Hot Starting

[MarkInstance]

I have a 1.6K series Caterham 7. It is a 2001 model. It is fitted with a starter button on the dash.

 

When starting from cold the car is fine.. Once it is hot, it only clicks when the starter button is pressed. The starter motor is not spinning or engaging. The car will bumpstart with no problems but this is hard to do it you are on your own.

 

What could be the cause of this? is there any other workaround other than a bumpstart.

 

Thanks

 

Mark

 

 

[Nick Woods]

Its the dreaded K-series starter click again. The solution depends on wether your solenoid is on top of the starter or below it. Mine is on top and I just loosened and retightened the feed wire and so far havent had any more trouble.

 

the full solution is here

 

Nick

P8MRA - Red and Black 1.6K supersport, back on the road at last. See pictures of it being rebuilt here

[Cooper nut]

I would'nt bumpstart your car if its got a CAT fitted to it as this could cause damage

 

You're only suppose to blow the blo*dy doors off

[Chris W]

Mark

 

If you inspect the starter solenoid, you should find a brown/red thickish wire that connects to it. This wire is supplied with current by relay contacts in the Multi-Function Relay Unit (MFRU) which is a black box with one small and one large connector, ususally sitting atop the engine control unit (ECU). (Apologies if I am teaching granny etc...). The brown/red wire comes out of the larger MFRU connector.

 

There appears to be a problem with the contacts on this relay in that they carbon up and get pitted very easily from the sparking caused when the starter solenoid current is switched. The relay is activated by your starter button which supplies current to the coil of this relay via a white/red wire going into the smaller MFRU connector.

 

The test of whether the relay is indeed the issue is to connect a similar thickness wire to the brown/red wire at the starter solenoid end. making sure the car is out of gear, switch on the ignition and touch this new wire momentarily to the positive of the battery. The car should instantly start hot or cold. Switch off the ignition and disconnect the temporary wire from the starter solenoid.

 

The permanent solution then is to bypass the MFRU relay with a higher current relay which is far more immune to sparking corrosion. It is a fairly straightforward modification and many of us have done it. I can explain how to do it and where to get the relay etc once you have confirmed that this is the issue. I suspect very strongly, that it will be the reason your car is not starting. It's a well-documented problem on Techtalk.

 

Hope this helps

 

Chris

 

1.8K SV 140hp see it here

 

Edited by - Chris W on 22 Apr 2003 17:36:26

[Paul Richards.]

Mark

Your symptoms are very much like mine were.

Below are instructions for fitting a relay to overcome the problem. Although if wired as per previous posting, the following are slightly different and you should follow these:-

 

You need a 4 pin 30 amp fuse - they cost about £6.00 or £7.00 and are available from most car accessory shops. You connect the terminals of the relay (these are shown on the relay, but are often very small) as follows:-

 

30 - This is live feed and should be connected to positive terminal of battery - best to incorporate an in line fuse.

 

86 - Signal i.e connect the original solenoid wire to this terminal.

 

85 - Negative - connect to negative battery terminal.

 

87 - connect to the solenoid - where the original wire (now connected to 86 on relay) was connected..

 

If you are having difficulty, or can't follow, please drop me an e-mail. I have even produced kits for some people with all the bits needed already connected to the relay.

I'm also fitting at least one for somebody at Stoneleigh and if you're going can bring along an extra kit.

 

Paul R.

C7PPR

K series that starts when hot!!

[Chris W]

Paul/Mark

 

There is a simpler way of connecting up the relay which precludes having to run a wire down to the solenoid AND totally bypasses the MFRU relay. Although your wiring method of course works Paul, you still have the MFRU relay in circuit supplying current to pin 86 on your new relay.

 

I appreciate that the current passing through the MFRU relay is now only small (it's only the current required to operate the new relay which will be typically about 90mA), so pitting is unlikely to be an issue. However, if someone had a very badly corroded MFRU relay they may still get a problem, plus of course having two relays in series adds another potential point of failure. I also utilise the existing fuse system, as the original MFRU relay did,so no additional fuse is required and no connections need to be made to the battery terminals.

 

My alternative wiring layout is as follows: DISCONNECT THE NEGATIVE LEAD OF THE BATTERY BEFORE WIRING IN THE NEW RELAY.

 

(I make reference to a "tap" connector below. For those not familiar with this connector, it's a readily available small plastic connector which is used to join one wire to another wire without having to cut the wires concerned. It's very cheap, very quick and very effective and Vehicle Wiring products sell them for 15p each or 50 for £2.72 - page 16 in their catalogue, code C560. Any automotive store will sell them too.)

