Vauxhall HPC Misfire

[TANGO7]

I took my Vauxhall HPC (1992 on Carbs) out for a brief spin yesterday, due to bad weather and other commitments its not been run for a couple of months. On turning on the ignition I heard a continuous "clicking" (like sound from a flasher relay) this seemed to be coming from the area of the battery?? (not from fuse box) I experienced difficulty in starting it (plenty of charge in battery, engine turning over fine but not firing, then suddenly fired up after about 5 attempts) after starting it ticked over fine for some minutes.then stalled, repeat of above to start. Once running and on the road it ran fine for a couple of miles then stated misfiring badly, actually cutting out momentarily on occasions then cutting in again also accompanied by loud backfires. After doing this for about 2 miles it then ran fine, although I only did another 10miles or so.Prior to the above the car has run fine.

Anyone any theories as to the cause of the above? (I had simliar problems with a crossflow some years ago which I traced to a faulty earth lead in the engine bay - but I cannot see any similar lead on my car)

[Jonathan Kay]

Was the clicking associated with trying to start or with the ignition alone?

There should be at least one thick earth to the block but I'd try a few other things first.

What's the ignition set-up?

Any possibility of water eg in plug recesses?

Any work done on it recently?

What's the battery voltage at rest, during cranking and at 3,000rpm?

Jonathan

[gileshudson]

Take the K&N covers off and look into the carb trumpets to check that the venturi (17 on diagram linked below) of all 4 trumpets still make a capital M or W shape as you peer in.

If they don't, check whether the locking nut (28 on diagram linked below) that holds the venturi in place on the side of the carb trumpet is still in place.

They're normally wired on but not always as I found out to my cost at Cadwell when one fell out and one venturi twisted 90 degrees.

Car exhibited similar symptoms to what you're describing, but sadly this 2 minute job was the last the last thing we tried after ages and ages of head scratching and testing leads, coils, etc.

A two minute check . . . http://www.carburetion.com/diags/45DCOEDiaginfo.asp

[SM25T]

Does sound like a poor or dirty connection (in any of the big fat red or black cables between battery, engine, chassis or starter) ... or a dying battery.

[Paul Deslandes]

My first thought was that it was the fuel pump, until I read that it was coming from the battery area.  I assume your battery is in the usual place, on the top of the passenger footwell.

The clicking noise could be the Facet Solid State fuel pump which is usually located on the back of the rear bulkhead below the boot floor.

If your pump is playing up, it might explain the running issues, including the backfire, as the carbs go lean with fuel starvation.  I had one go bad once and replaced it with a Facet Redtop.  I subsequently put 24 Volts onto the 'dud' one and it's been as good as gold ever since and I use it to pump fuel between tanks and cans.

An alternative to the fuel pump is very low fuel in the tank and/or a blocked tank breather (fuel cap) not letting in air and starving the carbs of fuel.

Daft question, but the clicking isn't the hazards operating is it?

Keep us posted

Paul

[TANGO7]

Hi All, Thanks for all your help and suggestions. A case of systematically running through the options, I guess. However, in relation to the "clicking" - it occurs as soon as the ignition is switched on and continues whilst trying to start the engine. Also what I should have mentioned , the battery is in a strange position - in the "Boot" on the nearside -  above the fuel pump? So perhaps this does point to the pump, perhaps the points sticking? If this is the case, and the pump is at fault, does anyone know a fix or is it a replacement of the pump?

[Jonathan Kay]

Stick a stethoscope (or stick) on the fuel pump to see if that's what's clicking. If it is then disconnect, inspect, clean and reconnect both ends of the feeds and earths to the fuel pump.Then tell us if that has made any difference.

(Some people would run a temporary good feed to the fuel pump but I'd do it this way round.)

Jonathan

[Paul Deslandes]

If original, the pump is almost certainly a Facet solid state pump which clicks all the time, so it sounds as though it's working okay, unless you have a blocked filter or pickup or, as said before, a blocked fuel cap  breather.  If the pump has been replaced with a larger capacity Facet Redtop (which also clicks), these have a built in filter but unless you have a really dirty tank I doubt it's blocked.  The solid state pump is a metal cube, roughly 50mm sides.  The Redtop is cylindrical with a mushroom-like top cap.  The clicking is louder to start with as the carbs fill up with fuel and gets quieter as demand drops, until you start the engine.

Ruling out electrics for a moment, it sounds like the fuel supply to the carbs is failing, either because the pump isn't picking up fuel or the line is blocked.  You could try disconnecting at the carb end and checking that you have a good flow of fuel.  Have you tried filling the tank?

To check for tank venting, when the engine stalls, remove the filler cap and see if you get a woosh of air going in.  If you do it with the engine stopped but the ignition on, you may hear a change to the pump noise too.  Do you have the standard chrome twist on cap or a later Newton lever release type? The latter should have a small breather hole drilled in it, usually under the lever.  If you have one of these, check for the hole and that it's clear.

Paul

[paul jacobs]

I couldn't help but pay attention when you mentioned the battery position as I did this exact same mod to an HPC I built back in '91/92, and just wondered if it could be my old car, which I think was red / ali one, at the time, though could be quite different now?

I hope you sort out the clicking problem, it sounds as if it could be fuel pump related as there aren't any solenoids in that area, which do cause clicking sometimes.

[TANGO7]

Hi All,

Thanks again for all the help and suggestions. I found a suspect earth (main one in the engine bay) which was slightly loose and  also covered in oil mist from oil breather. Cleaned up and tightened and now all ok - will have to modify the breather pipework and catch tank. Incidentally the fuel pump is a Facet solid state, still merrily clicking away.I have cleaned fuel filter as a precaution (though there  was no sign of a blockage and fuel is flowing freely). Also I have the Newton type petrol tank cap, but this has no evidence of a vent hole, but also no evidence of vacuum/air rush when cap is removed, during/after running the engine. (Is it possible it vents through the key hole/lock?) The venturis on the carbs were in the correct position, locked in place with the nuts (which were wired in place).

Thanks again to all.

[Paul Deslandes]

The Newton cap is designed to be fuel (and air) tight and either needs a tank breather in the hose somewhere like newer 7s or a hole drilled in it, as below.  The length of time taken for there to be a breathing problem probably depends on how full the tank is and, hence, how much air is in the tank.. If it's nearly empty it might take a while before the engine gets starved.

[TANGO7]

Original problems occured with only a small amount of fuel in the tank. Anywhere between 1/4 full and empty as indicated by the fuel guage when driving. This begs another question - does anyone know how to "damp out" the fluctuations in the fuel guage to get a true(ish) reading when travelling? All the 7's I've owned have had this problem.