Diesel pump blowing Fuse 9?

[styn29]

Hi
I am really struggling to find the problem in my 2.5TD diesel that keeps blowing the 15amp fuse on the far left of the middle row. I turn the engine on and it will run for roughly 30 seconds to a few minutes before the fuse blows. My diesel pump was leaking before but the leak has now stopped and I'm wondering if that is what is blowing the fuse? If I put my foot right down on the accelerator while it runs loads of black smoke comes out. I've tried to find the wiring diagrams for fuse nine to give to my mechanic but can't seem to find the right one. Any help from you people who know way more than my rather limited knowledge is so much appreciated
Thank you

[g8dhe]

What year is your van ? The pump is mechanically driven but does have some electrical feedback involved in the timing of operations internally. I've never seen any reports of it causing fusing problems. However year is important as the design of the pump has varied over the years.
You can find the mechanical diagrams here for the correct year under "around the engine (Diesel)" and then choosing fuel pump. https://www.lushprojects.com/bongopartsmk2/
The electrical diagrams are based on the old Flash software which current browsers don't support but a still working browser (I use it myself) is available from this link viewtopic.php?p=723668#p723668

[styn29]

Hi Geoff
Thank you so much for your reply. It's a P registration so I think it's 1996. I just cannot work out what is blowing the fuse. It blew about 3 months ago but seemed to be an old fuse so just put a new one in. I had no problems up until last weekend when it blew after about two hours into a journey on the motorway. It then continued to blow if I put a new fuse in. I'm lost 🫨 Thanks again mate

[g8dhe]

Yes just checked other than the fuel cut-off valve all the fuel pump bits are fed via the ECU supply which is also fed from that fuse but controlled by transistors in the ECU, normally transistors will fail faster than fuses can blow! Fuses protect wiring primarily and not what is fed by the wiring.
On most occasions (not all like glowplugs) when fuses blow its down to a fault on the wiring insulation itself, especially when intermittent! Which can make diagnoses a real pain.

[styn29]

Thanks again Geoff
Someone did suggest buying an ECU and fitting that but I just don't want to guess at it and keep throwing money away. Such a shame as I love this van but looks like after around 10 years of fun it's finally had it's day with me
Thanks again

[styn29]

Just a thought but is there any way of me testing the ECU board or looking at it myself to see any obvious signs of failure?
Thank you

[g8dhe]

No there really isn't anyway to check it out, I wouldn't expect to find a fault in it either, if fuses are blowing then a damaged wiring loom tends to be the first suspect, not faulty electronics.

[styn29]

Oh..that's a shame...sounds like a bit of a nightmare to find.. wouldn't even know where to start
Thanks a lot for your help mate

[styn29]

If it is a damaged wiring loom would anyone know why it doesn't blow the fuse straight away? I'd have thought it would blow as soon as I turned the ignition on but sometimes the engine will run for 30 seconds, other times a few minutes even though it makes no difference if I turn lights on, rev engine etc
Thank you

[g8dhe]

Vibration, heat many reasons why it may not short all the time. Normal method of tracking these problems down is list all the end points and connectors and then disconnecting/unplugging and testing at each point you can intercept the loom to test, this also leads you to look at the physical loom to see if you can find damage.

[styn29]

Hi Geoff
Thanks again for all your help. I've got an auto electrician booked in to come and have a look . I'm really hoping he can trace the problem. I'll let you know how it all goes
Thanks again mate.. really appreciate all your help