bongo starting issue

[richrx]

Hi folks,

I'm having issues with my bongo 2.5 td not starting in the cold weather. I'm not very good electrically so i may have missed the obvious.

The glow plug relay was checked initially and was clicking on and off as normal with the ignition and the light is showing up on the dash as nomal. The under dash fuse tests good too.

So obvious choice is the glow plugs needing renewed,so i renewed the glow plugs with the same result, non starter.

I then checked the new and old plugs were working with a positive line to the top and negative line to the threads with all plugs glowing as they should.

Next was check voltage at the rail, the rails showing 11.5v. A test of the battery shows 12.6v

The wire with inline fuse shows 12.5v at the relay end so theres power going there too.

Of the 2 wires connecting to the glow plug in a block one shows 11.5v when the ignition clicks on, the reduces to 0 when the relay clicks off, the other wire shows 0.3v? ( I'm useless with electrics did i mention that?) .

I did buy a relay from Halfrauds but couldnt get it to fire with that. But the relay did operate with the same 12.5 v on live and 11.5v droping to 0 when the relay is off.

Finally if i connect a jump lead directly to the rail it won't fire. If i connect a negative to the engine at the same time it fires within 1/2 a turn of the key. If i try with just a negative connected and no positive then it wont fire.

Any ideas I'm stumped?


Thanks


Richard

[wonkanoby]

check the engines earth strap

[wonkanoby]

http://igmaynard.co.uk/bongo/forum/view ... ap#p667771

[richrx]

I will do, although the fact i still cant start the van when the negative is connected to the engine makes me think theres something else going on.

All other systems work ok.

Rich

[wonkanoby]

http://www.ebay.co.uk/itm/MAZDA-BONGO-2 ... aLg6A8kzew

if not done before worth doing,mine were worn down one side to depth of a fag paper

[richrx]

http://www.ebay.co.uk/itm/MAZDA-BONGO-2 ... aLg6A8kzew

if not done before worth doing,mine were worn down one side to depth of a fag paper

Starter works well, no issues with that.

Rich

[cmm303]

Next was check voltage at the rail, the rails showing 11.5v. A test of the battery shows 12.6v

11.5v sounds low but I have not had to measure voltage drops on glowplugs myself so somebody else may advise. in the meantime it could be useful to determine where the volt drop occurs by working back towards the battery terminal.

Of the 2 wires connecting to the glow plug in a block one shows 11.5v when the ignition clicks on, the reduces to 0 when the relay clicks off, the other wire shows 0.3v? ( I'm useless with electrics did i mention that?) .

what 2 wires are you looking at here?

Finally if i connect a jump lead directly to the rail it won't fire. If i connect a negative to the engine at the same time it fires within 1/2 a turn of the key. If i try with just a negative connected and no positive then it wont fire.

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?

[wonkanoby]

check to its not part of glow plug rail shorting some were,only recall one wire to rail on mine

[rita]

Hi Richard, the 11.5 Volt at the glow plug rail is Correct,glow plugs run at 11.5 Volts .

Are you using a Spare battery or the starter battery when you carry out this Operation?

"If i connect a negative to the engine at the same time it fires within 1/2 a turn of the key. If i try with just a negative connected and no positive then it wont fire."

[richrx]

Hi folks

Huge thanks for the ideas so far...

I'm going to double check my voltages tomorrow or tuesday when I'm not working. I think there are a few bugs....

I'm going to check the earths and trace the glow plug rail power back to check for splits as well as double check my relay readings (now I've had an explanation to the glow plug relays operation).

I'm convinced the answer is simple, but its the hours of tracing wires that i hate .


Rich

[richrx]

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

[richrx]

what 2 wires are you looking at here?

Thats the 2 connected wires, one is from the ignition i believe the other to the rail.


Rich

[windywatson]

Hi,
Your making the assumption that the fault is electrical. From your description of what you have replaced, the correct voltages measured & saying that the starter is working. But you have made no mention of fuel, are you sure that you are getting fuel to the cylinders?
If your plugs are getting correct voltage & you've tested them to see that they are glowing & you've measured the voltage between the engine block & plug connector then the circuit should be good as you are effectively checking back to ground by using the block as the negative during testing. Have you actually removed any of the fuel line at the injector to check that there is delivery of fuel?

Cheers

[rita]

Hi,
Your making the assumption that the fault is electrical. From your description of what you have replaced, the correct voltages measured & saying that the starter is working. But you have made no mention of fuel, are you sure that you are getting fuel to the cylinders?
If your plugs are getting correct voltage & you've tested them to see that they are glowing & you've measured the voltage between the engine block & plug connector then the circuit should be good as you are effectively checking back to ground by using the block as the negative during testing. Have you actually removed any of the fuel line at the injector to check that there is delivery of fuel?

Cheers

I thought that might be the case but,

"Of the 2 wires connecting to the glow plug in a block one shows 11.5v when the ignition clicks on, the reduces to 0 when the relay clicks off, the other wire shows 0.3v"



Finally if i connect a jump lead directly to the rail it won't fire. If i connect a negative to the engine at the same time it fires within 1/2 a turn of the key. If i try with just a negative connected and no positive then it wont fire.

[windywatson]

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.