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Post by atlex on Dec 6, 2018 17:45:54 GMT
So my '89 car has had some trouble the last few months. It wouldn't always start up correctly. Symptoms were: I'd turn the key to start and it would turn the engine over, but there wouldn't be any fuel going in. The fuel pump wasn't running. It would prime 1/4 of the time and the relay was definitely the thing causing it or not causing it to prime. If I heard the relay, I'd hear it priming immediately after. If you know your car you should always expect to hear the hum from behind your ear of the fuel pump priming, before turning the key the last bit and the engine firing up. Anyway, this got worse and worse - it would prime less and less often - sitting there turning the key back and forth... It's either a bad contact or a fuel pump going - I mean, it's a car that was assembled 30 years, what do you expect ? Contacts get oxidized, especially the ones used regularly. I replaced the fuel pump with an R35 GTR one, so it probably wasn't going to be that. Probably, definitely, bad contact. The solution was to unhook this wiring connector (in white) from the socket in yellow, that's just next to the steering column and give it a blast of contact cleaner. Bob's your aunty. It starts up and the pump primes merrily. Problem solved, I hope, for some time.
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Post by wannabe on Dec 6, 2018 17:47:04 GMT
Thanks for the fix!
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Post by Horney on Dec 10, 2018 6:48:18 GMT
Corroded contacts will be something many mk1s start its suffer with these days. Dodgy earths are always a pain in the rear canoe as well.
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Post by wannabe on Dec 10, 2018 9:29:41 GMT
atlex - I'm sure you've already posted the name of it previously, but can you link to that contact cleaner stuff? I think it would be worthwhile to clean up a few of my engine bay contact points!
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Post by atlex on Dec 10, 2018 12:15:18 GMT
I tend to swear by the wynns stuff (https://www.opieoils.co.uk/p-146821-wynns-electric-contact-cleaner.aspx), but any 50-70% Isopropyl alcohol mix sprayed on should work. Wynns tends to be for automotive, but any computer contact cleaner or general electronic contact cleaner will do the same thing. Spray the connector, then plug it in, then unplug, spray again, and reattach. I have some unproven theory that the act of connecting and spraying a second time somehow helps clean the contact.
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Post by JamesMk3 on Dec 10, 2018 12:58:39 GMT
I have some unproven theory that the act of connecting and spraying a second time somehow helps clean the contact. This is far from an unproven theory. It is a well known phenomenon in the electrical/ electronics industry. When contacts are left for a while, an oxide layer forms on the exposed surfaces, if the contact is not a 100% hermetic seal (it won't be). This effect is made worse by heating of the contacts, and poor environmental conditions. Automotive applications are one of the worst environments (marine is worse) for making good contacts. A combination of temperature, vibration, low voltage/high current, and cheapness of manufacturers. By the wiping action of the contacts, breaking and re-making the joint removes some of this oxide layer, thus giving lower contact resistance. See this link (PDF) for some more in depth info. May I draw your attention to the diagram on page 6.
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Post by atlex on Dec 10, 2018 14:56:12 GMT
Glad someone else did the research :-) I just have this weird habbit of doing these things twice because something whispers in my ear that is the right way to do it.
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