Car runs poorly after sitting for about a week, then ok

F

flatcrank

Low Mileage
1979 X19

Odd situation, the car runs perfectly when used regularly. But after sitting for about a week, the car will start but feels like it is missing a cylinder, have to keep the revs up to about 2500rpm, once warmed up it runs perfectly. After cool down, say overnight, it will start and run fine. But every time after sitting about a week, the problem recurs, but only on initial start up. Hard to diagnose becauase one has to leave the car alone for a week and try to catch the problem for the fairly brief warm up period. Not obvious that it would be caps, rotors, plugs, which are all reasonably new (<5,000km), carb was rebuilt a while ago.

The car is a high mileage vehicle (original owner is my father) and due to his age it sometimes sits longer so the issue has become more problematic of recent.

Any thoughts as to what to look for? Runs fine warm or cold, just after sitting does the problem present.
 
It may be a function of the fuel bowl draining down or the fuel evaporating out of it. I would start looking there before looking to much farther afield.

Try pulling the excite wire from the coil and then letting the car turn over for a minute before plugging it back in. Don't pump the pedal or anything, just turn the engine over to get the fuel pump to prime the carb with fuel.

After that it may start and run properly. If not, its on to the next thing.

The next thing might be just tightening the carburetor down onto the manifold as it may be a bit loose and allows some air past the gasket but once it warms up things expand and allow it to run properly.
 
Thank you, that was a very quick response. Will get on it, and see if that id's the issue. If the fuel bowl is draining, what causes that?
 
flatcrank said:
Thank you, that was a very quick response. Will get on it, and see if that id's the issue. If the fuel bowl is draining, what causes that?
Click to expand...

There can be a number of things.

First and formost is evaporation. This can be exacerbated by someone removing the evaporative emissions system. It might take a week to do so and would explain why you don't have a problem overnight or on recent restarts.

Secondly and quite likely is that one of the membranes for the accelerator pump or one of the other membranes has a leak in it that slowly drains the fuel bowl. Again it might be a small drip that evaporates nearly immediately so you don't notice it over a short time period. A complete rebuild kit should have the parts you need in it but check to verify before buying one. Many of the kits don't have all the replacement parts in them anymore.

Some other areas that could be a problem are the anti drain back valve on the fuel line such that the fuel pump loses some of its prime or needs to push fuel fresh fuel through and takes a bit to replenish the bowl so the car runs poorly in the meantime. The fuel pump might be starting to fail but seems unlikely given that you don't mention other running problems.

I am sure someone else will come along with some much better suggestions or an experience they have had.

Good luck.
 
This is why many of us install electric fuel pumps, to get the carb primed after the car sits for a week or more.
 
Mileage is not a "best by date". That myth needs to go away as actual condition of the car is FAR more important than mileage.
Age of the contents and actual condition of the contents are a much more accurate and precise metric of the car's condition.

Better to check, replace, rebuild and do what is needed to assure the condition of the entire fuel system (carb, hoses, filter, pump and all related) is in known prime condition. Leave nothing alone as modern fuels are not vintage fuel system friendly. Once the fuel system has been confirmed in prime condition, move on to the ignition system and do the same.

Don't skimp on replacement part quality. Use only OEM equal or better replacement parts. This is where penny saved will ended up dollars wasted will apply.

Do give your exxe an Italian tune-up once the power train has been warmed up. This is one of the very best things to do with an exxe, keeps it healthy and good for the driver too.



Bernice
 
Yes indeed. Ed Cohen bought a very low mileage X and still ended up replacing all the rubber lines with much Improved running. When I used to do track days (the ultimate Italian tuneup) my Fiats seemed like a different animal afterward, brakes were much better and engine seemed happier. Your Fiat likes strenuous exercise just like your dog does.
 
You must log in or register to reply here.
Back
Top