Talk Morgan Forums Morgan Sports Cars Morgan Plus Four, Supersport & Plus Six (CX & CXV Generation Vehicles) Plus four fuel gauge

Hi Guys


The fuel gauge of the Plus Four ( and probably also the Plus Six) is a bit of an enigma :-). I used my ODO meter instead of the fuel gauge to know when she needs filling up. Great fun so I started examining how she work.

When it shows empty I have done only around 300km ( 185miles) but with a fuel thank of 43L the fuel consumption looked a bit steep.

This morning I was driving the car on the highway and suddenly I felt a lost of power but no engine light on. I had done around 430km (267miles) on this tank of fuel. The car went into some sort of a limp mode ( it felt like only 2 cilinders were firing max 60m/h) and I made my way off the highway to the closest petrol station. I filled her up completely 37,9L and started her and off I went again. So the useful capacity of the tank is a little less as 38L.


So to be safe I will now do 400km ( 267miles) and then fill her up.


I hope this could be interesting for other!

That seems very odd Pigo and worthy of further investigation. The Classics including my Roadster with very accurate fuel gauge and DTE readings take 55 litres and on one occasion with several miles left to go it took over 50 litres to fill. I cannot find fuel capacity figures for the more economical Plus Four but it should be in the manual you have. Do you not have a DTE readout BTW?

I did wonder if you have a weak fuel pump that only manifests itself with low tank

ETA: found a tank capacity of 46 litres for the Plus Six so assume yours is the same and still worth investigating if you have issues at 38 litres!

Agreed it does seem odd Richard.
PIGo on our Roadsters the petrol station fuel pump cuts out after filling about 3/4 tank. You can then add up to 10 l by pumping in fuel slowly. Some filling station pumps work better than others.
I would hope the new Plus Four doesn't do that but next time you fill her up I would check that.

According to the Owner's Manual - the "Capacities" are listed on page 4 of the PDF I downloaded. It states 43 litres (10 US Gallons) for the fuel tank.

To add to the confusion slightly.

When I had my tank out recently, I checked all the dimensions accurately and the capacity came to 57 litres although Morgan state 50L in the manual.

The reason I bring that up is to question whether the manual gives absolute capacity or usable capacity.

Most quantity surveying is "a wild guess to two decimal places"

Hi PiGo,

When my Plus Four warning light came on I filled up within 10 miles but could only get 26l in the tank. And that was filling slowly, stopping and starting the fill again, just to test how much I could get in. The manual gives a tank capacity for my car of 43 litres.

Based on that I had around 17l left in the tank when the the light illuminated. Interesting contrast to the manual which says that the warning light illuminates when 6l remains in the tank! The calibration/setting is obviously way out and I'll get the dealer to have a look at it along with a couple of other issues when we are out of lockdown.

Yes, tank capacity is 43l according to my manual.

Personally I wouldn't worry too much about the misfire and entering limp home mode as that is very unlikely to be the pump. Depending on the misfire detection system used in the B48 engine (probably crankshaft torque sensing rather than a spark ionisation system) the car's OBD system will shift to a reduced power mode to protect the catalyst from damage when it detects a certain number of misfires. This misfire could be down to a lack of spark or a lack of fuel but the detection is by torque only so the outcome is the same.

If the MIL was not on after refilling and power reverted to normal I think all is well. The error code in the ECU will be deleted after a certain number of misfire free engine running cycles.

Hi Ian


Thanks for the analyses. I was surprised that the engine had such a function :-). In other cars when the tank is empty the engine just dies. I was surprises that the car gave me the opportunity to drive slowly to a very close petrol station. I only found it a little strange that the engine light didn't came on because I would think that certain sensors would pick up that the engine was not running normally. It felt like it had shut down two cilinders or so. But after refueling all was well again. And now we know how we have to read to fuel gauge :-) :-) :-).






Pieter