'bucking' at road speed problem.....

I have a 1978 1800cc with carburator. When I get up to road speed (about 50 mph), the car starts to 'buck' violently. At low speeds this is not a problem. It started a few days ago and has gotten worse. I am thinking something with the distributor but am not sure about this one. Any Ideas?

Possibly a fuel delivery issue: it could be that when you get to 50 mph, your fuel requirement is more than the system can deliver. Check your fuel filter and pump.

Hey,

Stange, I have the same problem. I have done diagnostic research on it, I too think it is a fuel delivery problem. To comfirm that hypothisis I install a timining light on the main coil lead, stuck the light outside the hood, closed the hood, then took it for a spin. My Spider bucked down again but the timing light was consistant (good). So it the fuel somewhere. unless it is an advance timing issue, but because the problem happen some times I don't think it is the advance.

I am rebuilding the carburator tonight, let you know how it goes.


Bob
79 X 1/9 (USA)
74 Spider (USA)

Fixed it!

Althought the carburator had lots of dirt in it, the more pressing problem was crumbs in the fuel pump. It took the fuel pump apart and rebuilt(clean) it too. It is a very easy task. but, if you plan in taking this electric fuel pump apart yourself watch for that tiny ball bearing inside! don't lose it.

The strainer on my fuel sender was gone, I install a fuel filter between the gas tank and the fuel pump.


All good now.


Bob

Man...I guess this is a popular problem! I have the same problem, except I have a 1979 Fiat Spider 2000.

When i get to about 40-50 mph, the engine starts cutting out, but then I take my foot off the pedal a bit and it works fine. This only happens occasionally, but it is definitely not safe.

I will try removing the fuel pump and cleaning it out, but is it necissary to do the carb too? If I can I would like to avoid it...

daddyo88 - did you ever get yours working?

I don't think the carb is necessary if the problem is fixed after cleaning the feul pump.

*When disassembling your fuel pump watch for the small ball bearing, don't lose it (I learned that the hard way). Place yourself a clean shop surface.

I put a clear filter at the engine compartment to watch it fill; it doesn't fill very fast. Maybe the pump is getting old, I will order a new one anyways.

The carb is easy to disassemble and clean.



Bob

Guys,
I dropped my fuel tank and had it cleaned, blew out the lines with a compressor and changed the fuel pump. Starts and runs for a few moments but then starts sputtering and dies. Trying to restart, I have to grind on it for a good while but it will eventually restart. I removed the little check valve (?) between the fuel pump and the carb because it was hard to blow through and I thought it might be part of the original problem. Did I screw up?
I'm gona pop the top on the carb and see if the float bowl is clean. I cleaned it BEFORE I dropped the fuel tank and was probably out of sequence on that one. Sigh, does it ever end?

Yes, you screwed up. The check valve is to keep fuel from draining back when the car is off. With the valve removed, the fuel drains back and you have to crank the engine until the fuel is pumped back up. Put a new check valve back in.

Do you have fuel pressure (4-5 PSI I beleive, my is at 4psi)? You should if you did all of that. There is a fuel filter on the carb itself (right at the entrance of the fuel after the fuel filter), maybe it is plugged (remove and then clean type). Maybe the fuel passage are somewhat plugged in carb entrance, or the fuel float needs to be check for the right height.

The check valve is not issue if you took it off and it does the same problem, unless you put in the reverse way.

Now that I think of it I think that my problem was that the electrical fuel pump was not quite getting enough juice to turn fast enough and pump up fuel. What clues me in on this, is that my filter, right before the carb, is transparent(so I can see the fuel going throught) was always at 1/4 full while running. I put my car on the hoist for an after restoral check and found that my alternator belt was too loose and it was not giving enough juice to electrical system. I don't your prob is this one.

Are you getting sparks even while driving?


Bob

hey guys.

I just did a big tune up on my car and the problem seems to have gone away. I replaced the Condenser and the fuel filter as well. I think that one of those had something to do with it, because I know of cars having similar problems due to a bad condenser or clogged fuel filter. I suggest that if you haven't solved the problem yet, then replace the condenser and fuel filter aswell...

Jacob