line for the SRM type! Comes from commenting when out in the Bongo, whilst Ed was cooking

[eoptio]

Hi

well the joy did not last long: tried to start this morning, fuse blew instantly. Once fuse replaced it started first time. Suggesting the intial surge on cold is way over 30A, lower after the first start.

Measured the whole circuit through again:

*glowplug resistance is between 1.7 and 1.8 Ohms each, with the rail disconnected
*the relay works ok, clicks and outputs 12V for 10-15secs after ignition on
*wired up a new cable connected directly to the battery (but fused with 30A) - fuse did not blow
*used the same cable connected to the relay (ie instead of the cable in the car to test if there is a problem in the current cable somewhere) - fuse did not blow
*tested for voltage drops between the relay and the glowplugs using both the replacement and orginal cable - no voltage drops as far as I can see in either (suggesting the orginal cable is not damaged?)
*checked the glow plug wiring again for damage - nothing found in the immediately accesible places

I guess one of the problems is that once it has started once, on repeated starts there is less strain on the system and the 30A fuse will not blow even though there may still be a problem somewhere.

At a bit of a loss now as what to do next (other than giving it to a garage which I was hoping to avoid), one solution is to replace the glowplugs as they may be on their way out, but that is quite costly if not certain that is the problem.

Any suggestions welcome....

K

[missfixit70]

Did you try as Dave suggested?

With all 4 plugs in situ and connected, have you measured the resistance from the rail to ground? If it's less than 0.5Ω then you have some additional path to ground. Try the same thing with the relay disconnected. Try again with the plugs all out of circuit as well - there should be no path to ground at all.

It's just a case of breaking the circuit down into logical blocks and eliminating known good elemenrts until you find the bad bit.

If you get the glowplugs from the link earlier in the thread, they were only just over £30 delivered for a set of 4 NGKs, not a massive amount.

[roofraisers]

Glad you made it back to the UK & sorry to still hear of your problems.

I've been outside & measured a glow plug on mine. Results are as follows:-
Outside ambient air temp 15*C
Glow plug resistance when cold 1 ohm
Heat glow plug for 5 secs (tip glowing red) resistance 48 ohms.(This value falls back to 1 ohm very quickly as the glow plug cools)

This shows that each glow plug is drawing between 12 Amps when at ambient air temperature & 0.25 Amps when hot.

I suggest that you fit a proper new fusible link.

If you can't get a Mazda one, you should be able to obtain one from a vehicle garage (Ford, VW ) that deals with diesels.The crucial part is that the fusible link is fitted to a four cylinder diesel engine. I'm sure if you speak to a "parts person", they'll know what you are talking about.

Have you actually removed the glow plugs from the engine & inspected them.?
If you haven't it may be worth doing just to rule out any problem.
To test the glow plugs once they are removed from the engine, you connect the positive pole (using fairly thick wire) to +12 volt & the screw/thread to battery earth. The glow plug tip should glow red after about 5 seconds, if they do this you can stop the test as the glow plug is working OK.
WARNING. The glow plug body will get hot during this test.

My NGK plugs have this & the number stamped onto the socket flats. This may help you identify what brand of glow plugs you have fitted.

Nigel

[eoptio]

Hi

thanks, yes tried that the readings I am getting:

*plugs connected, relay connected = approx 1.5ohms
*plugs connceted, relay disconnected = approx 1.5ohms
*plugs disconnected, relay connected = infinitive
*plugs disconnected, relay disconnecetd = infinitive

not sure what the interpretation of the above is, but as I understand it as long as the reading was above 0.5ohms it's ok?

K

[missfixit70]

Doing a search on "fusible and link" plenty of people seem to have used a 30amp fuse replacement ok, only time it's blown, seems to have been traced to an earth issue, eg
http://www.igmaynard.co.uk/bongo/forum/ ... sible+link
I reckon you've either got an intermittent earth in the wiring, or mebe one or more of the plugs somehow?