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Questions about Fuel Systems



  • alcanalcan Posts: 2,550
    Oxygen sensors generate a voltage signal relative to the amount of oxygen in the exhaust stream. The engine control computer uses this signal to fine tune the air/fuel mixture. The voltage should be constantly changing from about 200mV to about 800mV as the computer increases/decreases fuel delivery.

    Scan tools display data stream, the actual signals being received by the engine computer from all input sensors, and can range from Actron's $300 CP9135 to Snap-on's $5000+ MT2500.
  • I'm getting the same problem on a '98 Expedition. I used to have a '97 Tahoe & its fuel flter was near the right side just under the passenger door. Is the Expedition filter similarly located?
  • swschradswschrad Posts: 2,171
    just about any OBD-II adapter that allows for a PC or Palm display will allow you to watch the crossings of the oxygen sensors. I built a BR-1 adapter and use a junkpile laptop for the purpose. some scantools with complex LCD screens might allow watching the crossings directly on the tool, Alcan would know more about that grade of tool. you can check directly in the reviews at to see if they have reviewed any that will do it.

    you can also use thin wires slid into the connector to bring the signals out to a general-duty oscilloscope.
  • swschradswschrad Posts: 2,171
    the two fords I've owned plus one my sister had a few months all had the fuel filter inside the chassis rail under the drivers side, position varied from ahead of the seat to behind the seat. think like a designer who doesn't want to be sued for a moment. they want the fuel lines and filter protected, but availiable for repairs. so it has to be inside the chassis box someplace and behind the engine. the fuel lines are usually way high next to the body near the top of the chassis. they'll dip down to a fuel filter. look with your hands if you don't see it right away, there's one there.
  • I have a 1995 hyundai accent that was stored for 4 years. Now with a new battery and fresh fuel there is no fuel getting to the engine. Does anyone know if there is an access pane under the rear seat to get to the fuel pump? Or any other uggestions would be greatly appreciated.
  • andreusandreus Posts: 1
    My truck is seems to be losing power to the fuel system. I have changed the fuel pump and filter 10 months ago (8000kms) so I don't believe that it is that. The fuse is good. I changed the fuel pump relay and that masked the problem for a week or so. I seem to only have the problem when the engine warms up (after 15 mins). It sometime hesitated kinda like the fuel filters plugged and then it just stopped and I can't get it started again. Any Ideas?
  • 1991 suzuki samurai i just bought it starts good and idles good drive 1/4 or 1/2 1/4 just like its runs out of fuel.but can start it back up but dose the same . changed the fuel felder didnt help
  • 0patience0patience Oregon CoastPosts: 1,620
    Air filter good?
    No restrictions in the intake? collapsed hose and that sort.

    Another common cause of that symptom is a clogged cat.
  • The fuel warning light started flashing. Manual says it means gas cap loose, bad gasket on it , not put back on properly or a "fuel Leak" somewhere in the system. The cap seems tight enough so I started talking to mechanics. One mechanic said he could do a "smoke test" to see where the leak is but this could be costly. Another one said "buy a new cap; the gaskets do wear out." Even caps for MB's aren't cheap ( especially if that's not the problem) Does anyone have any ideas on how to proceed? Also, the retractrable hardtop has just stopped working...HELP.
  • paisanpaisan Posts: 21,181
    I'd go for the gas cap. That is 99% chance the problem. Heck it takes a few re-test the system so it may only be that it was loose. Gas cap from pep-boys should fit even a MB.

  • I have a 1992 Lincoln Town Car Executive that I am being told that the fuel pump is going out. Where is it located and how would someone know this?
  • 0patience0patience Oregon CoastPosts: 1,620
    fuel pump is in the fuel tank.
    What kind of problem are you having?

    The only way to confirm if the fuel pump is having a problem is to check the fuel pressure and see what it is.
    Or, if it is making unbearable noise.

    But before replacing the pump, the fuel filter should be changed if it has been a very long time since it was replaced.
  • car is making a whistling sort of noise and someone told me it was the fuel pump. It does need a new fuel filter so I will do that and have the pressure checked. Thanks so much for your reply
  • 0patience0patience Oregon CoastPosts: 1,620
    Is the whistling noise a bussing noise or a whistling noise?
    Is it coming from the engine compartment or the rear of the vehicle.
    If it isn't coming from the rear of the vehicle, in the area of the fuel cap, then it isn't the fuel pump.

