Tuning 1974 Fiat 124 Special TC: runs badly

[bizzeebeever]

Ok, I needed to do a tuneup on this 124 Special TC. The car was running perfectly, but everything needed to be checked, as we have emissions testing here (Denver, CO, USA) every year.

This car HAD emissions equipment, like an air pump, EGR valve, and other assorted crap, but most of it has been removed and capped off, and it's run fine since the removals.

I cleaned the spark plugs, cleaned the points, replaced the condensors, cleaned the ignition rotor, and replaced the cap, which had a crack in it. I checked that all settings were nominal (on this car: timing: 10 deg BTDC; dwell: 55 deg, +- 3; point gap: 0.016"-0.018"; fast idle: 1300 rpms, +- 50). I've been doing tuneups on Fiats for 15 years.

When I started up the car after all that, the car ran like crap at curb idle. It misfires like crazy; it doesn't die usually, but comes close. I checked and RE-checked all the settings. I then replaced:

-the points
-the condensors
-the rotor
-the cap (already replaced)
-the plugs
-the plug wires
-the coil wire
-the coil
-the coil relay
-fuel pump filter

I also bypassed all the car's wiring, by wiring the coil to the battery, and also wiring the points directly to the coil. I checked every possible setting for the timing btwn 10 deg and 0 deg BTDC, but nothing solved the rough running. I checked the engine timing, just in case one or both of the cams, or the crankshaft, had jumped a notch on the belt or something (they hadn't). I also compared the new distributor cap to the old one just in case there was any discrepancy. I also searched for vacuum leaks, found 2 small ones, but fixing them didn't solve the problem. I cleaned the carb and choke and throttle linkages with that carb spray, and looked for any disconnected linkages; when I sprayed it down the throat of the carb, the car nearly died, instead of revving up, so I'm betting that the problem is not too LITTLE fuel.

Anyway, car still runs like crap; I'm just looking for some ideas. Since the car was running fine before I started, I'm assuming that it was SOMETHING i did, or something I broke, or something that broke while I was messing around in there.

Any help you can give me would be appreciated.

 

[a73uk]

I`d say check the inlet manifold to head & to carb base gaskets for an air leak.

If nothing doing then I`d have to strip, clean & check the carb,

Any kind of anti stall or anti run on equipment? Has it got an accelerator diaphram, had it got a distributor with a vacuum advance?

Also check the engine earths, battery connections engine/distributor wiring + joints.

Ok, I needed to do a tuneup on this 124 Special TC. The car was running perfectly, but everything needed to be checked, as we have emissions testing here (Denver, CO, USA) every year.

This car HAD emissions equipment, like an air pump, EGR valve, and other assorted crap, but most of it has been removed and capped off, and it's run fine since the removals.

I cleaned the spark plugs, cleaned the points, replaced the condensors, cleaned the ignition rotor, and replaced the cap, which had a crack in it. I checked that all settings were nominal (on this car: timing: 10 deg BTDC; dwell: 55 deg, +- 3; point gap: 0.016"-0.018"; fast idle: 1300 rpms, +- 50). I've been doing tuneups on Fiats for 15 years.

When I started up the car after all that, the car ran like crap at curb idle. It misfires like crazy; it doesn't die usually, but comes close. I checked and RE-checked all the settings. I then replaced:

-the points
-the condensors
-the rotor
-the cap (already replaced)
-the plugs
-the plug wires
-the coil wire
-the coil
-the coil relay
-fuel pump filter

I also bypassed all the car's wiring, by wiring the coil to the battery, and also wiring the points directly to the coil. I checked every possible setting for the timing btwn 10 deg and 0 deg BTDC, but nothing solved the rough running. I checked the engine timing, just in case one or both of the cams, or the crankshaft, had jumped a notch on the belt or something (they hadn't). I also compared the new distributor cap to the old one just in case there was any discrepancy. I also searched for vacuum leaks, found 2 small ones, but fixing them didn't solve the problem. I cleaned the carb and choke and throttle linkages with that carb spray, and looked for any disconnected linkages; when I sprayed it down the throat of the carb, the car nearly died, instead of revving up, so I'm betting that the problem is not too LITTLE fuel.

