Had a stray follow me home yesterday. Like the title says. Seems to start ok the first time, or if you shut it off without it being funky. Issue is, after about a minute or two of running, it almost seems like it is running out of fuel. Can hold the pedal full down and it doesn't do anything, eventually (after about a minute) it'll take off and run ok, then back to crap. Changed filters, both were full, but did get a sucking noise when I pulled the primary. Here are a couple pics, the return is kind of goofy, the return from the head goes to the pump, then tees and a little line crosses over to the other side, where there is a cross-looking piece where the return to tank is attached. Going to put a gauge on the supply to the main pump to check transfer pressure tomorrow.
Lots of collapsed hoses on them..(internal) Main one is the long one from the tank to the 1st filter. U could try back blowing that line incase there’s a floater.. I can’t count how many “red rags” I’ve pulled outta those tanks.!! The supply pump is a known problem with them too.. I would mention the overflow valve but it wouldn’t be bad, then fix itself..
Replaced lines from tank to primary filter, and from primary to transfer pump. Drained fuel, put in new. Blew back through suction, seemed ok. Installed gauge between secondary filter and main pump. Was a real treat to bleed, even after using air to push fuel up to the transfer pump. Got it running and thought we had it fixed. Ran it numerous times, and then a buddy showed up at about 3 pm and when I started it for him, I knew it was back to it's old tricks. Runs fine for about a minute, and then you can here a miss, if you rev it a bit, it will get progressively worse until you can hold it wide open and it just slows down and stops like you shut the fuel off. Gauge shows plenty of pressure while it does this. I did attempt to simulate fuel pressure issues by pinching off the return line to maintain pressure, didn't help at all.
Truck VIN.
What is that green twist tie doing.?? Is there a stop screw that the throttle lever hits on at full travel.?? I can’t tell from the pic.. If there is no screw to limit the travel, it’s hitting the internal stop (inside the gov) and reducing the rpm..
Leave it to you to go nosing around something that isn't relevant********** I have no good answer, that ziptie appears to be holding a shorter arm with some holes in it behind the throttle arm. I'm not in the business of messing with things, so I haven't messed with it. The stop lever works, the throttle lever works (maybe not, I guess?) so I haven't fiddled with it. There isn't any kind of stop bolt that limits the movement of the throttle arm. This all being said, I struggle to understand how it's acting being caused by the governor. It will begin to miss (like it's running out of fuel) and then gradually the throttle will become unresponsive, and it dies. A few times, I haven't been able to replicate, if you hold it wide open, it will take off and run normally for a bit, but eventually degrades back to missing and then when you go to idle it just stops. Fuel pressure maintains the whole time.
I guess I should be a little more specific, the throttle doesn't get totally unresponsive, just kind of like a PT system with air in it.......
That shorter arm w the holes in it IS the pump throttle lever & it’s supposed to hit a stop screw.. If there’s no screw & it’s allowed to go further, it hits an internal stop and pulls the rpm’s down..
It doesn't move. Ever. What is adjusting the rpms then?
Let's assume that something is getting out of whack in the governor to cause loss of rpm control. What is causing the miss when you're just holding it right above idle, not moving the throttle?
If it doesn’t move, what is giving u a low idle.?? Is that an air actuated throttle.?? What’s the application.??
It appears that since the truck has a pto, it's a "hold" for the throttle. There's a switch in the dash that sends air to that little plunger that locks the throttle in whatever position you have it in.
Ok. So, I pulled the throttle lever off, and, of course, as you already know, that little lever is the stop points for low idle/high idle. Woodruff key and the clamp bolt missing, is was just banging around on the shaft willy-nilly. I managed to locate a woodruff key, and a new clamp bolt, and put it back to where it belongs. We did all think it was idling too slow. Idles good now, haven't ran it enough to see if it does it's fit thing. Now, the million dollar question. You have resisted commenting any further, obviously you knew something was amiss, I've resolved that. At this point, can I assume that the throttle shaft going back past idle basically uncontrolled can cause symptoms like I've described?
100%..
