UV Dye for Diesel Fuel

usa591 · **Posted:** Wed Aug 09, 2017 1:45 am

Hi All,

I need to find the source of a leak that is bedeviling me near the filter head.

I was going to head to O'Reilly's for some of this:
https://www.oreillyauto.com/detail/inte ... cs/4384811

Does anyone have a reason I shouldn't add this to my tank or have a product they'd recommend?

Thanks!

GordnadoCRD · **Posted:** Wed Aug 09, 2017 2:02 am

usa591 wrote:

Hi All,

I need to find the source of a leak that is bedeviling me near the filter head.

I was going to head to O'Reilly's for some of this:
https://www.oreillyauto.com/detail/inte ... cs/4384811

Does anyone have a reason I shouldn't add this to my tank or have a product they'd recommend?

Thanks!

Nope. Good diagnostic tool.

usa591 · **Posted:** Wed Aug 09, 2017 10:39 am

Any thoughts on concentration? I was going to wait until I was down to about 2 gallons left.

APC9199 · **Posted:** Wed Aug 09, 2017 12:14 pm

Not saying you shouldn't try that stuff, but if the leak is near the filter head it shouldn't be all that hard to track down. Clean everything with some light degreaser and watch as the engine idles. Unless it is an incredibly slow leak it should be obvious where its coming from. It doesn't evaporate like other fluids and leaves traces of everywhere it has leaked down vertical surfaces.

By all means, use the dye if it will help you track it down, but I've never had a tough time finding diesel leaks once I knew roughly where they were coming from.

usa591 · **Posted:** Wed Aug 09, 2017 1:45 pm

FWIW, the story:

I recently bought & installed a new head along with the Cummins lift pump. Been running it for about 2K miles.

About 1000 miles ago, I started smelling diesel.

Two days ago I noticed a small wet patch under my engine--yup, diesel.

I'm looking at where the head mates to the filter and it's pretty wet--diesel has pooled in the lip of the filter. While I was looking, I saw a drip or two seemingly originating from the bottom where the water sensor is.

Weird...new filter, new head but old water sensor.

I pulled the filter off, made sure that all o-rings were there, especially on the sensor, and firmly re-attached everything. Leak has slowed but is still there. Mystery.

Hoping UV dye will pinpoint leak.

I think coming home smelling like rock oil is sexy...my wife, not so much.

GordnadoCRD · **Posted:** Wed Aug 09, 2017 3:10 pm

Is it wet at the middle of the bleeder screw?

Bushman5 · **Joined:** Sat Jul 11, 2015 11:05 am **Posts:** 276

Diesel fuel lights up like neon with a good UV LED light. (Not the cheap ones. )

A good shop should have a UV LIGHT.

usa591 · **Posted:** Wed Aug 09, 2017 5:48 pm

GordnadoCRD wrote:

Is it wet at the middle of the bleeder screw?

Negative--it is dry.

GordnadoCRD · **Posted:** Wed Aug 09, 2017 6:49 pm

Ok good, so that's not the source.

For best results make sure to clean and dry everything the best you can first, so you don't get false leads.

rankom · **Posted:** Wed Aug 09, 2017 7:16 pm

yes i had this problem with the new FF head and it leaked at the sandwich o ring HEATER PACK , so i got a warranty on it , also make sure your banjo bolt washer is not leaking . in my opinion 2nd gen fuel head is not the best quality .

usa591 · **Posted:** Tue Aug 15, 2017 2:13 pm

Ok, here's the post-dye report:

Darn, that stuff works well! I put the 1oz container in about 3 gallons of fuel, drove it around for a day and put the UV light on it that night.

The dye caused the fuel to light up a fluorescent, unmistakable green. That stuff is fun.

It was collecting in the lip at the top of the fuel filter, where it's mated to the filter head. Because it's at a slight angle, it was pooling in the rear--all of this I already knew.

What was interesting, it that I couldn't see any other areas fluorescing--not any drips on the banjo bolts, the bleeder valve screw, manual pump or fuel line--nothing. I could not see any evidence that it was leaking at the joint of the heater/head, as mentioned by rankom. It that was the source of the leak, I was expecting to see glowing green diesel sweat, but it looked clean and dry.

So...is the leak between the filter and the head itself? Possibly--I really cranked the filter on last week and while the leak hasn't stopped (as evidenced by the dye), it's definitely less active.

I'll update as soon as more info becomes available.

