I wanted to learn about diesels, so I got a PennDOT '99 C3500 with the 6.5TD and 175K on it. School bus yellow. I've rebuilt motorcycles, so I have a clue, but Diesel is new to me. Though the info in this post is probably obvious to the masters, it took a lot of web reading for me to assemble. I'll summarize here, in hopes that other newbies might find this useful.
On the 6-hour drive home, in the wee hours, on the interstate in the middle of nowhere, the "Water In Fuel" light came on. Now I'd made it a point to fill up at a truck stop so I'd get clean, dry fuel. Oh well.
I pulled into a very dark, very empty rest stop & pulled out the manual. It did not mention a "Water in Fuel" (WIF) light. It did mention that I should look at the Diesel Supplement. Of course, I had no Diesel Supplement. So I called the 800 number for Chevy's 24-hour customer support. Nice people, not useful. So I pulled out my netbook, got on line and came to TheTruckStop.com. Folks said I should open the brass valve on the thermostat, but no one said where the thermostat is. Air-cooled motorcycles don't have thermostats. I finally found pictures. It's the little T-shaped brass valve at the top front of the engine, a little toward the passenger side of center. I bled 18 oz of water before I got diesel. I know because I was filling empty plastic bottles. The WIF light stayed off after that.
Some might question the wisdom of taking a 6-hour journey in a newly acquired used truck. I had my netbook and all my tools. I also had Allstate Motor Club's RV insurance, since AAA doesn't cover a 1-ton Dually pickup. (They say it's too big.) The truck had been serviced and inspected. I had no pressing engagements. I made it OK.
Next, I wanted to know if the fuel filter needed to be changed. I learned that the fuel system wants about 5 PSI feeding the injector pump. There's a pressure valve on the fuel return line that cracks open when the pressure reaches 5 PSI, letting fuel return to the tank. So I want to measure 5 PSI at a point between the fuel filter and the IP. The pressure at this point can go negative, when the IP is pulling harder than the lift pump is pushing, so the sensor needs to measure both vacuum and pressure.
I was looking at a wiring diagram, and noticed fuel pressure sensor wires feeding into the computer and/or PMD. I figured, why add sensors if they're already there? So I got CarCodes.com, and learned that the existing pressure sensors are not where I want them. CarCodes does provide great access to what sensors exist. I like the "soft" gauges on their dashboard.
I'm careful to bleed off fuel regularly and check for water. I bleed it into a plastic bottle so I can see. It's become a routine act, and today I was carefully watching for fuel to come out of the hose when I realized I'd been opening that valve longer than usual. Then the engine died. Bummer.
The bleed valve connects to the dirty side of the filter. Since fuel wasn't coming out, that means there was no pressure to the filter. It seems the lift pump had died, so the IP had been doing all the work to pull fuel from the tank. That's hard on the IP. I had checked for water that morning, and gotten good flow, so I'd been running without a lift pump for less than a day. When I opened the valve with a dead lift pump, the IP sucked air in and the engine died.
Why check for water in the fuel twice in one day? The truck had sat for a week or two while I worked on the bed, and I thought perhaps there might be condensation in the tank. I'm still learning what to expect with this truck. I figured running a few errands would run any water through the filter, where I could drain it out. I was curious to see if I got any water at the end of the day.
When you have no fuel pressure, everyone says to jump the fuel pump relay to run the pump. I found lots of instructions on how to do this. Many were for other 6.5 models. Some were flat wrong. If you pull the fuel pump relay, the pins underneath the relay are labeled. I put a voltage tester on mine, and pin 87 is always hot. Several web articles said pin 30 led to the lift pump. So I jumped 87 to 30, and heard the pump run. I opened the T valve and the bleeder valve on top of the filter, and got no fuel from either.
OK. The tank is 7/8 full. The lift pump is making noise, and we have no fuel to the filter. Something could be blocking fuel to the pump, but since the engine ran fine before I tried to bleed it for water, restrictions seemed unlikely. Any restriction that blocked the lift pump would also have blocked the IP, but the IP managed to pump the fuel just fine. Evidently the lift pump failed in such a way that it still makes its usual noise, but it no longer moves fuel.
