tii blew a fuse; is the fuel pump is ready to fail?

[layers]

Hi--

On the way back from the Tri-Valley Drive my '74 tii blew fuse #12. Everything, including the AC, seemed to be working fine but as I decelerated toward a stop sign I noticed the tach stopped and a warning light on. I pulled over and pulled the hood. While I looked at the distributor (no tach so no tach signal?), Paul (he was following; thanks Paul) noted that the #12 fuse was blown. I replaced it with my spare white (8-Amp) fuse, but when I tried to restart it blew again immediately (AC off). After a little ruminating I installed my spare 16-Amp fuse and everything (I did not try AC...) worked fine on the 20 miles home.

My key question: since this fuse protects the fuel pump, tach and brake fluid & oil warning lights, does it mean my fuel pump is on its last legs?

Thanks for your observations!

Larry

[jgerock]

Possibly..

When you turn the key to the "on" position, does the pump sound strained or louder than you can recall?

Might be drawing more amps due to a clogged fuel inlet screen.

One large one inside the tank.

One small conical brass screen at the inlet of the fuel pump (this one can catch lint)

[Mike Self]

seat belt warning system is connected to the same fuse as the tii fuel pump and the instruments--and this is NOT documented on the factory wiring diagram. I had the same problem with my 73, blowing the same fuse, and finally tracked it to one of the seat belt contacts shorting out against the seat frame. This is the contact that causes the warning light to illuminate if you don't buckle your seat belt--but a contact failure will cause the fuse to blow even if you've disconnected the warning light!

Check the underside of your fuse box at that fuse, and I'll bet you find a wire at the fuse that isn't in your wiring diagram. Clip that wire and you're good to go...but make sure the wire you clip is not on your wiring diagram!

Hope that's it.

mike

[OriginalOwner]

fuel pump !!! (at least I think so).

exact thing happened to me, it was the fuel pump. After 35 years of faithful service it had finally "frozen up" and popped the fuse.

I could not find a real-deal new tii pump, so this is the replacement I used, works great !!!

http://www.my2002tii.com/tii-fuel-pump_how-to.htm

Cheers,

Carl

p.s. I should have replaced it at 25 years, but what did I know at the time ....

[allbim]

Remove the fuse and connect an amp meter to the fuse terminals. I don't know how much current the pump should draw (I'm guessing about 8 amps), but it should not be anywhere near the fuse rating.

When the pump gets old, the bearings wear out and the rotor starts rubbing against the stator, causing an increase in current.

[layers]

Hi—

Thank you everyone for your helpful replies.

Even before I saw Allbim’s comment I checked the current passing through the fuse with my DVM: maybe 4.5 Amps initially when I turn the key, dropping to about 3.5 to 3.8 Amps otherwise. So I installed another new white fuse and everything seems to work fine (even AC, which apparently has no connection on this circuit).

I disconnected the battery and looked under the fuse block, but the only oddity was the #12 fuse connection for the thermo-time switch bypass relay that CoupeKing installed at restoration; those wires even have an extra sheath for their tiny path. And when I looked at the wiring diagram in my repair manual (purchased in 1973 when my late car was only a few months old) I found the fuel pump in any tii diagram hooked to fuse #11, not #12. My circuit reference was Carl Nelson’s fuse block decal, which he sent based on a ’74 tii. While I think Mike has a good point about stray wire short circuits, I do not have enough circuit details to really look much further. Besides, CoupeKing installed Recaros (now replaced by my restored Konig seats) so the seatbelt alarm wires are not identified or located.

I appreciate Jim’s comment about fuel filters, and since I have not checked the internal ones since I bought this car 2.5 years ago it is a good idea (I had enough problems with fuel filters on my late ’73, especially with an added Facet electric fuel pump). I checked the for screen in the pump but found none. Also, the pump looks pretty clean, suggesting that CoupeKing either installed a rebuilt pump or cleaned up one they had. Looking at the screen in the tank and replacing the filter next to the radiator could also be good preventative maintenance.

Now that I reviewed the fuel pump retrofit article, and realize that Bavarian Autosports only sells that 1980’s electric pump for a tii, I plan to get one and associated hoses and wiring so I have a spare ready. It sounds better than the rebuilt option or getting a new one for even $350. With my ’73 I found that carrying a spare fuel pump is a good idea.

Larry

[OriginalOwner]

just for FYI on a rebuilt pump, this is "my personal history" with some discussion and tech info .....

http://www.bmw2002faq.com/component/option,com_forum/Itemid,57/page,viewtopic/t,351937

and note that the tii fuel pump rebuilder is Fuel Injection Corp over in Livermore ......

http://www.fuelinjectioncorp.com/

Cheers,

Carl

[layers]

Hi Carl--

Thanks for your comments. Interestingly enough we drove in Livermore twice yesterday, once on Tesla Rd. heading East, then back over Patterson Pass to a pizza place for lunch (see [http]). The fuse failed about half way back to Walnut Creek, on the other side of Mt. Diablo.

Larry

[OriginalOwner]

MAJOR BUMMER !!!!!!

when I had my car back in the garage (after being towed of course), late at night when everything was very quiet I turned the key "ON" ..... I could hear the fuel pump straining very hard until the fuse popped.

Cheers,

Carl