Walbro Blowing Fuses

[dr phil]

Hi - what size fuse is everyone using with the 450lph e85 walbro pump?

I was on stock wiring for a few months (bad I know), R34 gt4 so no variable voltage, but then popped the standard 15A fuse.

Have just rewired with 8 gauge and a relay, ran for about 10 minutes, then blew a 30A fuse.

Any thoughts? Is the pump dead or do I need to go higher in the fuse rating?

[Dose Pipe Sutututu]

I think you've done something wrong.

I have a 25A fuse on my Walbro with basic 12ga wiring (as it's next to the battery) with a 40A relay and never has blown any fuses.

Not to mention at the track it runs 4.5bar of fuel pressure 80% of the time meaning it would draw approximately 17A for long durations.

Sounds like you've got a short somewhere... check inside your fuel tank to see if your chemical heat shrinks and/or crimps have come apart and shorting.

[dr phil]

Yes, ok thanks - it didn't sound right to me either.

Looking at the walbro specs I shouldn't be near 30A currently. Forgot to mention that both times it has broken on me, car was running for about 10-15 mins first, OK when cold.

So either have a problem in the tank, or pump is faulty.

[scotty nm35]

You relay is melting internally, seen it many times.

The coil on large relays needs over 12V to hold the contacts in hard, the car is only supplying 8 or 9 volts sometimes.

[Chris32R]

You relay is melting internally, seen it many times.

The coil on large relays needs over 12V to hold the contacts in hard, the car is only supplying 8 or 9 volts sometimes.

Hmmm so that's why my 40 Amp Narva really never ticked over with the ecu signal but the OEM one did

[GD51LA]

Mine did the same

Changed to a 20amp and never had a problem since

[scotty nm35]

20 amp seems a little small seeing they draw 25-30 but the smaller you go the less spring they have, which should fix the issue to some extent.

I posted a solid state relay circuit to feed 14v power to the relay coil recently, but I notice there are relays for sale with the solid state input incorporated into them these days, for this very reason.

[Dose Pipe Sutututu]

You relay is melting internally, seen it many times.

The coil on large relays needs over 12V to hold the contacts in hard, the car is only supplying 8 or 9 volts sometimes.

People usually use post OEM relay to trigger their relay setup (so relay on relay).. what you need to do is actually take the trigger off your OEM relay ECU to trigger your new relay setup.

I've done this on many cars and no issues. Alternatively a SSR is a better solution but they are pricey and often need heatsinks to work efficiently.

[dr phil]

So - the answer was bad insulation in the tank, wires shorting. Glad it didn't blow up!

Yeah I'm currently triggering relay from relay, will rewire that soon, and do the secret squirrel trick at the same time.

[Dose Pipe Sutututu]

ahhhhhhh I was right!

yeah the mixture is too rich to ignite