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Electrical gremlins -- 1.8K


John Vine

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My son-in-law reports the following symptoms with his 1999 1.8K EU2 Supersport-R (my old car, in fact):

  • Starter motor turns well but engine not firing
  • Fuel gauge not registering (plenty of fuel) -- dial illumination OK
  • Hazard lights working but not as indicators
  • Brake lights not working
  • Fuses appear to be OK

I've suggested the following:

  • Does the fuel pump prime when the ignition is switched on?
  • Are all the relays firmly pressed into their sockets?
  • Are all fuses truly OK (especially fuel pump and engine/ECU)? 
  • Is the battery 12v feed to the fuse box and individual fuses OK and not loose?
  • Is the thin wire from battery +ve to ECU OK?
  • Is the +ve battery terminal clean and tight?
  • Are the multipoint loom connectors firmly plugged in?

What else should he look for?  MFRU perhaps?  Any tips much appreciated.

  • JV

 

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  1. When was it last all working, and what has been done since then?
  2. Check all connections, both feeds and earths. Disconnect the relevant ones, clean and reconnect.
  3. Check relevant fuses.
  4. Measure the battery voltage at rest, during cranking and at 3,000 rpm.
  5. On the indicators: there's a known problem with bad contacts in the switch that causes this. Wiggle the switch and see if function can be restored, even temporarily.
  6. On the brake lights: short out the switch contacts and see if they come on. If they do fettle (spring is here!) or replace the switch. If they don't check the brake light earth with a meter or jump a new good earth as a test.

Jonathan

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Thanks, chaps. 

  • Re JK:
  1. Good question -- nothing, probably, as he's normally too busy replacing people's hips!
  2. Yes
  3. Yes
  4. OK, but judging by the reported starter action, unlikely to be a problem there.
  5. and 6.  Do you think there's a specific gremlin that causes the combination of symptoms reported (no indicators + no fuel gauge + no brake lights)?  I've studied the wiring diagram but haven't spotted a common factor.
  •  Re Mankee, good point -- I'll suggest it.  
  • JV

 

 

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In general I'd agree with you about the cranking test, but I'd always start with those voltages, because it can quickly exclude lots of problems, gives an early warning of battery problems and only takes a minute (and a meter). It is possible that the voltage is being pulled down to a point where eg the ECU won't play nicely. Jonathan

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The only thing that I can possibly think of to do with the indicators/fuel/gauge/brake lights is the rear wiring loom, which runs near the off-side rear wheel and could chaff. From memory, the earth is carried by this part of the loom, but wouldn't this knock out some of the other lights as well? And possibly the fuel pump actually.

 

I've just removed my hazards flasher relay so can send it over for testing if the switch trick and relay wiggles don't fix it. I think I also have a spare MFRU if the part number matches your/your son's one.

 

These bullet points do my head in...

 

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  1. No more clever ideas on the multiple symptoms. It does suggest problems with an earth because they are more often shared than feeds. Starting with the rear brake lights will reveal that, and explore Mankee's suggestion.
  2. Agree that an ECU problem doesn't sound right for all of that. What sort of dash?

Jonathan

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  • 1 month later...

An update....

After spending a day poking about with a multimeter, rechecking all fuses, relays and obvious loom connections, I finally discovered the problem -- a couple of wires had become detached behind the ignition switch.  I couldn't see exactly which ones, but they were clearly the switched 12v supply to the fuel pump etc.  Result!

JV

 

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