Out of Options No Pressure in Gas Line to Engine

Tiny
TURBOTAIL
  • MEMBER
  • 1986 MERCURY SABLE
  • 3.0L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 180,000 MILES
This is unreal.I've had every mechanic I know try to fix the problem with my 86
sable wagon-and yet, it is still just sitting there. I don't know squat about cars, but I will try to explain. We had to replace the fuel pump-inside the fuel tank-Had to cut the bolts to get the tank off. Replaced the pump. Didn't work-no gas to engine. Found leak in this line that goes to the front of the car. Took 3 days to find another one, that didn't fit without heating up one of the connector things with a match. Ha

The only other thing I know about this hose is that it has to be pressurized to 43 lbs (I think). While all this was happening, we had to deal with some emergency gas cut-off switch in the back seat area. I have looked for any problem that sounds even remotely similar to this on your site, but I can't find anything, or anybody who knows what's going on. I am at my wits end-this has cost me an arm-and-a-leg, and probably a friend or two, and I still don't have a car- that ran great before this 'pump' fiasco. Does anybody have even a remote idea of What's Going On Here? I will be forever in your debt.
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Thursday, February 12th, 2015 AT 5:59 PM

3 Replies

Tiny
CARADIODOC
  • EXPERT
The switch you're referring to is called the "inertia switch". I'm not sure where yours is located, but I can look it up. Basically it's a circuit breaker that has to be manually reset. Even with that reset, don't expect the fuel pump to run with just the ignition switch turned on. I seem to recall it will run for one or two seconds when you turn the ignition switch to "run", but after that it won't turn on until the Engine Computer sees the engine is rotating, (cranking or running).

There should be a fuel pump relay you can bypass to make the pump run for troubleshooting without having to crank the engine. I'd have to dig up a service manual if you need help with that.

Remember too that besides the 12 volt feed wire, you need a good ground wire for the pump. Sometimes if that is broken, the fuel gauge won't work either.
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Thursday, February 12th, 2015 AT 6:25 PM
Tiny
TURBOTAIL
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We bypassed the switch, and we can't get that hose connector to fit into the pump or one of the other hoses. There are 3 connections and two fit, but the other doesn't. The guy at the auto parts store said you had to heat it up to fit? The pump runs, it's just that we can't re-pressurize the line. Is something else wrong with maybe a vacuum line or? Is there another thing I should be checking? At first there was no electrical to the pump until we by-passed that switch in the back. Why is this so hard, and no one can figure it out? I can't be the only one to ever have this problem.I don't know what to do next. Thanks for answering
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Thursday, February 12th, 2015 AT 10:37 PM
Tiny
CARADIODOC
  • EXPERT
First of all, the fuel pump should not be running by bypassing the inertia switch. That is a circuit breaker that is tripped by an impact to stop the pump if everything else fails. The pump also will not run unless the engine is rotating, (cranking or running). That is a safety requirement. If a fuel line is ruptured in a crash, the engine can't run without fuel pressure. When the engine stalls, no signals are received from the crankshaft position sensor or the camshaft position sensor. Loss of those signals tells the Engine Computer to turn the fuel pump relay off. That stops the flow of raw fuel onto the ground and prevents a fire hazard.

Normally we replace the complete pump assembly because we know it's assembled correctly and it costs our customers less money for labor. It sounds like you bought just the pump / motor that gets installed into the assembly. If that hose you're having trouble with is hard plastic and shiny, you most likely didn't find a hose clamp on the old one, and the parts guy is right about having to heat the new one. Don't get carried away with a torch. A few seconds with a hot air gun will soften it enough to become pliable so you can push it on.

Another thing to look for on Ford products are the hoses in that assembly. It is fairly common for them to dry-rot and allow air to be sucked up instead of fuel. The clue is the engine will run fine until the fuel level gets down to 1/4 tank.

There's two other things that I've done that you might consider. The first is when you replace just the pump, on most of them you can mix up the two wires. If you connect them backward, the pump will run just fine but it will be running backward and will try to push air into the tank. The second thing is switching two hoses to the tank. I managed to do this twice on my van, even though the metal pipes are different sizes. The symptom was the pump would run but there was no pressure at the engine.

If you have a leak in the metal pipe running under the car, that can be replaced with bulk rubber hose, but you have to use the more-expensive fuel injection hose. That costs about four bucks per foot. Regular fuel hose for carbureted cars won't withstand the pressure from a fuel injection pump.
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Saturday, February 14th, 2015 AT 4:22 PM

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