Electrical confusion - 2.5 Diesel Bongo

[RChandler01]

Hi to all,

Our 2.5 Diesel Bongo has been amazingly reliable for the last 2 years of ownership, with minimal issues and 100% reliability. Currently it seems to be getting pay back by small and large (head-gasket failure) issues cropping up. Most of which have been straight forward to diagnose and then fix, mainly due to the shared experiences of this forum.

The new issue has got me foxed at the moment. Occasionally upon trying to start the van, the dashboard lights and all other electricals would go dead, I would pop the bonnet, wiggle the leads near the battery (no leisure battery fitted) and the lights would come back on and all was good. Never found anything wrong other than the positive lead connection wasn't tight (possible undone when the cylinder head was done), tightened this and then the latest issue started. The glow plug relay would click (the one with the plastic cover) unless engine revs were more than about 1500rpm, ie the engine speed was higher than tick over. The headlights would also dim too. I replaced the relay, however the symptoms remain. I purchased a simple digital voltmeter and it seems that the clicking starts as soon as the voltage dips under 14 volts.....

The van starts perfectly in the morning (ie from cold) however I swear it is running a bit rougher, however no smoke on start up that might suggest failed glowplug(s). There are no warning lights on the dash.

The alternator was replaced 2 years ago, the belts are new.

The battery seems to hold its charge overnight.

I am baffled. Some articles suggest looking at the earthing straps or maybe the alternator is starting to fail.

Look forward to your thoughts

[g8dhe]

So just what faults are you suffering at the moment ?
You mention that your dashboard lights would go out, but that you tightened the +ve battery terminal - did this fix that problem ?
The glowplug relay clicks unless your revving the engine -the relay is controlled by the ECU and will operate/release depending on engine temperature and engine speed, over the first few minutes until the engine is fully warmed up. So not sure you actually have a problem ?
The headlights would dim - when ?
The fact that the engine starts happily when cold would suggest that the battery is OK.
Rough running on a diesel is less likely to be an electrical problem as there is no requirement for the ignition/spark system as on a petrol.

[RChandler01]

Hi Geoff,

Thanks for your reply.

The 'fault' is that unless the engine is under load or kept at higher rpm when parked, the relay clicks more or less constantly. This happens even when the engine is up to temperature. When the relay clicks the lights also dim.

Yes tightening the + connection solved the lack of dashboard lights and no life at all issue.

Regards

Richard

[BongoBongo123]

Geoff is the man on the electricals and then some but does that not sound like the relay itself ? Is there anything you can do to the relay / get it out and clean its contacts/armature etc/drill a little hole and spray servisol switch cleaner in (leave it ona rad and avaporate that out) ? Or consider a replacement.

I may be wrong mind you, all I can think of.

[RChandler01]

Hi BB123,

Thanks for your reply. Hmmmmm it does point in that direction, so I purchased a 'tested' secondhand relay and fitted it. No better than the one before. I guess they could both be duff?

[BongoBongo123]

Crikey that turned up quick, teleported ?

[RChandler01]

Haha - Nope that was my first action to replace the 'old' relay. Put the new to me one in on Monday - didn't make a difference!

Also while on here - had to replace the drivers side window switch, found one in a scrapped Ford ranger, the components and switch all fit, just fitted it to the Bongo outer bit (plastic surround) cost the princely sum of ................ £2 #justsaying

[g8dhe]

If its clicking then that is the ECU commanding it to close or release, the relay is only doing what its told to do, have you checked the voltage on the busbar of the glowplugs, is the voltage going up/down in correspondence with the clicking? Have you actually checked that it is the glowplug relay that is clicking and not one of the others down that side ?
If it is the relay clicking and the busbar voltage is going up/down then it may be the temperature sensor that drives the ECU, that is the one on the drivers side mid-way along the engine, two wire connection, might be worth checking that the connector is ok?

[RChandler01]

Hi Geoff,

Thanks for your further thoughts. I can feel the relay clicking, its the one that has a PVC cover over it, I am sure this is the glow plug relay.

I will check the temp sensor lead you mentioned, as for testing voltage from the busbar thats outside of my expertise.

Thanks again

Richard

[g8dhe]

Its very simple to do if you have bought a meter already! SImply clip the -ve lead of the meter to chassis under the drivers seat anywhere convenient, and then put the +ve probe on the end of one of the Glowplugs , you should see a voltage a little less than the battery voltage at the time 12-14 volts when the Glowplug relay is operated, if the relay is clicking then you should see the voltage fall to zero and then back again on each operation of the relay. That will confirm that the relay is actually operating OK and that the clicking is from the right relay.

[RChandler01]

Hi Geoff,

Ah I understand, currently I only have a digital voltmeter that plugs into the cigar lighter orifice. I will get myself a proper voltmeter. Had a bit more of a poke about today, left the drivers seat up and started the engine. After it has gone through its normal starting procedure, slightly higher revs etc, I can see the idle control moving very slightly as if it is being informed to increase/decrease the revs, which I guess is the ECU doing its thing.....

I will have more of a look about tomorrow -check the earth leads and all other connections. Had a look at the ones you suggested (thanks) and they seemed fine.

Thanks

Richard