bobbym

Hi all. I'm new here, and didn't see anything like this already posted. I have a '78 toyota pickup with a 20R engine. I have owned the truck for close to 6 months.

The problem:
The gas gauge reads accurate until 1/2 full, then it stops moving. Its been like this for over a month, 2 weeks ago the blinkers stopped working but the other day they started working again. So I'm thinking that it's might be a loose wire somewhere˟or my instrument cluster or my fuel sending unit but I'm not sure. It's possible that the fuel gauge is working again since the blinkers came back on but it's hard to tell without running out of gas.

back story:
I just want to fill you in in case any of this ends up being important. It all started when the engine would turn over but the vehicle would not start and our mechanic said we need a new fuel pump. After we picked it up from the shop with a new fuel pump the same thing happened a few days later. It turned out the car was out of gas and it wasn't showing because something was wrong with the fuel gauge. He replaced the fuel pump relay to try and fix it but that didn't work. The mechanic said he tested the instrument cluster and said it was good and that it maybe the sending unit that was bad. Does this sound right to you? I am trying to get the truck ready to sell because I want a commuter car, so any ideas on what the malfunctioning fuel gauge or blinkers could be would be helpful.

Thanks in advance.
Bobby

kawazx636

iTrader: (3)

Fuel pump relay? Most 20R engines would typically have a mechanical fuel pump unless somebody switched it over to a electric fuel pump at some point. If it indeed has a mechanical fuel pump and your mechanic "replaced the fuel pump relay" then you may have been duped. But it is possible to have a stock or aftermarket electric fuel pump - just letting you know just in case your mechanic is shady. If you have a mechanical fuel pump it would look like this - located to the left of the engine hook in the picture below:


As for your fuel gauge issue, your fuel sending unit is probably seized up a little and won't drop or gets stuck when it nears a 1/2 tank. Mine wouldn't read anything at all on the cluster because it was corroded enough that the float wouldn't move in the tank. I pulled the sending unit, wire brushed the corrosion off, re-installed and it worked perfectly. I later ended up buying a replacement New-Old Stock sending unit that I found after about 2 years of search regularly (I was reeeeeally lucky and paid dearly for it so don't expect to find a new one like I did without a lot of patience).



Also, if your sending unit is corroded then likely your tank is as well. I would recommend dropping the tank and cleaning it out really well. Perhaps even using a tank coating treatment like RedKote as well.

For your blinker issues, I would go through and find all of you grounds and make sure that they are properly secured and not corroded. Most of the time when something works intermittently it is usually because of a bad ground. Also, if it is only your rear blinkers that aren't working properly and your fuel sender is working intermittently too then you could have a ground issue in the rear wiring harness since they are all tied together (or at least they are on 79-83 models). The ground should be on top of the rear frame cross member (again, that's on a 79-83 truck).

Terrys87

iTrader: (1)

The light sockets get really corroded inside the bulb holders. A good cleaning on the terminals and the socket that the bulb sits in sometimes will fix that.

The fuel float assembly can get rust build up on the pivot point and not let it operate like it should. A brass brush and some PB Blaster can get it operating like it should. Inside the box of the float, there is a potentiometer like mechanism that is made of fine wire, not much bigger then a hair. Once the wiper inside wears thru the wire, about the only option is to replace the float assembly.



Tanks do get bad as mentioned earlier. I would change the filter as well. Here is what you will need. More info if you need it>>> https://www.yotatech.com/forums/f199.../#post51633022
Part number for a new intank filter is #77023-12050. On ebay it is called a TOYOTA FACTORY NIB FUEL FILTER SUCTION TUBE DIESEL. It was selling for $4.50 when I finally found it. I paid $15 at Toyota. (83 pg 8) This filter is for carburated trucks.

83

A 78 most likely has an electric fuel pump. In fact most 20Rs have electric fuel pumps. Just not the last couple years before they went to 22R. Or maybe it was a 2wd vs 4wd thing? But all the old 20Rs have electric fuel pumps.

It's strange, I agree.

83Toyota88

iTrader: (1)

I used a dremel attachment similar to this and put in a cordless drill to clean out the sockets of my turn signals. Get in there real good and then you actually have to push the back plate in the socket back some because the spring has it pushed forward to make sure you clean the entire socket.

http://www.lowes.com/pd_72900-353-53...3D2&facetInfo=

83

And definitely find and clean the grounds. The are notoriously bad on all our trucks. I had crazy troubles with the rear blinkers on my truck. I couldn't find the ground, so I just ran a new one with thicker gauge wire, and a nice clean spot I sanded down on my frame.

83Toyota88

iTrader: (1)

I do know there is a ground on top of a cross member underneath the truck bed. Maybe that is it.