Ed Petry

Morning all,

I hope your driving season is going well. Getting hot here.

MY 1988 NA 5-speed

This 44 sat for a brief period (<6mts) waiting on a transmission.

When I fill up the fuel is at the fill neck, but the gauge reads 3/4 full. After 50-80 miles it typically reads about 7/8 full and then progresses down as the miles pile up. It tracks linearly as far as my eyeballs can tell.

I have been through the instrument cluster and that is within limits, especially the resisters. The traces are solid and continuous. The connectors were cleaned (both male and female) and "protected" with Caig protectant.

I have looked in the FWS manual and PET to see the hose routing. It appears the hosing allows for expansion and proper venting. My hosing appears to match the illustrations.

Is it possible there is an air bubble in the top of the tank or sending unit that is not being vented as I fill the tank? Driving makes this bubble dissipate.

931guru

No air bubble.

Caution: there will be fuel exposed when you do the following. Don't do it your garage, or when smoking...

It is probably your fuel level sender. To test it, remove it from the tank, reconnect it electrically, and alternate between having if right side up and upside down, while watching the gauge.
You will hear the float traverse up and down the wire, assuming that there is no blockage.

goblues38

mine does not register full either. goes 3/4 and is spotty down to empty.

I need to pull the sender and clean the wires per the YouTube video. Right now, I am just relying on reset of the trip computer. 300 miles = empty for me.

Ed Petry

Thanks for the advice.

Autobreza

I had similar issues with my fuel level gauge. The PO let the car set for years and the fuel evaporated and "crystalized" in the sump. However it did read fuel level up to about 1/5, but the low fuel light was a no-show. Wanting to save a few bucks, I disassembled and cleaned the sender which gave a more accurate fuel level reading, but still no low fuel light. Turns out it has a separate wire for that reading and mine was broken.

The most difficult part of the R&R was keeping the original hoses from fraying to the point of needing to shorten or replace them.

Zirconocene

@Autobreza : That picture will haunt me in my nightmares for years to come

Gasngo

Do what Guru said pull it out and clean the connections plus tilt it left rt upside down while connected and see what the gauge does. And yes when you pull it out it will have gas in it. Maybe run down to a 1/4 or less on the tank. Left it up part way and wait it will drain back. I dont know what the 88 cluster looks like regarding grounds but make sure they are clean and if it has the nuts on the back of the gauge then loosen and tighten once or twice the circuit board in the inside fluctuates from heat/cold and age. As for the unit in the pics above I would not even wast my time with that they are cheap enough. As for the earlier model you I rewired/rebuilt mine because 400 bones didn't sound good to me.

austin944

I have a similar hickup in the gas gauge except that it occurs when the tank is nearly empty and does not settle down. It oscillates between close to empty and all the way empty.

I disconnected the fuel sender wire (the 'G' wire that's purple on my 84) and connected a 500 ohm potentiometer in its place, and by varying the resistance I can see the fuel gauge hickup is still there. So I think there's something hanging up the gauge itself, like a bit of corrosion or dirt inside. If you've ever seen the inside of an analog meter, you know how delicate they are. I wonder if it could be replaced with an A/D converter and a digital meter?

I also cannot get the gauge to register past 3/4 full. The least resistance I can get out the fuel sender between the G and ground wires when I turn it upside down is about 37 ohms. According to the FSM it should read 3.2 ohms at the full mark. The 37 ohms corresponds to a little less than 1/2 full according to the FSM, so I am a little puzzled why there's a difference.

GrantM

I cleaned all the connectors on the harnesses that plug into the back of the instrument cluster and that solved the problem for me.

s85b50

Using the Chevron cleaning additives for 2-3 tanks consecutively can dislodge whatever's blocking the sender. It did in my case.

secondchris

Just be careful that the dislodged material doesn't wind up somewhere worse, like in your injectors.

s85b50

Would this ever happen when there is a fuel filter well before the injectors? Curious.

Dan Martinic

Only 300? I get 350 on my 951 and an NA should be well close to 400

My guage doesn't read full either.. but works after 3/4 and I am fine with that 😉