1500 FWD Rough Running when hot

[rhisiart]

Hi there - I wonder if any one can help or offer advice to an annoying problem I'm having with my '72 FWD 1500.
I've no technical knowledge unfortunately, therefore any descriptions I give are purely in layman's terms.

The symtoms basically are - after a long(ish) run of about 30 miles the car runs very rough indeed. It missfires, and is lacking in power. Sometimes it stalls completely but then restarts and struggles on at about 10mph. This stopping/starting routine can go on for a few miles. This has also happened after about half an hour or so of typical town driving - lots of stop/starts etc. Its come to the point when I now don't have any faith in taking her out anywhere!

The guy who does my servicing reckons it was pinking badly, so he retarted the timing. This has improved the general feel of the car, but it doesn't seem to have cured the above problem. Back to square one therefore.
The temp gauge never shows that it's running 'very hot' by the way, the needle stays in the centre of the gauge at all times. The car is relatively low milage - 30k.

Some background, in case it helps. The car was layed up for several years prior to my purchase. Consequently, I took out the petrol tank and had it cleaned. Fitted two petrol filters, just in case, and it's had a new petrol pump. I run the car on regular unleaded with Castrol Valvemaster additive.

Finally, if I'm pottering around locally in the car, doing around 30/40mph, the car behaves itself fine - never any problems. It seems that if the car comes under any sort of pressure, or driven 'hard' in any way, this problem appears. Perhaps it's just the fact that it's bone idle!

Any advice gratefully accepted!

[Jon Tilson]

Looks like you have some sort of fuel starvation. I would clean out the carburreter and fuel pump.
Not sure what comes on a 1500fwd but the pump is mounted on the engine block and may well have a removeble top with a guaze filter.
Clean that and try again. Also if yo have an SU carb its easy to take off thel float chamber cover and have a look inside. Clear out any drirt and blow through the jet. A bicicle pump is a good source of a quick jet of compressed air.

Jonners

[mbellinger]

If you can, replace your condensor and coil with known good ones. Do them one at a time so you can see if either makes a difference individually.

Check the thin vacuum pipe to the distributor is not pinched or damaged. Do the same with the fat rubber pipe from the servo to the inlet manifold.

Check for petrol leaks from the carb, and also that the gasket between carb and spacer block, and spacer and inlet manifold are in good nick (if you spray WD40 here with the engine idling and the revs increase you have a leak).

Finally if you can run the engine with the bonnet open in the dark and look for any arcing around distributor cap and leads.

Do these things plus what Jon says above, then report back.

[rhisiart]

Thanks guys. I'll give those suggestions a go and see what happens. I should have added that I've fitted electronic ignition to the car fairly recently. As I said, the fuel pump is new and I hadn't suspected that as being a possible culprit this time.

[1300dolly]

Do you have a heat sheild fitted betwen the carbs and block?

[1300dolly]

Do you have a heat sheild fitted betwen the carbs and block?

[rhisiart]

No I don't have a heat shield fitted. Would that make a big difference?

[mbellinger]

Yes it would as heat from the exhaust manifold will cause the fuel to vapourise.

Rimmers did have some NOS ones for 1500FWD. they also crop up on eBay from time to time. Or you can make your own from mirror finish stainless steel if you have another as a pattern.

[1300dolly]

IIRC the Rimmer ones were about £5.

[Jod Clark]

Check your fuel filler cap, this sounds like a classic case of tank vacuum to me....

When the car starts playing up, stop, remove the filler cap and listen for a whoosh of air as you remove it. Replace the cap and try driving again - 50p says it will be fine. You'll need to take the filler cap apart to rectify the blocked breather hole which is tiny.

[rhisiart]

That's an interesting notion, many thanks. I'll certainly check the breather hole in the cap and see what happens.
By the way, RIMMER'S still have the carb heat shield in stock at £5.73 + vat. I'll be fitting that as well... just in case.

[rhisiart]

Hi there.
A further - and hopefully - final chapter in this saga. Many thanks for all the replies and helpful suggestions.
Right, I went through everything methodically, trying to eliminate all the obvious causes. The carburettor was stripped and cleaned, but apart from wanting a good clean, it was found to be all ok.

I took the petrol cap apart and poked around with a small brush and pin, trying to get it clean. Couldn't for the life of me find the breather hole though. (Can anyone let me know its location?) When the car played up again a week or so ago, I stopped and opened the petrol cap - no 'whoosh' sound was heard - but I drove on for a while with the cap open, but this unfortunately didn't have any effect. The fuel pump is new, and the fuel filters were clean, so the fuel system was discounted as the source of the problem.

Thoughts were then turned to the ignition system. The (Lumination) electronic system was disabled and points and condenser re-installed. The car still wouldn't go smoothly. This left the coil. A new one was ordered and fitted and .... BINGO ... the car ran perfectly. Obviously when the old coil got hot, it wouldn't deliver the required voltage.
I've also fitted the carb heat shield I bought, just in case.
I took it for a 60 mile round trip today and pushed it hard along motorways and 'A' roads and it didn't miss a beat. So there we have it.
Again, many thanks to everyone for being so helpful, and I hope the saga can be of some help to anyone with similar symptoms the future.

[1300dolly]

Good to hear it sorted.

[mbellinger]

I too am glad you sorted it.

There are an awful lot of very poor quality aftermarket coils about the place nowadays. One of those things where it definitely pays to buy the very best that you can.