Fuel Relays

[Purple Frog]

I think we may have had as many as 4 fuel relays fail on zetecs at Road Atlanta. When asking an engineer why that could be happening, one answer I got was that possibly the power supply line to the relay from the battery was too small of a guage for the needed power. Thus that line heats up from excessive resistance and the heat contributes to untimely relay failure.

Just one opinion, and OBTW I don't even own a zetec, but thought I'd throw that out so we can reduce the issue. I want to see everybody on the track, not under their canopies working on relays.

[SteveG]

What's the failure mode of the relay? Open coil, shorted coil, fused contacts, open contacts?

Steve

[Jesse Yorio]

i fried an alternator - any feedback as to how that can happen to one that's 2 races old is highly appreciated.

[Purple Frog]

Jesse,

I think Al Sr. fried one also.... VIR rain/mud damage?

...that's right you skipped that part...

[JByers]

I had an alternator fry after the rainy 2005 & 2007 VIR events.

[Jesse Yorio]

hmmm..... more reason not to race in the rain.

[KevinFirlein]

we lost an alt before the rain at VIR and this weekend at atlanta we had the internal regulator fail on one so that it charged at a full 18v.

The alt at VIR had a broken post inside havent checked the atlanta alt yet

[Bob Wright]

It was me with the relay, not Al Sr.-my car looked like a swamp after the VIR agricultural racing incident

What was interesting about it was the relay and pump showed voltage, but the pump couldn't pull any amperage to run properly- drove us nuts trying to find the problem. I suspect it was corroded internally.

[Purple Frog]

Bob, you had one of the relays, but Al suspects he has a fried alternator.

[Alan R Guibord]

I am unloading tomorrow and will test the alternator. I think it's toast as I had a low voltage lithg on the whole racte. OBTW I stalled in the false grid and could not get it started and started last. The battery was on a charger for 2 hours bbefore the race. somethings wring with the electrical on my car. SWill past the findings
Al sr

[Rick Kirchner]

Just a shot in the dark, but ensure that the relay is not mounted such that the primary direction of shock and vibration tries to bounce open the contacts. If so, the arcing will burn the contacts up and eventually fail the relay. The momentary opening of the circuit may not be noticable because the fuel line could have an accumulator effect and the momentum of the pump rotor could keep the fuel flowing thru the off periods.

sometimes you have to disassemble the relay and analyze it - the actuator may have considerable mass (thus making it susceptable to shock and vib actuation) but it may operate the contacts in a different plane.

Usually rotating the relay thru 90 degrees in one way or another will solve the problem if that's the culprit.

It's also a good idea to epoxy all windings and terminations.

[Mark H]

Just an idea from street cars. If using an OEM Ford fuel pump relay they are suspect at best on street beaters. Many F-150's towed in dead because of this problem. Second, what is the thinking behind a 18v alt? 14.5v is the norm from Detroit, the coil packs jump the voltage to a zillion volts anyhow so I don't buy the "hotter spark" line.
I think the Focus that used that engine employed a control module to fire the fuel pump, cooling fans ect. anyway, so that system was never ment to be run through an anolog relay to begin with?
Another thing to look at is how many Amps the pump is drawing?