flanker

Spent all day changing the fuel sending unit and replacing the fuel pump on my 89 civic SI. WHAT A BITCH dropping that tank and all the BS that goes with it. Finally finished 8 hours later and the fuel guage is still showing a full tank and the F&*^ pump does not work. Got my stuff from partsgeek. The fuel sending unit lock ring did not even fit on the sending unit so I had to reuse the old one. I suspect the fuel pump is defective, I should have left well enough alone. I will not order from them again.

So I wonder what is the problem with the fuel guage? Maybe wiring?
I am tempted to put back in the old fuel pump but I will have to pay somebody because this was just too hard on my body.

Maybe it is finally time to get a new car!

thescr33nn4m3

Was the fuel sock and the angle the same as the OEM one? I know a couple companies make fuel socks that are shorter than the OEM one that will cause issues with the fuel gauge.

flanker

It was the exact same fuel pump, much to my surprise. It went on just like the old one. When I turn the key on I can hear the new fuel pump kick on for a couple seconds. So you would think it is working.

When I got everything back together and tried to start the car it would not start. Then I removed the service bolt on the fuel filter and turned the key on and fuel did spurt out so I put the bolt back on and then the car started and I drove it down the street and after about 3 minutes it started to die, but I was able to make it back home.

I tried starting it again and it would not start. Maybe the new fuel pump is bad or maybe I did something incorrectly, but I doubt it because I was extremely careful cleaning everything. I reused the same fuel that I put in containers and strained the fuel before putting it back into the tank.

There is no way I'm pulling that tank off again so I dunno???

thescr33nn4m3

What kind of fuel pump is it? It is possible that the new pump is bad. Have you checked for any leaks around the tank?

flanker

No leaks. I am going to tinker with it a little more today now that I am rested but still sore.

I was thinking that the fuel filter may have got clogged, but I will have to check. I went through this once before on my Nissan 240sx, the bad fuel pump still came on for 2 seconds when turning the key to start, but did not work under load conditions. At least on that car the fuel pump had easy access, no dropping the tank and I could do it in < hour unlike this Honda which is an all day back breaking job.

So I'm afraid if I cannot solve this today then I will take it to either the dealer or Pep boys or somebody, cause I am definitely not dropping that tank again, TOO much work.

As a side note, I do believe the problem with the fuel guage must exist in the wiring harness that goes to the tank/sending unit to the 4 P connector.

flanker

Quick update, You were correct thescr33nn4m3! I added more fuel to the tank and the car ran! I put about 4 gallons in after I was done working on it yesterday but apparently that was not enough because the new screen did not come with the extension of 1-1.5 inches like the original which made all the difference. When you mentioned sock I thought you were making reference to the pump and not the screen (sock). My ignorance sorry.

So until I replace that new sock I have to make sure the tank does not drop below 4 gallons but I still won't know because the sending unit is still showing full tank.

I read somewhere that a short in the wiring could cause the faulty reading, Maybe I should just get a new fuel pump that comes with the entire assembly.

Thanks again.

thescr33nn4m3

Glad you got it sorted.

flanker

Anybody have a link for that manual. I have a hard copy but only on certain sections, I was looking for section 61 for the fuel guage.

Thanks

fcm

What do you need to know about the fuel gauge?
It's a pretty simple system, fuel gauge sending unit supplies a ground through resistance. [veritable ground] to the gauge, [yellow/white lead] and if your CRX has a fuel warning light it is a thermistor, [on/off switch] supplying a ground to the light, [green/red lead] 12V+ is supplied by ign. switch, [when on] to other side of gauge and light. 94

fcm

Can you access the sending units plug without dropping the tank ?

If so, unplug it and see where gauge goes, should drop to empty, then with a 12V test light, [not LED type] ground test light and touch probe to sending unit wire, [should be a yellow/white] gauge should read about 1/2 a tank.
If when you unplug the sending unit the gauge does not go down to empty there is a short to ground on the sending unit lead. 94

flanker

I put a new sending unit and apparently the old sending unit tests ok. Lot of work and expense for nothing. This weekend I will play with it more.

So the connector to the sending unit has 2 wires on it, yellow/white and black. The yellow/white carries voltage? And black is ground?

So when you unplug the connector from the sending unit, the circuit to the fuel gauge opens and no voltage because no ground?

My understand is the more resistance (sending unit lever down ~ 144 ohms empty tank) to the circuit the less voltage and the gauge should read empty.
Higher voltage (sending unit lever up ~ 5 ohms full tank) the gauge should read full.

Thanks

fcm

Black is ground in and yellow/white is ground out, there is 12V+ to one side of fuel gauge the sending unit supplies a veritable ground through the yellow/white lead to the gauge. If you unplug the sending unit and test the yellow/white lead, it will test as a power lead, your just seeing the 12V+ on the other side of the load, [gas gauge]. 94

flanker

You were correct FCM, yesterday I had to remove the fuel tank and put the correct sock on the fuel pump. It went way easier than the first time I did it < 4 hours.

But here are the step I took to diagnose the fuel gauge stuck on full problem...
1) Before I removed the tank, I disconnected the 2P connector from the sending unit and the fuel gauge dropped to empty when I turned the key on. Good so far.

2) Then I checked the voltage on the 2P connector and it was approx. 6.2 volts which I believe is the correct voltage since the yellow/white wire originates from the B terminal in the fuel gauge assembly at a reduced voltage from battery voltage .

3) Then I checked the ohms on the sending unit and it was about 10 ohms which makes sense because I had almost a full tank minus about 2 gallons.

4) I then reconnected the 2P connector with the key still in the start position and the fuel gauge climbed back to full. Ok everything at this point seemed normal.

5) Then I again disconnected the 2P connector from the sending unit and this time it remained at full. I turned the key off then back to start position and the fuel gauge was still in the full position. This is BAD.

6) Then I checked the voltage on the 2P connector and this time it was battery voltage, approx. 12 volts. I then disconnected the 4P connector that connects to the fuel pump/sending unit harness and found the 2 wires that go the sending unit and checked the voltage and it was also 12 volts.

So in conclusion there must be a ground short coming from the sending unit wire somewhere between the 4P connector and the fuel gauge. As your theory confirmed FCM

My next plan is to remove the fuel gauge cluster in the dash board to see if the short is there. I have never done this before, do you need to remove the entire dash board to remove the cluster? Or is there a better way to do this. My fuel gauge might even be bad?

Thanks

fcm

You can pull the cluster without pulling the dash... Honda Automotive Parts 94

flanker

I did this afternoon, only took 20 minutes to remove the cluster unit. Then I removed the fuel gauge assembly from the cluster unit and noticed that the wiring on the coil looked bad (kinda frazzled). I applied voltage to the + and - terminals and the needle dropped to empty, but after doing it a couple more times it did not drop to empty. So in conclusion I thing I need a new fuel gauge.

The big question is where do I find one, junk yard I suppose?

Thanks again

welfarepc

I didnt read the whole thread, but


You dont need to drop the tank to replace or remove the sending unit. Only the fuel pump. The sending unit has an access hatch you can get to from under the rear seats if its a hatch, Under the rest of the junk if its a CRX.