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Forgot, was going to post this up for Mark T'subaru while he is away. He has done a mix and match with a few of his L Series and got CEL trouble - code 12 .

The condition he has is the fuel pump relay does not get power from the ECU re-phrase - does not power up at least on initial IGN ON

If I recall correctly CODE 12 throws for some no good reason and the flowchart test results in nothng but further anguish.

How is everyone elses memories on these?? Let's see if we can do some remote diagnostics for him before he gets back eh ?



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steptoe wrote:The condition he has is the fuel pump relay does not get power from the ECU

This is true and correct... the ECU does NOT supply power to the fuel pump, so if I'm reading this right, he is not getting power? which I hope is the case. The ECU should on the fuel pump circuit, switch to earth. There should be a wiring diagram here somewhere but the wiring I sent him should still have the fuel pump relay in place.

steptoe wrote:If I recall correctly CODE 12 throws for some no good reason and the flowchart test results in nothng but further anguish.

CODE 12 will come up if the starting circuit is not powered correctly. This comes up usually when the fusable link is blown (I've seen it happen) and I'm sure at other times too. If the circuit is not showing a sense from the alternator then this also happens. In the back of one of my manuals it shows things to check when ECU is flashing CODE 12.. here's the transcription

STARTER SIGNAL (CODE 12)

1. Check the starter motor operation and repair as necessary.
2. Measure the voltage at the ECU terminal C10 while cranking the engine. If the voltage is above 9 volts and code 12 continues, renew the ECU.
3. If the voltage is low, check the wiring for continuity and shorts to earth between ECU terminal C10, the ignition switch and the starter motor.

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Argh , yeah, caught again negative switching not positive. I've been encoraging him to use an LPG safety cut out device to power up the pump as a prime first, then it will continue power when running - maybe not a good idea to mix neg switching and pos switching there.

My diagrams are Australian model spec too, US could be different

steptoe wrote: Argh , yeah, caught again negative switching not positive. I've been encoraging him to use an LPG safety cut out device to power up the pump as a prime first, then it will continue power when running - maybe not a good idea to mix neg switching and pos switching there.

Probably not one of your best but good intentions none the less.

steptoe wrote:My diagrams are Australian model spec too, US could be different

They should be all the same.. Only the language is different as we speak English

Wonder if there was a gender swap between cars , auto to stickshift (American for manual ) maybe the ECU needs assistance on 'that' terminal?

Pin # 31 is either earthed or not between trans choices. Diagram indicates a switch. I never had trouble between my auto to manual conversion (admittedly was running on two plugs of the ECU at the time, but have since gone back to three on the odd occasion with no ECU indication of problems

Ahem [clears throat] I notice ECU controls both the relay supplying + to fuel pump relay as well as the - to the pump

I think that the ECU provides both negative switching (via the fuel pump relay) and negative grounding of the fuel pump. From memory, the the negative side of the pump is grounded when the ignition is on, and the fuel pump relay (supplying the positive side of the pump) is grounded when the ECU receives the engine rotation signal.

I know the starter signal sets fuel enrichment and ignition timing for optimum starting, but I dont think it has any influence on the fuel pump.

So back to the initial problem...

So does the fuel pump relay come on for 2 seconds when ignition is first turned to "ON"?

If it does, im assuming it is the negative side of the pump that isnt being grounded?

If you manually ground the pump, will the car run?

To quote an email from Mark

Trouble is the fuel pump
What Ive found so far.
1. with key on no power at fuel pump plug.
2. if I jumper the blue and red wire at f/pump relay plug I have battery voltage at pump connector ( already replaced the relay with a known good one )
3. When green test plugs are connected with the key in the "on position" pump will cycle properly.
4. after cycling the pump with the test connectors the engine will run for a bit.
Also getting a code 12 ( start switch )

Its a manual and has the neut switch on the clutch pedal, tested it and with the clutch pedal depressed there is no continuity, but I wonder if the fuel pump relay energizing curcuit is tied into the start switch? The conditions dont change based on the neut switch being open or closed either.

My best guess is the ecu isnt triggering the fuel pump relay. All my info is on the 4 plug stuff and im not finding what I need to check as far as pin outs and such.
Any knowledge would be greatly appreciated ,

Mark

steptoe wrote:1. with key on no power at fuel pump plug.

Power should be supplied to the fuel pump (via the ignition key and fuse) so I'd trace back with test light to find where the loss of power is coming from.

steptoe wrote:2. if I jumper the blue and red wire at f/pump relay plug I have battery voltage at pump connector ( already replaced the relay with a known good one )

Ok, so that kinda elminates the first fault (it's not the wiring to the pump) but it still can be the wiring to the relay.

steptoe wrote:3. When green test plugs are connected with the key in the "on position" pump will cycle properly.

Ok, again this shows the wiring to the relay is working (as this is supposed to happen when the green connectors are joined), so I'd start looking at ECU. Try using a good known one to compare.

steptoe wrote:4. after cycling the pump with the test connectors the engine will run for a bit.

This is showing the fuel is getting to the injectors and manifold but due to the ECU not getting the cranking signal, the injectors aren't pulsing anymore (after prime circuit).

steptoe wrote:Also getting a code 12 ( start switch ).

It still shows signs of ECU fault or wire from ignition start switch not getting to ECU.

steptoe wrote:Its a manual and has the neut switch on the clutch pedal, tested it and with the clutch pedal depressed there is no continuity, but I wonder if the fuel pump relay energizing curcuit is tied into the start switch? The conditions dont change based on the neut switch being open or closed either.

The clutch switch is there normally for turning off the cruise control (breaks circuit) and also for engine RPM whilst idle.

steptoe wrote:My best guess is the ecu isnt triggering the fuel pump relay. All my info is on the 4 plug stuff and im not finding what I need to check as far as pin outs and such.

Ok Jonno and Mark, try using that pinout that goes to ignition start circuit or another ECU.

I hope this helps in some way cause I'm not the full bottle on wirings (just enough to get me into trouble) but I'd say Gannon could be your man.

Think that was our guess also, hence my idea of using an LPG safety switch to take over from the ECU. Have to snip and insulate wires at ECU and just wire in the little 4 wire unit, earth it and BNGO - you'd hope. Just pretend it is a conversion

Great stuff Paul

steptoe wrote:Think that was our guess also, hence my idea of using an LPG safety switch to take over from the ECU. Have to snip and insulate wires at ECU and just wire in the little 4 wire unit, earth it and BNGO - you'd hope. Just pretend it is a conversion

Great stuff Paul

No probs bud.. anything to help hope you get it sorted.

Sorry for the thread dig but can anyone supply photos that match the instructions in the first post - i.e. what the check connector looks like and what the BW and BR stand for and so on - I need it dumbed down!
Also, when I turn key to 'on' only the CEL lights up - none of the other lights, its currently showing code 12 (hence this post), does the lack of other lights mean the ECU is rooted?

I fixed the dash light thing - that was a wire that had pulled from the alternator plug