My 1985 Thunderbird gave up on me a few days ago. The engine turns over
and I've got spark at the plugs. I'm guessing its a fuel pump problem.
Is there an easy way to check the fuel pump? Also, as I understand, the
pump is in the tank. Is there top access or do I have to drop the tank.
Last question: I've seen fuel pumps anywhere from $75 to $250. What
should I be looking for? Any illustrations or procedures would be
greatly appreciated. DLL
In all likelihood it's the fuel pump at this age, but, you need to check the
at the inertia switch in the trunk when you turn the key on. When you cycle the
there should be voltage at both terminals for about 3 seconds. If so, it's the
wiring to the tank. If not, look to the fuel pump relay. I know it's a crude
give it a shot of ether. If it fires and dies then the problem is likely from
relay to the pump. If it doesn't fire it's a concern with the EEC-IV system.
There is no access hole, you must remove the tank to get to the pump. It is
on the fuel sender assembly inside the tank. I don't know where you are located,
be prepared to replace the fuel sender assembly also. The tubes to the sender
prone to rust. Even if they don't leak now, once you disturb them they will. If
rust is light (and you are in a temperate climate) this won't be a concern. If
rust is "flaky" anywhere on either tube then replace the whole sender.
The design of the tank puts the outside of the sender in a depression in the
the tank. That depression holds moisture, dirt, mud, and SALT that splashes up
during use and leads to rust.
After typing all of this I remembered that your 85 may have 2 fuel pumps. If
has fuel injection that looks kinda like a carburetor (CFI) then it does have 2
The system is a bit more complicated. One pump in the tank (low pressure) and
pump on the right frame rail (high pressure). Cycle the key from off to on and
to the pump on the frame and at the tank. If one runs but not the other, the
is likely bad. If they both don't run, the problem is likely the relay or
the circuit. The same caveats about rust on the tank sender apply.
You made a good point. I didn't think of it but the fuel pump does
normally make a noise as soon as the key is turned before the starter
hits. I'm going to check that this morning. Whether there is a sound or
not will at least tell me more.
Tom Adkins wrote:
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