ArdWrknTrk Posted June 8, 2023 Share Posted June 8, 2023 The in thank pumps are there, but they are not connected and I don't know if they work. The on frame pump is pulling fuel through them. I will try to sketch something up on the current system. You might want to check that your pump is delivering a quart every 15 seconds to the carb (like the TSB says) Even if it is rated at 60 gph I have my doubts that it can pull that through the in tank pumps. Electric pumps are not so good at pulling liquid to get a prime. That's why any factory system has them in the bottom of the tank, where they are always full, and cooled by the liquid they are submerged in. Link to comment Share on other sites More sharing options...
CRittaler Posted June 14, 2023 Author Share Posted June 14, 2023 You might want to check that your pump is delivering a quart every 15 seconds to the carb (like the TSB says) Even if it is rated at 60 gph I have my doubts that it can pull that through the in tank pumps. Electric pumps are not so good at pulling liquid to get a prime. That's why any factory system has them in the bottom of the tank, where they are always full, and cooled by the liquid they are submerged in. I dropped the front tank and replaced the fill neck. I verified the in tank pump is working because I used it to pump the remaining gas out of the tank. I have to calibrate the sending unit though, it would rarely read above half. Sometimes if I hit a bump it would swing to full, but not drop to E. I assumed it was getting hung up on something, but I pulled it out and the range of motion is clear and unobstructed. I am going to put 5 gallons in and bend the rod until the float reads E and go from there. Out of the tank, full droop reads ~75 ohms, full raise reads ~9 ohms, but this puts the float above the locking ring so not a feasible full scale point. I did remove the float and checked for leaks. It's fine, no bubbles when submerged in a glass of water. For the rear tank, I ordered a new 87 tank and fill neck. I'm going to try to make my early pump assembly work since the difference is only the notches to align the assembly. That sender has the same trouble, rarely reads above half and acts like it's hanging up on something. I still have to drop the rear, but it's full so I'll have to spend some time draining it first. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted June 14, 2023 Share Posted June 14, 2023 I dropped the front tank and replaced the fill neck. I verified the in tank pump is working because I used it to pump the remaining gas out of the tank. I have to calibrate the sending unit though, it would rarely read above half. Sometimes if I hit a bump it would swing to full, but not drop to E. I assumed it was getting hung up on something, but I pulled it out and the range of motion is clear and unobstructed. I am going to put 5 gallons in and bend the rod until the float reads E and go from there. Out of the tank, full droop reads ~75 ohms, full raise reads ~9 ohms, but this puts the float above the locking ring so not a feasible full scale point. I did remove the float and checked for leaks. It's fine, no bubbles when submerged in a glass of water. For the rear tank, I ordered a new 87 tank and fill neck. I'm going to try to make my early pump assembly work since the difference is only the notches to align the assembly. That sender has the same trouble, rarely reads above half and acts like it's hanging up on something. I still have to drop the rear, but it's full so I'll have to spend some time draining it first. I think you will need the smooth grey plastic inner 'fill' hose as well. Not sure if the corrugated vent hose from an '80-'86 truck will flow or even fit an '87^ filler neck. Please let us know how it goes. Link to comment Share on other sites More sharing options...
CRittaler Posted June 14, 2023 Author Share Posted June 14, 2023 I think you will need the smooth grey plastic inner 'fill' hose as well. Not sure if the corrugated vent hose from an '80-'86 truck will flow or even fit an '87^ filler neck. Please let us know how it goes. I bought the later fill neck that has the inner hose for filling. My old inner hose was dishwasher drain hose that I am fully expecting to have melted by now. Once I get to the rear tank I'll know for sure. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted June 14, 2023 Share Posted June 14, 2023 I bought the later fill neck that has the inner hose for filling. My old inner hose was dishwasher drain hose that I am fully expecting to have melted by now. Once I get to the rear tank I'll know for sure. I didn't realize the fill tube came with the neck. (not that way from Ford) Parts from LMC? Or filler necks dot com? Link to comment Share on other sites More sharing options...
