bongo starting issue

[cmm303]

your jump lead test suggests you may have both a supply and earthing problem. I'd sort the earth as suggested then work along the 12v supply path.


When measuring voltages, where are you putting the black probe for earth reference?

Thats what I'll do, makes sense.

If im close to a battery then i use the negative terminal, if im in the engine just the block...


Rich

Given that an earthed jump lead to the engine helped (I appreciate it was only 50% of the solution), any measurements with the negative probe on the engine could be unreliable until you know the engine is properly earthed. It can be worth running a dedicated earth wire from the battery to connect to the meter's black lead, especially when measuring voltages at high drain devices.

[cmm303]

From your last description, it does seem to be very much an electrical fault. Have you disconnected the earth strap for the engine, cleaned & reconnected? If when you supply both Pos & Neg from the battery via leads it works then your on the right track. This also proves that he battery is up to the job. However can't understand why if you get 11.5v at the glow plug and you connect the block direct to the neg on the battery that that wont get it fired up, as you should have all that you need to make the plug glow. I don't have a lot of experience with diesels, but if the glow plug has two leads I suspect one is the pos supply & the other is the neg. I assume that native may be supplied to ensure a good circuit so as not to rely on the ground of the metal block. Have you traced that second wire that you measure 0.3 v to see if its an earth? You can check this by using the resistance Ohms range on your meter. Could be that the plugs own earth is not good.

I'm wondering from another response if the two leads mentioned (11.5v and 0.3v) are at the relay. Some wire colours may help. But voltage measurements maybe unreliable as earth point may not be a good earth.
Glowplugs are self-earthing with single supply rail fed by Black/Blue chunky wire. http://www.g8dhe.net/bwm/bwmanualp.htm?1995/Page_30
Glowplug relay black wire picks up earth point 16, bottom right of this wiring page: http://www.g8dhe.net/bwm/bwmanualp.htm?1995/Page_31

[richrx]

Hi,

Just for clarity yes i removed the fuel lines after the pump and fuel is firing through ok.

I had a play with it again, the original relay is still clicking but its operation isnt consistant so maybe it does have a fault.

I'm getting no continuity between earth and chassis, so definetly a bad earth. But when i do connect 12v to the black wire on the relay ( red live, brown earth, purple ignition, black to glowplugs?) the voltage drops to .2 or .3. If i Jump 12v onto the plugs i get a reading of .2 or .3 on that same wire so I'm sure i have a short between the relay and bar)

Can anyone tell me where the thick black/blue wire to the relay comes from (100 amp main fuse? Or 60 amp ignition?) and where the black wire from the relay goes and how the power gets from the small black wire to the thicker wire, is there a resistor?

I appreciate all the help, but its tough to reply to individuals using my phone.

Rich

[richrx]

Also I'm no longer getting power to the glow plug bar, 0.3v is the most ive seen recently, if i connect 12v to the black relay wire I'm getting melting of wires, unless its connnected to the glow plug then just a .3v reading ( voltage drain due to a short or bad earths all round?)


Rich

[teenmal]

I think you need to have your vehicle looked at by an Auto Electrician before you do some Real Damage, if your Insurance Company get wind of this (excuse the pun) you will Not be covered in the event of a Fire.

[cmm303]

Hi,

Just for clarity yes i removed the fuel lines after the pump and fuel is firing through ok.

I had a play with it again, the original relay is still clicking but its operation isnt consistant so maybe it does have a fault.

I'm getting no continuity between earth and chassis, so definetly a bad earth. But when i do connect 12v to the black wire on the relay ( red live, brown earth, purple ignition, black to glowplugs?) the voltage drops to .2 or .3. If i Jump 12v onto the plugs i get a reading of .2 or .3 on that same wire so I'm sure i have a short between the relay and bar)

Can anyone tell me where the thick black/blue wire to the relay comes from (100 amp main fuse? Or 60 amp ignition?) and where the black wire from the relay goes and how the power gets from the small black wire to the thicker wire, is there a resistor?

I appreciate all the help, but its tough to reply to individuals using my phone.

Rich

Somebody (could have been g8dhe) fairly recently highlighted a place where some insulation abrades and breaks down, giving a short on the glowplug feed. Try some searches on here with criteria like insulation AND (break OR breakdown OR wear) AND glow