Fuel Pump Fuse

[m1kux]

Hi all,

after some advice on the above issue.

Car is a 1.8 Zetec (silvertop) on Jenveys.

Change up to second gear and accelerate (very) hard, the fuel pump fuse blows and of course the car dies.

I can drive the car smoothly and it runs fine. I can have it sitting on the driveway, nail the throttle as hard as I like and it is fine. It is only when under duress after changing up to 2nd that the fuse blows.

Replace the fuse and the car starts.

I have changed the fuel filter and the fuel pump relay. Have had a good look for any loose / broken / frayed connections but nothing obvious.

Before I go and throw £150 at a fuel pump, any other ideas?  Or is it definately the pump?

Cheers

[Martin Keene]

As I understand it a fuel pump runs at a constant rate, i.e. it flows a certain amount of fuel, within reason, regardless of load.

So if the fuel pump fuse blows under load, the only thing I can think of is the slightly reduced back pressure in the fuel line is causing the pump to run harder and drawing more current.

What size fuse is it at the minute? I'd be tempted to put a slightly larger fuse in for one second gear blast and see what happens. This would only be if I was happy with condition, size, etc of the wiring.

[m1kux]

Original fuse was 20A. That was first to blow. Only replacement I had at the time was a 25A which also blew. Westfield recommend a 10A in the manual I have so suspect if a 25A will blow then going higher could be dangerous?

Running a 10A at the moment - perhaps I should put a 20A back in as original and give it a go.....

[m1kux]

Forgot to mention I haven't tried anything higher than a 10A since changing the fuel filter

[m1kux]

Forgot to mention I haven't tried anything higher than a 10A since changing the fuel filter

Have now. 20A also blows.

[SparkyB]

I wouldn't go any higher on the fuse (even 20A sounds a bit extreme), your close to the max rating of the cabling and if you exceed that then the cable will burn rather than the fuse....which is bad!  A 20A fuse will not blow instantly at currents fractionally above 20A, so if the fuse blows as soon as you accelarate hard it implies an extremely high current spike.

You say you are running Jenveys, in which case are you running a low pressure pump -> swirl pot -> high pressure pump or using just a high pressure pump?  

My gut is telling me that you have chafed a supply wire somewhere and under accelaration it is shorting.  Try bouncing the back end of the car a bit when stationary with the pump running and see if it cuts out.  Does it cut out under hard acceleration in 1st or 3rd?

[m1kux]

I wouldn't go any higher on the fuse (even 20A sounds a bit extreme), your close to the max rating of the cabling and if you exceed that then the cable will burn rather than the fuse....which is bad!  A 20A fuse will not blow instantly at currents fractionally above 20A, so if the fuse blows as soon as you accelarate hard it implies an extremely high current spike.

You say you are running Jenveys, in which case are you running a low pressure pump -> swirl pot -> high pressure pump or using just a high pressure pump?  

My gut is telling me that you have chafed a supply wire somewhere and under accelaration it is shorting.  Try bouncing the back end of the car a bit when stationary with the pump running and see if it cuts out.  Does it cut out under hard acceleration in 1st or 3rd?

10A already inserted, 20A was a test.

Just high pressure pump (didn't build the car but can only see single pump > fuel filter.

Gave it a really good bounce at back end of car but idled fine.

Doesn't cut out in first - haven't got up to 3rd under hard accelaration. If I am progressive with the throttle as opposed to lead footed, I can get full rpm in 1st, 2nd & 3rd.

[SparkyB]

Bit of a mad thought....probably nothing...

Had a similar issue with an industrial pump once, turned out the pipe supplying the pump was collapsing blocking the fluid supply and tripping the motors breaker. It was down to the breather on the supply tank being restricted and the pipe was the most flexible thing to deform under low pressure.

Check the pipe between the tank and the pump for any cracks and check the tank breather, if thats blocked it might explain things.

[m1kux]

Hose is braided so no cracks and little chance of it deforming as slightly stiffer than standard piping, its a straight line feed into the pump as well.

[Martin Keene]

Jesus.

H.

Christ.

DO NOT replace the fuse with anything higher. My HP fuel pump runs on a 10a fuse so something is really wrong.

When you say the supply pipe to the pump is braided, is it proper braided stainless with crimped fittings like the brake pipes or does it use normal jubilee clips?

If it uses normal jubilee cllips then it is not braided hose, it is a stainless overbraid to normal rubber fuel hose, which is bad nes because the rubber will still age and deterioate, but you can't inspect it because of the braid.

[m1kux]

Stainless overbraid

[Matt Seabrook]

Are you sure the fuel pump is the only thing on that circuit? A fuel pump will draw the larges current draw when you try to stall it ie trying to make max pressure. The current draw will not change a massive amount by nailing the throttle. And dont put a 20amp fues in a 10 amp circuit you could end up with a fire. Can you not borrow a fuel pump from another local member to test the pump?

[Major Stare]

Is the car spluttering or hesitant before blowing?

I think this is more pump/fuel than electrical problem!?

Id the fuel line on good condition before the pump?

Is the fuel filter before the pump upto standard? Not a cheap item? Blocked?

Do you have a return from the TB's to the tank?

[m1kux]

Yes have a mate with a Westfield similar setup to mine so will buy him a beer over the weekend  

[Major Stare]

Having read your previous posts else where on the forum....... i'd look at what i mentioned above !