Water in fuel light

[Gene Obie]

After about an hr on the road the "Water in Fuel" light came on. Flashed a few times then stayed on. Luckily I found a weigh station to exit. Checked the manual and it said to not continue due to possible injector damage.

So following the manual I shut off the engine, and with ignition on and press the purge button on the Racor. But nothing seemed to happen. No light and no indication of any water coming out. Should the light come on when I depress purge regardless of whether water is detected or not? Perhaps I have a blow fuse or bad solenoid in the Racor?? So after this failed attempt to purge I restarted the engine and magically no "Water in Fuel" light any more. I drove another 2hrs to destination with no issues. I'm sure I need to replace the filter but I'm sort of an isolated spot here. Can I just remove the connection at the bottom of the filter to manually drain any water?

I filled the tank last time out at Loves so doesn't seem like I would have gotten bad fuel at big truck stop. Weather here is in the 30's so wonder if cold is contributing? Unfortunately, I didn't pay enough attention to the big note in the manual indicating one should always carry a spare filter. Live and learn.

[Dave Atherton]

Gene, the lamp that you are talking about is telling you that your secondary fuel filter 1R-079
has reached its end of useful life and needs to be replaced. The lamp coming on and going off
Is a warning sign on your computer that filter needs to be replaced. If you continue to operate
engine after 13 psi back pressure resistance within the fuel filter your engine will derate to 37 %
of your engine power. Last this fail safe system is set up for use of caterpillar filter 1R-0749 only.
Installing aftermarket fuel filter in replacement of the caterpillar fuel filter will remove the fuel
System fail safe while using something other that Caterpillar fuel filters in the fuel system.
Dave Atherton Retired Cat Mechanic

[Bill Lampkin]

Last spring I had the fuel filters replaced at our local CAT dealer, at least I though he changed both the primary (Racor) and CAT (secondary) filters. Not long after we started out trip, the 'water in fuel' light came on, intermittently. I checked the sight glass at the bottom of the primary filter, no water. The mechanic had not replaced the primary filter. The light came on intermittently for the following week or two with no other symptoms. Same scenario happened on our first trip with the coach  in 2015.  No damage done, but next time I'll make sure they change both filters.

I don't know how the secondary fuel filter would be able to turn on the "water in fuel' light.

[David T. Richelderfer]

Bill - there must be a back-pressure switch inline.  Dave said over 13 pounds back pressure turns on the light.

[Bill Lampkin]

That's the thing, to measure pressure drop across a filter, you need two pressure sensors, one on either side of the filter. Then (I guess) the ECU makes the calculation and turns on the light. this circuit would have to be in parallel with the water in fuel circuit, the one in the filter bowl that looks for ground when there is water in the fuel. I don't know of any such series of pressure sensors, but I am not at all an expert on CAT engines!

The point of my post was to say the same thing (water in fuel light on) has happened to me, right after the secondary filter was changed (its happened twice now). One time we were in Colorado and I had some white smoke on start up, changed the secondary fuel filter and smoke went away. No water in fuel light that time.

[Gene Obie]

I order a new Recor S3230p equivalent primary filter from Napa (best I could get anywhere reasonably close to where I'm at.)

But now I see there's another "secondary" CAT filter" 1R0749. Any guidance on where that is located?

Thanks for info so far. I'm getting more concerned I shouldn't drive the rig at all until both of these are replaced. I'm at a state park 2-3hrs from any cat/diesel shop and really wet here so getting under this beast trying to find and replace fuel filter may be a bit of a challenge. Bummed at the last minute I decided not to load my safety blocking I use for getting under the rig.

[Bill Lampkin]

The Racor primary filter is the one you can see easily, the CAT secondary filter (I think) is behind it, it mounts to the engine block. I wouldn't be concerned about driving the rig if you can't find water in the Racor bowl. Like I said, the water in fuel light has come on during two separate occasions to no ill effect.  You've checked for water in the bowl, I would just drive to your next destination and find a shop along the way to change the filters. BTW, I think the mechanics replace the smaller Racor filter with a larger filter from WIX, don't know if it makes a difference. I think they have a harder time getting the Racor so they just go with what is available.

[Bill Lampkin]

Re-reading Dave's post, I think what happens is that CAT monitors fuel pump pressure, if that exceeds 13 psi then the engine could derate. High fuel pump pressure (due to a clogged secondary filter, say) could lead to reduced fuel delivery to the injectors, not a good situation. I think the proper CAT filter is a 1 micron filter (correct me if I am wrong). 

[Gene Obie]

Confused on the terms. It looks like the output of the primary (Racor water separator filter) goes directly to the fuel pump located on the back of the c13 block? And the "secondary" filter input is from the fuel tank? Is that correct?  If so, seems reversed to call the first filter the "secondary".

[Bill Lampkin]

https://www.blog-teknisi.com/2018/12/fuel-system-c11-and-c13-caterpillar.html

[Gene Obie]

Thanks Bill, that helps.

Seems last owner put in 3rd party secondary filter - not a CAT.  How much could they have saved with some after market filter - geez.

Based on what I'm reading here best to use only cat filter. I think I will pick up Napa filter FIL3674 for emergency use on ride out of here next week but replace secondary with CAT if I make it home ok.

[Bill Lampkin]

As long as its running ok now, I wouldn't worry about the light, just get 'em changed when you can. Gonna rain here like it does in Puget Sound starting tomorrow. Batten down the hatches!

[Fred Brooks]

  Gene,
Ask Dave, he will share how Caterpillar engineered it's CPU around that 1R-0751 2 micron secondary filter. That is how the computor measures the resistance in the system. I believe "Fleetgard" is a 15 micron filter thus nullifying the computor monitoring. The return fuel line on the pump on the back of the engine is the "input" into the secondary CAT filter (1R-0751)
  You may want to inspect both hoses on the pump, mine was oozing diesel fuel. Hope this helps, Fred

[Dave Atherton]

Gentlemen, how the caterpillar fail safe works within the fuel system and caterpillar fuel
filters are used. Caterpillar fuel filters are rated as a 2 micron new and installed on
engine sets up a 5 psi back pressure resistance with fuel flow through the fuel filter.
Remember the secondary fuel filter the 1R-0749 is under pressure from the fuel transfer
pump and the primary fuel/water filter is under suction to the fuel transfer pump. When
secondary fuel filter is nearing its usefulness at 10 psi lamp on dash will come on and go off.
When the fuel fines reach 12 psi lamp on dash will come on and stay on, than when 13 psi
back pressure is reached the engine will derate engine power to 37 % . Last replacement
With new caterpillar 1R-0749 fuel filter engine lamp will go out and engine power restored.
Dave Atherton Retired Cat Mechanic

[Gene Obie]

Thanks for the great explanation Dave. Along with the attached diagram from the link Bill sent I have much better understanding of basics of this system.