Mechanics

FUEL PUMP

1984 Ford Thunderbird

Engine Performance problem
1984 Ford Thunderbird V8 Two Wheel Drive Automatic 114000 miles

1984 ford tbird ELAN 5.0, digital dash. The car runs like it has a bad fuel pump. Sometimes it runs ok, can never punch the pedal for it trys to stalls, runs rough, sometimes it starts great, sometimes very difficult. Sometimes dies while driving, or idling, burns lots of fuel, smells lots of gas, passes emissions.
Fuel filter was very dirty, I took to sun devil auto in Glendale AZ, was told that the low pressure was too low, and high pressure wasn't right, when they ran an engine diagnostic. I have done some studying and it seems that there are a few things other than the fuel pump could cause all these problems too. I read that and was told that the fuel tank must be removed. I went to www. Automd. Com and it says to get access by removing the rear seat. Do you know if I can get to it through the rear seat? And do you know of any other things, like a sensor, could be the problem? I got the impression that the engine diagnostic was a tool used to help diagnose the fuel pump, but that it wasn't 100% like when a diagnostic tells you that a sensor is bad with a code in newer cars. I want to fix but can't change every part it may be either. I really must know if you know if from the info I provided, if it is the fuel pump or something else. I couldn't get a straight answer from the shop who ran the diagnositc, just a guess that they were comfortable. I read in my research that this could be caused from other things. The car has had other problems for years as I have fixed them but hasn't run right for a few years, yet I only put about 500 miles a yr on the car. Hope you can help on this. I am trying to find an answer before spending money on unneeded repairs, and still have the same problem. Thanks.
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Togetrepairs
March 20, 2010.




Hi, how you doing today? My info says you have two fuel pumps. One is low pressure in the tank, the other is high pressure pump located on the frame rail. If the pump in the tank has a problem, I'd drop the tank. That way you can inspect the inside of the tank, run your arm in the tank, drag your hand around inside the tank, if you find a lot of rust or junk in the tank, you need to have the tank cleaned or replaced, first.

JDL
Mar 22, 2010.
Regarding the reply to my question about the fuel pump. I asked if after the diagnostic, and was told they feel comfortable that the fuel pumps are the proble, yet I couldn't get a 100% guarantee that that was the problem, do you thin it is the fuel pump or pumps? I have been told that when the in tank pump is bad that mechanics always replace the other high pressure pump.

Tiny
Togetrepairs
Mar 22, 2010.
Thanks for that info, much help. The other problem I really needed to know about was, whether you think it is the fuel pump from the description and info I wrote. Can you help there?
Thanks much

Thanks. The answer that I need to remove the tank was great help. I did remove the back seat and there is at least 12 to 16 inches from the back of the seat to the front of the tank.

The unanswered question was whether or not you thought that the fuel pump is the problem. I've been told that there are other things that can cause the problems I have been having, for a few years, but has fradually become worse to the point of the car being unreliable now. And as for that high idle, I just don't know if a bad fuel pump can do that. I know the timing is set. I don't know if the throttle body fuel injection automatic choke assembly if bad can do this. I went to a coupld repair chops but it seems that there aren't any mechanics in the Phoenix AZ area that knows the car, being 26 years old now. It has a total of 114,500 miles plus idle time for repairs, warm up, and stoplights, etc.
This car used to run so much different and better. It seems like it has been years with this problem of the car's performance getting worse, as I have repaired many things, that always seem to help, but never totally get rid of the problem.

I did check every vaccumn line under the hood. There is one line I can't find that broke off when I removed the fuel filter, still searching, but that isn't enough to cause these problems. I hope I can find out where that vacumn lines connected to the air cleaner goes. If there is a major vacumne leak, I had hoped the engine diagnostic would haave indicated that. I stripped every harness and checked every wire and vacumn line and couldn't find a a problem. I even changed the MAP censor. It didn't need that. It actually acts, like it needs a fuel pump or carberator, but doen't have a carberator. But what is weird is that it runs good sometimes and runs bad sometims, and sometimes it starts great and sometimes it is a battle to get it to start. There is nothing that is a uniform ongoing problem as it happens unexpectedly, excapt you can't punch it while in drive for it trys to dog out, but runs, and sometimes I can punch it in park and it sounds good, yet most of the time, it trys to stall, like it hesitates before it speeds up rpms. And then again, it also stalls when I punch it. Totally unprodictable, except how bad it will run. Sometimes it runs just a little bad, sometimes it runs ok, and then dies, or doesn't. It is the most inconsistent problem I have ever come across. I don't even know if it is an electrical problem, but if it is an electrical problem it affects the fuel flow. The fuel flow is always a factor. The cause is what is not uniform, nor predictable. I worked on the car last month for example, drove the thing as hard as I could, stp and go, everything and it ran great. I told the wife it was fixed. She used it the next day and she barely made it home.

Tiny
Togetrepairs
Mar 22, 2010.
I'm sorry, I can't tell exactly whats wrong, without doing my own testing. Do you have a fuel pressure gage? I can't tell from your post, exactly what is the problem? To say, somebody said this or that, I can't work that way.

JDL
Mar 22, 2010.
Get both fuel pump's pressure checked out by using a fuel pressure gauge and get back with the readings asap- I need this info to knock out the fuel system before I get to parameters and actuators being controlled by the computer or you can do below and get back with some testing results

Oxygen sensor.
Catalytic converter.
Fuel injectors dirty/sticking.
Mass airflow sensor/Airflow meter.
Throttle position sensor.
Manifold absolute pressure sensor.
EGR Valve
Fuel pressure regulator leaking or defective fuel pump.
False air leakage.
Fuel contamination.
Foul/defective spark plugs.
Open spark plug wires.
Ignition coil/Coil packs defective.
Incorrect ignition timing.
Cap and rotor.

Note: If it doesn't apply disregard.
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Rasmataz
Mar 22, 2010.
I contacted the shop that did the diagnostic. They told me that performed a pressure gauge test and both fuel pumps failed the the pressure tests, D you think with all the information provided that he fuel [umpes are the most likely culprits? I am more familurte with the manual fuel pumps and am aware of how a 77 monte chevy acts with a bad fuel pump, but not in tank and in line electric pumps. Do you thing that is the problem since the pumps failed the pressure tests?
Thanks,
Nathan

Tiny
Togetrepairs
Mar 22, 2010.
If its not producing the correct fuel pressures when it turns On its no good

Rasmataz
Mar 22, 2010.

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