drop in power and puf puf sound

85Santana3 · Feb 6, 2014

I have a 85 series 3 (petrol) and we have recently changed carb, fuses, distributor, plus a lot of engine work. None the less occasionally without any apparent reason there is a drop in power, puff puff sounds come out of exhause (simultanous shake). It is driving me mad because every time I take the the truck back to the mechaic everything is perfectly normal and eninge runs like a clock.

Today as a test I tried to remove the cables going to each of the spark plugs (while engine was running) and got a shock touching the third cylinder's spark cable.

I have tried to find a pattern when this drop in power happen : When fuel in the tank is low (less than 1/5 left) or when weather it is cold.
Does these signs tell you anything? What can it be?
thanks in advance.

CalumM · Feb 6, 2014

Changed your fuel filters?

85Santana3 · Feb 6, 2014

It did not have one, I added a new fuel filter last week. It is not original LR but very similar. I installed it just before carb (right location?) Also you said "Fuel filters". Is there more than one?

Carrington224 · Feb 6, 2014

Sounds like one or more HT leads tracking, stick a new set on an see what happens.

joe27979 · Feb 6, 2014

HT tracking or bad engine earth. spark always finds easiest route to ground-if it liked going through the lead into you then it doesn't like going though the engine earth back to battery.

check your engine/chassis/battery earths as well as a new set of leads chief

85Santana3 · Feb 6, 2014

I will change the leads, thank for suggesting it guys.

How do I check for earth being messed up?
Where is it supposed to be on engine?

I am convinced this is a problem (if not the problem) becasue the red light on instrument panel is almost always on.

samc88 · Feb 6, 2014

Red light is a charging problem which could be linked to the alternator circuit.

I think if I remember right, the starter motor is earthed to the block and the block is then earthed to the chassis.

ronsealdeath · Feb 8, 2014

joe27979 said:
HT tracking or bad engine earth. spark always finds easiest route to ground-if it liked going through the lead into you then it doesn't like going though the engine earth back to battery.

check your engine/chassis/battery earths as well as a new set of leads chief

I had this problem and it was leads as suggested, good practice in this damp weather to do a service on electrical components. Most people use crap quality parts but if you can try and buy bosch leads and champion plugs etc

85Santana3 · Feb 8, 2014

Thanks for your replies everybody
Earth was OK. I changed the leads and fuel pump and the problem seemed solved for now.
Probably saying this is going to make me look like a fool but I went through the manual and there is only one fuel fiilter so hopefully its the end of it.

ciderman · Feb 12, 2014

Change you plug leads, modern one always seem to fail after a while, britpart even sooner.............

drop in power and puf puf sound

85Santana3

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CalumM

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85Santana3

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85Santana3

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