Is this battery or fuel pump...or what?

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tweedandbriar

tweedandbriar

Active Member
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Somerset
Hi, have a look, but more to the point 'listen' to this video for me. My 1999 110 struggles to start (you can hear the fuel pump in the background, does that sound right to you)?

Then I link to two batteries and she fires up almost first time. What do you think, duff battery, fuel pump on the way out?

Thanks...

 
From what I hear the engine is turning fast enough to start with just one batt.
It may be you have air leaking back into system and two batt just speeds up pump some to get rid of it.
 
I'd first check that there is 12V on the fuel pump, with just the 1 battery, then both.

I don't have a TD5 but it does strike me that the pump runs for some time, surely there is a non-return valve somewhere, or were you just holding the starter operation so we could hear the pump ?
 
If that's a battery "Volts" display then your battery is stuffed.
On cranking the volts dropped to 8.5.
Was assisted by the second battery, so it fired up quicker, and the pump ran better because the starter hadn't pulled the volts so low.
 
tottot said:
From what I hear the engine is turning fast enough to start with just one batt.
It may be you have air leaking back into system and two batt just speeds up pump some to get rid of it.
Click to expand...
miktdish said:
I'd first check that there is 12V on the fuel pump, with just the 1 battery, then both.

I don't have a TD5 but it does strike me that the pump runs for some time, surely there is a non-return valve somewhere, or were you just holding the starter operation so we could hear the pump ?
Click to expand...

@tottot - I had thought of that. Whats the best way to check for an air leak? I had recently replaced the non-return valve on the fuel filter housing

@miktdksh - fortunately I have a hatch already cut out to access the pump. If it's not getting 12v, what's the likely cause?
 
tweedandbriar said:
@miktdksh - fortunately I have a hatch already cut out to access the pump. If it's not getting 12v, what's the likely cause?
Click to expand...

Cables and connections.
Wires that are to small (so can't pass the current) and dirty connections.
A bad earth will also reduce the current available.

If you run a wire from the (#1) battery directly to the pump, does it still sound slow ?
 
miktdish said:
Cables and connections.
Wires that are to small (so can't pass the current) and dirty connections.
A bad earth will also reduce the current available.

If you run a wire from the (#1) battery directly to the pump, does it still sound slow ?
Click to expand...

Thanks, I had the pump out recently to check for blockages, it was fine. I also cleaned the connector, didn't check voltage though - will get on that. I assume if its receiving 12v but still underperforming, it needs replacing?
 
Air in system. I am not a Td5 driver but on my Tdi I have a section of clear pipe to check for bubbles where fuel arrives in engine bay installed when I had issues with fuel being drawn in the line from tank.
However as Td5 has in tank pump if it is air it will be getting in at any point [ connections ] to the engine allowing fuel to drain back to tank. Is yours with fuel filter by the back wheel?
Take it non return valve is on exit of fuel filter?
 
tottot said:
Air in system. I am not a Td5 driver but on my Tdi I have a section of clear pipe to check for bubbles where fuel arrives in engine bay installed when I had issues with fuel being drawn in the line from tank.
However as Td5 has in tank pump if it is air it will be getting in at any point [ connections ] to the engine allowing fuel to drain back to tank. Is yours with fuel filter by the back wheel?
Take it non return valve is on exit of fuel filter?
Click to expand...

There's no clear pipe on the Defender - at least not on mine! It was actually the Air Bleed Valve that I replaced, I have just ordered the Non-Return Valve too now - not sure how much of a difference that will make.

I saw that someone had put some cable ties on the fuel pump hoses and had a noticeable improvement in their drive. Not a permanent fix obviously, but I will give it a go along with other potential fixes.
 
...also, re' the non-return valve (with the rubber duck) - I am seeing varying opinions about whether this is required on later TD5's, I have ordered one anyway, but need to check exactly whether it fits to the rear or front of the filter housing. One video stated its categorically wrong to fit it at the rear (fuel tank side) and it needs to go at the rear fitting at the FRONT of the vehicle (engine side) - can someone confirm one way or another please?

Thanks!
 
The non-return valve is just that, it stops any fuel running back into the tank, through the pump/filter.
If the valve is faulty the fuel will fall backwards and if there is a small leak in the low pressure system the pump will need to refill itself, the filter and the fuel lines before the engine will get enough fuel to start .... the fuel pump stops when the pressure is high enough (there is a pressure switch) and all the air has been purged from the system.
The lower the pressure/the more air in the system the longer the pump runs for.

I would fit it at the front of the engine so that the pump. filter and low pressure fuel lines are always full of fuel.
In a ready to go state, so to speak.
 
miktdish said:
I would fit it at the front of the engine so that the pump. filter and low pressure fuel lines are always full of fuel.
In a ready to go state, so to speak.
Click to expand...

Ya see, thats contrary to this...???

Screenshot 2024-10-07 101000.png
 
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