| Author | Message | ||
| Dan (Cintrepd)
Registered Member Username: Cintrepd Post Number: 3 Registered: 8-2008 Posted From: 65.93.167.74 Rating: N/A |
Good morning all, After two months away, my MC9(Manual trans) started up right away, first crank. I then ran it for fifteen minutes and shut it down to check for leaks, and what do you know it would not start? The engine turns over but doesn't fire/catch. No smoke/exhaust present when cranking. I suspect a fuel problem, and from what I have read here, I would like to check the fuel filter and prime if necessary. Does anyone have any pictures of the location of the fuel filters they could email or possibly upload here? My email address is: cintrepd@sympatico.ca Thanks very much, Dan(cintrepd) | ||
| Dan (Cintrepd)
Registered Member Username: Cintrepd Post Number: 4 Registered: 8-2008 Posted From: 65.93.167.74 Rating: N/A |
Hi again, I have reviewed my Maintenance Manual and there is a schematic of the fuel system, but no diagram/picture showing where everything is located. From looking at the engine from the rear, it appears as if there is a filter to the lower left of the engine near the lower belt pulley attached to a housing with a red placard. Could that housing be the fuel pump? I have also noticed that there is a small solenoid on that housing, that normally has two wires attached. The wires on the solenoid have both come off. Could they have something to do with my starting problem? What do you think? Dan | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 540 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Morning Dan, It does sound like you are describing the fuel filter, and your comment "no smoke" does indeed mean NO fuel is being injected. A "solenoid"? near the fuel filter sounds like the fuel pressure switch... MCIs are equipped with low oil pressure and hot engine shutdown, which work with air pressure to stop the engine, also a fuel pressure switch which stops the starter as soon as the engine fires. The start relay overrides the low oil/hot eng shutdown as long as the start button is held down. As the shutdown cylinder takes air to push the stop lever on the governor, none of the buses of this vintage will stop after being started until air pressure is built up. The "Skinner Valve" is bolted on the bulkhead above the engine, and controls air to the shutdown cylinder, located in the middle of the vee, with the one air hose connected between them. This valve is electrically "normally open," which means that air flows thru it unless it has power. The fast idle solenoid valve, bolted next to the Skinner, if equipped, has two cylinders teed together, one prevents the throttle linkage from moving in fast idle, the other is down on the side of the governor. Anyhow, all of that said, the engine would not crank if the fuel pressure switch was disconnected. If the fuel pressure switch has been bypassed, you could engage the starter with the engine running! (Read expensive!) The engine would indeed have started the first time, due to no air pressure to shut it down, but would have died when air pressure got up to about 80 psi, if the skinner valve had failed previously. So, what's wrong now? Maybe you win the DS award for the month. Are all of the switches, front and back, in the proper position? If so, my bet is a stuck shutdown cylinder holding the shutdown lever in the stop position. Look at the cylinder, there should be less than 1/4 inch of piston visible. If there's an inch plus, there's the problem. Wiggle! If the piston goes in, you're in. If it won't, second possibility, is a Skinner valve failure, or a loose wire to it. This can be easily verified by taking the hose loose on the shutdown cylinder, and checking for air pressure. Don't just take it all the way off to start with, there could be up to 120 psi, or in other words, a short wild hose! With air pressure up, master switch on, dead eng, oil pressure alarm on, no start button, PRESSURE IN SHUTDOWN HOSE. Start button depressed, air SHOULD release immediately, audibly from Skinner valve, and piston should retract, of course the eng. will crank. In the run position, the stop piston should not quite touch the stop lever, and you should be able to move the stop lever about an inch further away from the piston easily. The only other possibility is that the fuel rack stuck in the closed position when you shut it down. To be politically correct, 92 series bus engines are equipped with spring-loaded fuel racks, and were not equipped with emergency shutdown flappers as standard equipment. Also, you have told us "NO Smoke," which rules out a tripped flapper on 71 series engines. Ignore all of this if you have a DDEC engine, and please realize the "award" is made with humor!!! Don't go under an aired-up air-ride bus, or between the tires and the wheel wells, without blocking it securely at the jacking points! Good luck, happy Labor Day, and please post back with what you found. Regards, George (Message edited by George Mc6 on September 01, 2008) | ||
| Dan (Cintrepd)
Registered Member Username: Cintrepd Post Number: 5 Registered: 8-2008 Posted From: 64.230.36.146 Rating: N/A |
Thanks, George, My 6V92TA is an 1989 and I think it is a DDEC, although I'm not sure which version. Here is a picture of the solenoid I described. Is it a fuel pressure solenoid and if so,could the broken wires cause this no start? Thanks again, Dan(cintrepd)  (Message edited by cintrepd on September 02, 2008) | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 542 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Dan, If you are talking about the round black "thing" just above the red label, it looks like a water temperature or pressure sending unit. The red label is definitely on the water pump. The canister on the left is the fuel filter. DDEC won't allow an engine to run when it thinks there is no water in the cooling system, so all of the wires to the sending units must be connected. I'm sure someone here with a DDEC engine will offer to help with finding the problem, which will involve reading codes. Good luck, George | ||
| Dan (Cintrepd)
Registered Member Username: Cintrepd Post Number: 6 Registered: 8-2008 Posted From: 70.51.246.201 Rating: N/A |
Had a look at a friends' '89 MC9 today. Compared the wiring to try and determine which wire goes to which lead, on the solenoid. I guess I will have to trace the wiring a little further. I wonder it anyone might have a spare waterpump sensor/solenoid from a bus they are parting out? If so, please contact: cintrepd@sympatico.ca Thanks, Dan/cintrepd (Message edited by cintrepd on September 03, 2008) | ||
| Dan (Cintrepd)
Registered Member Username: Cintrepd Post Number: 8 Registered: 8-2008 Posted From: 70.51.240.124 Rating: N/A |
Success today! Able to start my engine this morning by pushing the air shutdown piston in, as in George's post above. After running for a period of time I shut it down only to find that the air shutdown piston will not retract. I can hear air slowing escaping from it, however. So my next question is it just a sticky valve? and, Is there a way to release the pressure and push the valve in without waiting for the air pressure to drop by itself? Next step is to repair/replace the waterpump temp. sensor, and I am back in business. Thanks again George, for your input. Dan(cintrepd) | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 547 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Dan, With the master off, there will be pressure to the shutdown cylinder. The Skinner valve is open when it has no power to it. With it energized, it stops the air supply from the auxiliary, and drains the air from the hose to the cylinder. If you can push the piston in, and it stays in after the bus has aired up, you have power to the Skinner valve. You can unscrew the shutdown cylinder from the plate, and start the engine. You will have to stop the eng by pushing the lever. With the eng running with the switches on, there should be NO AIR to the cylinder. You can loosen the fitting on the cyl to find out. My guess at this point, is that the Skinner valve is sticking part way, because you can get a start with no pressure in the bus, and the eng keeps running after pressure builds up. Electrical trouble is a possibility also, wiggle the wires to the valve, take a 3/8 long shaft nut driver to all of the nuts in all of the junction boxes, the number of loose ones will surprise you. HTH, George |