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fiat spider 124 1979 FI dies when hot

Posted: Sun Aug 04, 2019 9:18 am
by masa

I have an issue with my fiat 124 (injection 2.0 engine from 1979). it works well when cold, but as soon as the engine warms up, the engine dies and will not start anymore (starter is ok). if by luck i start it again, i have to keep the revs above 4000 rpm so it runs, else it just dies. once cold, it starts like a charm again.

I took it to my local mechanic in france and we changed the distributor cap, the idler bearing, the water temperature sending unit front, the water tempertature sending unit rear red, the sensor unit water-T-housing.

it did not solve the issue. we are now thinking to change the airflow meter and the lambda gauge as the AFM seems to be catching a little (was already a rebuilt one) and my mechanic thinks it might get stuck and engine gets flooded...

before I try that (which is going ot be a pain as I have to order a rebuilt AFM from the US as there are none available here in europe apparently) I was wondering if you guys on the forum might have other ideas.



Re: fiat spider 124 1979 FI dies when hot

Posted: Sun Aug 04, 2019 2:15 pm
by bartigue

I'd say the problem with the AFM needs to be address no matter what, if it sticks then the engine is going to have issues.

Usually when I have a car that runs well cold and then dies hot I change the temp sensor - you did that - and if that doesn't fix it I test the cold start injector. If the injector is staying open then you have too much fuel when running, which is why it would run at high RPMs or when cold but not at lower RPMs or when hot.

So check the CSI and thermo time switch.

Re: fiat spider 124 1979 FI dies when hot

Posted: Sun Aug 04, 2019 7:28 pm
by miker
The GM HEI-4 module under the coil can also fail first starting when it gets hot which I will admit usually takes longer than just the first engine warm-up. But it's a cheap part and if the module isn't your problem, keep the old one you replace as a spare, it will fail eventually. Where are you in France, by the way? My daughter lives in Toulouse.

Re: fiat spider 124 1979 FI dies when hot

Posted: Sun Aug 04, 2019 9:04 pm
by rridge
An air leak between the AFM and the throttle body would explain run cold, stop hot. A rich cold mixture will cover a lean condition caused by an air leak. The usual leak source is a crack in the plastic hose between those two components. Sometimes the crack opens and closes as the engine rocks on its mounts. The AFM is a reliable component.

If your mechanic thinks the Lambda sensor is a possible cause, search for a new mechanic. The L-Jet system was used on many European cars of the period. By the way, Spiders did not come with fuel injection from the factory until the 1980 model year.

Re: fiat spider 124 1979 FI dies when hot

Posted: Mon Aug 05, 2019 2:30 am
by masa
thanks to all who have replied so far. I will tell the mechanic to check the various parts you mentioned before changing the AFM and lambda gauge.
if any other ideas, let me know.
@miker, I live in Dubai (united arab emirates), but the car is close to biarritz where I typically go for the summer.