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Old 25-06-2020, 13:35   #1
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Perkins 4.108 Fuel Pump Leak

I seem to be having a leak at the junction of one of the high pressure fittings at the fuel pump. The leak does not appear to be coming from the line fitting itself, but seems to be coming from the nut just below it. I assume this nut is for bleeding the line? I tried tightening the nut but it seems very tight already, so my inclination is to just loosen the nut and then re-tighten it. Before I did that, I wanted to ask if anyone else has had this issue and what they did to resolve it, & does my solution seem like a good idea?
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Old 25-06-2020, 14:21   #2
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Re: Perkins 4.108 Fuel Pump Leak

The "nut" you are talking about is there for you to put a wrench on while you tighten the injector line nut, so you don't break things.
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Old 25-06-2020, 19:00   #3
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Re: Perkins 4.108 Fuel Pump Leak

The nut is below, behind and 90 degrees to the fitting.
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Old 25-06-2020, 20:42   #4
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Re: Perkins 4.108 Fuel Pump Leak

Ah, it's not a nut, it's a bleed screw. You should paint all the bleed points with a bright color. White is best at night.
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Old 25-06-2020, 22:18   #5
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Re: Perkins 4.108 Fuel Pump Leak

Does any of this look familiar? The low pressure bleed screws are circled in red and the high pressure union is in yellow. Its unusual for a high pressure union to simply leak because that would have an effect on engine performance. If your injector pump is the mechanical governor as in the pic take a look at the throttle and stop levers, if they leak, the fuel can make its way down under and make it appear that the HP unions have a leak. Click image for larger version

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Old 26-06-2020, 10:17   #6
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Re: Perkins 4.108 Fuel Pump Leak

Thank you everyone for your help. Here are some more details.
1) The pump is a hydraulic style pump.
2) the leak appears to be manifesting at the bleed screw on on of the HP ports.
3) It does not seem to be coming out of the area around the fitting to the line, but from the bleed screw
4) It only drips when the engine is running
5) I did clean the area all around the fitting just to make sure the leak wasn't coming from another part of the pump, then I ran the engine again and no other area around the bleed screw was wet.
6) the engine itself is running fine. No missing, hiccups or any other anomaly.
7) The HP port that is leaking is on the side of the pump away from the engine. I have attached a pic of a similar pump with an arrow showing the port that is leaking

Any suggestions are welcome.
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Old 26-06-2020, 16:00   #7
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Re: Perkins 4.108 Fuel Pump Leak

Copper washer needed?
(& then check again?)
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Old 26-06-2020, 18:10   #8
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Re: Perkins 4.108 Fuel Pump Leak

Here’s a photo of a retired CAV pump high pressure outlet banjo and the 2 sealing washers. The washers are steel and also a specific CAV part, not just a copper washer off the shelf. Click image for larger version

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Old 26-06-2020, 18:27   #9
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Re: Perkins 4.108 Fuel Pump Leak

Skipperpete, do you think it makes any difference using the specified CAV steel washers instead of "off the shelf" copper washers?

Just curious..
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Old 26-06-2020, 20:36   #10
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Re: Perkins 4.108 Fuel Pump Leak

When the HP pump internal seals fail (fairly common), you get a leak from around the throttle shaft.
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Old 26-06-2020, 20:41   #11
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Re: Perkins 4.108 Fuel Pump Leak

Quote:
Originally Posted by Wotname View Post
Skipperpete, do you think it makes any difference using the specified CAV steel washers instead of "off the shelf" copper washers?

Just curious..


The space available for the washer is limited and a copper washer with such a narrow sealing surface would be a bad choice. I have never seen a CAV DPA pump with anything other than steel washers. Copper might be ok in an emergency but a failure of that joint could spray a lot of fuel around the engine room.
Do the HP banjo unions on your QM yanmars use copper or steel to seal the joint?
Pete.
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Old 30-06-2020, 17:47   #12
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Re: Perkins 4.108 Fuel Pump Leak

Quote:
Originally Posted by skipperpete View Post
The space available for the washer is limited and a copper washer with such a narrow sealing surface would be a bad choice. I have never seen a CAV DPA pump with anything other than steel washers. Copper might be ok in an emergency but a failure of that joint could spray a lot of fuel around the engine room.
Do the HP banjo unions on your QM yanmars use copper or steel to seal the joint?
Pete.
Sorry for the delay in getting back to you Pete. The ones of my QM HP unions are copper and I expect they are original. I don't recall seeing steel ones on other QM engines but that doesn't mean much as I never took much notice - just assumed they were copper.

I will have a look at the CAV IP on the tractor sometime!
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Old 30-06-2020, 18:47   #13
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Re: Perkins 4.108 Fuel Pump Leak

[QUOTE=skipperpete. Copper might be ok in an emergency but a failure of that joint could spray a lot of fuel around the engine room.


That is so ridiculous. The only danger from using a copper gasket is if you squish it out the side of the joint from to much torque, or the pressure is 10x times what is really is on that engine
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Old 30-06-2020, 20:47   #14
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Re: Perkins 4.108 Fuel Pump Leak

[QUOTE=Ecos;3176073][QUOTE=skipperpete. Copper might be ok in an emergency but a failure of that joint could spray a lot of fuel around the engine room.





That is so ridiculous. The only danger from using a copper gasket is if you squish it out the side of the joint from to much torque, or the pressure is 10x times what is really is on that engine[/QUOTE]



The operating pressure is between 2,000 and 2,500 psi. I take your point, rubber orings on hydraulic systems often handle much higher pressures but if CAV decided that steel washers were necessary why change to copper and risk failure
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