Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 M3W EML/CEL - P0173 - Help?

There is usually a reason for the Check Engine Light being on, sometimes a faulty sensor but not all the time. If you fix the reason it doesn't come on......... Clearing all the fault codes using Protune2 is a good starting point.

Search P0173 for another string here discussing the code and the various issues associated with that code. I chased that P0173 forever on my car.

Note the rear cylinder typically gets the fuel second, not first, and P0173 is the usual code that gets thrown. Although I have seen the fuel system plumbed both ways on M3Ws- where the rear cylinder gets the fuel first and the front cylinder second. S&S says to feed the fuel to the cylinders simultaneously - Morgan did not do that and saved about $1 on fuel line....


My P0173 did not go away with a replacement fuel pump, although I believe fuel pressure was part of the culprit. Once I fitted the car with a better fuel system from Emil at Morgan Customs my P0173 went away and I have not seen it in 5k miles. Emil's system includes an actual fuel pressure gauge and adjuster, a proper fuel filter that filters fuel before delivering it to the cylinders (Morgan filters fuel on the return line(!)), and routing that feeds both of the cylinders' fuel at the same time.

Another common culprit for the P0173 code is leaking intake gaskets, which allow unmetered air into the combustion chamber and the ECU eventually figures that out and throws the code. Have you tightened or loosened your air filter lately? Often that is enough to tweak those gaskets. It is pretty easy to get the intake out of whack enough to cause an air leak. If you pull it apart you can see how fragile the seals are on the intake manifold. Especially when those gaskets live their entire life in the hot V of a vibrating V-Twin. I had an air leak as well because a prior owner was using an aftermarket air cleaner that was completely unsupported by anything other than being screwed to the throttle body. My poor gaskets didn't have a chance with the entire weight of the intake, throttle body, and air cleaner hanging on those gaskets. The side supports on the standard air cleaner screwing into either side of the V are there for a reason....to stabilize the intake and prevent breaking up the intake gaskets.

At the end of the day, P0173 is your ECU telling you your rear cylinder is over 10%+ or - off of where it should be for either the air or fuel mixture. It could be 11% off, which you are not likely to feel driving the car. If it is 25% off, you are going to feel or hear a difference.

Based on the fact that your code is coming and going I would say you are running right around the 10% off threshold in either fuel or air. As others have said, the stock fuel pump is trash and should be replaced with the Walbro build. Do that and see what happens. You can try and test for air leaks around the rear cylinder intake gasket with starter fluid but that did not work for me despite the air leak.

I would say that P0173 is probably the most common code to be thrown by the ECU on the M3W. Others may disagree - but the way Morgan did things in the fuel system, and the inherent problem with air leaks on the intake design, create something of a perfect storm for that code. Good luck and keep us posted if you find the culprit.

+1

well, that explains mine... Sadly Emil is no longer selling stuff.... I can live with the idiot light

Although not as elegantly engineered, you can achieve a very similar result to Emil's fuel system for considerably less outlay using some of the shelf items, a VW Polo fuel filter, extra hose and clips and a "Y" piece connector. The details are in the MTWC Bulletin articles dated January and July 2021. I have been running this system for 7000 miles with no issues.

+1

So while test-driving a Super 3 last weekend, the dealer had a look at the EML. They've cleared the code and advised that the system can't clear itself so once you hit it once, it's common to have the EML come on and off again until it gets properly reset.
The helpful technician didn't seem worried about it and put it down to a possible change in driving style which the ECU has recognised. I don't know enough about the ECU in these cars to comment but it's been about 40 miles now and it's stayed off so let's see what happens.

The Super 3 was a little underwhelming though, it has to be said!