Hard Starting revisited and hopefully fixed

James West · Post by **James West** » Sun Feb 14, 2010 1:19 pm

All,
You may remember a few weeks ago I was having trouble getting my truck started after sitting for a day or two. I had the idea that it may be a vacuum leak somewhere. Others suggested fuel issues, still some suggested electrical. I took all advice to heart and proceeded to check the fuel lines, fittings, pump, carb, you name it. Next was the electrical. I pulled the distributor out, checked all connections, triple checked timing, bought a meter and checked resistance at the plugs and at the starter, put in the two biggest batteries that fit under the seat, still no better. I could pump the fuel pump a few times and it may start. It would pull start in 20 feet or less though. I just couldn't figure it out. When I was just about ready to throw in the towel, I think luck found me.

While under the hood pumping the fuel pump lever, I heard a hissing sound coming from the pressurizing line that runs from the u-neck of the carb intake to the oil filler tube. The hissing was coming from the brass fitting on the side of the tube. I tightened the flare fitting and when cranked the engine hit and ran smoother than ever. This has worked for a couple of days now. Maybe I did have just enough of a leak to cause the carb to loose prime. Time will tell.

MSeriesRebuild · Post by **MSeriesRebuild** » Sun Feb 14, 2010 7:31 pm

I may not understand exactly what you have done, sounds like you are speaking about the vent tube that is simply the crankcase vent for the closed vent system used on M37 engines. Runs across the head from the intake elbow to the oil fill tube. Doesn't add up with your previously described issues in my mind. Makes me wonder about your fording valve position if you have that in place, (are you running with it closed as if set for fording?) or possibly whether your PCV valve is operating properly. Sounds like possibly there is a restriction in play. I wonder have you noticed any oil leaking from the flywheel housing area, usually a restriction in rhe crankcase vent system will result in pressure build up from within, which sounds like may be going on based on your description. Most often if the crankcase is pressurized, oil will be forced past the rear main seal and into the flywheel housing. Do you have the 3/4" NPT plug installed in the bottom cover? It should not be except when fording, if it is installed, I would suggest you remove it and check to see if any oil has been leaking into the housing. I sure would like to be able to have a look at this one for myself, somewhat strange happenings here.

James West · Post by **James West** » Mon Feb 15, 2010 5:05 am

Charles,
It is indeed the vent tube that you described that I tightened. As for the fording valve, it is wired open. The drain plug is out and there is no oil around it or inside where my finger can reach. I can't explain it myself, just that it seemed to work. As for you looking at it, I would be honored. The 8 hour drive in the M37 would be a killer though. I don't trust my old farm truck that I pull a trailer with that far either. If you ever come to Kinston, just let me know.

MSeriesRebuild · Post by **MSeriesRebuild** » Mon Feb 15, 2010 9:41 am

James West wrote:Charles,
It is indeed the vent tube that you described that I tightened. As for the fording valve, it is wired open. The drain plug is out and there is no oil around it or inside where my finger can reach. I can't explain it myself, just that it seemed to work. As for you looking at it, I would be honored. The 8 hour drive in the M37 would be a killer though. I don't trust my old farm truck that I pull a trailer with that far either. If you ever come to Kinston, just let me know.

I'm glad the situation has improved for you, but it simply doesn't add up in my mind. As the saying goes, "there is something wrong with this picture." Unless something is out of kilter, there should not be pressure built up in that tube to escape. I would suggest you remove that tube completely and the elbow fitting where it connects to the intake elbow to check it for restriction. I've seen the fitting openings soldered shut, obviously by someone who didn't understand the system. I may be preaching to the chior, but are you sure the fording valve is wired open and not shut? If none of this nets an answer, I'd next remove the PCV valve and open it up for inspection and cleaning. It disassembles easily.