No check engine = no fuel pump prime

[Sikes15]

Hey guys not sure if this is an issue with the ecu as i have had an auto elec look over the signal to tell the fuel pump to prime 

but my issue is when trying to start up if the check engine light doesn’t turn on the fuel pump will not prime

it just randomly started out of nowhere and the tuner said it sound like its an ecu fault but was just wondering if anyone else has come across this before, if my check engine turns on the car will start and drive normally. and its not consistent either it sometime will be fine when i put the key in to accessories the light may come on straight away but if i turn it off and on it may not turn back on, sometimes it may take 3-20 key turns into accessories for the light to come on for the fuel pump to prime.

[LeighY60]

Hi mate,

I am having similar issues to you. Mine is in an older vehicle that was EFI converted so no check engine light to reference. I’m not sure on the cause yet but I have a G4X Fury and have recently started having the same issues. I replaced fuel pump relay and pump itself and confirmed good wiring to the pump. When connected to the ECU on the laptop it shows Aux 1 - Fuel Pump Active when it primes. When it doesn’t it remains inactive… I can’t identify unique error codes when this occurs. Looks like I have to contact the shop that installed it for me. I’d be keen to hear if you find the issue. If I do I’ll post it up here.

Cheers,

Leigh

[LeighY60]

Tech support suggested a backfeed as a possible cause. They suggested disconnecting the battery and reconnecting, then if the pump primes every time after, the most likely cause would be a backfeed from an active 12v source with car off. Idea being that if ECU doesn’t power off properly, it doesn’t see the key on event. Today I went through and tested all ECU loom pin outs at both states, where pump had primed and not primed and found 12v at a number of pins but no difference in the values either way. With the key switched off there was no voltage at any pin. The fault also occurred with no prime straight after disconnecting then reconnecting the battery so perhaps this isn’t the issue after all. I have emailed tech support again.

I’ve emailed them again, will have to wait to see what other ideas they have.

[LeighY60]

Latest progress here, i’ve exhausted all testing suggested by the workshop that installed my ECU and by tech support. Have sent my ECU for testing. Hoping the testing shows an issue or I’m not sure what the problem can be.

[Sikes15]

Thanks for the updates hoping to get my car back soon to try an under go some testing on its as well i might start by swapping ecm relay and fuel pump relay even tho i highly doubt thats the issue and take it to my tuner as well to see i they can see anything i’m not seeing as well, ill update you if i find any results 

[LeighY60]

Some positive progress to report.

Link in Aus had to send the unit back to NZ. They identified an issue with the bootloader. They updated and tested it and it is now back in my car today. So far so good, primes the pump and starts every time!

Hope you get yours sorted.

[koracing]

I know my brother's Celica ST185 intermittently does this, but these Celicas are notorious for weak power to the factory ecu power pin (i.e. low voltage) due to possible corrosion in the factory fuse box and ignition switch.  We have the factory power wiring triggering a relay to the ecu so that when it does power up (like 90+% of the time) it gets accurate voltage compared with what the injectors and coil are seeing.  I would say it could be ecu related, but it's done it with two different ecus.