$$!??#%%! Fuel starvation when it's raining

[mtngoat]

No heating at all, nope.

 

Stopping for a couple minutes did nothing, after 12 miles of highway. that's aways enough to melt it out

 

Plus, this was happening in the summer too, just not as badly.

[smoke]

Well, icing will happen in the summer too, as long as humidity is up. But since we are talking air filters, are yours by chance getting water flung on them?

[mtngoat]

I doubt it. It isn't covered but it's dry. I checked that too. On bad days like monday it drive like crap before I'd even gone a mile in light mist, air filter was dry.

 

I know it sounds like icing but I have never seen icing not fade for at least a bit after shutting down a few min.

 

And there's the empty filter biz. It never used to do this, normally half full or better.

[smoke]

A few ways to check on the fuel, one would be to install a pressure gauge in line. I have one if you want to borrow it.

[datzenmike]

Is the tank vented. If cap loosened is there an inrush of air?

 

The filter is between tank and pump and so is on the suction side. A loose hose clamp or a small split will let air be sucked in. Easier to suck air in than lift heavy gas up from the tank.

[banzai510(hainz)]

Even weirder, when I got my three days of snow it was never above freezing, and the car still ran fine. The day it warmed up and the rain started was the day it ran terrible again!

 

after a snow melt off I will have condensation under the dizzy cap.

 

as for icing. its its just above freezing and raining my Weber DGV iced up. as the head did not use a water line. (a import l18 head with no holes)

SUss should be harder to ice up as its a sidedraft and the airvol is slower.

 

My Mikunis have no proplems on cold days and run not heater line(most times they leak and I plugged them)

[datzenmike]

The water warmed manifold doesn't really help much for the carb icing as it's right at the venturi where it freezes. On a regular Hitachi or weber down draft the warming effect is on the bottom of the manifold below the carb. Same with side drafts. Only way to prevent carb icing is a warm air set up using exhaust manifold heat.

[tdaaj]

Or a hair dryer hot wired into the system

[smoke]

I have a funnel under the steering wheel, hooked to a garden hose pointed at the carb, when it starts to ice up, I pee in the funnel.

[mtngoat]

Smoke that's a great idea. I have a full fuel pressure gauge kit I picked up for troubleshooting my fourrunner. I could put in the t fitting and run the gauge to the passenger seat. Thanks for your kind offer!

 

I failed to get to messing with it last night once again.

 

Another couple data points..

 

This morning I checked the filter after another flawless run home last night. Filter totally full. So full I wasn't sure there was anything in it (white, not clear, plastic). I grabbed a screwdriver and pulled a line... Bubbles! Sure enough, full to the tippy top.

 

Light rain today, about same temp as yesterday. Run to work... Some lean missfiring if I really pushed it, but ok at cruise. Checked filter before I went in... Nearly empty.

 

Sure looking like its sucking air. I came in early so I'm leaving early and tonight Im going over every inch of line, hard or soft.

 

I might have a combo of factors with it.. 44 year old hoses at the back and maybe a crushed hardline making it worse if the softline is bleeding air into the system?

 

I know hardline problems could be in the mix because of decades of rock crawling. I had to replace a section of line which was crushed last year. That spiral wire jacket springs back and hides crushed areas. I've been thinking about using the return line as a main due to its more protected location in the drive tunnel.

[DanielC]

Obvoiulsy, you are checking fuel pressure. 

more important that pressure is fuel flow.  Off the top of my head, a stoch L-16 fuel pump should flow about a quart of gas, at 1000 RPM, in a minute.

[smoke]

Right, I should have mentioned that. You can still have good pressure with low volume. But in your case, it seems as as if fuel bowl is going dry. If this is what's happening the float will be at the bottom, the needle will be off the seat and very little fuel will be coming in. So, unless there is a clog between the carb and the gauge, you should see a drop in pressure.

[mtngoat]

What does a WO2 sensor show if you're icing.... Richer or leaner?

[smoke]

Lean on most. But if it's really bad, like on a plane, rich.

