Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Intermediate rough running

Update: The "noise is coming from the inlet side of the fuel pump. It sounds like the impeller (?) is turning but not pulling gas. Almost 1/2 tank full.

Is it possible that there is a problem inside the tank? Is there a sock-type filter inside?

If there's a in-tank filter, why isn't it plugged all the time?

There is no in-tank filter the filter is engine side just after the pump. When you have been driving and you open the fuel cap do you get a woosh of air going into the tank?

Did you change the ignition amplifier?

Yes, I get the woosh of air
I'm pretty convinced that I have a fuel delivery problem. As soon as I get my new credit cards (LOST MY DARNED WALLET) I'm going to order a pump and filter.
Why? The pump shouldn't be making any additional noises other than the whir of pressurizing the system. I tried to get the phone close enough to record them, but didn't work.
and, it's not an every-time noise. It's random.
While I have all that apart I'll replace the filter and rubber fuel lines.

Haven't done the ignition system yet. After all the years I've worked and taught auto mechanics my head keeps tilting to fuel delivery. I' I'm wrong, well, I'll have s spare fuel pump, new filter AND an original ignition system.

I DO appreciate your input. A lot.

Thanks
Tom

Do you not think this revelation worthy of investigation first, especially as you suspect a fuel delivery issue?

Yes - I'd give it a run with the cap off and a bit of rag stuffed in the aperture if it were me..

Well, It's a Stant cap marked "Caution: Rotate cap one-half turn to vent." and "After Hissing Stops Continue Turning to Remove."

Seems like it's supposed to "hiss" or Swoosh.

Fuel tanks need to be vented to allow air to replace fuel drained from them and thus prevent tank collapsing not to mention compromising fuel pump suction. Irrespective of what is printed on your present cap which is likely not OE, it's a simple test to go for a short drive with cap removed and some form of plug from a freely breathing rag in its place.

BTW I have heard of ethanol bloating seals in caps that otherwise allow some air flow.

I've often wondered about this as my fuel cap is none vented, but I suspect the the vaccum that would be created by using fuel must be relieved via the evap cannister. I think that there is a one way valve on the cannister, because if there wasn't, it would defeat the purpose of it think. I get a whoosh when I open my fuel cap, but I'm sure this is the build up of fumes coming out as opposed air being sucked in. I wonder if those with a vented fuel cap suffer from fuel evaporation.

My guess about the whoosh is air being sucked in. It’s very unlikely that evaporating fuel will lead to a pressure build up to create the whoosh out. As fuel is used by the engine the tank empties creating a partial pressure drop. From my distant physics/chemistry past ( gas laws and related partial pressure/ latent heat effects) I doubt the fuel fumes could lead to a pressure increase but, at best, partly reduce the pressure drop caused by fuel removal. Just remembered...place water in a vacuum chamber, pump the air out. The water boils as the air pressure drops. This demonstrates how fuel can evaporate a bit as a partial vacuum is created in the tank by fuel being pumped out. The pressure will, at best, only reach atmospheric and not go higher to result in an outward whoosh.
Many tanks have additional vents that include roll-over sealing mechanisms. These can seize up to prevent venting inwards to balance the fuel being used, hence the whoosh.
Check for such a vent and function.

The woosh is air being sucked into the vacuum created by the Evaporative Emission System EVAP. When the fuel evaporates inside the gas tank, the harmful vapors get moved to a charcoal canister stored at the front of the vehicle. When the fuel to air mixture becomes normal, it's transferred back to the engine. After this process, a valve makes a vacuum, drawing vapors into the engine. These vapors combine with fresh air from built-in vents and valves for more efficient combustion. The issue can be the degree of woosh or vacuum created this can happen when the engine and fuel heat up and there is a blockage or one of the valves is not working correctly. As suggested above driving the car without the gas cap and with a rag in it's place to see if it performs better would be an indicator of an issue with the EVAP system. Your EVAP system like mine is a basic manual one and relies on the valves and cap to do the job, over time these can stick and wear causing too much vacuum that can effect the flow of petrol from the tank.