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Thanks. I guess I’ll have to pull the sender out and take a look again. The issue is my Dads 78 front tank needed a sending unit after it eventually quit. Before that it would get to a little less than a half tank and it would run out of gas. He had always figured it just read incorrect.
So now that I have it I pulled the sender out and it had the short arm float. From what I read it should have the longer one so I bought from Jbg. So now sitting on level it reads just as the old one did just below a half and still runs out of gas on a incline if I let it sit and run. As I go up a hill it reads about 3/4 maybe a little more and down hill about 1/2.
When I put the sender in I would guess there is close to half tank in it. When It died on me this weekend I had about 2 gal in a can that was just enough to get it started again and back on the level. Almost seems as if the pickup tube isn’t long enough.
So I pulled the sender and it does appear to be long enough. I put 2 gal to get it started and 2 gal at the pump to make sure I got home Saturday. I have gas right up to the hole for the sending unit so about 3/4.
Gas gauge shows empty float all the way down and full when float is up. Gas gauge currently shows 3/4 so that’s believable. I don’t understand why the gauge fluctuates so much at half tank nor do I get why it runs out of gas.
Fuel pump is about a year old and when I dumped that 2 gal in it immediately put fuel back in the filter. Before that sucked it dry.
So I guess I’ll keep 5 gal with me and see how far I go.
Does this fluctuation happen at level driving? Since the front tank is mounted along the frame rails, fluctuated readings can be expected when the tank is less than 1/2 full on inclines and declines. And your gas can run out if your level is low enough and the incline steep enough. Just have to be the right conditions for it to happen. Based on your earlier comments, I take it that the rear tank is not working? After reading the rest of the last post, you might want to pull the suction tube again and check to see if there are any pinhole leaks on the tube.
Last edited by 84espy; Aug 8, 2018 at 11:01 AM.
Reason: Additional info
Sure sounds like the pick up tube is not long enough. Are you for sure getting the correct sending unit? One for a plastic tank and not the 2wd metal tank? Just a thought.
I thought about the pin hole potential after I just put it back in....go figure. The fluctuation does happen while driving up hills. That’s kinda why I asked if they have baffles to
slow the fuel but if they don’t that would explain that. My 79 only has a rear tank so I don’t see fluctuations like this.
The rear tank doesn’t work but that’s a project for another day. The bumper and hitch is welded to the frame so all that needs cut off before I can get the tank out.
The pickup does appear to reach the bottom holding it next to the tank. From my understanding this is the one that belongs in it not the short float that was in it that definitely was not orig.
Were all the long-bed tanks the same capacity? Mine is 30 gallons, but I thought there were smaller ones.
Maybe the differences were just the length though, and the depth was the same? In that case, the sending units might all have been the same anyway.
Never had an issue running it dry either. All the way to the point it would not suck fuel, then I could put 30 gallons exactly into it. Agree there are no baffles (or should not be) in the plastic tanks.
Can't think of anything that would consistently block your pickup from grabbing as while still half full though, unless someone literally stuck something in there for some reason.
So you have 2 issues:
1- it run out of fuel at or near half tank. Does the pick up have the filter sock on the end?
I know you said it looks to be long enough to reach the bottom not you need to pull the sender again to check for pin holes.
Maybe you can pull the sock off and put a rubber hose on the end put the sender back in place so the rubber hose is pushed up, pull the sender and measure how long it is then pull the hose and measure again to see how short the metal part is.
2- the gauge not reading right. If I under stand right the gauge only goes down to half when it runs out of fuel.
Did you say the tank still has half or is it empty? If half then there may not be any thing wrong with the gauge/sender but if it is empty you got a issue.
When the sender is out to do the above ohm out the sender. I don't know what min / max is I am sure someone will post it, but if the sender is not with in spec replace it.
You can also hook the wire(s) back out to the sender and make sure it is grounded and run the float thru it's sweep to see if the gauge does the same.
If it is with in spec and the gauge sweep is also good then the float arm needs adjusting by bending it. I would rather have it read right at lower fuel levels than high so I would not run out of fuel.
That is how I would go about checking it out.
Dave ----
I was only asking about the baffles just because of how much the slosh seemed to change the gauge and possibility of running away from a potentially too short of pick up.
My pick up does have the sock on it and does appear to be correct length.
I did verify the gauge seems to read what it should be according to float level. There was more than a plenty in when it ran out the last time. I have not had s chance to drive this one at all since I posted this. As soon as I get some time I will try to duplicate what happened and see what's going on.
As for gas tank size I thought the plastic side tank was 18 gal on this one.
Thanks for the thoughts. Once I figure it out or it lets me sit again I'll report back.
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