edwinsmith

Well, I thought I had this problem fixed. Whenever I get down below 1/2 tank the truck doesn't want to start. Apparently it's sucking air someplace. I tried pressurizing the tank to see if I can find a leak but nothing. I cut a hole in the bed to take off the fuel pickup unit and cleaned a bunch of crud off the screen and it seemed better.

This morning the wife went out to move the truck off the street for the sweeper so we wouldn't get a ticket and nothing. I worked the primer button a couple hundred strokes and... nothing. Finally I loosened the injector lines and cranked it over until fuel spurted out then tightened them down and it fired right up.

Anyone have any ideas?

Edwin

oliver foster

Keep looking for your leak...It is there.

I have struggled with this problem on several rigs, sometimes for years.

If it comes down to it just replacing all the fuel lines and all connections from LP to fuel tank is not that much work or that expensive.

bannerd

You can snag a Mighty VAC from harbor freight for $19. Hook it up to the hoses and watch the pressure drop. Has to be somewhere.

The pump holds quite a bit of fuel, if it happens right away it has to be upstream I would say.

AND My wife tells me I lost my prime..

edwinsmith

IIRC there's an O-Ring in the connector on top of the tank unit. Anyone know what size this is? Mine could be leaking after 30 years.

jimbo486

You mentioned it only seems to happen at a 1/2 tank and below ... I might turn my focus to inspecting the supply hose on the fuel sender assembly / canister in the tank. Seems to me that this would be a continuous issue from a full tank on down if the leak was anywhere outside of the tank.

oliver foster

I have found that the lower the tank gets the more drawn the fuel gets to return to the lower level in the tank. This stronger suction will make leaks in the system from the tank to the motor show up.

A trick I like to do when diagnosing an air leak on a 1st or 2nd gen that tends to get intermittent air leaks, that tend to happen more the lower the fuel level in the tank gets. I like to park the truck nose down hill with a half tank and see if it still gets air in the line over night. If after a few nights it seems fine...now park it nose up and see if it gets air in the line. If it suddenly will not start in the morn. now, an air leak up by the LP or other connection by the motor is a likely culprit.

The nose up makes the fuel want to syphon back to the rear of the tank even more, which can help locate the leak.

The in tank unit might be bad, like you said, but I think I remember Ed saying he pulled it out and checked it out pretty well before.
A pin hole in the '89/'90 metal fuel pick up line would give him these problem as well.

This problem can take a while to solve.

edwinsmith

I cut a hole in the bed and pulled the tank unit and found a bunch of crud was partly plugging the screen over the pickup tube. I cleaned that off but I had no way to clean the remaining crud from the tank. I may have to do that once we get to OK. Here in the trailer park I'm really limited in what I can do to it. I'm going to replace the o-ring on the pickup fitting on the tank unit and see if that helps. Does anyone know what size it is? I just have to remember to fill up when it gets down to 1/2 tank. I think I can drive it lower as long as I don't turn it off. Then I can refuel at the truck stops along the way. Wish me luck.

Edwin

edwinsmith

Took off the cover over the fuel tank. I checked the plastic connectors and the O-rings therein. One of the o-rings was the wrong size. It was on the 5/16 side but was a 3/8 o-ring. It was the same size as the other side. I bought a bunch of o-rings at O-Reilly's but the small space makes it very difficult to get one in properly. In the meantime I found the replacement connectors. The 3/8 side is a Dorman 800-212 and the 5/16 side is a Dorman 800-081.

I have ordered both of them so if the o-rings didn't fix it I can replace the whole connector. Hopefully the wrong 0-ring was the problem.

Edwin

Rug_Trucker

Hopefully you installed some non-black O-rings. Any percentage mix of biodiesel will destroy them.

edwinsmith

That could be very well what the problem is. I took out a black one and replaced it with a brown one. I won't know if the operation was a success but I have new fittings coming in soon so I'll probably just go ahead and change them and see what happens when the fuel gets below 1/2 tank again.

Does the methanol in Biodiesel attack the black rubber ones?

Edwin

Rug_Trucker

Does it have methanol in it? I have no idea. I know there is glycerin in it. Around here we used to backhaul B100 from Owensboro Grain in Kentucky. It was made from soybeans, and other additives. I used to haul fuel and ethanol gas would cloud up and crack the sight glass on our loading heads. It would eat the black rubber gaskets in our hose couplings too. The company would supply green ones...........sparingly.

Biodiesel will clean all the crud out of your tanks and dump it into the filters if you have build up. I researched the heck out of getting biodiesel rated fuel lines for my truck. Finally found some that was rated to B20 if I remember correctly. There was a company in Idaho selling some that was rated higher than that. Didn't have it in stock when I wanted to buy it. I had to research it myself and then call NAPA and order 2 rolls of it, one in each size. I'm thinking there was nothing wrong with the factory lines. Harbor Freight sells the brown, and green (??Viton??) seals in metric and SAE sizes. Whatever I bought didn't have the right size. My buddy had some he brought and we found one that fit.

At Loves when I fuel the company rig there is no mention on the pump if it is bio-mix. Yet on the satellite pump it says B5. Maybe they were just lazy about removing the labels?


I am still having problems with mine losing my prime.

edwinsmith

I only ran B20 in it once when I got some in Oklahoma. My pump had already been rebuilt to Biodiesel specs so no prob there. I replaced all the fuel lines with black hose however. I haven't seen any leaks and I tried pressurizing the tank to force fuel past any air-sucking leaks but no joy. The last time I was able to pump the primer while opening the injectors with a crescent wrench to get it going again. Once it's going it runs fine it's only after it sits a few days with the tank below 1/2 that it loses prime. Is that your experience?

Edwin

Gunch

Edwin just curious has your truck been running fine up to this point.I mean no idling problems sometimes when first starting or anything like that.

Rug_Trucker

I'm probably going to do the pressure thing too. I was hoping the fuel problem was fixed. The next step was going into the VE pump and checking why it isn't fueling up. There may be nothing wrong with it at all. Just sucking air. I might just toss it on a rollback and take it to Dixie Diesel in Columbia TN to get it fixed.

edwinsmith

The truck ran fine until the fuel pump went out. I replaced it with a piston type. Then I had a problem with the piston pump putting out to much pressure which pushed the front seal out of the VE and filled the crankcase with 5 gallons of diesel. I got the proper pump and then the problems started. It runs fine until the tank gets down to 1/2 and then it starts running rough when starting. Eventually it won't start at all so I have to prime the injectors. Fulling it up with fuel fixes it until next time.

Edwin