fuel pump electrical supply, 1984 T-Type
 

Due to failure of the fuel pump and rust issues on my 1984 T-Type, I replaced several parts of the fuel system:
gas tank
straps
pump
sock
rubber fuel lines between the tank lines and the body lines
metal fuel line that runs from above the rear axle to the bottom of the fuel filter
fuel filter.

The new fuel pump is not working. With the key on, I do not hear the pump turn on. Maybe the wiring went bad.

The wiring diagram that I found does not agree with the wiring going to the tank. I need help identifying which voltage should be on which line. There is a 3-pin connector near the rear bumper, connecting to the fuel sender assembly in the tank. tan/white, red (or pink?) and black.

A few questions:
Someone please tell me which wire carries the power to the pump.
This wire should have battery voltage for a few seconds after the key is on, right?
What is the lowest voltage acceptable coming to the pump wire to still operate the pump?
Does the pump get ground through the black wire? It must be, since there is no metal to metal contact from tank to body.

Is it safe to temporarily connect 12V and common on the pump wiring to a power source while it is installed in the tank in the car? I would wire it directly to the car battery, or to a spare battery not connected to the car electrical system. I would apply full battery voltage to the pump.

Thanks

Re: fuel pump electrical supply, 1984 T-Type
 

The black wire is ground.
The pink wire is a resistance signal from the level sender.
The Tan/white wire is to supply 12v to the pump.
It wont hurt to do what you want to to test it. Just DON'T hit the pink wire with 12v.

Re: fuel pump electrical supply, 1984 T-Type
 

digging around in an old service manual for 1984 CCC (V6 turbo)...

It appears that the TAN or TAN/WHITE wire (connector 209 circuit 120) powers the pump. I'll the bet the other wires are ground and sender signal.

BLACK is ground.

I'll be there's RED wire for sender signal.

Re: fuel pump electrical supply, 1984 T-Type
 

I got home from work and connected a lawnmower battery to the tan and black terminals. The pump ran. So I guess I have bad body wiring or a bad fuel pump relay.

Now another problem appeared. When the fuel pump pressurized the lines, some fuel leaked from the top of the tank. The fluid that came out was dark. The tank hissed even after the power to the pump was removed.

There is one new line from the tank up to the filter, and a new filter. It's hard to believe any fuel was in the rest of the system for 6+ years.

The engine did not fire up. It sputtered like it was starved for fuel. I didn't check fuel pressure.

All this is making me think I crossed up the pressure and return lines above the tank. If that was the case, I'm thinking the pressure line would see the wrong side of the regulator and the pressure would have nowhere to go. The line would have excessive pressure and find its way out somewhere.

Am I on the right track?

Re: fuel pump electrical supply, 1984 T-Type
 

That sounds reasonable ... if you were pushing pressurized fuel up the return line, that'd do some strange stuff ... I would think that the pump would dead head against the regulator.

Put a pressure gauge on it as a quick check ... or undo the lines from the tank one at a time (into a bucket) and verify routing.

Re: fuel pump electrical supply, 1984 T-Type
 

I checked out the lines and found that they are not crossed. The pump outlet line runs to the inlet of the fuel filter. I have a rubber fuel line piece under the frame halfway to the fuel filter and it is flowing OK up to that point.

If there was a restriction or blockage in the fuel return line, so that no fuel returned to the tank, I think the line would be at high pressure. But so high that fuel would leak at the rubber lines?

Re: fuel pump electrical supply, 1984 T-Type
 

A gauge attached to the fuel rail test port shows about 9 PSI. It takes 1 to 2 seconds to climb from 0 to 9 PSI. This is with the fuel pump powered from a lawnmower battery. The battery voltage measures 12.6V.

With the fuel feed line disconnected half way to the front, the fuel flow into a can looked light (i.e. not 40 PSI).

It's a brand new fuel pump.

Nothing comes out the return line. The fuel tank is hissing after the pump is off, and fuel is trickling down the side of the tank.

Re: fuel pump electrical supply, 1984 T-Type
 

Something is either blocking the line or the new fuel pump is not working (unlikely).

I'd look for kinks, pinches, collapsed hose (and they can collapse internally) or something misrouted.

Another thing .. try just the shortest hose you can from the top of the fuel pump and verify flow is about 1 gal/min or better with no "load" or pressure. Then move forward to the fuel filter and try it again there ... and so on.

Re: fuel pump electrical supply, 1984 T-Type
 

I found the problem. There is a pinhole in the fuel outlet line on top of the sender assembly. Where the fuel outlet line (i.e. pump pressurized output) turns horizontal after making the 90 degree bend out of the sender top plate. The pressure is being lost there, and washing the top of the tank with a fine spray of fuel.

The top side of the sender mounting plate and the three lines were very rusty so I sandblasted them before installing in the new tank. The blasting must have thinned the metal so it is porous now. When not spraying, it weeps fuel.

