Fuego issue...likely electrical

FuegoFan

Member
Tadpole
Joined
Apr 23, 2011
Messages
66
Location
Doncaster East VIC
Hi all

My ‘85 Fuego has been with my mechanic all lockdown and is nearly ready for club rego, but there’s one thing that’s been hard to trace.

The engine is breaking down under load around 4500rpm. The TDC sensor has been replaced, along with the distributor cap, leads, plugs and coil.

Anyone had the same issue, and if so, what’s the next piece of the puzzle to check?

Cheers.
 
Last edited:
Check that your new TDC sensor actually works with your multimeter - should have resistance. Also next step would be your coil. If you need one I have but am sure you could probably get one locally.
 
Thanks Barry. I appreciate it.

My mechanic has tried 2 coils and 2 TDC sensors without success. Very hard to figure out what’s going on.
 
If you can lay your hands on another Vacuum capsule (the coil is also mounted on the capsule frame) unit. I have had one unit fail in the past and was lucky enough to source a replacement from Neil Hartrick at Le Fix (moved - location unknown) and that fixed the problem, similar issue to yours - new ones unobtainium sadly, very hard to diagnose the problem.

Ken
 
If you can lay your hands on another Vacuum capsule (the coil is also mounted on the capsule frame) unit. I have had one unit fail in the past and was lucky enough to source a replacement from Neil Hartrick at Le Fix (moved - location unknown) and that fixed the problem, similar issue to yours - new ones unobtainium sadly, very hard to diagnose the problem.

Ken

Thanks Ken! Will do. Hope you’ve been well.
 
Are you sure it is electrical??
Could it be a fuel supply issue?
The complete fuel supply system on a fuego is not that great. Pretty much from the tank to the carby is a disaster waiting to happen. rusty steel tank, Blocked breathers and roll-over valve, non venting caps, damn octopus of doom, old barely adequate fuel pump, temperamental carby.......

4500rpm is getting near to peak torque.

For the record, I have never had a TDC sensor go bad. Being a Renault, the connector might have made a suspect connection, or the tip may have been covered in crud, but I can't say I ever remember any of my TDC sensors not working.

Being a dumb dizzy, not much can go wrong with those either, at least compared to one with points.
Assuming it is more or less pointing towards the right cylinder when bang is needed, you'd have to be really determined to make one fail.

Cant really comment on the other components because I always ran EFI.

Jo
 
Thank you for all of the replies. These are all things I’ll keep an eye on as I get back behind the of a Fuego after so many years.
Might have some good news from my mechanic...
“Sorted out. Now running well, looks like it may have been out of timing for a while.. found dist timing has been played with, advanced tIming to fix it.”
 
Thank you for all of the replies. These are all things I’ll keep an eye on as I get back behind the of a Fuego after so many years.
Might have some good news from my mechanic...
The distributer has no timing. it simply distributes an already timed spark...
Anyway, I won't let details ruin your day that seems like it is getting better with a well running engine.
 
When you say it is breaking down under load at 4500 rpm is it a sharp miss (electrical ?) or a hesitation miss (Fuel?)

I have found over the years, the only way to detect a fault is to laboriously chase it through until you locate the fault.

With electrical I would firstly run it after dark, to reveal any visible earth tracking, then methodically work through the electrical system, visual examination, test and replacement with a new part when I had those on hand. new plugs - new leads

Fuel - I would check the pump and filter, look for loose or cracked hoses, missing bits, check around the exhaust manifold for cracks, signs of vapour escape (white residue) or ingress of air - all of that will cause missing at certain speeds. Has the owner fiddled with the idle speed knurled mixture jet - is the mixture too rich or too lean - Check the idle speed mixture jet, C02 adjust screw at the base of the carburetor (often has a cap fitted to prevent fiddling with this) Screw this in gently and then back it off 1 and a half turns, and then adjust between the knurled mixture jet and the idle speed jet at the base of the carburetor, take it for a test drive and do minor adjustments till it runs well across the range.

If that doesn't fix the running, start working your way through the fuel system, the tank cap, does it build up pressure in the tank when running that gives a whoosh when the cap it opened - if so it probably hasn't been modified . Try a vented cap or just leave it off and see if it makes a difference, then it is on to fuel lines right through to the carbon canister that captures excess fuel vapor. I have come across and fixed so many problems it is testing the memory now to list them. Anyway that is a start, clean the filters and don't forget the small one in the carby inlet (if it is still there) My next check would be the Constant C02 cutout canisters are they connected and working correctly.

Maybe teaching people to suck eggs, but logical checking through with Fuego running problems solved all problems and saved time in the long run. To the point you enjoyed using the vehicle.

Ken
 
Thank you for all of the replies. These are all things I’ll keep an eye on as I get back behind the of a Fuego after so many years.
Might have some good news from my mechanic...

Often that sort of problem indicates that when the timing belt was replaced the toothed belt might be one tooth out, so the distributor range has to be slightly adjusted. Mind you moderator Mistarenno (Richard V) used to modify the TD Sensor bracket (fixed position on the quadrant mounting over the flywheel) by elongating the bolt holes to give the flywheel sensor pick up extra advance on his car - and better performance.

He also modified the carby choke settings for better running after startup.

Ken
 
Thanks for the info Ken. The car has been with the mechanic since the start of lockdown so I haven’t driven it, but I should have it back soon. I’m told it’s running well now that the timing‘s been adjusted.
Hopefully Melboune is lifting restrictions soon so I can get it on the road.
 
Just had a similar problem with my son's Fuego - missing under load when it got to normal running temperature. Changed a lot of things, especially with the ignition, and it seemed to make no difference. Then decided it may be a fuel problem so replaced the pump and the fuel filter and had the carburettor reconditioned. The problem was still there and so I then decided to have a good look at the fuel tank end of the car. To my surprise there was another fuel filter just near the tank outlet and it was really dirty. I don't know if this is a later modification on this car but changing it seems to have finally made a difference.
 
the fuel pressure regulation of the Fug is a hit 'n miss affair relying on the continued viability of a tiny bore steel tube return circuit. The r20 has the same silly system. Both are excellent candidates for an electric impulse pump, my r20 gave much improved running, better economy and performance after fitting a "Fedtro 40104" under the floor, near the tank. A new filter between the pump and the tank is good move.

cheers,
Bob
 
Just had a similar problem with my son's Fuego - missing under load when it got to normal running temperature. Changed a lot of things, especially with the ignition, and it seemed to make no difference. Then decided it may be a fuel problem so replaced the pump and the fuel filter and had the carburettor reconditioned. The problem was still there and so I then decided to have a good look at the fuel tank end of the car. To my surprise there was another fuel filter just near the tank outlet and it was really dirty. I don't know if this is a later modification on this car but changing it seems to have finally made a difference.
Thanks Fregate. I’ll check it out on my Fuego.
 
the fuel pressure regulation of the Fug is a hit 'n miss affair relying on the continued viability of a tiny bore steel tube return circuit. The r20 has the same silly system. Both are excellent candidates for an electric impulse pump, my r20 gave much improved running, better economy and performance after fitting a "Fedtro 40104" under the floor, near the tank. A new filter between the pump and the tank is good move.

cheers,
Bob
Cheers Bob!
 
had issues with some of the return fuel lines to the tank 'causing suctioning ' closing off - old rubber lines causing a miss and fuel starvation
 
Top