So I went and bought a new lift pump from the local parts store, as well as flare wrenches and their best penetrating oil for freeing rusty bolts. I had to scrape off rust so I could get the wrenches on the fuel pump fittings, and they were so frozen that I stripped the nut. A 5/8 flare wrench on a 5/8 fitting, and all it did was mangle the corners of the fitting. The wrench rotated, but the fitting did not. So much for the top-end penetrating oil.
So I couldn't replace the lift pump. So I put a funnel into the bleeder hose, opened the bleeder valve and the filter bleeder, and poured diesel into the funnel. When it came out the top of the filter, I closed the bleeder valves, and started the engine. It had to crank for a bit, due to the air in the injector lines I imagine, but then it caught and ran fine. I wouldn't run it much like this, but it works well enough to drive to my local mechanic, if I need to.
So now I guess I'll have to replace the entire fuel line, from tank to filter. I tried to find a fitting that would go from my new lift pump to 3/8 hose, but the pump fitting is not NPT. I guess it's 3/8 straight threads. I think I'll return the OEM pump I bought and get a Walbro with the fittings I need.
I also need to get to the top of the tank. They say it's easier to remove the bed than to drop the tank. OK. I broke off 8 of the 12 3/8 in carriage bolts trying to turn the nuts. One I drilled out, one had no nut so I drove it out with a hammer and punch. The last 2 were the most fun. They were carriage bolts that spun freely, so I had to cut off the nuts with a dremel cutting wheel and a cold chisel.
I need to get a lift so I can get the bed off. It's a utility body, so it probably weighs over 500 lbs empty. Once I have it off, I can access the fuel tank and replace the fuel line with 3/8 rubber. At least that won't rust! I'll also do what I can to get rid of the rust on the frame. I'm looking at some combination of naval jelly to remove rust, picklex 20 to convert any remaining rust, and Rust Zero to paint the de-rusted frame. I'll also be using wire brush, cold chisel, pressure washer, and elbow grease to remove existing rust.
So imminent plans include removing the bed, replacing the rusty fuel line with rubber, de-rusting the frame, and installing a pressure gauge between the filter and the IP. Then come the recommendations made elsewhere on this site: spare remote PMD, ground refresh, feed the beast, etc.
I hope someone finds this post useful. I'd have been sunk without this site.
Thanks everybody,
-jpg
PS I know some folks would prefer pictures. Sorry, don't have any yet. I'll try to add some.
On the 6-hour drive home, in the wee hours, on the interstate in the middle of nowhere, the "Water In Fuel" light came on. Now I'd made it a point to fill up at a truck stop so I'd get clean, dry fuel. Oh well.
I pulled into a very dark, very empty rest stop & pulled out the manual. It did not mention a "Water in Fuel" (WIF) light. It did mention that I should look at the Diesel Supplement. Of course, I had no Diesel Supplement. So I called the 800 number for Chevy's 24-hour customer support. Nice people, not useful. So I pulled out my netbook, got on line and came to TheTruckStop.com. Folks said I should open the brass valve on the thermostat, but no one said where the thermostat is. Air-cooled motorcycles don't have thermostats. I finally found pictures. It's the little T-shaped brass valve at the top front of the engine, a little toward the passenger side of center. I bled 18 oz of water before I got diesel. I know because I was filling empty plastic bottles. The WIF light stayed off after that.
Some might question the wisdom of taking a 6-hour journey in a newly acquired used truck. I had my netbook and all my tools. I also had Allstate Motor Club's RV insurance, since AAA doesn't cover a 1-ton Dually pickup. (They say it's too big.) The truck had been serviced and inspected. I had no pressing engagements. I made it OK.
Next, I wanted to know if the fuel filter needed to be changed. I learned that the fuel system wants about 5 PSI feeding the injector pump. There's a pressure valve on the fuel return line that cracks open when the pressure reaches 5 PSI, letting fuel return to the tank. So I want to measure 5 PSI at a point between the fuel filter and the IP. The pressure at this point can go negative, when the IP is pulling harder than the lift pump is pushing, so the sensor needs to measure both vacuum and pressure.
I was looking at a wiring diagram, and noticed fuel pressure sensor wires feeding into the computer and/or PMD. I figured, why add sensors if they're already there? So I got CarCodes.com, and learned that the existing pressure sensors are not where I want them. CarCodes does provide great access to what sensors exist. I like the "soft" gauges on their dashboard.
