sailcail

Sold. Sorry Guys, I didn’t get any email notifications for the last couple of weeks and then they all came in the morning.....

Used M20J Service and Maintenance Manual Plus Illustrated Parts Catalog. Bought these from Lazar. Asking $125

Thanks for the advise guys. Does anyone have a pinout of the meter? I've tried to get the model number off of the data plate but it's blocked by the air speed indicator. We would like to add a temporary ground wire as suggested by Anthony and see if that solves the problem. Thanks, Simon

Hey Guys, I’ve been having an issue with my volt meter for the last few months. It intermittently fluctuates above and below the actual 28 volts. I have a EDM 700 and the voltage remains steady at 28.1 volts and I have also tested it with a Fluke meter. It’s definitely the instrument indicating incorrectly vs the actual buss voltage fluctuating. My mechanic has cleaned the plug behind the instrument and the canon plugs in the wiring harness. The wiring diagram shows five wires, one ground and two wires to the load and alternator shunts. In the video you can see how the voltage fluctuates above and below 28. Any ideas? Could it possibly be the instrument itself? The plane is a 1988 M20J 205. Thanks, Simon 848D9A40-5045-40A2-A72C-E7AD1901E6A6.MOV

Yes, turning the boost pump on would stop the pressure and fuel flow fluctuations. It would also allow me to lean the engine without any missing. My belief is that the sticky servo would some how get in sync with the pulses of the engine driven fuel pump. Turning on the boost pump would provide a steady pressure that the servo could handle better, just a theory. It would be nice to borrow a servo and see if that fixed the problem. Unfortunately, is quite a bit of work to swap it out.

We had a similar issue with pressure and fuel flow fluctuations. Above 9k the fluctuations would start, about half a gallon an hour and 5-8 psi. The EGT's would also fluctuate slightly. If I leaned more than 20 ROP the engine would occasionally miss. Turning the boost pump on would stop the fluctuations. The engine driven pump was replaced (twice), boost pump replaced, fuel hoses replaced, gascolator, fuel selector and servo overhauled. Two shops performed pressure and vacuum tests on the fuel system and found nothing. Finally we replaced the rebuilt fuel servo with a different unit. The shop inspected removed servo and found it was hanging up in a particular spot. Evidently this is where it operated at higher altitudes. Anyway, after the second servo was installed the problem was solved. Hope this helps, good luck, Simon

The issue was the Bendix (Precision Airmotive) fuel servo which controls the fuel flow to the injectors. The problem was intermittent and only occurred above 8k. The pressure would drop/fluctuate for a short period of time. This would change the fuel flow a few tenths of a g/hr, raise the EGT and few degrees and, if the engine was leaned, it would cause it to miss. The line to the pressure transducer (gauge) connects directly to the fuel servo. The change in pressure acted very similar to the one shown in Byron's video. Hope this helps. Simon

We had a very similar problem on our J model after the installation of a reman engine. We replaced the mechanical pump twice, rebuilt the fuel selector, rebuilt the gascolator, rebuilt the flow divider, replaced the boost pump, installed new fuel cap O-rings, replaced all of the flexible fuel lines, tank vents checked clear and had numerous pressure and vacuum checks of the fuel system by a number of shops. In the end it turned out to be the fuel servo. The shop that rebuilt the servo found a small piece of wire inside. They think it might have come from a small wire wheel that may have been used to clean the parts. The fuel pressure fluctuations only occurred above 8K and the boost pump restored the pressure to normal. In our case enriching the mixture did not affect the pressure.