Wondering how to go about trouble shooting this. I have a 650 engine in a car a bought from near sea-level. I've bought it up to 3000ft altitude where I live. I have a hard time believing its just running so rich to be washing down the walls of the cyl to have so much in the sump. Car runs great and doesn't smoke.

I was first thinking the fuel pump must be leaking. Not sure how to check it but was going to remove it to look. Thing is, my pump has a rather large spacer and doesn't appear to be able to come out without removing, or at least moving, the alternator. Is this the case? I should snap a pic...the pump is also not like any ive seen listed as both fuel lines point straight up. Regardless, if I get it off, would I be able to confirm if it leaking or not?

So next its running a Delortto 32/28 carb. I removed this late last night maybe expecting to find a stuck float needle or a cracked float full of gas but neither were true. It's still on my bench and I found the float adjustment specs so I'll confirm that when I get home. Anything else on the carb to check?

Thanks

Oh, another thing I'll mention...while I was there tinkering with the fuel pump I changed the alternator belt finally. While doing this I was hand cranking the motor. I did start the car recently while doing all this and when I stopped it I noticed lots of clean gas dripping off the bottom fan shroud. This would normally have ended up on that tinware down there but I had removed it. I assume the gas must have been coming from up top and down front of the motor and it appeared that under the carb was wet. This is why I moved on to the carb.

Could hand cranking the motor have caused this problem if the carb was otherwise fine? Or does this confirm the culprit is the carb overfilling and leaking fuel down the manifold?

It appears that your carb is flooding. Float may be punctured or porous, or needle valve worn out. Some older floats and needle valves are attacked by the ethanol in current fuels. May need to source ethanol resistant items.

Pump may be putting out too much pressure, but this is unlikely unless it is new and the wrong one. If it has been on there a while, any overpressurisation would have shown up sooner.

Check that the needle-valve (in the float chamber) isn't sticking---if it is staying open, that will cause the engine to flood. Also, give the float a shake---check that there is no fuel in it--this will also cause the carb to flood. By the sound of it, something is causing the carb to flood (and no, hand cranking won't cause the problem). The big spacer between the crank-case and the fuel pump is correct. There are 2 shapes of fuel pump---1 is designed to be fitted to the engines with alternators--the bottom of the pump is angled, to allow easy removal (with the alternator still in place). the other shape of pump has a flatter bottom, and can be a real bugger to remove!

I appreciate the reply.

The carb is on my bench with the cover off and the floats seems fine/empty. How do I diagnose of the needle valve is worn out?

The pump definitely doesn't look new but it's also not any typical pump I've seen listed for a 500 or 126. I've only owned the car since last fall and then its only been on the road for a couple weeks so if the pump is over pressurizing this would be me noticing for the first time. Gas smell in the Oil was my first clue last week, changed it out and was smelling like gas again in just a couple days and 20km of driving.

Hi Sprockett,

This may help.

https://www.fiatforum.com/500-classic/423634-dellorto-32-28-fzd.html

Chris

Thanks for that.

Reassembled the float and tested the float valve holding the carb upside down and blowing into the fuel Inlet. No leaks. Trying to put the lid/float back on the carb took more fiddling than it should have though. Held the carb upside down and blew...was able to force air past the valve

Turns out that in order to fit the lid, the float pin had be driven so far through the slotted bracket that the keys on the pin were interfering with the floats movement. I ground down the key side of the pin and everything went back together much easier. The upside down test confirmed a good seal on the float valve.

So I changed the oil again and see if this fixes the issue.

Have you checked the diaphragm in the fuel pump as a leak could drain back to oil.

Sprockett said:

Turns out that in order to fit the lid, the float pin had be driven so far through the slotted bracket that the keys on the pin were interfering with the floats movement.

Click to expand...

The keys on the float pin should engage with the non-slotted support and should be nowhere near the float itself. Is this what you mean?

Chris

Maigretnz said:

Have you checked the diaphragm in the fuel pump as a leak could drain back to oil.

Click to expand...

No not yet. As mentioned above, my car has an alternator which appears to trap the current pump on its studs so I haven't invested more time to figure out how to take it out.

Bambino said:

The keys on the float pin should engage with the non-slotted support and should be nowhere near the float itself. Is this what you mean?

Chris

Click to expand...

My pin looked longer on the keyed side. In order to fit the center part with the emulsion tube into its spot in the carb, my wiggling of the lid drove the pin past the mount until the keyed part was just touching the float hinge and interfering with its movement.

Maybe it's backwards and pin should go the other way with the key in the split? I didn't try that. Regardless, I ground off just a bit from the pin and it fit.

Was really hoping that the sticky float was the issue but after just a couple long trips the smell of gas is in the oil again. I guess the next step is to check the fuel pump but does anyone have any suggestions how to get it off?

An engine mounted mechanical pump should not ever have enough push to unseat a float valve, so unlikely to be the issue. It might of course be leaking into the sump.

If you can get the bolts out, it might be possible to wriggle it out. Otherwise, it looks like the alternator has to move.

When you soted the float pin, did you check the float valve and seat? If worn it can leak, causing a high fuel level and overflow.

Thanks for the reply.

As noted above, as far as I can tell everything in the carb is working fine. The pump leaking into the sump is my next best guess.

I have removed the nuts holding the pump on but there isn't enough room to wriggle the thing out. How does the alternator move? it appears to be bolted in place both through the fan shroud and to the block?

Got the old pump out by removing one of the studs along with it.

Got a new angled fuel pump from MrFiat but can't install it. The existing spacer is too short and the pin driving the pump prevents it from bolting down if that makes sense. The existing spacer is 20mm thick. Seems like I only need like a millimetre or two to get it work. Any clue which spacer I'm supposed to have? Most don't have measurements.

Edit: did more searching and really can't find any spacer other than 10.5mm or 20mm and can't find any pin that isn't 178mm or 189mm. I don't understand how my pump/pin length can be off like this but I definitely can't get the pump to seat against the spacer. Comparing the pumps, the lever on the new pump definitely sticks out further than on the old pump...I took pics but can't seem to upload them right now.

As well as the spacer you then get the length right with gaskets. You should have a 1mm gasket against the block then the spacer and then you add a gasket on the face of the spacer to get the length right. You can get them in different thicknesses

With the gaskets and spacer in place the push rod should protrude 1 to 1.5 mm on the low point of the cam.

Thanks for the reply guys.

The current pump has/had 1 gasket between the spacer and the engine and two gaskets between the spacer and the pump. I guess I could buy and build up gaskets but something is definitely different here as I mentioned.

The new pump's lever that the push rod pushes sticks out from the mounting face by a mm or so. The old pump's lever is inset by mm or so. Not sure If me description makes sense.

New pump



Old Pump