With my engine running, my SECS monitor shows around 12.7V. I've confirmed this with a meter. Is this sufficient for the ECU, or should I have more (I gather that the ECU voltage has an effect on the fuelling).

I should also add that the voltage at the battery is 'only' 13.2-13.3V.

The voltage between the alternator casing and the output wire is a tad over 14V. Between the battery earth and the alternator output is the same, so I guess the earth is all good

Am I right in thinking that the only things that can cause this is bad wiring between the alternator and battery +ve, or the vehicle systems drain?

Am I making work for myself, or am I likely to have some kind of problem?

Any pointers would be ace!

Neil.

 

Too Low IMO.
Wants to be battery voltage there really, but battery voltage should also be around the 14mark or at minimum 13.7 with electrics all off.

Look at teh battery "Fusible link tails" They look like 2 small crappy burnt out wires.... follow them 6" and learn that they are the main fusebox feeds!! Dead Common.

 

Yeah, I had fun soldering new ones of those in last year!

I'll keep poking, see what I can find

Neil.

 

Does anybody else have any input on this?

How can the condition of the fusible links affect battery voltage?

Neil.

 

Cause the voltage is going up them before it gets to the ECU mate

Replace them with a proper bit of wire and a decent seperate huse holder located by the battery

 

I meant BATTERY voltage, i.e. measured at the battery

I can see that the fusible links are a likely cause of the drop to the ECU, thing is, this ECU voltage is only about 0.5V less than battery. I repaired them last year, but I'm thinking that your way might be a useful mod

I've run a jump lead from the alternator to the battery positive tonight, this didnt affect the voltage at all. I can't see how the battery voltage is so far down from the alternator voltage

The only way I can imagine it is that the rest of the vehicle electrics are dropping the voltage at the battery, or that the battery is poor...

Cheers for the input Chip

Neil.

 

look at the alternator as well..


i think mines on its way out..

I have an optima top bollock battery and used to see 13.9's to 14's on my secs..

now im only getting 13.4's

trivial I know.. but i prefer it higher!

 

Alternator voltage is just over 14V Dave

Neil.

 

oops, didnt see that

 

No bother

At least you tried

Neil.

 

Two recent threads

https://passionford.com/forum/viewto...843&highlight=

https://passionford.com/forum/viewto...888&highlight=

 

neil, not sure how relevant it is, and i know shit all about electrics before you ask but mine sees 14.1 at the ecu according to the secs monitor when its running so based on that fact alone....too low lol

stu, you'll be able to elaborate more on the ecu compensating the fuelling for voltage drop, mine went banana's with the old wiring loom, fuelling at idle was all over the place, voltage dropped a good 2 volts with all electrics on (fuse links smoked and burned out!!). only drops half a volt now since new loom and proper loom fuses. karl did tell me why having a stable voltage was soo much better but im fooked if i can remember his nev like techy waffle

 

Thanks Lynne - I had read those earlier this week, and am currently in the process of measuring the current draw

Matt - I think I'm headed towards re-wiring as per Karl and Chip. Any idea what/where Karl did, or could you find out?

Neil.

 

ding made me a new loom, then karl mapped it again, problem solved lol

 

Neil - For the sake of money for a new loom/alternator i'm going to keep an eye on your thread

 

https://passionford.com/forum/viewtopic.php?t=53903

take alook at this neil try the cable between alternator and battery mine was fooked and had the same problem and as stu says the links at the battery

 

Alan - I was looking for that post earlier!

I posted on there at the time as I had recently replaced one of the fusible links.

This time, I will strip the fooker right back and replace them all.

Soldering the large cables is a right ballache Reading that post brings it all back!

After some fiddling, The residual current with everything off (doors closed etc) is about 40mA. Also I have 13.5V @ the battery at idle with no load. I'm happy with this for now.

Next step is to get the ECU voltage as close as possible to this.

Thanks all for taking the time to read the post and put some thought into it!

Neil.

 

this needs a post about fuelling voltage compensation!

 

Agreed - I'd like to read the reason behind it!

Neil.

 

Neil i can tell you what to do without a new loom, as long as its in good condition.

I have got 14.32 volts to the pump from an alternator creating 14.35

I aint posting ths though will tell you on msn.

So know what I am doing.

 

steve's back.


at my ecu, With dingy's loom i run 0.1 volt lower than @ the alternator.

and run same voltage @ fuel pump.

 

OK, I'm pretty clear with how to get the ECU voltage up now thanks to Dingy

Whilst checking the rest of the lives, I found this:





This is the wiring to the 3 ABS relays, they supply the ABS valve block!

Must have been done before I got the car

Another job!!

Neil.

 

as battery voltage drops, responce time of the injectors gets slower, so the ecu needs to allow for this! so one of calculations the ecu does too the fuel base figure is battery adder!

 

Battery Adder!? Is that an electric snake or something?

 

DazC

 

Wot amount should the ecu be compensating?

i think wen mines runing with all the lights etc etc on, 13.4-6volts @ ecu, inj's and fuel pump.

wot % should the fulein be changed if voltage goes down to 12.5volts?

 

Cool - Cheers Gareth

Neil.

 

im not sure how too work it back,, ive noticed on the secs ecu its 500 μs per volt

 

Not mega then?





Neil.

 

your so right aswell

 

edited cos im a dick

 

Edit it back cos now I look like the penis!

'We extend the injector duration by 500 mega seconds per volt, or 953 years, whichever is sooner'


Seriously though, just messing I always enjoy reading the techy stuff

Neil.

 

i cant believe i wrote M for milli,,, what a cock,, only done electronics for 12 years

 

OK, I've replaced the fusible links and now have 13V at the ECU. Battery Voltage is around 13.2V, so it's a bit better now

What should the alternator output be ideally?

Mine is 14V, sometimes just under.

Cheers!

Neil.

 

i believe 13.8 - 14.0 @ any rev's over idle, and even with all lights & heater on.

 

neil I have exactly the same reading as you did to start with! exept if i load the electrics i see about a 2v drop in all readings, did your fuseable links look dead mine look ok but i still suspect they may be to blame, what did you replace them with?

 

is it worth replacing my links to my battery while i have no engine in place? LOL

 

So these 'fuseable link tales'

are 2 wires coming off the battery to the fuse box??

sorry just adding things to my list of checks for my car
over the winter!!

 

bump

 

Well check voltage drop.

i test voltage at

alternator (usually 0.2 volt higher than battery
battery,ecu feed and outputs, fuel pump, inj. (all these about the same with in 0.1 volt, except fuel pump wen connected)

if you get low readings on something, put a better + and earth to it.