Momentary engine cut out.

[richard bradbury]

Whilst accelerating at about 4000rpm in 4th gear, the engine died and then continued normally. It only lasted about a second. I was not pressing hard on the throttle. This is a little worrying as the last thing you need when overtaking or pulling out of a turning is to be deprived of power! I thought the problem had gone away but, about 50 miles later it did it again whilst accelerating gently in 2nd. This sort of thing is obviously difficult to diagnose. My engine is a Vauxhall XE and has a DTA engine management, with coil pack and a crank speed sensor. The Webers have a throttle pot. The battery was renewed in Jan 2015.

i have checked obvious things like loose connections. As this has only happened twice and both times when applying throttle, I wondered if the throttle pot may be playing up. What I would like to know is what happens if you disconnect the throttle pot, would you expect a complete loss of throttle response.

[elie boone]

You didn't touched the ing key with your knee ? otherwise check and clean all connectors.

[Paul Deslandes]

Hi Richard

there's a weakness in the Vx engined car wiring at the back of the alternator.  There are two thick brown wires that go to two separate but linked terminals on the back of the alternator and link the battery +ve to the rest of the wiring loom.  One or both of these wires can suffer from exhaust manifold heat and become brittle and either snap or the push-on connectors fall off, or both. If these have initially become intermittent it would cause your issue.  This is exactly what happened to me some years ago on a track day and was quite alarming at the time.

There is another thinner wire that connects to another terminal at the same point and a fourth, sense wire, which is quite separate.  I'd check them all while you're in there.  You might want to disconnect the battery earth before you wiggle them as they're live even with the ignition off!

Caterham's loom simply had three right angled blade connectors crimped to the wires without any support or protection.  I replaced mine with a proper plastic shell and crimped on new connectors.

Available here or on ebay

Good to hear that you still have the car and are driving it

all the best

Paul

[Mark Durrant]

Do you have a battery master switch as these can be unreliable and give the symptoms you have described.

[Kevsta]

My car did this (K series) and it took ages for me o discover the problem, I eventually found it though and it was the fuel pump (in the tank). 

 

I hope you cure the issue soon.

 

Kev

[richard bradbury]

Hi Paul,

funny you should mention that wiring. I had an incident a few years ago when The engine cut out completely. The clip at the back of the alternator had come off. I had been running on battery only for some time as there was not enough juice to restart the engine. I had to get some help to push start it.

I will look at this area in more detail. Many thanks for your reply. Other than this, the old girl has been going splendidly.

kind regards,

Richard

[Paul McKenzie]

I've done the same as Paul and used the proper plastic shell plug with crimped connectors and solder .  I found that the worst heat-affected wire ie most brittle, was the fourth sense wire which doesn't connect into the plug - I wrapped this in a glass fibre insulation sleeve.

As Paul said don't forget to remove the battery earth before you start fiddling

[Jonathan Kay]

Pauls: How do you diagnose the cooked bits... look and feel? How about poking the wires and connectors with a wooden spoon while the engine is running and seeing if the fault can be provoked? Usual precautions.

Jonathan

[Johnh]

Reading post 3 and was wondering if there is heat shielding available for the alternator..I have had an intermittent fault where the battery light comes on whilst driving ..I had the alternator off and checked out by a specialist auto electrical company ..the wires/connections looked fine.. was told it was ok so refitted it with new belt and was ok but the problem happened again but this time was in heavy traffic and the engine was running a little hot .. when I got moving again the engine cooled a bit and light went out..I think the heat from the manifold is cooking the alternator enough to cause an intermittent fault??

if there is no heat shield available has anyone found permanent solution before I start making up something of my own?

[Jonathan Kay]

There are references to heat shields in the archives. Does your set-up have the option of rerouting any of the cables away from the heat even if it makes the runs longer?

(In practice I think that most people replace them eventually once they're fully cooked.)

Jonathan

[Johnh]

I fitted new connector block on refitting but on my car the connection block is so close to the No 1 manifold pipe it's obvious some heat will be transferred.. basically it needs shielding..I'll check the archives 

[Paul Deslandes]

A heat shield would probably help although its benefit will depend on the exhaust manifold and its proximity to the alternator.  Heat could certainly cause the regulator, which is built into the body, to misbehave before finally giving up thr ghost.  I don't think rerouting the cable would necessarily help as it's the terminal end of the cable that is too close to the exhaust.

I seem to remember that the copper spade connector had parted company with the cable in my case.  The cable's plastic sleeve goes very hard with the heat, and vibration causes the wire and terminal to fatigue and break off.  Soldering can eventually lead to fatigue failure so crimping alone is preferred although I often solder as well to be sure of a decent connection, and the plastic shell will give some support and help protect against fatigue.

Hopefully you'll find the problem and solve it easily Richard, and don't forget Mark's suggestion of the cut off switch if you have one.

Paul

[Stridey]

I've put a Summit Racing heat shield wrap over my starter motor, I'm sure it would fit an alternator, though Take care due to the proximity of whirly bits. (I put it around a new starter motor as on a Crossflow its in a pretty hot place near exhausts.) I bought it in an auction but they are sold here on 'buy it now'  http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR0.TRC0.H0.TRS0&_nkw=SUM-350118+-+Summit+Racing®+Starter+Heat+Shield+Wraps&_sacat=0

On my alternator, I had occasional cutting out after it got pretty soaked one night. Mine did not have the plastic plug, so I retro-fitted one that goes under the clip. It's one of those simple things I feel should have been like that in the first place, it's vulnerable down there to dampness.