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Author Topic: 8V71 Fuel Pump Weep Hole  (Read 2198 times)
Rick Brown
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« on: December 27, 2008, 04:50:38 PM »

Hya Busser Kids:
I've been plugging the engine compartment fluid leaks in my 4905 in order of descending magnitude and have now gotten down to the weep hole in the fuel pump as the greatest offender.  That is a threaded hole that appears sized for 1/8 pipe thread, but I haven't confirmed that yet; it is set in a very tight location.  I've pulled the coolant tube above and can now just barely touch the hole.
My goal is to plumb the weep into my slobber catcher.  It looks like a 1/8" 45 deg male/female elbow may screw in (something that should have been done before the fuel pump was placed in the engine).  If so, then it should be easy to add a tubing adapter and tube down to the sc.
Do you know if that is, indeed, a 1/8 pipe threaded hole?  How do people who know what they are doing do this?
Thanks for your comments
-RickBrown in Reno, NV
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Brian Diehl
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« Reply #1 on: December 27, 2008, 05:18:06 PM »

Hi Rick, I had the same problem on my 6v92.  It turned out to be the case that I needed a new pump.  You don't want the pump to be leaking as this indicates a potential for it to also be leaking internally and causing fuel to get down in the oil.  A new pump solved my problem.  Having the cross over tube out already makes replacing the pump a simple task.  I think my pump only cost $80 about 4 years ago.
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Sojourner
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« Reply #2 on: December 27, 2008, 06:41:57 PM »

Yes Rick...by all mean you have a leaking shaft's seal in fuel gear pump. The hole you mention is an indicator hole to see if it leaking or not. This applied to water pump...it has a hole between impeller blade and gear wheel to let you know if the pump's seal is leaking.

Do what Brian suggested.

I have known of someone who had a leaking water pump's seal and keep driving as long he keep the coolant full. However, later he was getting water in engine's oil and rising on the dip stick. It has a relief or indicator hole...it was dripping but he didn't think it was bad until water was adding to engine's oil.

In other word, don't gamble; replace it before fuel can leak even worse so that it can get in engine's oil.

FWIW

Sojourn for Christ, Gerald

Happy New Year!
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JohnEd
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« Reply #3 on: December 27, 2008, 11:01:24 PM »

What they all said and do not tarry. Tongue

John
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Rick Brown
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« Reply #4 on: December 28, 2008, 08:11:04 AM »

Ok, but I'm confused as to why the hole is threaded.  My fuel pump was supposedly rebuilt a couple of hundred hours ago.  If it was a bum job I can accept that.  What I think I hear is that 'any' leakage there is a failure indication and that on your DD 8V-whatever the hole is open (no plumbing to it) and clean.  Is that so?
Is there anything tricky about replacing the pump (drive gear orientation or timing or close tolerances)?
Thanks for your comments
-RickBrown in Reno, NV
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Airbag
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« Reply #5 on: December 28, 2008, 09:27:28 AM »

Weep hole would be threaded for a drain line to carry any fluid away from combustion soarces and a well trained driver can spot a leaking fuel pump easily on a pre-trip inspection just by looking under the bus and knowing what the line does.

Depending on how accessable the pump is I myself would probably do something silly like change the garlock seal for $2 rather than rebuilding the pump, but I am a cheap screw.

There is no timing issues with a fuel pump, simply stab the pump in place.
« Last Edit: December 28, 2008, 09:44:47 AM by Airbag » Logged
OneLapper
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« Reply #6 on: December 28, 2008, 09:38:13 AM »

Rick, I recently installed a new fuel pump in my 8V71.  It wasn't too difficult, but I did remove the muffler for easier access.  I have a replacement engine for my 4106 sitting on the shop floor right now and noticed that it's fuel pump, and the replacement, rebuilt fuel pump I installed (both from Nimco & both out of NYC transits) had RTV to plug up the lower hole!  Not a good idea to do.  It shouldn't leak at all if it's in good working order.

Mark
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Sammy
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« Reply #7 on: December 28, 2008, 10:36:24 AM »

Rick, all the ones I replaced had the weep hole facing downward and hole was open.This was to provide a visual check for leaks, if and when the pump was beginning to go bad.
!/4" swivel sockets work good and an old distributor wrench (from a car) help to get those bolts in and out.
Best of luck with your repair.  Cool
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CraigC
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« Reply #8 on: December 29, 2008, 12:02:38 PM »

Rick
When you take the pump off you will find 3- 1/8" NPT threaded holes. Two should be plugged and the one pointing down left open as a drain hole. I have seen in the parts book a piece of tubing looks to be about 6" long for the weep hole. They do not list a part number for it and I have not seen one on any engine in service. This pump is used in many different DD applications. When you replace your pump make sure the replacement pump looks exactly like the one you have taken off. The arrow is pointing the same direction for engine rotation. The 3/8" fuel inlet, 1/4" outlet holes and the bypass are in the exact same location. 
 
Quote from a training manual. "Locate the weep hole in fuel pump with finger. If you feel fuel around the weep hole, the pump seal is defective and the pump must be replaced."

A leak there may be causing you other problems like hard starting, excessive smoke after starting, running rough at first start for 30 seconds or so and possibility loss of power at all rpm's, engine surging  going down the road. This would all be due to air entering the fuel system due to a bad seal and, or worn shaft. This air can enter both while the engine is stopped and running. If enough air it could even damage your injectors.

As all of the other above post-- change it now.
« Last Edit: December 29, 2008, 12:08:51 PM by CraigC » Logged

Craig C
4104 8V71TA/V730
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