    If it is a whistling noise in the engine compartment, then it could be a belt or pully.
    Hard to say.
  • It is a whistling sound and I hear it when I am in the car so hard to say where it is coming from. It does not make the sound all the time. Another question I have is how do you get to the fuel pump? Does the whole gas tank have to be dropped and access gained that way?
  • 0patience0patience Oregon CoastPosts: 1,620
    Another question I have is how do you get to the fuel pump? Does the whole gas tank have to be dropped and access gained that way?
    yep, the tank would have to be dropped.

    Honestly though, if it is a whistling noise, I seriously doubt it is the fuel pump.
    I Can't hear the noise, so I could be wrong.
  • Question. The new 2007,2008 Dodge Rams, in the event of an emergency, could a person run A-1 kerasene without damaging the diesel engine, or would it even start using kerasene? I understand the new engines, that the computer won't like the stuff. The new low ultra sulfur stuff is all it takes. Some one told me that kerasene would destroy the fittings, seals, fuel lines, fuel pump ad fuel injectors. Again however, in an emergency, how far could you drive and would it damage anything electrical? I understood that you could run kerasene and that in fact thats basicly what was being used in the winter time from the gas pumps. However, hearing about the new ultra low sulfer diesel makes me a little worried. What do you think anyone. Thanks
  • 0patience0patience Oregon CoastPosts: 1,620
    Some one told me that kerasene would destroy the fittings, seals, fuel lines, fuel pump ad fuel injectors

    Yep, pretty much.
    The new engines aren't as forgiving as the older diesels.
    I wouldn't run kerosene.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 57,595
    I can't imagine an emergency where kerosene would be easier to find than diesel fuel anyway. Diesel fuel is not particularly volatile, so it could be carried in the truck, if securely fastened.

    I would imagine you'd destroy your injection pump using kerosene, which has no lubricating properties whatsoever----diesel fuel does.

    I think you've been misinformed. Some people have added small amounts of kerosene to diesel fuel in brutal winter conditions (the Russians did this to their tanks in WW II, before the Germans copied the idea) but those were primitive older diesels.

    Modern diesel engine are pretty fussy as to what you put into them.

    So, in short---don't even THINK about doing this. ;)

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  • Hello everyone,
    I need some help. I have a 2001 Chevy 3500 van with a 5.7 v-8 engine. When I turn the key to start, the starter works and the motor runs. As soon as I let the key go, the motor dies. Happens everytime. Any ideas?
    My E-mail is
  • kiawahkiawah Posts: 3,666
    Sounds like a bad ignition switch.
  • sap1sap1 Posts: 4
    I have 1992 toyota camry v-6 that i had the gas filler pipe replaced. After replacing this and filling my tank i noticed i had a gas leak from the tank area. When i took it back the mechanic stated the small braided hose to the filler pipe was the problem so i replaced this. When I filled it up it leaked again dripping down from the tank. The mechanic then said i have a hole in the tank. This problem did not exist before i replaced the filler pipe.

    When you drive it about 40 miles i do not notice any gas leak. What else can I do. The gas tank on this car is very expensive and i do not want to replace unless necessary
  • dtownfbdtownfb Posts: 2,918
    Seriously, take it to another mechanic for second opinion. Your first one is simply guessing and replacing parts at your expense.
  • I just replaced the head on the 2.2 L dodge omni. The timing is correct, fuel is getting to the carb and good spark to all cylinders. But, the engine won't start, I think when I had the head off I fliped over the head and activated the fuel shutoff safety device. How do I reset the fuel shoutoff safety device?
  • kiawahkiawah Posts: 3,666
    Do a compression test on the cylinders, to confirm that your camshaft timings are correct.
  • I have a 93 ford thunderbird 5.0 and i have to crank it for a few seconds to start it at all times but when its very cold it dies sometimes and the second time i crank it it fires right up and fuel pump is making noise at all times as well other than that it runs perfectly no hesitation and plenty of power also idles smooth is this the start of a major problem replies appreciated thank you.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 57,595
    I would check pressure in the fuel rail. Perhaps the fuel pressure regulator is bleeding off. Also perhaps the rail is not being primed when you turn the key to "ON", before you crank. This would be a relay problem.

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  • Thank you, but do you mean the fuel pump relay or a diffren't one also what about the fuel pump noise its working but is very annoying and i don't know how to test the fuel pressure ty again.
  • Listen very carefully for the noise when you turn the key to the on position do not start the engine if you hear the noise then its probably the pump.It will run for a few seconds when you turn the key on if not I think you may have a vacuum hose leak.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 57,595
    Yes you need a gauge and a T fitting to test pressure in the fuel rail. Also there is a fuel pressure regulator that might be leaking. What I'm driving at is that at night the fuel pressure may bleed off in your system so that the fuel pump has to prime the entire system before the car can start.

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