Cummins - sticking fuel pin? what lubricant?

[Extreme-Duty]

Yet another repair needed on the Case IH 5120. We cannot go beyond approx. 1800 rpm without getting misfire. It only happens randomly. The engine never smokes black and I'm hoping it is a supply problem. A fuel filter change did not help. Next is a supply pump replacement, we're still waiting for an adapter to arravive.

In the meantime, I would like to remove the diaphragm on the VE-pump to access the fuel pin for a little lubrication.

What's safe to use in terms of seal compatibility? Does WD-40 swell seals?

What about petroleum jelly or a dedicated seal grease, such as Parker O-lube?

 

[George7941]

I use Silicone grease on seals since it does not harm rubber and silicone is pretty inert.

Since I keep SilGlyde on hand, that is what I end up using.

Now that you mentioned replacement of lift pump, I have to ask - did you hook up a pressure gauge to it?

 

[Extreme-Duty]

Ooops, excuse the misspelling in my OP.

I should have known about the silicone grease being suitable, before I went to town yesterday. They had plenty of it. I bought some petroleum jelly, which is recommended for the steering valve seals I am going to replace.

If the lower/small fuel pin is not stuck, I might just leave it alone and lubricate the AFC fuel pin only. The only option we have at the farm, right now, is some Petro Canada calcium sulfonate grease, which is much smoother at low temps than the 5% moly grease we use for general lubrication.

Regarding the fuel pump, we haven't tested it and I doubt it's the cause of our problem. It has about 9,000 hrs. on it, so it might be time to retire it.

 

[slammds15]

Any chance gasoline is in your fuel tank? Its not a stupid question, trust me it happens more often than you know.

 

[slammds15]

Which engine are we talking about as well?

 

[Extreme-Duty]

It's a Cummins 4BT3.9 aka Case 4T-390. You can never know what the fuel jobber is brewing, I guess, but the other diesels on the farm (CT8.3 and IH D-155) do not have this problem. Finally, I pulled the fuel pin out yesterday and had to discover that the diaphragm has got a crack. Also, the small fuel pin is a little too sticky for my taste.

Aside from the broken diaphragm, IMHO, the real problem with our fuel is the mandated biodiesel content of 4.4 to 7%. Thank you, German government.