Dodgy Relay - 930

[GUT]

Gotta love an intermittent problem...

A few months ago I was driving along the freeway from Phillip Island and my '88 930 cut out, then came back to life, cut out again, came back etc. This went on a while till it stopped altogether.

After a bit of fruitless cranking I gave it a rest for 10 mins. Started straight up. Drove home with no issue.

It's been fine since, until today.

It cut out pulling into my work carpark. I rolled into the spot and went inside. Half an hour later I went back to check it. Started first go. Ok cool. End of the day, I go to start the car - no go. It cranked over fine but no ignition.

So here are the things of note:

• Sudden loss of ignition
• Complete absence of spark
• No CDI whine
• Then CDI whine and fuel pumps running on ignition. Fuel pumps shouldn't run without the engine turning. Still no spark/ignition
• I then left the ignition on, fuel pumps running, CDI whining and fiddled with the big yellow relay - the Air flow sensor/charging pressure relay apparently
• The fuel pumps cut out, the CDI whine continued
• Cranked it over and she starts

So, I think it's safe to say I have a dodgy Air flow sensor/charging pressure relay. I think I'll be buying 2 just in case.

Having said that, I don't understand what that relay has to do with the CDI...

 

 

 

[LeeM]

  Wouldn't be the round plug (if they're round on yours) that goes to the fuel pump relay? 

 My 78 SC had a similar problem which we traced to the plug. Well, Craig at Buiks told me to look at. If you are unaware, the female part of it on the plug are numbered once you take it off (culprit was 87A I think) which had splayed out and kinda rusty, so I spread out the male pin on the relay so that it contacts a lot tighter 

 Might be worth a look anyway

  Lools like this one

https://goo.gl/images/vxYoe9

[GUT]

Thanks @LeeM

Anything’s possible. I did fiddle with that too and the relays at the front but it was when I fiddled with the yellow one with the ignition on that the pumps stopped (they shouldn’t have been running). Then it started. But it might have just been a coincidence that touching that one may have moved the bracket and that might have helped the fuel one. Who knows?! It’s going now anyway.

[Zelrik911]

Yes - do what Lee says. Make the male posts in the relays bigger by widening the split slightly and clean the female holes with electrical contact spray.

Exactly this happened to me on my old SC. Eventually the relays get so sloppy they can fall out. Have some racetape &/or duct tape in your toolkit in case it happens to you. ( I had the shame of my SC being rescue towed down the road by a CITROEN 2CV !!!!! ohh the indignity.....)

[Scott930]

That yellow relay sounds like the "over boost" relay. My 930 started to just randomly (instantly) die whilst driving, then start again after a few seconds (felt like minutes!), thought it may have been one of the 2 front fuel pump relays, but replacing those made no difference, so replaced the overboost/charge pressure relay... problem fixed and hasn't happened again (nearly 12 months on)

[GUT]

29 minutes ago, Scott930 said:

That yellow relay sounds like the "over boost" relay. My 930 started to just randomly (instantly) die whilst driving, then start again after a few seconds (felt like minutes!), thought it may have been one of the 2 front fuel pump relays, but replacing those made no difference, so replaced the overboost/charge pressure relay... problem fixed and hasn't happened again (nearly 12 months on)

Yes - sounds exactly like my problem.

I’m 99.9% sure it’s the yellow relay that’s the culprit.

 

[LeeM]

There's always that .1% of doubt ?