Fuel filter puzzle

[KamperBob]

So I'm bringing back an 84 k30. This past week was my first trip camping in the San Bernardinos. Going up it did okay. Coming down yesterday a leak developed. Apparently fuel from the box filter bleed port. I was concerned it might've been something more serious. But could it just be that the bleed screw wasn't seated tight enough? I hadn't touched it. Nor checked it. I pulled the screw and the pointed bottom looked fine. So I made sure it was snug.

Before that, however, I didn't even know that it was the bleeder. I thought maybe it had to do with water in fuel and purging. So I rigged up a catch bottle to examine and make sure what it was. Then after studying available manuals and online searches today I learned it was the bleeder. So it's supposed to leak when opened to purge air from an empty new filter. Not otherwise. So I'll leave the catch bottle and monitor to see if any more presumably unwatered fuel comes out. I just ran to the store tonight, maybe 10 miles round trip, and so far so good. But I'm planning a longer camping trip into the Sierra Nevada next week. I'll have more data after hundreds of miles.

Meanwhile, I'm puzzled because the shop manual said the water in fuel sensor was in the tanks and mentioned a purge siphon by the frame rails. So far I haven't found that. Maybe I'm just missing it. I hope to trace down the sensor wires to confirm. The shop manual also shows the water fuel separator, including drain, on the fuel filter. Is this just a case of belt and suspenders? The dash light comes from tank sensors and the larger volume of water at the root source can be siphoned there, yet what gets up to the filter can get trapped and drained there as well? Or is the water in fuel sensor in the filter housing? That 411 might help. TIA

 

[Blue Ox]

AFAIK all of the things you are referring to are on the filter assembly. There is another one of those valves near the bottom of the filter to drain water. The water sensor is in the base that the filter attaches to. There is also a vacuum switch that lights the WIF light if the filter becomes restricted.

I believe the earliest trucks which used spin-on filters had the tank drains, but my experience was that was an '82 only thing.

 

[Rickf]

There wasn't any "water in fuel" sensors in my mid 80's CUCV blazer fuel tank, only on the firewall box filter housing.

 

[KamperBob]

AFAIK all of the things you are referring to are on the filter assembly. There is another one of those valves near the bottom of the filter to drain water. The water sensor is in the base that the filter attaches to. There is also a vacuum switch that lights the WIF light if the filter becomes restricted.

I believe the earliest trucks which used spin-on filters had the tank drains, but my experience was that was an '82 only thing.

Thank you! I found the drain valve. That doesn't seem to leak. But I might could pull the draincock screw. Probably the same as the bleeder screw. See how they compare. I wonder if they can be replaced. Plastic could be worn. Hm

That vacuum switch tidbit is particularly interesting. The vacuum pump is blown. A replacement is back ordered. Since I have SM465 and the R12 AC is out I figured the only harm now without vacuum was the vent controls are stuck in their default (spring return) positions. Which isn't the end of the world short term. Pioneers lived without AC. I can too. Although fresh air would be nice. Anywho. Once my other half's travel plans catch up with mine, her internal thermostat will then make AC become a top priority! LOL

I think the fuel filter was replaced shortly before the truck got mothballed. It doesn't act plugged so I put it back on to focus on the fuel leak for now. When I get the vacuum system working it will be interesting to see if the WIF lamp glows. Hm. Maybe today I'll rig a hand pump...

Thanks again!!

 

[KamperBob]

Attaching a few relevant pages on WIF info from 84ck service manual.

 

[Blue Ox]

Thank you! I found the drain valve. That doesn't seem to leak. But I might could pull the drain **** screw. Probably the same as the bleeder screw. See how they compare. I wonder if they can be replaced. Plastic could be worn. Hm

That vacuum switch tidbit is particularly interesting. The vacuum pump is blown. A replacement is back ordered. Since I have SM465 and the R12 AC is out I figured the only harm now without vacuum was the vent controls are stuck in their default (spring return) positions. Which isn't the end of the world short term. Pioneers lived without AC. I can too. Although fresh air would be nice. Anywho. Once my other half's travel plans catch up with mine, her internal thermostat will then make AC become a top priority! LOL

I think the fuel filter was replaced shortly before the truck got mothballed. It doesn't act plugged so I put it back on to focus on the fuel leak for now. When I get the vacuum system working it will be interesting to see if the WIF lamp glows. Hm. Maybe today I'll rig a hand pump...

Thanks again!!

The screws are the same. There was a production change between the tapered tip and a rubber tip. If they don't match one of them was changed. Be careful, they break easily.

The vacuum sensor illuminates the WIF lamp when the filter becomes restricted and the injection pump starts to pull vacuum against the restriction. It's sensing vacuum in the fuel system. It has absolutely nothing to do with the engine vacuum pump and the climate control, transmission modulator etc.

 

[KamperBob]

The vacuum sensor illuminates the WIF lamp when the filter becomes restricted and the injection pump starts to pull vacuum against the restriction. It's sensing vacuum in the fuel system. It has absolutely nothing to do with the engine vacuum pump and the climate control, transmission modulator etc.

Ah! So the WIF lamp means more than just water in fuel. It could mean filter restricted. Either way means service fuel filter. Which suggests better wording for the indicator but I suppose hindsight's 20/20.

Thanks again!!

 

[KamperBob]

The screws are the same. There was a production change between the tapered tip and a rubber tip. If they don't match one of them was changed. Be careful, they break easily.

Any lead(s) for replacement screws?

 

[Blue Ox]

Stanadyne P/N: 27953 Looks to be obsolete

Fuel Sentry products appear to be owned by Parker now: EE94370

You don't want to know what Parker wants for that.

 

[KamperBob]

I've been scratching my chin about the discrepancy between the WIF system as described in the service manual and what I'm finding on my truck. (Note: sections attached previously, post #5.) Special thanks to BlueOx for real world ground truth.

Rereading 84 specs there's mention of standard equipment on diesel models. (page attached)

Bullet 6 seems subtle yet now clear enough that WIF "unit" means firewall mounted filter separator bleeder drain module. Maybe no tank sensor because of dual tanks. Shrug

Also, the next to last bullet does imply the WIF lamp also could mean the filter itself. As in clogged or restricted.

It does seem odd that the service manual would be less accurate than specs. Since SM is what mechanics would follow. Shrug

Bottom line: all this info improves my confidence in the truck. Thanks again!!

 

[KamperBob]

Stanadyne P/N: 27953 Looks to be obsolete

Fuel Sentry products appear to be owned by Parker now: EE94370

You don't want to know what Parker wants for that.

So far I haven't found much on either lead. But thanks all the same.