| Author | Message | ||
| J. Grande (Jay)
Member Username: Jay Post Number: 685 Registered: 10-2001 |
I'll start a new thread! | ||
| James Selevan (Jselevan)
Junior Member Username: Jselevan Post Number: 209 Registered: 6-2002 |
Jay - Let's examine this further. Has anyone a technical explanation for why our cars don't explode everytime the low fuel idiot-light goes on? When the contact closes in the tank, what keeps a 12 volt spark from developing? Jim S. | ||
| J. Grande (Jay)
Member Username: Jay Post Number: 679 Registered: 10-2001 |
James I've wondered about that everytime I see the bare wires and connections inside a fuel tank! Makes me nervous...but I quickly put it out of my mind  | ||
| James Selevan (Jselevan)
Junior Member Username: Jselevan Post Number: 202 Registered: 6-2002 |
Solved my problem. Got access to another unit, checked continuity between "fingers" and "boom". They are suppose to be electrically connected. Corrosion must have broken connection. I re-soldered and it now works fine. Question: What keeps a spark from developing when the idiot-light contact closes? I know this is 12 volts, but 12 volts will spark. Is the electrical path to the idiot-light contact in series with the rheostat, thereby further reducing the 12 volts to something lower? Jim S. | ||
| J. Grande (Jay)
Member Username: Jay Post Number: 677 Registered: 10-2001 |
James I had a similar problem. One of the tiny copper wires was cut, almost impossible to see with the naked eye. Ferrari wants about $450 for the entire arm witht the sending unit. I got one from a Fiat spider brand new for just over $100. The arm is different but the sender unit is exactly the same. I am speaking of a 308 GT4 but from what I have heard, all early senders are the same. It would be easy to check since you have it out of the car. Here is the Fiat sender on the Ferrari arm and float.  | ||
| James Selevan (Jselevan)
Junior Member Username: Jselevan Post Number: 201 Registered: 6-2002 |
Great photo - this helps in the discussion. Notice the copper "finger" that will contact the tab with movement of the float. The finger sits on the "boom" (my terminology) moving off to the left of the picture. Is the finger suppose to be insulated from the boom, or is there to be conductivity? That is the essence of my question. There are two "fingers"; the one that swipes the rheostat is seen through the window of the plastic housing just at the right edge of the opening. The two copper fingers are continuous metal, thus electrically connected. However, they sit on the end of the boom, but in my example, they are insulated from the boom. Therefore, how does the signal get to ground? Thanks. Jim S. | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 384 Registered: 4-2002 |
I get the impression that the '296' figure just might be a little conservative. And, yeah, we should twist his arm to do a 308 DIY manual. It could sell really well with a title such as "308 Exposed!!!" "See the dark hidden secrets that Enzo never wanted you to know about. Leaking gaskets! Worn bushings! Haywire wiring! It's all here!!" | ||
| magoo (Magoo)
Advanced Member Username: Magoo Post Number: 3401 Registered: 2-2001 |
Hans, Let me tell you that this guy has enough pics from his work on his 308 to fill a workshop manual which I think he should publish. Peter is a perfectionist in his own right and it shows in his photos as well as his posts to tech problems. | ||
| '75 308 GT4 (Peter)
Intermediate Member Username: Peter Post Number: 2152 Registered: 12-2000 |
I bought a new computer last week and was transfering the old files to this new one. 296 to be exact (and counting...) | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 381 Registered: 4-2002 |
How many tech-type photos do you have Peter? | ||
| '75 308 GT4 (Peter)
Intermediate Member Username: Peter Post Number: 2150 Registered: 12-2000 |
I was able to register changes on my gauge, with the sender out of the car. I don't know if yours is the same as mine, but there is a third wire - that is the ground - that attaches to the one of the mounting bolts and therefore makes contact with the body. I assume this grounding point continues the circuit for the little fingers. I haven't taken it apart, only the little access port on the housing to see what was inside...  | ||
| magoo (Magoo)
Advanced Member Username: Magoo Post Number: 3395 Registered: 2-2001 |
James, I am just stabbing at this but isn't there like a brass connector lead or strip that runs from the top insulated terminal of the guage down to the rheostat? This should be your power supply and the tabs that lightly brush the rheostat are to ground. I would think the boom should act as a ground attached to the guage housing. If there was enough rust, corrosion around the rivets, I believe, it could affect continuity. Use a continuity tester that has a penlight battery in it and check continuity at each of the points. I am going from memory here and as I said above just a shot. While you are checking the continuity use alligator clip test leads to bypass the rivets. | ||
| James Selevan (Jselevan)
Junior Member Username: Jselevan Post Number: 199 Registered: 6-2002 |
I am attempting to rescusitate my fuel level sending unit. It is for a 1972 vintage Ferrari. The gauge has a low level warning light, as well as the standard gauge. The "boom" has on one end the float. The other end has a right angle bend, then enters the little plastic housing. Spot welded to the boom, at right angles, is an arm that holds two copper "fingers". One of these fingers swipes the rheostat, which reads relative fuel level. The other copper finger makes contact with a tab when the float level is near minimum. Here is my question. Are the two copper fingers suppose to be electically insulated from the boom on which they sit, or is there to be conductivity? The two copper fingers are not electrically connected to the boom, yet it seems that they should be. When I try the sending unit in the car, it does not work (not in the tank, but properly connected outside of the tank. It appears that the signal from the gauge is not making it to ground, despite my carefully grounding the unit. I suspect that the swiper/float boom is the path to ground, but these copper fingers are electrically insulated from it. The fingers are attaced to the end of the boom with what appears to be a press fit. Is there an insulating washer, or is there corrosion that resulted in a bad connection? I do not see how corrosion could have gotten into the press fit. The unit was encased in rust when I took it out. The car had been sitting for 10 years with, as I now suspect, an empty tank. Thus, moisture and condensation. Your help is appreciated. I suspect help will come from someone who has dismantled these before, or has one sitting on a shelf. Thanks. Jim S. |