671 "Hesitating"

[Lin]

Gus,

I had a bad toggle switch for the main that made lose power and recover.  It seemed to be happen most on acceleration, but that could be that it was just more obvious then.  I think I decided it was the switch because I remembered one of the contactors wiggled the last time I had looked under the dash.

I was told by a local electrician that we should be using switched rated for DC.  He said those that are only AC rated will pit and fail more quickly.  This may not be the problem this time, but keep it in mind that next time you change a switch.   We actually want some of the stuff we turn on to stay that way for a while.

[gus]

Dallas,

I don't think it is filters unless it is an air leak at the primary filter on the suction side.

I've had clogged filters before and they didn't cause momentary power loss, they caused a slow, steady loss of power. I really don't want to get into the fuel mess until I eliminate electrical.

I suspect the switch because I've had a few fail in recent years.

[Just Dallas]

Removed

[Busted Knuckle]

Gus, that's my point....

IT could be a bad gasket on the fuel filter, either primary or secondary. Ask BK how we know this!  Except his died on a two lane road with no shoulder about a half mile from home.

My choice in looking for Detroit problems is always the fuel first, electrical second and air third.

Dallas is correct we had a filter problem in a very bad location in between 2 hills on a country 2 lane no shoulder and average rednecks speeds of 60-65 mph in a 45!
On top of that I was dressed up in my driving attire and not about to crawl under the bus before going to pick up my group! (was also the very first trip for "Suzy" my at that time newly acquired Garmin 7200. Which after I got out on the open empty interstate on my way to pick up my group, erroneously showed me running 93 mph while "making up for lost time!" I know it was erroneous as the bus was governed at 78 mph by the DDEC! )
  BK 

[Don4107]

Gus if you think it might be electrical and your shut down cylinder is similar to my 8V then just loosen the bolts on the shut down cylinder and move it to the side so it can't push on the shut down lever.  If it still hiccups, look to the fuel system.  To shut it down you will have to push the shutdown lever by hand.


The reason I suggested running the return line into a container and checking for air bubbles is any air leak on the suction side of the fuel pump, fuel lines and primary filter, will show as bubbles in the stream of fuel. 

Good luck
Don 4107

[gus]

Thanks again to all.

It will probably be at least a week before I can get to it but I promise to post the results.

[Ed Hackenbruch]

The way the weather has been so far, it might be August before you will get to it!

[gus]

I was able to do some checking and found the primary fuel filter top bolt loose. This is the original stacked disc filter. I changed the gasket just before leaving home so I'm hoping this was the problem

I don't have the bus in a location that allows engine testing but this may be the problem. I really can't even spend much time in the engine compt without getting into trouble with neighbors, this is not like being at home on the farm!

I also checked the engine run switch by jiggling the panel and watching the voltmeter but it showed no movement.

[gus]

After tightening the primary fuel filter can bolt things got better.

It gave a some trouble the first day on the road over Steven's Pass in WA but hasn't caused any problems since. It was only a problem in 4th and 3rd, mostly 3rd, but none in 2nd for about three miles over the top of the pass??

Maybe I got rid of all the air bubbles before I had to shift down to 2nd?

Anyway, thanks for all the ideas - hope this is the last of this problem.

   New Subject:Right now I'm spending my fourth day in Livingston, MT waiting for new bolts for the rear air bags. I had all the parts but the bottom bolts turned out to be too short. Seems the early 4104s had different thickness bottom bag bases. I ran across the same thing with rear hub bolts!! Mine is a '54, the second year it was built.

[gus]

The bad news is the RR air bags still leak down in about five hours vs 1.5 hrs before. This after $400 for replacing the bags and adding plates.

However, we were hundreds of miles from the repair shop when we discovered they still leaked! I'm not upset, it was a heck of a hard job for the guy who had never seen anything like it before.

I'm glad I didn't tackle this job myself after all the problems we had with bolts. When i do the left side I'll know all this ahead of time.

The good news is the new bags sure air up fast!!

The air leak can only be in a few places so all I have to do is get out the soapy water and find it!!