I'm careful to bleed off fuel regularly and check for water. I bleed it into a plastic bottle so I can see. It's become a routine act, and today I was carefully watching for fuel to come out of the hose when I realized I'd been opening that valve longer than usual. Then the engine died. Bummer.
The bleed valve connects to the dirty side of the filter. Since fuel wasn't coming out, that means there was no pressure to the filter. It seems the lift pump had died, so the IP had been doing all the work to pull fuel from the tank. That's hard on the IP. I had checked for water that morning, and gotten good flow, so I'd been running without a lift pump for less than a day. When I opened the valve with a dead lift pump, the IP sucked air in and the engine died.
Why check for water in the fuel twice in one day? The truck had sat for a week or two while I worked on the bed, and I thought perhaps there might be condensation in the tank. I'm still learning what to expect with this truck. I figured running a few errands would run any water through the filter, where I could drain it out. I was curious to see if I got any water at the end of the day.
When you have no fuel pressure, everyone says to jump the fuel pump relay to run the pump. I found lots of instructions on how to do this. Many were for other 6.5 models. Some were flat wrong. If you pull the fuel pump relay, the pins underneath the relay are labeled. I put a voltage tester on mine, and pin 87 is always hot. Several web articles said pin 30 led to the lift pump. So I jumped 87 to 30, and heard the pump run. I opened the T valve and the bleeder valve on top of the filter, and got no fuel from either.
OK. The tank is 7/8 full. The lift pump is making noise, and we have no fuel to the filter. Something could be blocking fuel to the pump, but since the engine ran fine before I tried to bleed it for water, restrictions seemed unlikely. Any restriction that blocked the lift pump would also have blocked the IP, but the IP managed to pump the fuel just fine. Evidently the lift pump failed in such a way that it still makes its usual noise, but it no longer moves fuel.
So I went and bought a new lift pump from the local parts store, as well as flare wrenches and their best penetrating oil for freeing rusty bolts. I had to scrape off rust so I could get the wrenches on the fuel pump fittings, and they were so frozen that I stripped the nut. A 5/8 flare wrench on a 5/8 fitting, and all it did was mangle the corners of the fitting. The wrench rotated, but the fitting did not. So much for the top-end penetrating oil.
So I couldn't replace the lift pump. So I put a funnel into the bleeder hose, opened the bleeder valve and the filter bleeder, and poured diesel into the funnel. When it came out the top of the filter, I closed the bleeder valves, and started the engine. It had to crank for a bit, due to the air in the injector lines I imagine, but then it caught and ran fine. I wouldn't run it much like this, but it works well enough to drive to my local mechanic, if I need to.
So now I guess I'll have to replace the entire fuel line, from tank to filter. I tried to find a fitting that would go from my new lift pump to 3/8 hose, but the pump fitting is not NPT. I guess it's 3/8 straight threads. I think I'll return the OEM pump I bought and get a Walbro with the fittings I need.
I also need to get to the top of the tank. They say it's easier to remove the bed than to drop the tank. OK. I broke off 8 of the 12 3/8 in carriage bolts trying to turn the nuts. One I drilled out, one had no nut so I drove it out with a hammer and punch. The last 2 were the most fun. They were carriage bolts that spun freely, so I had to cut off the nuts with a dremel cutting wheel and a cold chisel.
I need to get a lift so I can get the bed off. It's a utility body, so it probably weighs over 500 lbs empty. Once I have it off, I can access the fuel tank and replace the fuel line with 3/8 rubber. At least that won't rust! I'll also do what I can to get rid of the rust on the frame. I'm looking at some combination of naval jelly to remove rust, picklex 20 to convert any remaining rust, and Rust Zero to paint the de-rusted frame. I'll also be using wire brush, cold chisel, pressure washer, and elbow grease to remove existing rust.
So imminent plans include removing the bed, replacing the rusty fuel line with rubber, de-rusting the frame, and installing a pressure gauge between the filter and the IP. Then come the recommendations made elsewhere on this site: spare remote PMD, ground refresh, feed the beast, etc.
I hope someone finds this post useful. I'd have been sunk without this site.
Thanks everybody,
-jpg
PS I know some folks would prefer pictures. Sorry, don't have any yet. I'll try to add some.
