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Yay! Finally eliminated the MFRU from the starter circuit


Myles

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'bout bleedin' time!

 

The 'bypass relay' (actually still triggered by the MFRU) was causing more trouble than good - so I've eliminated the MFRU relay entirely and now drive a standard relay direct from the starter button. That'll sort my click-of-doom out...

 

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Alcester Racing

7s Ecosse™

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Alcester-Racing-Sevens.com


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S'wot I've done from the standard ign switch. Brought a new, fused, feed into the spare relay position in the Caterham fuse/relay panel, new wire back out to the starter solenoid, and new wire from the "start" terminal on the ign switch. New earth too, obviously, for the relay.

 

Twice for the click of doom in 7 years was too many times . . .

 

Bri

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I took the power for the relay straight from the main starter connection - no need for a fuse. The relay sits near the battery (used to be zipped to the MFRU) and earths straight to the battery negative (last bodge before I sussed where some of the problems were coming from.

 

The whole car is covered in spaghetti now though - a rewire has been on the cards for a winter project for the last few years - just haven't had the time or place to sort it.

 

          🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻

Alcester Racing

7s Ecosse™

🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻

 

Alcester-Racing-Sevens.com


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Ought to add that it's (nearly) always been a wiring problem recently for the starter - the proof has been that touching the solenoid wire to the battery (usually) gives a really vigorous turn-over. I've had a few chugs under hot conditions (bit of a worry - overheated battery? Brise on the blink?) but a push-start has always solved that one.

 

But yeah, my advice these days would be *not* to follow the instructions on my site for the relay-'bypass' and to dive straight in and fit a dedicated 30-Amp relay.

 

          🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻

Alcester Racing

7s Ecosse™

🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻

 

Alcester-Racing-Sevens.com


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I did this during my rebuild a couple of years back. Out of the 4 relays in the MFRU only the Injector & the fuel pump relays are still operational. Some day I intend to rewire the engine loom etc & rationalise everything. The MFRU will go to be replaced with individual relays.
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my advice these days would be *not* to follow the instructions on my site

 

Now he tells me 😬 Wonder how long this fix will work *rolleyes*

 

Done the relay mod (worked for a bit - click), cleaned the solonoid (click),

put in a new relay + new solonoid wire (click), new battery/FIA switch cables (click).

Haven't done the "deburr the copper fork" thingy yet.

 

It ALWAYS starts when I dab the solonoid cable on the battery +ve, but it seems

a bit brutal. Surely the solonoid doesn't need that much current, and I might damage it. Putting a HUGE relay directly connected to the battery/starter + associated battery lead spaghetti would probably work, but I'm not convinced the solonoid would like it long term.

 

Forgive my numptiness, but isn't the problem that the relay clicks, its just that not enough current/volts/whatever is getting to the solonoid when it does. Or was your relay not working at all, and you are solving a different problem?

 

Also, FIA switches seem to get blamed alot for this - which part of the switch should I be looking at/replacing?

 

(I got the click at Castle Combe on Monday, and was going to bore Peter C who happened to be there - but I think he was having alot more fun playing with a Radical!)

 

AB

 

 

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It ALWAYS starts when I dab the solonoid cable on the battery +ve, but it seems

a bit brutal. Surely the solonoid doesn't need that much current, and I might damage it. Putting a HUGE relay directly connected to the battery/starter + associated battery lead spaghetti would probably work, but I'm not convinced the solonoid would like it long term.


 

It’s no more brutal than how it is already connected. The only difference is you are removing a bunch of contacts and (more importantly) a fuse. The solenoid will only pull the its rated current (unless it is faulty), the shorter the path to it the better. I can’t get my head around just how poor the Rover electrics are.

 

Every contact/connection in the signal wire is a potential loss, check all the contacts to see if there is any corrosion/pitting as this reduce the current getting to the starter. I currently have a click which I am going to fix by wiring a relay direct.

 

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