andyborris
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It's only .3 of an amp, I've got 11.5 amps showing and 11.8 amps is the minimum that the ECU needs to work.....or so the internet says! Volts not Amps ![;)](//storage.proboards.com/forum/images/smiley/wink.png) Re the jump leads, the amount of current in each cable will carry depends on the resistance of each cable i.e if they are the same resistance the current would be shared equally. I have my doubts that voltage is the problem at 11.5v, not usual for a battery to drop to 11.5 while cranking I hang my head in shame...really, what chance do I have of getting it running....... ![:D](//storage.proboards.com/forum/images/smiley/grin.png) And I hope you're wrong about the voltage drop or I'm really screwed, everything else is working, a drop of petrol down the throttle body and it fires, the fuel line has pressure, the engine is spinning fast enough to start, it's just while I'm cranking, the ecu isn't seeing any rpm and won't fire the injectors. Or so I think! Maybe I'll wire the coil & ecu directly from the battery, crank it and see if it fires in the moment when I stop cranking but the engine is spinning. As mk2cossie said I'll have to change rpm start threshold, if I can.
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if it gives a spark, itll be seeing engine revs. If it is then it should be giving fuel. have you connected the fuel lines up the right way? the regulator on the return line
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andyborris
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if it gives a spark, itll be seeing engine revs. If it is then it should be giving fuel. have you connected the fuel lines up the right way? the regulator on the return line Not sure about this, but my understanding is that the spark is independent of the ecu, it's points and a old fashioned coil, that will make a spark if you can open and shut the points by hand quickly enough! However, the ecu reads the neg side on the coil to switch the injectors on/off and I think if it doesn't get at least 11.8v in that pulse, it will ignore/not read it and not switch injectors on. The spark isn't what you'd call healthy, but more like a spark you'd see if the coil wasn't getting full fat 12 volts. Probably enough to fire with a carb doing the sucking, but I need the injectors to inject. The coil doesn't control the 2 (one in each barrel) injectors, just tells the ecu to turn them on or off because the engine wants to run/stop. The fuel system doesn't have a return, the in-tank pump is regulated internally.
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andyborris
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The wire that tells the ecu the rpm can also be used to run a tach.
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jimi
Club Retro Rides Member
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I've built quite a few circuits for different functions on cars or battery operation normally you design it to be tolerant of a range of voltage. Resting voltage for a fully charged good car battery is normally around 12.5v when the engine is running that will rise to 13.5/14.5v. When cranking it could drop to 11/11.5v so you design your circuit to be tolerant of that sort of range I just can't see anyone designing an ECU that will fail to operate at 11.5v, but that's maybe just me. Are you sure the ignition switch is providing power to the ECU/distributor/coil in both the ON and Start positions?
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Black is not a colour ! .... Its the absence of colour![](https://jlawson.co.uk/images/Jimisig04.jpg)
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andyborris
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The ecu is showing 12.5v on the screen before cranking with all functions available, it then drops to 11.5 when cranking. I've tried wiring the ecu power via the ignition switch, via a relay operated by the ignition switch and direct from the battery.
Seen a few posts about non working ecu's that were fixed by upping the volts to 11.8+ volts.
Guess the Americans, being a bit new to EFI dropped the ball slightly. I'll find out when the new battery cables go in, 50mm and 345 amps should cover it.
Was surprised at how few amps the braided earth strap could carry, 90 amps! And it was at the opposite end of the engine to the starter.
In the States now, 16 volt batteries are in fashion.....
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andyborris
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Jul 10, 2024 16:15:34 GMT
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New 50mm cables in and now I've not got a bloody spark!
It's been about 25 years since I tried to troubleshoot points, anyone got a link to a website that'll show me how to do it, preferably one that's not got an American talking at me like I'm a idiot.
I know I am, just don't wish to be reminded of the fact.
Or could someone please post the page from an old Haynes manual that deals with ignition troubleshooting, seem to remember they were quite clear.
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Jul 10, 2024 16:46:13 GMT
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oh are the points new? did you take the grease off the contacts?
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andyborris
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Jul 10, 2024 16:59:59 GMT
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oh are the points new? did you take the grease off the contacts? No, I didn't, will look. Thanks.
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andyborris
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Jul 11, 2024 12:43:27 GMT
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Sorted the non start, the king lead needed a firmer push to fit than I'd given It!
And nothings changed, still getting the voltage drop, even with the 345 amp battery leads.
Think something may wrong with either the ECU or the supplied loom. This is where I find out if they're good people to do businesses with!
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Jul 12, 2024 18:51:10 GMT
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I don’t think that 11.5v while cranking is unreasonable. As already said further up the thread, automotive electronics has to be able to cope with a fairly wide voltage range with resting battery voltage being the midpoint at 12.5 - 12.7. I reckon 10 - 15v would be a reasonable design range.
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1967 Triumph Vitesse convertible (old friend) 1996 Audi A6 2.5 TDI Avant (still durability testing) 1972 GT6 Mk3 (Restored after loong rest & getting the hang of being a car again)
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Exactly what system is it? Brand and model I mean.
It does read/ show rpm when you release the key back to "non starting " position? Have I got that right?
Have you pulled a plug and verified that you actually have spark when cranking the motor? If not, make sure to check also when you let go off the key and it registers rpm, does it spark then?
You maybe have already answered this, but there is actually 12 v at the ignition coil when cranking?
Best regards, David
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andyborris
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I've found the answer......I've put the carb back on.
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andyborris
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OK, now I've given everyone a good laugh....
With the help of Justin Richardson in Glasgow, Kentucky who led me through some troubleshooting remotely, it was a couple of issues, none of them related to the voltage drop!
1st was a non return valve in the fuel that didn't flow in either direction.
2nd is a blocked injector or maybe 2 and because it only has 2 injectors, it's quite important!
Now whether it's something I've done or a manufacturing fault I don't know, taking the injectors out of the throttle body to find out will invalidate my warranty.
I've emailed the manufacturer about returning the throttle body and this is where I find out how good the customer service is.
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