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RE: [T3] FI fuel pump relay and 70 FI Auto update


Hi Jim, Thanks for replying.


> In normal operation the pump runs all the time, but it's controlled by the FI
> brain, which shuts it off if the engine isn't turning over. So what you've
> observed is normal.

Good, I figured as much, but good to hear confirmation.



> > So, any hints on what I did to kill the pump?
>
> Well, in the first place, I'm not a fan of tank sealants. I suspect that you'll
> soon be looking for an unsealed tank because the sealant has sealed up some
> internal passages which are going to be important to you. But none of this
> would keep your pump from spinning.
>
> OTOH, if those passages are sealed, as I suspect, you'll now need a lot more
> than 2 gallons of gas before any will be able to reach the pump.

Well, I did this test to see if the POR15 tan k sealant would or would
not work.

Mainly because I had the sealant and extra tanks, so I might as well
test it and have something to contribute to the knowledgebase.

If it works great, if not, so be it.

However, after treating the tank I did some bench testing of the flow in
the tank - the same testing I did before and now that the rust was gone,
the flow was much improved from before!

I poured liquid into the tank and watched as the center bowl filed quite
quickly and the supply tube and return tube are visibly clear, So I
really don't think it will be as big of a problem as you have
suspected.


> It's possible that while you were doing all this other work, the pump just
> dried out and now can't get itself started.

Now this is a possible scenario.  It has been about 2 months since it's
been disconnected.



> > Any suggestions on what might be done to save the pump?

> Jumper the relay, then go under the car and gently tap the pump motor body with
> a small hammer. Tap in various directions until you manage to shake it just
> right and release whatever got caught in there. Once it starts to run, try to
> run the car.

I'll give it a try.

>
> > Do I need to prime it somehow? (and if so, how?)
>
> You'll have to get gas into the central cup in order for gas to be able to get
> to the pump. The pump WILL spin when dry, but you don't want to do this for
> long, as that is hard on it.

actually I was wondering if I needed to fill the pump with gas similar
to bench bleeding a master brake cylinder, but we'll see if the
knocking with a hammer will get it to spin.



> > So, where is the fuel pump
> > relay?
>
> The fuel pump relay is under the dash, against the firewall, up and left from
> the steering column. It is the same part as the main FI power relay. To jumper
> it, just use a clip lead to short between the two red wires. If you get a small
> spark that means that the pump shows continuity. If there's no spark then it's
> likely that the pump brushes aren't making good contact with the commutator.
> Either way, a little shock on the pump body will usually eventually correct
> this.

And I should probably disconnect wire 19 from the control module to
protect it, right?

>
> Don't overdo the hammer trick. The pump motor has 2 brittle ceramic magnets
> just inside the shell. If you break one of them, you'll be buying a new pump.


Will do. Thanks for the warning!

Big Al
Houston

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