APC9199 · **Posted:** Tue Aug 15, 2017 2:37 pm

I would spin it back off and inspect the mating surface of the filter head for scratches or cracks. Also, flip the gasket over or replace it and see if that helps. Something as simple as the gasket not being cut perfectly straight can cause a leak like yours.

Do you have an inline fuel pump, and if so, what pressure is it creating?

WWDiesel · **Posted:** Tue Aug 15, 2017 3:14 pm

Make sure you do not have two (2) filter gaskets in place. It has happened before! :roll:

usa591 · **Posted:** Tue Aug 15, 2017 7:42 pm

APC9199 wrote:

Do you have an inline fuel pump, and if so, what pressure is it creating?

I have the Cummins in-tank pump. Don't know about the pressure, other than "standard".

I put the pump in at the same time I replaced the head. The only reason I replaced the head was the assumption that it was some how better than the OEM version. It wasn't leaking.

However, I was having an air-in-fuel issue somewhere because I was having to bleed off air every few days, which doesn't happen with the new head and pump.

Good call on checking for a doubled up gasket, too--stranger things have happened.

flash7210 · **Posted:** Tue Aug 15, 2017 8:41 pm

I doubt that your in-tank pump is the problem.

You were having a fuel leak and air-in-fuel problems at the same time?
I suspect the two problems are related.
If fuel can leak out, then air can leak in.

rankom · **Posted:** Tue Aug 15, 2017 9:26 pm

Dodge lift pump is 15 psi , pressure , i did replace banjo bolt (4 copper washers) with Cummins 5.9 12v rubber flared style washers , part number _ tork cummins - bs 14mm and they never leak , the oem copper washer not seal well under high pressure > go with CUMMINS banjo washers .

GordnadoCRD · **Posted:** Wed Aug 16, 2017 2:12 am

There is another possible source of leakage at the fuel filter head. Even if you have the filter properly installed, and even if it isn't leaking it's self, fuel can still drip down and pool where you describe.

If you remove the filter, then remove the fuel filter head, then turn it over, you will see that the part that the filter threads onto is essentially a double-male fitting with hex in the middle. This fitting is the only thing that holds the fuel heater/fuel temperature sensor ring 'donut' to the body of the filter head.

There is an o-ring gasket between the heater 'donut' and the filter head body. If this o-ring has been compromised OR if the fitting isn't tight enough, diesel can seep at this point, and will pool at the top of the filter, and in back as described.
If you pull this apart, make sure to scribe a mark on the filter head body and on the 'donut' so it goes back indexed correctly.

It's also possible that the plastic shell of the 'donut' has cracked and permitting seepage that way.

WWDiesel · **Posted:** Wed Aug 16, 2017 10:46 am

GordnadoCRD wrote:

There is another possible source of leakage at the fuel filter head. Even if you have the filter properly installed, and even if it isn't leaking it's self, fuel can still drip down and pool where you describe.

If you remove the filter, then remove the fuel filter head, then turn it over, you will see that the part that the filter threads onto is essentially a double-male fitting with hex in the middle. This fitting is the only thing that holds the fuel heater/fuel temperature sensor ring 'donut' to the body of the filter head.

There is an o-ring gasket between the heater 'donut' and the filter head body. If this o-ring has been compromised OR if the fitting isn't tight enough, diesel can seep at this point, and will pool at the top of the filter, and in back as described.
If you pull this apart, make sure to scribe a mark on the filter head body and on the 'donut' so it goes back indexed correctly.

It's also possible that the plastic shell of the 'donut' has cracked and permitting seepage that way.

Good thought on the "O" ring between the two parts; the fitting could simply be loose!

and you stated: "If fuel can leak out, then air can leak in."
Do not believe this is possible with an in-tank pump since the entire fuel system all the way from inside the tank to the back of the CP3 is under 10-15 psig of pressure so fuel will always leak out and air will not leak in at any leak point in the system....
If any air were to somehow leak in like say when the engine is off, it would be expelled immediately as soon as the key it turned on and the pump pressurizes the system :wink:

rankom · **Posted:** Wed Aug 16, 2017 7:55 pm

if you find that the new fuel head is faulty , you should be getting a warranty on it , i got one for mine from the dealer and also i just like the rubber washers for banjo bolts beacause cummins had updated their P 7100 pumps back in the late 90 s so i did keep some in my tool box , anyway hope you get a warranty on yours ,

UV Dye for Diesel Fuel

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