I know I'm showing my newbie ignorance but I'm not sure from the manual how to bleed the Universal M-25xpb. Do you activate the fuel pump by just depressing the pre-heat button or do you crank the engine by depressing both?
If you have to press both, how do you stop the engine from actually starting?
Is there a easy way to put a jumper on the fuel pump to just activate that from near the engine?
Never did this before and fear blowing up the whole thing.
Larry, first it won’t blow up. Second, the M25XPB should be self-bleeding. It doesn't appear to have a knurled knob on the injection pump, from the M25XPB engine parts available on this very website (I found it by Googling M25XPB!!! - this is a great site!
). You do NOT, ever, need to crack injectors on that engine. More good news.
Fuel pump operation: It all depends on how it’s wired. In most cases, for the M25, M25XP and M25XPB engines, the fuel pump is simply connected to the ignition switch, so when you turn it on, it runs all the time.
You should also never need to push both the start button and the glow plugs (whether energized by a key switch or by a button). The operation is: hold glow plugs, release glow plugs, push start.
Newer engines have a more complicated operation for the fuel pump. That is covered in the links included here:
http://c34.org/bbs/index.php/topic,5078.msg41829.html#msg41829
Please read the links in that post.
While it says for M35 engines, it is applicable to all engines that have the dual fuel pump parallel wiring.
The way to tell on your engine is this: Does the fuel pump start when you turn the ignition switch? If not, does it only turn on when you hit the glow plug button? Then it will shut off until the engine starts and restart when the engine is running (when the oil pressure comes up and closes that circuit). This is detailed and explained in the link.
If so, the “workaround” is to provide a separate power source to the fuel pump with a simple toggle switch I/O to run the fuel pump when you want to. Also discussed in that link.
If it runs when just the ignition switch is turned on, you have it made, pretty simple. In fact, I installed a fuel pump shutoff I/O toggle switch in my engine compartment so I could shut
off the fuel pump when I was bleeding the secondary filter on the engine without having to jump up into the cockpit ignition switch.
You may also be interested in this:
Bleeding 101
http://c34.org/bbs/index.php/topic,6377.0.html
Also has lots of links.
Also, our C34 Tech wiki has a ton of M25 series engine information:
http://www.c34.org/wiki/index.php?title=Diesel_Engine
Good luck, it’s a lot easier than you think!
