Strange cutting out fault

[Tant]

..This one has got me pretty foxed.....

I did some work on the car today, cleaned/gapped the plugs, removed the airflow meters and removed what little oily deposits were in there. The car was running great so popped out and did about 30 miles or so. On the way home the car stuttered slightly and then just cut out.

When I turned the ignition on, I couldn't hear the fuel pump kick in so I thought it must be the fuel pump fuse.

I found a fuse blown, but wasn't sure what it was as I didn't have a diagram with me, but I replaced it anyway.

After about 1/2 a mile, as I go to pull away in traffic...same thing happens. Checked again, same fuse blown. This happened 3 times , until I managed to nurse it home on low revs and gentle starts.

The fuse in question is the one nearest the relays, in the corner (which is top right as you look at it in my footwell, but it may have been remounted). My book says this is the Engine run sensor, fan and primary relay.

Any ideas what this actually does please, and why it should be blowing.

Cheers

Ant

[Barkychoc]

Does this help Ant?

Could it be the engine fan kicking in?
Maybe tired motor & drawing too much power?
You could try putting an ammeter across the temp sensor terminals to see how much current it is drawing - well maybe briefly before the fuse goes pop!

Edited by Barkychoc on Saturday 26th July 20:10

[Ray S]

Check for loose terminations especially on the fuse box this can cause massive power loss across loose joint or even worse hopefully it's something more simple .Ray

[Tant]

Thanks Chris and Ray

It looks like my fuse box is a little different to yours, but it is the 15Amp fuse in the corner near the relay (it was a 30 amp in there on mine), that is blowing. I'm guessing that to blow a 30 amp fuse, there is possibly a short somewhere, but god knows where the wires run...

The cooling fan temp switch only switches the supply to the fan relay so in theory shouldn't be drawing a lot of current, but it's worth a check, thanks.

If there is anyone who has a photo of a S2 fuse box and layout it would be appreciated.

Ta

Ant

Edited by Tant on Sunday 27th July 09:24

[clarenceboddiger]

Tant said:

Thanks Chris and Ray
The cooling fan temp switch only switches the supply to the fan relay so in theory shouldn't be drawing a lot of current, but it's worth a check, thanks.

Ta
Ant

Edited by Tant on Sunday 27th July 09:24

Could it be that the coil in the relay has gone short circuit, may be worth pulling the relay and checking its operation?

[Barkychoc]

Note that fusebox is V8S.

[Tant]

That's a thought Ken...I'll take a look later and let you know how I get on

Cheers

Ant

[brow]

I have had the same symtoms. It turned out to be a blown resistor that sits next to (on the same connector block) as the Fuel injection relay (Brown) seperate from the fuse board-S3.
I failed to find this fault and had to use my local TVR garage.

[greymrj]

Hi Tant, had a similar fault on a different car some years ago. This is the fuse which feeds the fan. The fault isnt immediate but occurs after a period. Could it be that the fuse blows when the fan tries to cut in? This could happen if the fan has seized or there is a fault in the fan wiring (perhaps a wire disturbed while you were working in the engine bay) which causes a short ONLy when the otter switch causes the fan circuit to 'make'. Run a wire from the battery to one fan connection and earth the other connection and see if the fan runs, if it does then it could still be on the fan wiring but not the fan motor itself. Make any sense?

[Tant]

Thanks for the replies gents.

I took the fuse box out and couldn't find anything wrong, and the cooling fan ran fine when I tested it, so I started looking elsewhere.

In the engine bay there is a loom that comes out from the NS wing, over the washer bottle, round the back of the engine and to a number of connectors on the inlet plenum.

I found that this loom had dropped down and was touching the back edge of the exhaust manifold near number 6 cylinder. It had melted a small hole in the outer sheathing, and one of the wires inside was exposed and touching the manifold. Going by the previous repair here, it's not the first time it's done it.

Soldered in a new section of wire and tie wrapped the loom up and all looks good.

It's probably worth checking on other cars, as I can't see anywhere where this loom would be supported and it seems destined to sag down.

I guess that explains why it was blowing 30 amp fuses then.....

Cheers
Ant

Edited by Tant on Monday 28th July 20:24

[spivvy]

Tant said:

Thanks for the replies gents.

I took the fuse box out and couldn't find anything wrong, and the cooling fan ran fine when I tested it, so I started looking elsewhere.

In the engine bay there is a loom that comes out from the NS wing, over the washer bottle, round the back of the engine and to a number of connectors on the inlet plenum.

I found that this loom had dropped down and was touching the back edge of the exhaust manifold near number 6 cylinder. It had melted a small hole in the outer sheathing, and one of the wires inside was exposed and touching the manifold. Going by the previous repair here, it's not the first time it's done it.

Soldered in a new section of wire and tie wrapped the loom up and all looks good.

It's probably worth checking on other cars, as I can't see anywhere where this loom would be supported and it seems destined to sag down.

I guess that explains why it was blowing 30 amp fuses then.....



same thing happened to me a few years ago except i broke down on a roundabout at Le mans !
an easy fix once you find the problem

Cheers
Ant

Edited by Tant on Monday 28th July 20:24