Fuel System Problems

Scott Long

Registered User
Ok put the new pump in, put the tank back up, plugged in the connector....

Key on: gas level gauge reads proper, but pump won't run. Doesn't even prime. I swapped the old relay back and no difference.

My connector at the tank was all broken so it's directly wired to the prongs on the lid. I put a ton of die-electric grease over them to keep moisture out. I'll get a new harness and connector but I want to make sure it runs.

I don't know what to do now? Re-wire the pump w/ it's own relay? Is a 30 amp relay enough to run the pump? What about a 30 amp inline fuse and 12 ga. wiring? Sound like a plan? I can trigger the relay with something switched w/ the ign. But if the pump runs anytime the key is on then, would it automatically re-circulate back to the tank or would it build pressure at the rail?

If I put a fuel cell in, could I use the BRAND NEW 255 LPH pump that I bought today? What about fuel lines can you use the stock ones or do I need to go to like -8 or -6 and run new up to the fuel regulator and rail?

This car is pissing me off!!!!
 
About the connector. There are circle type connectors that slide down over the prongs. I put them on and pinched them tighter with needle nose pliers. The connections are good no doubt.

However I suspect maybe the harness itself may have a short or the harness from the relay to near the resonator may be shorted.

I found 12 v at one of the relay sockets, and the fuse under hood is constantly hot. When the key was on I read 10v at the pumps 12+ prong on the harness at the resonator, haven't checked it at the pump plug inside the tank.
 
Did you try jumpering the EEC test connector to trigger the fuel pump. You could also tap the power line to the pump and stick 12v to it to see if it'll work.

grrr.. car problems...
 
Well I'm going to try and run a wire from 12+ to the 12+ wire prior to the connector by the resonator and see if I can get the pump to run. If I do that, I might just wire the pump up with all new wiring, a 30 amp relay, and switch the relay from something on the IGN circuit. Then when the key is on the pump will run. But... if for some reason the key is turned on and the engine is not running, will the pump burn up or will it just pump fuel back through the return lines and circulate the fuel until the engine is cranked?
 
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There is such a thing as too much dielectric grease. You do realize that its non conductive right?
 
I put it on after the connection was made. Coverred the top of the connectors to keep moisture out. If it didn't work right, then why does my fuel gauge still work properly? It's one of the connections in the harness.

Also there was a little metal hat looking thing above the pump between the metal line. I took it off and used the hose to connect the pump outlet to the line. I've never seen that thing before and wonder if it was important? I see the pics show just a hose...
 
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I've decided to wire up the fuel pump seperately from the factory wiring. Now, is 12 ga. wire big enough or should I use 10 ga.? I assume a 30 amp relay and inline 30 amp fuse will be enough since the factory underhood fuse for the fuel pump is only 30 amps.

Might just put the relay on a switch like in a race car.
 
Guess I'm going to pioneer this. I will probably go with 10 ga. wire if I can find some spade connectors for it to hook up to the switch and put an inline fuse on the main power wire just in case.
 
Thanks Mike. The factory wiring looks like 16 ga. or so which I thought was pretty small.

Maybe I should wire it straight to the terminal at the tank?
 
I would find the problem at hand instead of creating some new ones. You dont need anything more than 16ga wire by the way....
 
Is there power out of the pink/black wire at the fuel pump relay(green relay)connector?? Is there power in and out of the fuel shut of (inertia)switch (next to the fuel pump relay)? Is there power at the pink/black wire at the fuel pump connector itself. One of these will result in the answer no. Or the fuel pump is crap. Keep in mind alot of new fuel pumps are as reliable as the one you are replacing it with...
 
If this fuel pump is no good, then I will be really upset seeing as how I just went through 2 coil packs in a row from SCP that were no good.

I'm starting to think the old pump isn't bad, so I will hit it with 12v just to check it very quickly. If it works, I'll buy a new TBird sock for it and sell it with the new harness I didn't use and maybe make a few bucks back.

I need someone to help me check the voltages while one of us cycles the key off and on. I can't do it by myself and I've been working on this thing alone in the shop without help from anyone else. Shop is open tomorrow so I can go try to do some testing on it.

I don't see how rewiring the pump would create more problems. Obviously something is either wrong with the wiring or the pumps I have are no good. If the wiring is bad, I'd solve it by rewiring it. Also if I put the pump on a switch it would double as an anti-theft device.
 
Scott,

I would wire in the safety switch as well. Replacing the stock wire isn't a bad idea, though completely wiring it differently isn't great but it is doable.

A common issue on high performance SC's is a fuel pump that isn't outputting it's rated fuel flow due to low voltage at the pump. A bigger wire, less resistance, more voltage at the pump.
 
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