You have already heard the main symptoms of the car – sudden (otherwise inexplicable) poor idle, rough running below 2,500 rpm, poor fuel consumption, and no real signs of trouble from the Rovacom except a split between the stored and current throttle voltages.  Kevin had done some diagnostic work and found that the +5 volt supply to the Throttle Position Sensor had failed, and sent the ECU to be repaired – but when it was returned there was still no +5 volt supply when it was installed and it was assumed that the ECU was still faulty.

The problem turned out to be the pressure sensor in the fuel pump unit, which is also supplied by the same +5 volt drive from the ECU.  This had failed to a short circuit and was effectively grounding the +5 volt line - as soon as the sensor was disconnected things returned to normal.  This sensor was introduced in the 2002 model year with the installation of the “advanced evaps” (Advanced Evaporative Loss – AEL) system.  This system depressurizes the fuel tank and uses the pressure sensor to check for leaks, and is (was) required for US emission compliance.  This sensor failure in Henrietta required the replacement of the fuel pump assembly – which was not entirely unfortunate.  GEMS cars (at least the 2002+ cars – perhaps the earlier ones too) - have some instances of the tank being contaminated by silicon sealer extruded from the pump/tank interface when it the pump is installed.  This is then ingested into the valve at the foot of the small tank that surrounds the pump (and which is designed both to prevent the pump running dry and provide cooling at low fuel levels) and prevents it from retaining any fuel – and this, in turn, results in the pump overheating.  Henrietta had a lot of this contamination in the tank and stuck in the valve.  You can (usually) remove the pump by undoing the tank retaining bolts and moving it around until you can maneuver the pump out, but this proved to be difficult with Henrietta and so the tank was removed and the silicon vacuumed out.

So, as in all good stories, the heroine was restored to her former glory.  I think that it is worth replacing the IACV and the TPS if there is the slightest sign of a problem; they are both mechanical (unlike the other sensors) and so have a finite life, even if it is often a long one.  Richard may choose to have this done.  The later IACVs also have a shorter time constant (they move faster) than the earlier ones.  You are probably aware that if the time constant of the control system approaches that of the system being controlled the combination can become unstable, so an IACV with a faster response is additional insurance against problems in this regard.

So what are the lessons from all this?  Here are some suggestions:

1. It is worth pulling the fuel pump on all GEMS cars and checking for silicon contamination, cleaning the tank if there is silicon present, and replacing the fuel  pump (as a precaution) while the thing is apart.  The philosophy of “if it ain’t broke don’t fix it” may be attractive, but chanting this mantra is not going to help when the pump fails in the rain on the beltway at 3.00 AM.

2. Spontaneous failures are unlikely to be the ECU; it has an excellent reputation and is very well engineered.  Sensors are of a more disposable nature, and many of them share common electrical circuits (grounds, if not power, like the two culprits in the story).  So if you do have an odd failure it is worth investigating to see if there are any common elements that would cause complex results.

3. If one had written a manual for the GEMS system it might be worth updating it in view of any developments that might have occurred in the intervening years.  One might even consider publishing the GEMS electrical schematics as a service to Morgan/GEMS owners.

4. Morgan/GEMS owners who feel that they would like the GEMS electrical schematics before the manual is updated might like to contact the writer of the manual Off-Group and ask for them. N.B. Webmaster If he is not off again on some damn fool expedition to God knows where. (affectionately)

FUEL CAPACITY AND RANGE
by Lorne Goldman and David Poole

GEMS became required on Plus 8s in 1998 (Overseas) and the rest of the world in 2000. They came with an "advance evaporative emission system.  This consists of:

SERPENTINE (FAN) BELT
by Lorne Goldman and the Owl

It is often the case that the Morgan Factory uses front belts other those that are originally used by the engine's manufacturer. The reason for this is simple. Morgans rarely carry the same range of equipment that the original manufacturer does..for example, no power steering and often no air conditoning, both of which have pumps run by the originals belts. This is very much the case with Morgan Plus 8s and is also the case with the GEMS engine. In this case, the Factory turned to the aftermarket, specifically a Gates belt # 7PK-1025. Since then there have been complaints of squealing belts and pulley scoring. Here is the Owl's story and he is sticking to it!

March 4, 2009 from the eMog Pub.

Greetings old chap,

The squeaking and shrieking used to drive me nuts, and everyone was an expert: 'add this shim, remove that shim, use this spray, do not use that spray' .. and so on, and so forth.

I remember a few years ago I spent forever with spanners and sockets and rulers and what-have-you and finally, finally, got the blasted thing perfectly lined up and quiet. It stayed quiet for some months, the first months that it had EVER been quiet. I then took it to a well-known Morgan establishment and when I picked it up some time later the boss smiled at me warmly just before I drove it away and said, ''Oh! You'll be pleased to hear .. one of our mechnics saw that your belt was out of line and adjusted it for you".  I drove away contemplating murder listening to the bl**dy thing shrieking again.

However, here is the good news. I fitted a 6PK-1025 and now, at last, no more problem. It is slightly narrower than the existing 7PK belts, and so slightly narrower than the pulleys.

CHANGING THE GEMS AIR FILTER
by Chris Towner

1. Undo the 3 clips which hold on stainless snorkel on the right side of the engine and remove the snorkel.

2.. Central to the bonnet are 2 large diameter jubilee clips, loosen  these.. (there is a sensor probe residing  in  the  middle).

3.  On the left hand side, there are 2 clips hold the feed tube. Unclip these . (They are next to the heater insulation box and more or less central to the bonnet halfs. Watch out as there is an O ring in there as well.

4. The stainless filter tube housing can now be persuaded off  the 2  grommets at the bottom base and  slid  past the grommets at  the right side  vertical.  This now allows the filter tube housing in a friendly position and allows the filter to be  removed. The tube is now in a position that allows the air filter to be removed without obstruction.

5. There is a center nut and flat cover that holds the filter in place,  remove this and replace filter with OE or K&N.

Reverse  the sequence for reinstallation.