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So my main winter project was to rewire the Herald, 20 years of adding various electrical items had left it like a birds nest behind the dash.

I have run all the cables, connected fuse boxes and relays etc so now it was time to do some testing. The good news was that everything seems to work. Lights, Flashers, Heater etc etc. all good until I added fuses to power up the Microsquirt ECU. Turn on the ignition and you hear the Fuel pump kick in and then stop as it should, but if you turn on the indicators or hazards the the Fuel Pump powers up, Injectors Click and the IAC Valve open & closes in sync with the on/off of the flashers. You also get a similar thing when pulling out the main light switch to the on position, but with that it's just the once.

12v supplies and earths for EFI & everything else are separate, the only common areas are the fuse boxes below. The one on the left supplies everything ignition fed the one on the right perm lives.The fuse boxes are the type that are powered at a single point and then feed 10 fused connections to relays & electrical items. The Ignition fed fuse box is supplied by a 40amp relay.

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This is the Fusebox for everything EFI related

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I thought it may be low battery or bad earth, but have ensured both are fine, and I have retraced the wiring for flashers/lights and they are seem to be right.

The only change on the EFI wiring has been relocation of the relays to a base in the centre of the car and I have swapped from EDIS/Ford Coil Pack to VW Coil Pack (No EDIS), the car starts but sounds like a bag of nails, but that maybe just to set-up of the new ignition, but I run out of time and had to leave for work.

I will go back and recheck everything, but thought I'd ask the question here just in case there is something obvious it might be that I am just missing.

Darren

 

 

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Ouch.  Poltergeist or gremlins.  Exorcism?

Clearly there is a link as the indicators etc are turning the ECU on and off.  I suspect you have an earthing issue where it's you have contact between a collection of earths but not an actual connection to earth at that point......

 

I don't fancy diagnosing it with the car at hand, never mind from my desk.  Though my desk is likely a bit warmer just now.....

 

Nick

PS. are any of relays clicking in time with this? Most likely the one that powers the ECU.  It really doesn't take much current to energise a relay coil and sometimes a reverse current will do it too.

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I did probe the 2 relays whilst the flashers were on, the one that feeds the ECU, Injectors & IAC Valve was a constant 12.xx volt, the one that operates the Fuel Pump & 02 sensor which earths through the ECU was pulsing in time with the flashers. I could remove this relay though and the IAC Valve & Injectors would click in time.

I didn’t try with just the ignition on again after I started the car this morning, when I got home this evening I tried again and it’s now not doing it all, how does that work?.....:huh:

I think I’ll double check the EFI earthing, this has always been on a bolt through the bellhousing/engine backplate. I did disconnect it, shorten and connecting to a bolt further round that bolts through the bellhousing straight into the engine block, I guess there could be oiled in between the surfaces prevent a clean contact.

Will have another play on Sunday.

Darren

 

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I would addan earth wire direct from battery to that earthing point on the engine.

When I took mycar to Bailey Performance, he spent an hour or so going through the installation, setting all sorts of things and noticed some "noise" on the power side of things, cured by adding an earth back to the battery. Biggish cable too (at a guess I would say 30A or more)

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Plus one for that.

While ago mine was charging badly.   New, more powerful alternator made no difference.

Friendly electrician came, equally baffled, until dusk came on, and he noted the corona glowing around the alt.

Length of starter cable between block and battery earth sorted it and its stayed ever since.

John

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I added an additional earth strap from battery to engine a couple of years ago when the starter was intermittently lazy, this connected to one of the starter motor mounting bolts. The EFI earth's are a few bolts round on the bellhousing, so are nearby, but think it will be wise to use the same location for both. 

All the earth's for everything else are at one point behind the dash, bolted in to a rivnut. A chunky cable back to where the earth strap connects to the body can't do any harm either, so will do that also. 

Thanks for the replies. 

Darren 

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The rivnut would worry me. My experience is that they can wiggle about, and though not stressed I would prefer a proper bolt or stud. Adding a chunky earth cable back to the battery would do the trick though as the rivnut would just be a connector, not the actual earth. 

 

 

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2 hours ago, zetecspit said:

The rivnut would worry me. My experience is that they can wiggle about, and though not stressed I would prefer a proper bolt or stud. Adding a chunky earth cable back to the battery would do the trick though as the rivnut would just be a connector, not the actual earth. 

 

 

Yes, I concur.

 

If practical my preferred option is to weld a nut or bolt to the body, but obviously that means painting after wards.

I also like to have a second engine earth cable to body....

 

 

 

Ian.

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Initially I though the rivnut was a good idea, newly drilled hole with fresh clean metal and the rivnut crimped in against it, but completely take the point it has the potential to work loose. I have now run a 30amp earth cable from the rivnut back to where the earth strap from the battery bolts to the body. From this point there is also an additional earth strap down to where the starter, backplate & bell housing bolt together and this is where all the EFI earths come to, so I'm now pretty confident that earthing is well covered....time will tell when I connect up the dash again to do some testing.

Many thanks.
Darren 

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Dashboard all connected up and everything behaving normally now, so earthing was the issue. 

Thanks all for you input and encouraging me to recheck the earths! :thanks:

Next job is to see if the move from Ford Coil Pack & EDIS to VW coil pack is working OK.:unsure:

Darren

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Everything works fine now, all electrical circuits, the change to VW Coil Pack and car is running nicely again......that was only after I had the car running like a dog for ages, wondering why it was running very, very rich to the point it was struggling to run at all. Then I wondered why the MAP sensor reading was around 1 bar........oh, that would be because I hadn't connected the tube from the plenum back into the sensor....:lolu:...what a numpty.

 

 

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