Anyway, car still runs like crap; I'm just looking for some ideas. Since the car was running fine before I started, I'm assuming that it was SOMETHING i did, or something I broke, or something that broke while I was messing around in there.

Any help you can give me would be appreciated.

 

[Mreg]

Trust me, its the coil! I had a 124 special OHV but still ran fab until I decided to do a tune-up, move the coil so it was accessible, big mistake! It ran like an agricultural wagon! It was all down to a hot, poorly insulated and worn-out coil. Try it, let me know and good luck.

 

[bizzeebeever]

Ok, well, thanks for both your answers. I actually couldn't find this post, so, here I am, three or so weeks later, and I figured i'd re-post, just to let everybody know what the deal turned out to be.

When I went to order the distributor cap the first time, they had pictures on the computer of 2 distributor caps, both of which looked exactly like my old one. So, I ordered the cheaper one.

When the car started running crappy, I SUSPECTED the cap, but I didn't swap it out until I spoke to the local Fiat Guru, at Aspen Import Auto. Turns out, all the fiat Marelli distributors with the posts (those "arm"-looking jacks where the plug wires hook up) oriented in the same direction use the same cap (dot dot dot) EXCEPT FOR THE 1608 cc ENGINE!!! The cap for the 1608 engine looks exactly like MY cap, except that (dot dot dot) the posts inside, as well as the rotor contact brush, are SHORTER. That means the car will still run, but the spark will continually be jumping from the rotor brush to any of the posts, including the right one. (i.e., the car runs like s***.) I couldn't even find the discrepancy, until I'd held my old cap and the new one up, side by side.

Anyway, I'm sure nobody else has a Fiat 124 Sedan TC, but some folks might have the 1592 cc Spider. If you do, make sure you've got the right cap, and don't just "eyeball" it!

 

[Mreg]

Thanks for that info. I thought it had to be down to the spark/coil! Fiat seemed to change its manufacturer of caps, ignition coils, leads and ignition systems from month to month back in the late 60's, 70's and 80's! Well done though and happy driving.

 

[angeloj]

Just a long shot (but one that has happened to me I'm embarrassed to admit) - have you checked that that plug leads have been reconnected to the correct plugs?

 

[bizzeebeever]

Yep, all the leads are connected properly. You know, for our convenience, on this particular cap the leads are marked with the appropriate cylinder number (1 3 4 2, in order, clockwise from the left).

 

[Mreg]

This may again sound silly, I have been guilty of this but has the cam belt 'skipped a notch'? this can result in the engine running from very lumpy to popping, and backfiring. I did a belt change many years ago (22 in fact) on a old Beta saloon. I failed to align all the timing marks on the cams, crank and distributor pulleys. at first the car simply ran as if it was on 2 or 3 cylinders but then started to backfire badly indeed, it threw up flames through the carb! A check on the timing marks revealed one was out of alignment, causing the issues mentioned

 

[rallycinq]

The dizzy cap does sound suspect, if that doesn't sort it do a plug lead pull test to find which cylinder(s) are not firing.

Does the engine smooth out above idle?

Cheers

SPD

 

[bizzeebeever]

>>Mreg: just in case you didn't notice...from my original post (heh, heh)....

...I checked the engine timing, just in case one or both of the cams, or the crankshaft, had jumped a notch on the belt or something (they hadn't)....

Once again, thanks for all your comments. Everything has been solved with the cap!

:slayer:

 

[warbirdal]

Hey, I am the new owner of this car. It has been a fun car. 2 days after I registered it, it got hit in the left fender hit and run. After I got it fixed, it got hit again in the parking lot hit and run same fender. Man what is up??

 

[Cus Habong]

Check the engine timing maybe timing belt slipped over or the initial adjustment is off
( 1, 2 belt teeth off timing) can make an engine running like crap!

Best regards

Cus