I painted the tank and freshly blasted sender top hoping to keep one part of the car from rusting. Amazing how quickly the paint washes away.

Re: fuel pump electrical supply, 1984 T-Type
 

Son of a gun! I wouldn't have thought of that, but makes perfect sense. Glad to see you found it!

Re: fuel pump electrical supply, 1984 T-Type
 

RockAuto lists the SpectraPremium FG156A sender, strainer, and float for $91.79. FG156A is claimed to fit 1984 through 1987.

The FG156A part listing does not mention digital fuel gauge or analog fuel gauge. Are there different senders for the two applications?

There is one offered in our Parts For Sale but it's described as for an analog gauge.

Re: fuel pump electrical supply, 1984 T-Type
 

Yes, they have different resistor values in the sender, from what I remember.

Re: fuel pump electrical supply, 1984 T-Type
 

Reading various postings online and the scanned Turbo Regal parts book online, I see for the 1987 GN:

meter, fuel (in tank)(3.8 - 7)(EXC U52) 25092745
[metering unit, 90 ohms full scale, for analog fuel gauge]

meter, fuel (in tank)(3.8 - 7)(W/ U52) 25092748
[metering unit, 120 ohms full scale, for digital dash (U52) fuel gauge]

The SpectraPremium FG156A part is 90 ohms. I read complaints that some finesse is necessary to get it to fit in a Turbo Regal tank (assuming that means an OEM tank). I have a replacement SpectraPremium GM307 tank.

So I'm looking at buying the new sender unit in order to get rust-free fuel pipes. I could transplant my old (but cleaned up) fuel-measuring rheostat and anything else needed to make it a 120 ohm unit.

Re: fuel pump electrical supply, 1984 T-Type
 

I patched up the main fuel line coming out of the sender assembly at the top of the tank.

New tank, new straps, new bolts, new intermediate lines to the rubber cushion area above the rear axle.

New return line up to the front of the car. Main fuel line was replaced ~1998 and still is OK.

Fuel pump does not prime for a few seconds at key on. Fuel pump runs off lawnmower battery.

With the fuel pump fed off the lawnmower battery, the car started and ran. Idle was very poor. It didn't want to rev much with throttle input, but did rev a little while releasing throttle. Days later, I tried to repeat this, but the engine would not fully fire up... just sputtering. Fuel pressure is about 35-40PSI at the fuel rail test port.

Re: fuel pump electrical supply, 1984 T-Type
 

Check fuel pump relay and oil pressure switch (for the non-priming problem).

The pressure sounds good, but the rough running/no start almost sounds like something electrical:

• Check to see the battery voltage is good ... more than once I've been bitten by low voltage ... the wiring is getting old and brittle in these things
• Check the grounds at the back of the block/head and the battery strap ground at the bottom of the turbo mount. Bad ground = all sorts of chaos
• Check the cam sensor clocking and the interrupter ring inside ... if it wiggles or is loose, that's a problem
• Injectors may be gummed up or bad from bad fuel/old fuel residual
• Check for good spark ... Casper's coil tester is pretty handy for that
• Check plugs
  

That's kind of a brain dump ... hope it's something simple like a ground.

Re: fuel pump electrical supply, 1984 T-Type
 

Found good continuity on tan wire from body harness connector at tank, to fuel pump relay connector tan (or is it gray?) wire.

FYI, in case someone else has this problem:
A long (10 feet?) wire helps make this test. Insert a wire into the fuel pump body harness connector and lay it just right, so that the test wire touches the exposed harness pin in the WeatherPack connector. Run that wire all the way to the engine compartment, to allow checking continuity to the relay harness connector near the passenger side fender, using an ohmmeter.

Next, I jumped the relay hot (pink-black) to relay load output (tan, or gray). The fuel pump energized and brought the fuel rail up to about 38psi.

I guess I have a bad fuel pump relay. On my 1984 Regal, the OEM relay has part number 10027719. There is brown greasy stuff on the wiring connector that plugs into this relay and also the connector for the A/C cutoff relay next to it on the passenger-side metal bracket.

Re: fuel pump electrical supply, 1984 T-Type
 

With cranking the engine, it sputters, but won't run.

A few days back I had it running very poorly (ran with a sound like pup pup pup...). I fiddled with the wires and connectors on the front of the engine below the coil pack. This made it almost stall. :idea:

Today, same crank - sputter - won't run. I felt around the coil pack, and found a harness connector under the coil pack, that has wires that lead up toward the intake manifold. I felt it un-mate while poking around in there.

After plugging it back in, the engine started and ran! :winkgrin: ! :winkgrin: Pretty smooth for the engine not running for several years!

I think rodents have been trying to disassemble my wiring harness wire by wire. To make a nest. Or to sell it on ebay.

Re: fuel pump electrical supply, 1984 T-Type
 

It happens! And those gremlins [not the AMC kind] come around every so often as well, just to see if you are paying attention to the old Buick... LOL