Thread: Major engine trouble

Check the diaphrams in the carbys

Originally Posted by Bang_Bang

Hi everyone,
I registered my '78 2 door rangie on friday and got 3 days of trouble free use until yesterday when the engine decided to start playing up. I've spent several hours tinkering with it trying to solve the problem but come up with no solutions so I'm hoping somebody on here may have a clever idea about what it might be. at the moment its producing about a quarter of its usual horsepower and wont rev (i dont have a tacho on it but id say it isnt reaching 2 grand at full thottle). my first thought was a vacuum line and i found the spark retarder vacuum line to the distributor was broken off up at the intake so i fixed that but it didnt solve the problem. iv checked the plugs for spark and reset the gap on them all and checked the timing. i did have a problem in the past where the linkage between the 2 carbies (it has the twin strombergs) was missing when i bought the thing and i didnt realise for a while because it ran reasonably well on one carby but then that carby started doing exactly what is happening now (no power or revs). replacing the linkage fixed it and it ran better than ever and continued to do so up until yesterday which suggests a problem with the carbies but it was such a sudden change as i drove it to uni at 8 oclock with no dramas at all then at lunchtime when i started it to go home it was playing up. it has trouble starting cold (it usually fires straight into life all the time) and i need choke to get it going but once it has run it will consistantly start first go and it idles perfectly. even revving in the low revs is incredibly smooth which seems so strange to me when its producing such little power. anyway if someone has had similar issues or has any suggestions to things i could do to fix this id really appreciate hearing about it. my only ideas at this point are that its a fuel supply or carby issue but i didnt want to race in and pull things apart when i dont completely know what to do.

Jack Stephens

yep, seconded, sounds like diaphragms in the carby to me..

Ive got it down to 20ish minutes to change both.

drop me a line if you need a hand and failing that limp it to MR automotive.

How many uni students can you fit in a 2 door during O week? Bit OT, but there must be an answer.

DL

Thanks alot guys ill look into it. i dont know a whole lot about the carbies, can you give me the jist of whats involved in replacing the diaphragms?

remove the dampners from the top undo the bolts retaining the tops of the carbies, pull the piston and diaphragm out noteing the orientation of all the bits on the way out

undo the screws that secure the diaphragm to the piston, remove the plate, the diaphragm, replace and then put it all back together.

you should carry at least on spare, a complete rebuild kit isnt that expensive and may be worth looking at especially if you have any fuel staining under the carbies.

From memory, you remove the intake tubes, and maybe the filter box.

Then 4 screws on the carby tops, and lift off.

Grab the big spring, and put aside.

The piston and diaphragm assembly just lifts out. ( but make sure you note the position of the piston, as it should only go back the same way - there is a notch in one side, from memory) and don't disturb the pin that protrudes from the bottom.

A few screws hold the diaphragm in place. Just remove them, take out the diaphragm, and replace with the new one.

Follow the steps in reverse, to put it all back together, and don't forget to top up the oil in the reservoirs (under the the little black caps on the carby tops) at the end.

A pretty simple operation.

We've actually made them out of a couple of layers of glad-wrap once, when we broke down in the Flinders Ranges. Worked long enough to get back home again.

good call guys both were buggered, put 2 new ones in and it hauls ass now, its clearly been running on 1 and a bit carbies the whole time iv had it. i cant believe how well it goes now, thanks alot for your help.

dont forget now that youve messed with the carbies check the balance of them....

its unlikely that they will be out but if its been "tuned" with a shot diaphragm now that its got new ones the "tune" will be out.