Losing power and stalling

[72928]

Not sure if this is in the right topic but... Got a 75 Spitfire 1500. Its always been reliable bit over the last year it's had a problem which is stopping me using it. It starts fine, then after around 10 miles (sometimes more, sometimes less) it starts juddering and losing power. This progressively get worse until the engine stalls. After a while it will start again, then the same thing happens. Eventually I can manage to limp home, although there have been occasions when a breakdown truck has been needed.

 

It's been in a garage a number of times with no verdict because it runs fine until hot. I thought it was getting sorted out after replacing the fuel lines and pump but it just went a bit further before the same story.

 

The fuel lines have all been replaced, also the fuel pump and it has a new glass filter, plugs, points, HT leads, coil and condenser. The carbs have been refurbished and its been tuned, all to no effect. I've tried lifting the petrol cap in case its a vapour lock but there's no rush of air and no effect. Winter or summer temperatures makes no difference.

 

It has had an electrical problem (an issue with the hazards switch), hopefully sorted today but, due to heavy showers I haven't ben able to try it out.

 

Does anyone have any suggestions as I'm at my wits end and will soon be losing another summer's fun?

[AndyTV8]

Not sure when the change-over to ballast took place - but do you have the correct coil for your set-up? 1.5 ohm for ballasted, 3 ohm for non-ballasted.

 

HT-wise I'd complete the replacements by replacing the distributor cap and rotor arm.

You could also rule out points/condenser with a swap to an electronic ignition - at £25 a powerspark (which includes a decent red rotor arm) probably wouldn't break the bank.

 

....... Andy

[Red Devil]

I'm really no expert in these things but if you come to a standstill does it cut out altogether? If so it sounds just like the breather problem I had on my gt6 when I purchased it but which was soon resolved by running a hose down away from the engine instead of the little pancake air filter that was attached to the breather on the rocker cover. I'm not saying it is this but the symptoms certainly sound similar.

 

At least it gives you something else to consider or rule out.

[Pete Lewis]

This has all the hallmarks of a sticking choke mechanism under the carb

 

Just check after pushing the choke in that the jet base returns fully up to its adjusting nut

just a prod with a finger under the carb will work , if its pops back then thats the problem and the

micky mouse levers need examining for distortion misalignment and some lubrication

 

if the jets have temperature compensators /waxstats then they may well be in need of replacement

or read about removing the waxstat and replace with a 1p

Do the simple prod test first

 

pete

[72928]

Thanks for the suggestions. With the coil, I've no idea what sort it should be. However, the one that was put on when the car was originally rebuilt worked fine for years until the problem developed last year and the same type was put on a replacement so I'm guessing its the right sort. I want to keep the car reasonably original so have never wanted to go down the electronic ignition route. I'll look at the distributor cap and rotor arm again though.

 

I genuinely don't think its a breather problem for the same reason as above, its run excellently for years.

 

Sticking choke's interesting and I've not heard of that one before so will look at it further if I can figure out what to do . This may not be relevant to the issue but the revs at idle used to stay quite high (about 1000rpm) but after everything done recently they are dropping down to round 600-ish and staying there.

 

Thanks a lot. Any more advice welcome.

[Colin Lindsay]

Pete might be on the right track with flooding; I had this experience once when I detected an engine misfire and stopping at the roadside with no diagnostic tools adjusted my carbs to run too rich; after about fifteen miles the GT6 ground to a halt. After a few minutes of inspection it ran fine, until the next time - the few minutes with the bonnet up allowed the excess fuel to evaporate and the car ran as normal, until the fuel built up again and it flooded. A friend adjusted them for me when I reached the show I was going to and told me that if I touched them again he'd remove both my hands at the wrist.

[72928]

It's some time since I posted this, and things have finally developed. After two (or possibly three) replacement rotor arms and a developing relationship with the AA the spitty finally died completely at around the same distance from home earlier this year following the same symptoms. However his time it wouldn't restart at al. The AA guy who came out took a look and said the rotor arm was shot and it was back home on a truck again. This time I bought a red rotor arm from the club, fitted that and it started straight away and behaved quite reasonably for the short trip out as a test and sounded far more positive.

 

I also replaced the voltage stabiliser behind the dash which seemed to fix the non-working temperature and fuel gauges so it all seemed to be sorted out. Went out this weekend in the heat and everything seemed fine except that after about 10 miles or so the idle speed seemed to be sticking at about 1500 suddenly and there were a couple of hics but nothing bad. Out again the next day and the same thing happened, together with no temperature or fuel gauge, and suddenly the rev counter stopped working. They were OK again after a stop and cool down, then on the way home a coupe more hics and the revs went back up o 1500 on idle.

 

I think the rotor arm may have sorted most of the original problem but what's going on now? We're back to high idling again and I'm starting to wonder if I'll ever be able to go anywhere.

 

Any further suggestions very welcome.

 

PS. Just bought a couple of new carb springs and cable in case they need replacing (the cable has a kink in it), plus a new oil filter.

[Pete Lewis]

if there is no slack /free play in the throttle outer /inner  when temperatures rise the outer expands which opens the throttles

adjust the threaded abutment or cable to give some slack at idle 

 

do check the choke is fully returning, stick finger under the jet and push upwards , if it moves its sticking on choke when you think the knob is fully in its not so at the carb end.

 

as for odd electricals the normal culprit is the fuse box , the bladed that contact the fuse caps use the cap to feed extra circuits

the fuse cap bridges the two sprung blades ,, either end of the fuse ,  have a look and a good clean .

 

Pete