Technical Engine cutting out after hard acceleration

[Flipyoung]

Morning! So wonder if you could help me out with a problem that has just started on my 500, a have scanned the net to no avail.

The symptoms are that after hard acceleration the engine cuts out, leave it for a minute pump the accelerator and it will start fine again. It seems to be okay ish if you only accelerate slowly and it will accelerate hard but only for a while then it starts to sound like it's starved of fuel and die.

I was wondering if it's the fuel pump? Any help greatly appreciated

Many thanks indeed

 

[gordinir8]

After the hard acceleration and when your engine cut out check if your fuel line is empty of fuel. I am talking for fump to carb part, normally it must be full with fuel. If it is transparent or has a clear filter it will help you.

 

[Flipyoung]

Yes it does have a clear fuel filter and yes it is empty when it cuts out, does that it's mean it's the pump?

Thanks indeed

 

[the hobbler]

From experience, I have found that the fuel-pump on the 500s and 126s give very little trouble. From your description it sounds that the carb mixture is possibly incorrect, leaving the carb starved (or even over-rich) when accelerating. Check that the choke is FULLY off (pull it off at the engine end) and check that the float isn't slightly punctured. Even a very small crack in it will allow fuel INTO the float, but sadly NOT out! If the float has got fuel in it, buy a new one---for the cost of them it is not worth while trying to repair. It is also worth while while checking your coil and condenser for electrical connection and continuity.
Just for the record, the standard carbs on the 500/126 engines don't have an accelerator pump (technically, it doesn't have choke either--we call it the 'choke' but it is actually a 'fuel enrichment device'), so "pumping the throttle" will have no effect what so ever.
As I have said on many occasions--check the small items first, before you start buying expensive "it might be this" parts--basic 'bush mechanics'

 

[Flipyoung]

Thanks for this.

It is a 650 engine and the carb. Is from a later polish engine with the solenoid cut off but it actually runs really well normally. I think the carb float is a good idea I will check that, but I was rather focussed on the fuel filter (which is fitted just before the carb after the pump)
Being empty hence thought it was a bit further up the food chain? Either pump or small blockage before that?

 

[jjacob]

If the fuel filter is empty then you need to replace the fuel pump. Either the pump itself is bad, or the push rod that actuates it is worn.
John

 

[fiat500]

Thanks for this.

It is a 650 engine and the carb. Is from a later polish engine with the solenoid cut off

Either pump or small blockage before that?

Easy to verify the pump; just take the plastic or rubber pipe off at the carb inlet or pump outlet and crank the engine. It should gush out regular glugs of fuel, more than enough to keep it going at any speed. (Obviously avoid dousing any potentially hot or sparky parts of the engine ).
If it does then it might be worth checking that the solenoid cut-off isn't sticking half closed and restricting the supply.

 

[AndrewHarvey]

I would consider checking the carb float level before more extreme works are undertaken

 

[Vitesse]

Easy to verify the pump; just take the plastic or rubber pipe off at the carb inlet or pump outlet and crank the engine. It should gush out regular glugs of fuel, more than enough to keep it going at any speed. (Obviously avoid dousing any potentially hot or sparky parts of the engine ).
If it does then it might be worth checking that the solenoid cut-off isn't sticking half closed and restricting the supply.

I concur with Peter. Take the solenoid off, two minute job and apply 12v’s to it. Positive to the spade connector and negative to the body of it. You should hear a healthy clicking noise. They are prone to jamming.

 

[Flipyoung]

Many thanks indeed for the replies I will try and check all this tomorrow and report back.

Help really appreciated

 

[looigi]

Hi All,

At the risk of contradicting others here, my 500F has a clear glass type fuel filter between the tank and the pump. It regularly seemingly has no fuel in it and the car runs fine. However my situation may be different to those talked about here as my filter is under suction on the pump inlet rather than pressure on the outlet.

I have tried filling it up with fuel then connecting it to the pump full, but the next time I check it has emptied again. I suspect it is getting gulps of air from the tank when the level drops or fuel sloshes around. Haha, I don't know how it works like that, but it does, so I am not so worried.

One thought on the issue at hand... In addition to the other guys excellent suggestions here, I would also check that the needle valve under (above) the float hasn't got a bit of debris caught in it.

Cheers
Chris

 

[Toshi 975]

All good ideas here with the mechanical fuel pump I agree with the idea of checking the condition of the push rod and its setting. Off the top of my head I believe that with the pump removed the rod should protrude 1.5mm beyond the outer gasket on the mounting spacer at the low point on the camshaft and 4mm on the high point. If you do not have that then the fuel pump will not function to full capacity. There has also been speculation about wether the differential expansion between the steel push rod and the alloy crankcase can diminish the push rod settings on a hot , as in temperature , engine. There are different thickness gaskets made that can help. Also check the flatness of the fuel pump mounting flange. If this has been over tightened , especially if the thicker gasket has been installed between pump and spacer instead of between spacer and crankcase , then I have seen deformed flanges that will loose you up to 1.5mm of the push rod travel. Depending upon type of fuel pump the cam follower can wear quite badly and there are rebuild kits available that include a new diaphragm, valves etc if the rest is OK.

 

[Flipyoung]

Well good evening all and many thanks for the advice.

So armed with this I scientifically tried to narrow down the fault, it seem to only occur after either I had been hard accelerating for a while or cruising at about 70k for 5 minutes or so.

Each time it happened the fuel filter looked empty and when running normally it was full. So I thought it must be the fuel pump. I actually have a spare as I have another 650 polish engine I am thinking of fitting if I rebuild the one in it. Anyway I tried to take the pump off but realised this is not an easy job, you have to take the alternator off too....so instead i thought I would check to see if fuel flowed out the tube to the fuel pump smoothy ...it seemed to be slow so I checked the tube all the way back to the tank and just on the bung where the fuel pipe went from the front tank to under the car the pipe was slightly bent, don't know how this suddenly occurred but I straighted it and played with it a bit and then put the fuel pump back and tried the car ..... all fine! So thanks for all the advice and especially the try the simple things first....i think we inheritently think we need to change something when we have a problem but sometimes it really is a simple fix. Car runs great now and coasts alone nicely at 55mph. The 30 carb on a 650cc is a nice combination.

Thanks again ...