Humbug
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| posted on 5/6/10 at 11:07 AM |
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Fuel pump / blown fuse part 2
Following on from
my earlier thread, I have now checked out the wiring and can't find any
shorting, etc. I've also done the following:
1. Put a new fuse in (20A instead of the original 15A which has lasted 5 years) and idled it for about 5 mins. During that time I revved it up to the
limiter (7000) with the throttle in the engine bay, which presumably should put the fuel pump under full load? Absolutely no problem.
2. Put it into gear and started to reverse off the drive - fuse blew
3. Put in a 30A fuse (ran out of 20A) and idled it for a bit more. Put it into gear and drove round the local road for about 250 metres. No
stalling/fuse blowing or any other problem.
btw, on idle the fuel pump noise seems to be back to normal, but I notice what appears to be vacuum buildup (or pressure) as I get a hiss and a strong
smell of petrol when undoing the filler cap. I don't remember noticing it before (but I haven't been particularly trying to find a
problem before, either...). I have no breather, btw, though this hasn't been a problem for 5 years to date.
Now I have a bit of a dilemma:
- do I assume that it's now OK (but why would it suddenly need a 30A fuse, and what extra load is it putting on things without blowing?)
- do I assume it's the fuel pump and replace it (but it is a bit expensive if it is NOT the pump
- is there some way I can test the pump by removing it from the car?
- or something else???
Ideas, chaps?
TIA
Simon
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GeoffT
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| posted on 5/6/10 at 12:52 PM |
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Hi Simon,
Is the fuel pump the only item that runs off this fuse - maybe it's worth seeing if anything else isn't working when the fuse is
blown (or out), if so then these circuits become suspects too.
If it's just the pump then my guess would be that you have some shorted windings in the pump coils (maybe intermittently) and it's drawing
excessive current.
You could prove it fairly easily by putting a temporary line fuse close to the pump - if it blows it must be the pump or the wiring beyond the fuse at
fault.
Edited to add: The hiss from the tank may just be a bit of pressure caused by the warmer weather but if it's vacuum then this could be causing
the pump to work much harder, and may well be a factor. Either way you need to get some sort of breather on the tank......
[Edited on 5/6/10 by GeoffT]
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Humbug
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| posted on 5/6/10 at 03:00 PM |
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Thanks Geoff. Some other stuff doesn't work, e.g. speedo, but nothing that (I think) would draw much current.
Putting a temp inline fuse sounds like a good idea to test it.
Re breather - any ideas how I could do it without having to take the tank out of the car? Could I put a "nut with a hole" (technical term)
just under the filler cap with a tube venting to the outside? If so, are there any easy to fit scew in fittings available and what are they called? -
then I could just take the fuel cap bit off, drill into it for the breather then refit.
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norfolkluego
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| posted on 5/6/10 at 03:08 PM |
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Agree with Geoff about other stuff may be causing the problem due to a shared feed (my pump shares a fuse with the indicators). You could try rigging
up a temporary switched live feed (with in-line fuse) and taking it for a drive see if it sheds any light. The other thing about the pressure/vacuum,
my Facet would blow a fuse if you ran out of juice (presumably to protect it from running when there's nothing going through) a big enough
vacuum could possibly cause the same problem.
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GeoffT
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| posted on 5/6/10 at 04:49 PM |
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quote:
Re breather - any ideas how I could do it without having to take the tank out of the car? Could I put a "nut with a hole" (technical term)
just under the filler cap with a tube venting to the outside? If so, are there any easy to fit scew in fittings available and what are they called? -
then I could just take the fuel cap bit off, drill into it for the breather then refit.
I think Conrod found some tank connectors where you could simply drill a hole and fit them from the outside. Maybe one of these somewhere near the top
with a hose looped up high then down to the bottom would do the trick? Worth a u2u maybe.
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l0rd
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| posted on 5/6/10 at 05:51 PM |
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Can i please make a stupid comment?
Please remove the 30Amp fuse and do not do it again. Try to find the problem but no by increasing the fuse size.
You are begging for a melted wire and a car on fire.
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02GF74
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| posted on 5/6/10 at 06:19 PM |
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quote:
Originally posted by Humbug
- is there some way I can test the pump by removing it from the car?
I would have thought disconnect pump oitlet and fitting hose ending in a bucket would cause the pump to work at its maximum rate?
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Humbug
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| posted on 5/6/10 at 09:20 PM |
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Thanks for the various suggestions
Geoff - will contact Conrod re breather fixing
l0rd - it was not my intention to run a higher rated fuse permanently; I was just trying to see what was going on
02GF74 - sounds possible, but it will just show whether the pump is pumping and then either blow a fuse or not?
norfolkluego - sounds like the best method so far to try to isolate the problem to the pump, or show that it is not the pump.
Off to the local spares shop for some more fuse tomorrow a.m. for me 
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Humbug
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| posted on 6/6/10 at 12:37 PM |
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So... went and got several more of the correct fuses this morning.
Put the back of the car on stands, checked connections to the fuel pump again - OK
Checked where loom goes under the rear bulkhead to see if the diff had crushed the wiring and caused a short - No.
Checked wiring loom by gear lever to check nothing was fouling and causing a short - No.
Checked wiring connections under the dash - one had come off a switch but the terminal was shrouded so possibly but unlikely to have been causing a
short. This was the only thing apart from the fuel breather question that I found out of the ordinary. I suppose it could just conceivably have
contacted a piece of metal and caused a short...
Started up the car on the stands and ran it for 5 mins or so, including revving it up and putting in 1st and 2nd gears - no problem
Took it off the stands and drove round the estate for a few hundred metres - no problem.
So now I am no further foward, though the problem seems to have sorted itself.
Next step, I think, will be to go out for a longer drive with SWMBO following in the tintop with a tow rope
[Edited on 06.06.2010 by Humbug]
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l0rd
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| posted on 6/6/10 at 06:42 PM |
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quote:
Originally posted by Humbug
Thanks for the various suggestions
l0rd - it was not my intention to run a higher rated fuse permanently; I was just trying to see what was going on
Yes, i know that it was a sort term solution.
I just said that for your own safety.
The wire could have lasted 1 min or even 10 minutes.
Not playing smart @rs3 or something. We have seen quite a few cars on fire.
I bite my tongue and knock my head on wood.
Better safe than sorry.
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Humbug
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| posted on 7/6/10 at 09:47 AM |
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quote:
Originally posted by l0rd
quote:
Originally posted by Humbug
Thanks for the various suggestions
l0rd - it was not my intention to run a higher rated fuse permanently; I was just trying to see what was going on
Yes, i know that it was a sort term solution.
I just said that for your own safety.
The wire could have lasted 1 min or even 10 minutes.
Not playing smart @rs3 or something. We have seen quite a few cars on fire.
I bite my tongue and knock my head on wood.
Better safe than sorry.
No worries - thanks for your concern
btw, is your username a thinly-disguised alias, and you are really a member of Lordi? 
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