Your going to have to do a , no-load rpm test.. Warm up the engine, get a hand held photo tach and check the rpm at hi, with the lever hitting the stop screw. Once that established, move the lever ever so slightly BACK off the screw and watch the rpm.. IF it increases, you’re on the internal stop.. I’m assuming someone fiddled with the stop screw and that’s why it was disconnected.. not knowing they created a bigger problem… Next your going to have to reset that outer “break back” lever.. put the lever on, get someone to mash the pedal to the floor and see where the inner lever is in conjunction to the stop screw.. Ideally you want the inner lever hitting the stop screw and the outer lever breaking over a little.. If it breaks over to much and bottoms in its self, it’ll put to much pressure on the shaft and wear it out.. then u have oil leaks and end up pulling off the pump.. Good luck
I spoke a bit with a guy at a pump shop in Devils Lake. After describing the symptoms I was having, he suggested to keep running it until the engine got good and warmed up. Unresponsive throttle, and dying when returning to idle came back. He said to get it in the rhythm of where it becomes unresponsive, and then let off a little, increase, let off, increase, let off, do that three or four times, and then let it die. Wait there by the pump and listen close, if you here a click or snap, he says there are seals around the barrel/plunger that are bad, and allowing pressure to hold up the plunger(s). Sure enough, if you can get it wound up just the right way, after it dies you can hear that click, and it'll start right up and run ok for a bit, until you start playing with it.
Good luck with that..
Good luck with what? We've checked the high stop like you said, engine slows as soon as you take a little pressure of the high screw. We set the breakaway lever like you said as well. What's the next step? What is that click we're hearing after it quits?
Didn’t mean anything by it.. Good luck w your project.. I guess next step is pulling the pump.. u should time it before removing it.. If u remove the big hex towards the front, just under the #1 cylinder, (10mm?)..u can rotate the engine in the correct normal rotation and watch that tappet in the hole.. When it JUST STARTS TO MOVE, STOP…your on #1 compression stroke.. find your timing marks… probably on the flywheel.?? And set the engine to the correct timing mark.. NOW pull the pump.. Good luck..
Forgot to mention.. If u take a brass drift and smack that hex plug a few times, you can almost back it out with your fingers.. If u don’t, your gonna end up smacking your Allan wrench with a hammer to get it to turn. ITS TIGHT.!!
Are there indexing marks like a B-pump?
No.. the timing degree should be on the valve cover.. It looks like the tappet is on its way up, so just find the correct degree and your all set.. Looks like someone already marked it in WHITE.??
Just to get it out there, does anyone have the proper installation procedure for this pump/engine?
I have a complete PDF I bought from Barrington that covers that engine. But because I have been branded a sour old individual-I won't change that idea.
I expect that--looking free info.
Let me check.......... Nope. Didn't necessarily ask for anything for free.
Can u take a pic of the gov. that’s behind the oil fill spout.. Is there a cap or 8mm Allan hex.??
I dropped it off at Lake Region Diesel today. That plug is a 8mm cap. The guy told me that is where you lock the pump for install?
Yes, that’s correct..
I ordered this today, since I seem to be freeloading asking for service info. I maybe should have asked, but I assume this is a 4 valve head? Pumpguy, I'm hoping it'll say in the book, but is this pump supposed to be spill timed? Never did that in school. My pump guy wasn't sure if the drive hub can be installed with the pump on the engine (he's not a Mack guy) and you have to rotate it off of TDC #1 for it to clear the gear train to remove or install.
No spill timing.. the plug in the gov is hiding a pointer.. it’s spill timed on the test stand and the pointer is locked onto the cam shaft.. In other words, the pointer is your spill timing.. U better find someone else to do that pump.. u need a special jig to set that drive hub.. Is this the same people that told u how to diagnose the problem in the first place.?? Oh, u have to degrease the cam shaft and drive hub and torque it to 200 ftlbs.. otherwise it’ll spin on u..
PMed you.
Update on the old Mack. Turned out the first guy doesn't do enough of these pumps on Mack engines, so he didn't have the tooling to hold the cam and torque the nut for the drive hub. Under his suggestion, called Midland Diesel in Fargo and they were more than happy to help. They got it apart, and found sticky plungers and wornout governor. After an ultrasonic cleaning of the plungers, and a light lapping, they were ready to go. Rebuilt the governor, $1900 and done. Got it back, we had marked the drive gear and cam gear before removal, so getting it back on went pretty well. Since that stupid oil filler tube is directly in front of the timing plug, we used a phone with the camera to see in it to line up the pointer, and the bolts that hold the drive gear to the drive hub ended up virtually exact to where they were. Primed it, cranked it over with the fuel shutoff pulled until it made oil pressure, again until had fuel at injector lines, and after tightening those, when I hit the key I think it started on the first piston up. Everyone in the shop, myself included, can't believe how good it starts. This engine must either be in remarkable shape, or we got lucky and hit the timing on the button. Pretty good considering you're supposed to have this fancy-ass sensor and light box to do it according to the book haha.