CRittaler Posted June 14, 2023 Author Share Posted June 14, 2023 I didn't realize the fill tube came with the neck. (not that way from Ford) Parts from LMC? Or filler necks dot com? I ordered it from Amazon. I believe this is the same part that Gary ordered for his truck. I grabbed the number off a screen shot earlier in this thread. Fill neck and the separate outer vent hose: outer vent hose Link to comment Share on other sites More sharing options...
CRittaler Posted June 26, 2023 Author Share Posted June 26, 2023 I ordered it from Amazon. I believe this is the same part that Gary ordered for his truck. I grabbed the number off a screen shot earlier in this thread. Fill neck and the separate outer vent hose: outer vent hose alright, I dropped the front tank and used a bench power supply to run the in tank pump to drain the gas that was in it. I replaced the fill neck and the roll over vent and I adjusted the float to read just over E with 5 gallons in it. Put it all back in place and it seemed to fill reasonably well from the gas cans. I still have to deal with the rear tank and replumbing the fuel lines to go around the aftermarket pump. I also have to fix the wiring to connect the in tank pumps back up. I was able to drain ~14 gallons out of the rear tank using the in tank pump and bench supply and with any luck I should be able to drop the tank today. Link to comment Share on other sites More sharing options...
CRittaler Posted June 26, 2023 Author Share Posted June 26, 2023 alright, I dropped the front tank and used a bench power supply to run the in tank pump to drain the gas that was in it. I replaced the fill neck and the roll over vent and I adjusted the float to read just over E with 5 gallons in it. Put it all back in place and it seemed to fill reasonably well from the gas cans. I still have to deal with the rear tank and replumbing the fuel lines to go around the aftermarket pump. I also have to fix the wiring to connect the in tank pumps back up. I was able to drain ~14 gallons out of the rear tank using the in tank pump and bench supply and with any luck I should be able to drop the tank today. ok, I just dropped the rear tank and was pleasantly surprised by the fact that my dishwasher drain hose has survived acting as a vent. It hadn't swelled or gotten spongy at all. I also opened the box for the new tank. This tank is a later model, '87 I believe. It has nothing in the fill neck opening to support the inner hose for the replacement fill neck. I'm tempted to try to 3D print something out of nylon to slip over the inner hose and hold it near the top of the filler opening. Not sure yet if there is supposed to be some kind of support there or not. I also have to see how far off the tabs make the pump assembly sit. I might cut new notches to fit the old assembly. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted June 26, 2023 Share Posted June 26, 2023 ok, I just dropped the rear tank and was pleasantly surprised by the fact that my dishwasher drain hose has survived acting as a vent. It hadn't swelled or gotten spongy at all. I also opened the box for the new tank. This tank is a later model, '87 I believe. It has nothing in the fill neck opening to support the inner hose for the replacement fill neck. I'm tempted to try to 3D print something out of nylon to slip over the inner hose and hold it near the top of the filler opening. Not sure yet if there is supposed to be some kind of support there or not. I also have to see how far off the tabs make the pump assembly sit. I might cut new notches to fit the old assembly. Right. The '87> tanks don't constrain the lower end of the fill tube. If you have the MPC illustration or the new filler neck you should see how they clamp at the top. When you're looking at the sender/pump assembly take note of where the supply and return are pointing. IIRC it's just one of the tabs that's different. Link to comment Share on other sites More sharing options...
CRittaler Posted June 26, 2023 Author Share Posted June 26, 2023 Right. The '87> tanks don't constrain the lower end of the fill tube. If you have the MPC illustration or the new filler neck you should see how they clamp at the top. When you're looking at the sender/pump assembly take note of where the supply and return are pointing. IIRC it's just one of the tabs that's different. I will have a look! I have another 87+ tank that has a pump assembly so I will compare it with my current one. good to know the lower end of the hose isn't constrained. I probably didn't need to replace the tank then, oh well may as well now since I have it. The filler neck I have has the inner hose already attached at the top, I'll take a closer look. If I can get away with just removing a tab on the assembly, even better. Link to comment Share on other sites More sharing options...
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