David Wheeler

I volunteered to help fix a friend's 67. The current problem of interest is the fuel guage always on empty. I started by testing the guage and it has a closed circuit and some resistance. Then I put 1.5v and 3v on it and the needle slowly moved to about 1/4 and 2/3 tank. So the guage seems to be ok, right? (A)

Next I check the sender and it reads 77 ohms. Some googling tells me this is within spec. Then I check the wire from the sender to the guage. I can read 77 ohms at the guage. Now I think maybe the sender is stuck. I take it out and it looks new and moves freely. It's range is 10 to 77 ohms which seems to be within spec. The tank is new as well. Should be no grounding issues there.

I put everything back together and put 10 gallons in the tank. Now the sender reads 16 ohms. That's working for sure. The fuel guage still is on empty even though I measure the 16 ohms at the guage.

Time for forum searches. I discover the CVR. A light probe on it shows it is getting power but pulsing power on the output side. I measure the volts but with a digital meter. The input is steady at 12v but the output oscillates between 0v and 3s, 4s, and 5s. It peaked once at 6 and 8 once. Since the
digital meter takes a little time to iterate onto the value, I assume it's about 5v. That's acceptable.

Maybe it's pulsing too fast for the guage which seems to have anti-slosh circuitry? (B)

I find conflicting info about the CVR pulsing. It seems to be typical but not always disabling. A couple of vendor sites state that pulsing is a sign of failure. So I have a pulsing CVR, a fuel guage showing empty always but have temperature and oil pressure guages seeming to work correctly.

I notice that the ground post nut for the CVR is a little loose. I tighten it with no change in results. I add a ground wire from the post to the frame. Still no change. So is the CVR bad? (C)

Getting a good CVR seems to be a 1:3 gamble. I found this from a MustangForum member

http://www.ebay.com/itm/280572904377...ELX:IT&vxp=mtr

Is that the way to go? Or do the homemade RadioShack version that seems to fix it with one case of the guage only reading 3/4 when full? (D)

In need of expert advice please. Thanks.
Dave

David Wheeler

Bump. No opinions on this?

scootchu

You check the gauge by grounding the wire from the sending unit to the gauge. If you do that and it goes to full it works, BUT they can do that and still be faulty. Try grounding the wire at the sending unit and watch the gauge, then go from there.

Oh and if your other gauges are working properly then the regulator is good.

David Wheeler

Problem solved. It was the sender. The contact inside was 1/2 broken. When I removed it to test, I held it on its side and it worked. When installed, it would only read 77 ohms. So the contact would fall into place on its side, but lose contact when upright.

Stangatic

Nice! Thanks for posting this info! I have the same problem and am pretty sure it's the sending unit. Waiting for CJs to send me my sending unit which has been on back order for 3 weeks now!

However, for the price, doing the radio shack upgrade to the CVR isn't a bad idea when the CVR is done!