Focus 9 DME Relay w/Prime

[dtxscott]

Edit on 6-6-23: ***** Cliff's Notes Version: Non-start due to faulty Reference Sensor. The F9 relay was not the cause. *****


Anybody else having no-start conditions after installing one of these? I bought it for the pump prime and more reliable solid state electronics.

I've experienced two no-starts at home (luckily). The pump primed, the car cranked and no joy. I attributed the no-star to potentially having low battery voltage.
I charged the battery or used a jump-box and still no joy.

Both times I swapped in the stock relay it the car fired right up.

My suspicion is that the relay has an under voltage lockout (UVLO) function that prohibits it from operating under certain conditions.

Email to Joe went unanswered so I'm asking the group to see if anybody else had a similar experience.

[grb008]

No issues so far. Only about 3 months in using it. Do you have the ones with the lights to see what the relay is doing.

What was your battery voltage?

[dtxscott]

I opted for no lights.

Batt voltage was 11.8V when cranking.

The stock relay functioned under these conditions.

[proporsche]

your batt volts are very low

Ivan

[ahh911]

Originally Posted by dtxscott

Anybody else having no-start conditions after installing one of these? I bought it for the pump prime and more reliable solid state electronics.

Is there an option where the pump doesn't turn on for several seconds allowing for oil pressure to build before fuel pump is turned on?

Phil

[mysocal911]

Originally Posted by dtxscott

I opted for no lights.

Batt voltage was 11.8V when cranking.

The stock relay functioned under these conditions.

Just re-solder the OEM relay. It will be more reliable over time!
The DME ECM will start the engine with the battery voltage as low as 10 volts,
so any DME relay should be reliable at battery voltages at or below 10 volts.

[dkirk]

dtxscott - I have the Focus 9 relay with the LED option and fuel pump prime and have had no issues. I would say 11.8V when starter is cranking the engine shows that your battery is functioning correctly.

[pmax]

If it's UVLO, the pump priming function wasn't covered.

Agree with 11.8 at cranking being OK.

[cliyde]

Been using the Focus 9 (Prime) relay for 1Year+ and never had an issue. I think these may be prone to electrostatic discharge damage with the printed circuit boards. You might circle back with Focus 9 on a replacement or further advice.


Best of luck.

[proporsche]

Originally Posted by pmax

If it's UVLO, the pump priming function wasn't covered.

Agree with 11.8 at cranking being OK.

right..did not know he mented at the starter....
ivan

[jmh61]

Unfortunately I have had too many no start conditions... The stock DME was the culprit more than once. Since I bought a Force 9, no DME issues.

The first thing I'd check are the hall engine position sensors. Mine seem to go bad every 5 to 10 years. You can check them by measuring resistance, see the Bentley manual. When they start going bad they can be temperamental. Car won't start, then a few minutes later fires right up...

[Ironman88]

I've had mine for a little over a year.

Never an issue. Not once.

[GH85Carrera]

I have mine for a few years. Since they first came out. No lights on mine as it was not an option back then. I have driven many miles, and to multiple states, and from below freezing to 105+ degrees. Never an issue.

[mysocal911]

Originally Posted by jmh61

Unfortunately I have had too many no start conditions... The stock DME was the culprit more than once. Since I bought a Force 9, no DME issues.

The first thing I'd check are the hall engine position sensors. Mine seem to go bad every 5 to 10 years. You can check them by measuring resistance, see the Bentley manual. When they start going bad they can be temperamental. Car won't start, then a few minutes later fires right up...

Actually, the both reference and speed sensors on a 911 3.2 are variable reluctance sensors.

[grb008]

You can test the ref and speed sensor with an ohm meter. If they are out of spec you can get BMW ones. But before you throw parts you need to test everything one by one as per the Bentley manual.

[dtxscott]

Thanks guys. The speed and ref sensors check out.

I forgot to mention that, during crank, I get spark but no injector activity.

I may have a relay with a faulty internal voltage reference.

I think I will subscribe to Occam's razor (aka mysocal911's suggestion) and re-solder the original, 1988 OEM relay along with the "newer" one that is 6 years old. I'll run the newer one and keep the '88 version as a backup.

I'll tear down the original and run diagnostics to see where the injector pulses stop firing.

[GH85Carrera]

My last set of sensors I replaced tested out just fine in the car sitting in my garage. Once they got hot, they were as flaky as a drunk redhead chick doing meth.

I put in new BMW sensors, and all was well again.

[grb008]

Just in case remove the injector plug at the back of the engine bay on the firewall slightly off center on the driver side. Just make sure its still pretty clean and not corroded and push it back in.

[pmax]

Is the purpose of the pump prime function to fire up the engine "quicker" , fewer cranks ?

[jmh61]

pmax - There is a valve in the fuel system that maintains fuel pressure in the system when the engine shuts down. As the valves age they can leak, reducing rail pressure at start-up. The priming repressurizes the system.