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Need some help from members familiar with the CAT 3176 !!!!!!!!!!!

December 01, 2012, 10:05:41 pm

Jeesh! -- I just can't get this engine primed. I bought a new genuine CAT pump (as the old one was seized) and installed it today. Then -- on that same housing attached to the engine, I removed the spin-on secondary filter, filled it with diesel through the small holes as per Brett's instruction, and thought I was ready to prime it.

What's got me stumped is that the manual says to rotate the knob a quarter turn and start pumping. Well, a quarter turn ccw does nothing -- meaning the knob does not raise so you can start pumping (the "locked" and un-locked" symbols on the knob show ccw to un-lock, cw to lock).

It takes about six-eight full turns before the knob raises, and then you can pump, but the whole assy. wobbles as you try, and even though I can build some pressure this way, I'm also certain that the seals are not staying in constant contact with the bore, and I'm introducing more air into the system.

Now --the way it is supposed to work (according to the manual) is that it is hard to pump at first, then it gets easier (indicating air in the system), and then difficult at the end when you have all the air out -- and then you lock the knob. My set-up just isn't like that. I must have pumped it 300 times today, and I could build-up some resistance, but not enough to feel like it was bled. It would be difficult to push the knob back in against the back pressure until the threads would catch, and then it was that same six-eight turns cw before it would tighten.

Anyone know what is going on here?

Second issue. In front of the RR tire, and right above my three chassis batteries --- is a red baldwin filter with a small knurled knob on the bottom of it. I believed this was the primary filter, and opening up the petcock gives a clean diesel fuel stream. I bought a primary filter, but when I opened the box it was a canister-type insert, not a spin-on like the Baldwin. I took off the Baldwin and it was half-full of fuel. I filled it back up to the brim, and screwed it back on.

So what's this all about? -- you that have a U300 with the CAT 3176, what is your set-up like?. I'm perplexed here.

Now with the slight amount of pressure I was able to build-up with the wobbly pump -- I would try and start the engine. It would seem to catch on a couple of cylinders, but it would not start.

I'm at a loss over what to try next. Any help is greatly appreciated. I'm going over there tomorrow to make another attempt at it.

with regards,

Michael

1995 U300 40' w/ a 1993 Cat3176B

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Re: Need some help from members familiar with the CAT 3176 !!!!!!!!!!!

Reply #1 – December 02, 2012, 06:39:01 am

Mike,  The "Cat " prime pump that was on my engine only  took about 1/4 turn, as I said before that first attempt to pull the round knob up through the cap is VERY, Very hard. You need to really pull/pry on the knob to get it to move. It may be that there is a vacuum or it is just a tight fit. When you turn the knob more then 1/4 to 1/2 turn you are un-screwing the cap  or plunger system. Tighten it back in place, turn the knurled knob 1/4 -1/2 turn ccw, and pull very hard on the underside of that knob and it should unseat and be able to pump. You may have to use someting to get a better grip on the knob to help you pull on it. Wish I was a little closer I would give you a hand... Gerry  Don't trow that old pump away it may not be seized........

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Re: Need some help from members familiar with the CAT 3176 !!!!!!!!!!!

Reply #2 – December 02, 2012, 07:08:24 am

Agree, why I suggested greasing the new primer slide before installing, also it might be possible the valve to vent the air from system while pumping might be over looked, just a guess.
Good Luck
Dave M

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Re: Need some help from members familiar with the CAT 3176 !!!!!!!!!!!

Reply #3 – December 02, 2012, 08:37:46 am

The Caterpillar primer pump on ours required several rotations to unscrew the plunger so that it would move in and out.

And, yes, I pretty much have to be sure to move the plunger in/out, not getting it off center.

But, 300 strokes suggests that you have an air leak on the suction side. Could be the primary filter, or just as likely, a dry rotted or rodent eaten section of fuel hose from tank to pump.  Since it is on the suction side, it would not necessarily leak fuel, but could easily introduce air to the system.

You might get a length of fuel hose with the same fitting as on the inlet to the secondary fuel filter and stick that in a 5 gallon can of clean diesel.  See if that primes up.

Another diagnostic test would be to block off the fuel line at the tank and see if you can still move the plunger on the primer pump.  If you keep being able to pump it, suspect a vacuum leak.

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