 

 

1. Identify the white/red wire on the smaller MFRU connector. There is no need to cut this wire, just "tap" a wire to it and run this to pin 86 on the new relay. This wire is only carrying a small current (90mA) so almost any wire will do.

 

2. Connect pin 85 on the new relay to earth (chassis). Again the current is very small so a thick wire is unecessary. If you mount the relay on the firewall next to the fuel cut-off switch you can earth the relay very conveniently to one of its screws. This position is also really close to the MFRU so all the wires can be kept short.

 

3. Identify the thickish brown/red wire where it exits the large connector of the MFRU. This is the only wire which needs cutting. Cut it about 2" from the MFRU connector and tape up this short piece which goes to the MFRU.... you won't be using this piece again.

 

4. Connect a similar thickness wire (it's about 25 - 30Amp wire) to the remaining cut end of the brown/red wire using a tap connector and run this to pin 87 of the new relay.

 

5. Using the same thickness wire as in step 4. above, connect a wire to pin 30 on the new relay.

 

6. Connect the other end of this wire on pin 30, using a tap connector, to any of the 3 thickish plain brown wires which exit the large connector of the MFRU. It doesn't matter which brown wire as they are all connected together anyway in the loom. This supply is already protected by the 30A "ECU" fuse (No. 14 in the fusebox).

 

Incidentally, I usually put insulating tape over the "tap" connectors. It's not really necessary but I prefer belt and braces. Also tie-wrap the new short length wires neatly in place.

 

That's it - the MFRU relay is now no longer in circuit and the new relay will easily handle the current going to the solenoid. Connect up the negative lead again and ..... start.

 

I have put 2 useful photos of the finished relay installation on my photo website - just click below.

 

rgds

 

Chris

 

1.8K SV 140hp see it here

 

 

Edited by - Chris W on 22 Apr 2003 21:09:05

[Nick Woods]

No arguments with any of the above but remember there is more than one type of starter/relay.

 

ISTR that the fixes above work on the type with the relay below the starter , whereas the fix for the type with it above the starter is diferent. Follow the link in my original posting to see the original thread about these

 

Nick

P8MRA - Red and Black 1.6K supersport, back on the road at last. See pictures of it being rebuilt here

[Chris W]

Nick

 

Martin said in his first post he has a 2001 model 1.6K which will have the MFRU relay and wiring to the starter solenoid as I described.

 

If his problem is with the MFRU relay, this fix will cure it whether the starter is above/below or whatever in terms of the starter motor. If the problem is with the starter solenoid itself this is still a good mod to do anyway but it won't cure a bad solenoid of course.

 

I suspect though from the symtoms that this fix will cure the problem.

 

rgds

 

Chris

 

1.8K SV 140hp see it here

 

Edited by - Chris W on 23 Apr 2003 10:20:00

[MarkInstance]

Thanks for you help.. Guess I know what I will be doing on Saturday.... I will let you know how I get on..

 

Thanks again

 

Mark

[SLR No.77]

My starters got the relay above - certainly was last time I looked - and since doing the Paul Richards "fix" it hasn't missed once.

 

Stu.

[Luke Beaumont]

I've just done this, and an amendment to Chris' instructions makes it a bit easier and neater.

 

Instead of steps 3 - 4, open the big MFU connector and poke in something sharp to lift the plastic catch holding the Brown/Red wire in. You can then remove it, and peel back far enough to connect it directly to your new relay as it's already fitted with a spade. You can also easily reverse your relay wiring should the need ever arise. If you built from a kit, then one of the yellow plastic thread protectors from the copper brake lines can be pushed into the hole in the MFU connector to resume water resistance.

 

Now that's been said, I just want to thank the guys who have pioneered this mod, and Chris W in particular. Chris, your investigations into this and the MFU wiring diagram on your site have been incredibly helpful to me in the past week diagnosing a starting problem.

[Chris W]

Thanks Luke.. appreciate your thoughts. All of us have specialist knowledge in one area or another and it's great to be able to share it with others from whom I learn a lot about other areas which are less clear to me.

 

BTW, your amendment to the wiring for the relay is a great idea. It actually didn't occur to me to just take the wire out of the MFRU connector! Just shows how this forum is so valuable when everyone switches their brains on.

 

cheers

 

Chris

 

1.8K SV 140hp see it here