Need help diagnosing 4age problem.

[1337_86]

Can anyone please help me.

I've helped my friend put a s/h bluetop 16v in his ae82 due to his head gasket blowing and other problems with his old one. The motor has been imported from japan and he bought it from a place in shepparton. Everything went fine installing as it's not a very hard job.

The problem being the fuel pump loses power on cranking. It primes on ignition, then volts drop as soon as you crank(I tested the volts at the plug at the firewall). Without writing an essay these are the things I've tested
-E.C.U (swapped with test one)
-open circuit relay (swapped with test one)
-fuses and all plugs and connectors
-coil and igniter (though i can't see them being related to the problem)
-It has spark
-engine light diagnosis was okay

All the above are okay.I suspect maybe crank angle sensor in dissy, or maybe something to do with igintion switch. I'm gonna swap dissy's on the weekend. Also I haven't tested for injector pulse yet. Will do on weekend as well. Any help would be great.

[oldcorollas]

does it crank at normal speed? is there something else drawing more current than your battery can handle?
does it lose ALL power to the pump, or it just lowers the voltage? are you 100% sure the wiring is correct?

[oldeskewltoy]

Hmmmmmmmmm...... this sounds familiar to a common problem in the USA when people do 4AC to4AGE swaps....

Is this an AFM efi????

Since I've never actually had the problem, a bit more research on club4AG might have a few examples, but......from memory, the AFM is supposed to signal the fuel pump and doesn't...............

[The Last Streetfighter]

I'm sure JP has actually answered this before, but can't find nor explain it.

[1337_86]

Engine cranking is at normal speed and fuel pump volts go from12 to 0. I've gone over the wiring and plugs countless times (there's really not that much you can stuff up).

It runs a MAP sensor not AFM.

[oldcorollas]

so what you are saying is that the ECU stops providing power to the fuel pump relay, even tho the ECU still functions and provides spark and clicks the injectors when cranking?

[Pure_In_Sanity]

I didnt think AE82's primed on ignition?? I thought they run only when cranking, & once the ecu sees an rpm signal.
Sure the wiring is correct?

[BlitzRacing]

could potentially hard wire fuel pump to test?

[The Witzl]

Check the FC output from the ECU to the circuit opening relay. It should go to earth once the engine starts running.

Also, check that your EFI main relay is functioning correctly.

[1337_86]

oldcorollas - yeah basically. Though I havn't had a chance to check for injector pulse yet. Will do tomorrow.

PureInsanity - That could be right. it runs for a few seconds upon cranking ( which I thought was due to line pressure from priming). Could it just be the cold start injector?

The Witzl - Have checked FC pin on ECU and was okay. EFI main relay seems okay but I might swap with another one to be sure.

Cheers for the ideas so far everyone.

[sbyder]

could potentially hard wire fuel pump to test?

i agree. Hard wire it up with a relay and fuse and see what happens.