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1989 Chevy R3500 6.2 Diesel

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KAMCOBIL

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I replaced the fuel tank on the drivers side because it was leaking and fuel gauge was not working so I changed it too. I ran the truck on each tank and they ran well. Now that I try to run on the drivers side I get water in fuel light and it runs rough. Switch back to the right runs great and no light.. After hours of trying to get it running on the left tank, I decided to check for fuel pressure. When I took off the cap, fuel came gushing out of filler neck. Must have been a lot of pressure for sure. Lines hooked up the same. I'm Baffled . First time 60 years. :D Help! Please!
 
Welcome to the forum KAMCOBIL.
What year, make and model of a truck is we working on ?
Seems to me You must have a big slug of water in that one tank. Probably will need to drain the tank, remove it from the truck then turn it upside down to get out the water.
Others with much more knowledge than I will most likely jump it too.
 
1989 Chevy R3500 6.2 Diesel. It was a new tank, new sending unit and new fuel. How would water get in and why would water cause a gush of a couple of gallons of fuel out of the fill nozzle? Never seen that much pressure in a fuel tank.
 
Fresh fuel right out of the fuel stations pump can contain water.
You are fortunate You can run on the other tank until You get it sorted out.
Also, the below ground temps I believe is in the 50 degree range. If the tank was filled real full, then being out in the heat of the dsy, the fuel will expand and i er fill the tank.
I dont know if the 89 has vented caps, if caps are not vented then pressure will build and cause fuel to spray out of the filler neck when the cap is removed.
 
I think just the gusher but not sure. I'll have to check that one out. When I switch tanks it changes tanks and sending units. Not sure if it switches returns. I plan on running left tank with a 5 gallon can to see it it will run okay.

I'm not sure if water in fuel light will come on when low fuel pressure or not.
 
smokymtn65 said:
Is the fuel tank selector valve 6 port?
Click to expand...
I too am not sure when they went to the motorized tank switch over valve.
I know the old solenoid valve I think returned to only one tank, the motorized unit returned back to the tank they are feeding from. I think thats how they worked.
I did a conversion on the 1978 Chevy K20 that I had, from solenoid to motorized and that went well.
My plan was to install in tank fuel pumps and TBI or MPI system onto that old engine.
 
KAMCOBIL said:
I'm not sure if water in fuel light will come on when low fuel pressure or not.
Click to expand...

I recall it comes on for restricted fuel filter. But I am not clear on that as it happened to me once on our 1988 6.2. Dad changed the filter and didn't find any water. Possible fuel gelling at the time.

Sounds like the return line isn't switching tanks.

Have you drained some fuel from the filter into a glass jar? Look for water and sniff it for a gasoline smell. Water is the quickest way to ruin the injection system there is. Fix it and don't play with it attempting to "get by" "just run it etc." You find water or bad fuel it needs to be parked then drained/fixed: this may save the injection pump and injectors. Save your fuel receipts as your insurance co and you can go after them for water in fuel. Also turn the State inspectors loose on the station. IF you find water that is. Gas and diesel get mixed up now and then by the delivery truck. Ignorant owners let the tank fill paint fade till it costs them bigtime with a fuel mix up.
 
Low pressure will NOT cause the wif light to come on. Drain it, change the filter, and try again. If it comes on again- throw away all that fuel. Think of A couple hundred dollars worth of fuel just like a bad engine part. Because running it through the engine will destroy ip (injection pump) and injectors. Then to boot, bad injectors that go from water tend to create a stream of fuel that if the spray lines up with the hole in the precup, it can burn a hole in a piston top.

Water in fuel has always been enemy #1 to diesels, and now that we have stupid ethonal/ methanol in the fuel - that crap absorbs water and will let a certain amount go through no matter how good your filtering system is. So fight it all you can.

Word of warning about the mechanical lift pump. GM quit using them well before they ever added a turbo. Some people think they removed it for a place to drain the turbo oil into- not correct. There was a problem with thediaphragm of the lift pump failing, then diesel fuel going into the crank case and destroying the engine. There was talk about AC Delco making diaphragm out of new material, but they never did up until 1995 for sure. Why they would do it after the part quit getting sold to the factory is a funny question. So just consider the problem and for folks here know I push for a fuel pressure gauge at the ip inlet, but probably dont know this is why I originally wanted them. Later we learned having the gauge and seeing low fuel pressure is how we started getting almost double the miles out of injection pumps.


fuel tank issues.
I am thinking you need to check a couple items. First you should never be able to build pressure in the tanks. All fuel tanks have a vent with a roll over valve, so they don’t leak in the event of a roll over, yet allow air to come in. If it is sealed 100%, as you burn up the fuel driving- it would suck the tank into a vacuum and starve the engine of fuel. So if you are building pressure, that means the vent is plugged. Find and fix/replace it. I am not sure on the older rigs (can’t remember) it might be a vented fuel cap is how they did it- replace cap with correct one if so.

Next is: how did it build pressure in the first place. No more fuel can return than what is sent to the engine, so this leads me to believe you have a couple hoses in wrong location on the valve, or a wrong valve.

For the short term, maybe simplify and use one tank until you get re registered, and everything is working properly. Then get a new second tank.
 
I stuck between a rock and hard place. :D . I have to get my truck inspected but won't pass with a leaky fuel tank so I need to change it. Inspection was due on the 1st of may. I ordered a new tank and plan on using the same sending unit and fuel. I can work on the one not working later. Tank is suppose to be here on the 5th.

In the mean time I work on the problem tank on Tuesday. I am using the cap that was on the tank before. I know what you mean about the pressure. I'll get back Wednesday.
 
Okay, Here's what happened. I started out making a video what was happening. I switched from good tank to bad tank light came on after a few seconds but it was still running smooth and switched back to good tank. It was running on bad tank and when switching to good tank it stopped running. Low and behold 4 hours later I got it running. :D

Since it was about dark I decided to wait until tomorrow when new tank and switching valve comes. I'm going to replace valve and try bad tank and hope it works with right with new valve.

Another pause until Tuesday to finish.

Oh by the way Great Information.
 
Wonder if it is a grounding issue on the switching valve, or a partially stuck switching valve. Will switch fine one direction but hang up going nuther direction. 🤷‍♂️
 
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