My 1978 308 GTS died on the road this morning. http://www.ferrarichat.com/forum/143299305-post354.html The 8a fuel pump fuse blew. I immediately pulled the fuse cover (original) and pulled the fuse out of the block (original). The fuse burnt my thumb. I pulled the 8a to the left of it and it was hot too. The block cover says "Instrument revert-light belt circuit" for the second fuse. I inserted the second fuse into the fuel pump slot and it blew immediately. So this thread is to figure out what is wrong. I know there are flaws with the original fuse blocks but I really want to keep them as I like the way they look and they are original so I am looking to fix them if possible. So far this evening I have replaced both fuses and fuel pump runs fine without blowing the fuse or heating up. I ran it for less than a min without the engine running. I also tested the voltage between the fuse tabs and I do not see any drop. Next I will test the pump amp draw and go from there.
I suspect old fuses could be contributing to the problem. Both fuses that blew were old black color 8a fuses made of what appears to be aluminum. Both have deep grooves where they wore into the clip. I think modern 8a fuses are white, not black. Both have a dirty patina. Interestingly the PO left a full set of unopened Pudenz white color brass fuses with the car. I will slip those in with some Ox-guard on the tips then test drive and take temperature readings. Image Unavailable, Please Login
I took it for a test drive to see if the new fuel pump fuse overheated. It didn't but the car started sputtering. I limped home (not far) and made it halfway up my driveway before it stalled. I got out to check the motor and noticed a little coolant on the ground out of the overflow tank. I was watching the oil and coolant temps but they never went up. Then I noticed the headlights were up but not on. I had them up to try and duplicate my driving conditions when the fuel pump fuse blew. My initial thought is my alternator has died and the ignition slowly drained the battery. The lights on sped this process up. You can see only one light dropped when I shut it off. Battery is way down on power. I will now start down the charging system road. Somehow I think the blown fuses and the charging system failure are related. Image Unavailable, Please Login
I researched r/r the alternator and it looks like a rough job from the sides and underneath. I have a laundry list of other projects that will go so much easier with the engine out (hoses, suspension, undercarriage, sniffer tubes, smog removal, carbs, radiator) as well as engine out items (sodium valve removal, seals) that I am considering pulling the motor. I was going to wait until the next belt service interval (2 years) but the thought of driving it with sodium valves for that long, and all those really old fuel hoses makes we want to do it sooner. Struggling with the alternator does not seem like a good time either. I'm going to run a compression test to see if that gets me off the fence. If not then it's under the car with the alternator.
Noone seems to reply ? So I'll give it a try. I think there's a short somewhere in the fuel pump circuit or inside the pump itself. A loose connection or a damaged wire for example. Sometimes it draws so much current, that the fuse blows immediately. And sometimes it just draws so much power, that the fuse withstands it, but will drain the battery. Did you check whether the generator warning light is glowing while the fuel pump is running ? Your car is US-spec ? Then I assume it has a safety cut-off switch for the fuel pump ? BTW; except the sodium valves I see absolutely no reason for pulling the engine. And what's the problem with the sodium valves ? It's a 308 and not a 246. Pulling the alternator is an easy task. Disconnection of the wires on the starter motor from underneath. ( don't try to disconnect the wires directly on the alternator. This would be a major pain if not impossible with the heat shield on the back of the alternator ) And pulling the alternator through the passenger side wheel well. Best Regards from Germany Martin
I might add that you should remove the fuse box and inspect it for loose rivets. These things are notorious for failing with time. They can be repaired or replaced. As for your car marking its territory occasionally that is normal and perhaps bleeding some air out of the system will alleviate that.
That's interesting theory about the fuel pump draining the battery. Is there an easy way to test the charging system with the alternator on the car? I do want to pull the motor for more reasons than the sodium valves. I know all those other things can be done motor in but I find I am not a good contortionist. I know I will enjoy doing them with the motor off but hate myself motor in. Cheers, Ken
What I find interesting about the rivets (and perhaps I do not understand the fuse block) is that some fuses have a line in and a line out (fuel pump for example) and others have just a line out (fans for example). On the ones with line in/out I don't think current is traveling through the rivet but rather from line in, through tab, through fuse, through tab then line out. So I don't think the rivet can be a problem on the fuel pump fuse unless it's just a general heat problem. Again, I may not understand it. Another thing. I have two colored fuse blocks: one black and one white. Is that standard or perhaps one was replaced? I plan on taking the fuse blocks out to inspect. We'll see what I find. Oh yeah, I LOVE the dog metaphor! Will be using that one in the future
I think it will be clearer when you look carefully and see that in some cases two or more terminals are bussed together. So, power comes in on one tab and actually provides juice to two or more. IIRC there are two different color fuse boxes because they are not interchangeable due to what I mention above.
I managed to do some electrical system tests. Here is what I found. Battery overnight voltage off of charge = 12.69v @ 87 degrees Load test voltage = 10.9v @ 87 degrees (15 second cold crank, all other electrical shut off). Bounce back from load test = 12.67v after two mins @ 87 degrees Fuel pump amp test = 1 amp for 15 seconds car not running. Ignition on amp test = 2-3 amps with fuel pump running. Alternator charging voltage across battery terminals @ 3k RPM = 12.43v System leakage test = 0.7mA (from battery negative lead). From all that I conclude my alternator is not charging the battery as the battery post voltage needs to be 14.2v minimum. So I will r/r the alternator. I am still uncertain if this explains the blown fuel pump fuses. Is that a problem related to the alternator or not? The coincidence of both problems occurring in back to back drives and within 24 hrs seems unlikely to me. Thoughts please?
I'd doubt any strong relationship between them too -- unless your alternator warning light isn't working correctly as that can be a sign of a bad connection in the area that can generate heat and help blow associated fuses (even though the current isn't exceeding the fuse rating -- those fuses are thermal devices). Is the alternator warning light working properly -- i.e., it comes "on" with key "on" and engine not running, and it goes "off" with key "on" and engine running? If it just stays "off" all the time, that may look "OK", but IIRC it can actually impair the alternator operation (as an open circuit there de-energizes the field coil of the alternator). Is your alternator warning light working correctly? If you've still got the stock fuseblocks (regardless of whether the alternator needs replacement or not), at the top of fuses #1, 2, and 3, you should either solder the rivets to the plates, or solder some busbar across the three at the base of the male tabs, to provide a better electrical connection that does not just rely the mechanical contact/grip of the rivets. The top of fuses #1, 2, and 3 is the main +12V distribution network that connects +12V from the ignition switch to the ignition, alternator, and fuel pump.
Thanks for the reply. My light may not be working properly as it did not go off when my battery drained and it's not on now when my battery voltage is so far below minimum. How do I test that? Can I do a bypass test? Regarding the fuse block is that right or left one that needs to be modified? Are you counting left to right?
Nevermind the question about the fuse blocks. I understand which one. I need to look more at the alternator light issue though. Your guidance there is appreciated.