[datzenmike]

My stock Hitachi down draft formed a small ball of ice on top of the venturi during freezing rain events and if it was foggy when there was snow on the side of the road, cold and damp. Reduced vacuum = reduced fuel. (lean) The fuel that is sucked into the venturi will absorb heat as it vaporizes, super chilling it. The venturi temperature goes well below freezing and the cold damp air flowing past it frosts it over until plugged.

 

I noticed that pushing the pedal down did nothing, it was like turning the key off. I let up and there was a sputter and it would run but at less power than I needed and the truck would slow down. Eventually it would only idle along, which makes sense as the fuel for idle in on a different circuit. I could take the top off the air filter and flick the ice off and it would run normal for only a block at a time.

 

The snorkel on the air filter has a thermostatically closed gate but no hose down to the exhaust and no metal shroud to collect the hot air. I cut a Maxwell coffee can open and wrapped it around the exhaust manifold with stove pipe wire. Got a length of metalized hose (called a stove pipe) and hose clamped to the snorkel and shoved under the coffee can. Worked perfectly, problem solved. Next summer I found a proper metal shroud for an L20B exhaust. All you need is slightly warmed air.

[ggzilla]

Have you tested the filter flow?

[mtngoat]

Had a long look last nite. Inline carb screens above the needle valve, clean. Hoses to and from filter and pump, fine. Hardline fine.

 

Apparently someone had replaced the rear softline from hardline to tank before I got the car. It looks OK... But feels very very squishy. A small diameter hose like this should not feel this soft, it's suspect to me. Its easy to get to the hardline side of this rear hose, but the hose to tank connection is buried above the tank.

 

I pulled the float sensor cover hoping I could reach it though there, but no go. Looks like I'll have to drop the tank.

[smoke]

But it has a drain in the bottom right? Makes it a bunch easier.

[mtngoat]

'zillah, no I didn't test the flow. I was going to install my pressure gauge on a T, but ran into snags

 

No open holes left in firewall, instrument wiring fills all of em

Didn't have a t for this size line

Gauge is for injected systems, starts at 10 psi!

[smoke]

Okay, so if this does not work, I'll send you out what you need to test it.

[datzenmike]

Maybe they used rubber hose. That will dissolve in gas and may be why its soft?

[HRH]

One thing to note, old fuel line does not bode well with ethanol.  We finally switched our hoses over to the Barricade "California" hose.  This stuff works 100 times better than the old fuel line you get commonly and it's only about a buck a foot more.  I would think you're sucking in water/air from the pickup in the tank.  I would replace those rubber sections from the tank inlet and check your fuel filler cap for rubber gasket cracks.

 

Also, I don't think this is your problem, but I had a rain issue with my 620 in Arizona.  The rubber windshield gasket was cracked and when it rained, it would drip rain in down onto the parcel tray, then onto the transistorized ignition unit.  And then it would blow a fuse.  Couldn't figure it out as the water wasn't much, but it was enough to cause a problem.  Then one day I parked it in the right spot and the parcel tray filled with water instead of draining off.  Think I siliconed the windshield rubber instead of replacing it.  Solved the problem anyway.

[ggzilla]

Fuel flow test does not use a pressure gauge.

[mtngoat]

Update time.

 

It's been running somewhat better since I went end to end tightening clamps. It has been pretty rainy but the problem is not nearly as bad. It will still starve if I lean into it hard but it seems like snugging up all the clamps perhaps enabled it to pull a little harder in the line or not suck as much air when the rear hose is acting up. At least that's what I'm hoping.

 

I had been thinking about that rear hose and ethanol myself in the last few days. I've never touched that hose myself and I got the car before they started screwing up our gas with ethanol. Between that, the weird squishy feel of that hose, and the little black flecks I found in the filter I just replaced after I dug it out of the trash two nights ago, I'm hoping this is the answer.

 

Tomorrow I drop the tank and replace that hose.

[mtngoat]

While I've got the tank out I'm going to hoist the 17 gallon z tank I picked up into the space and see how practical a swap will be. Offhand it looks like it might not be too bad.

 

It's actually a shallower tank and the filler is in about the same place. Since I don't need the winch for the spare it's already gone and I can cut off the small bracket that registers the spare in place when you pull it up.

 

I guess I'd need to fabricate brackets and figure out how to add endpoints for the tank straps too.