intermittent fuel pump problem

Discussion in 'SN95 4.6L Mustang Tech' started by triplblk98, Jul 11, 2009.


  1. triplblk98

    triplblk98 New Member

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    I have a 1998 GT with no mods. I stored the car for the first time in 10 years over the winter ( in MASS ) and now I seem to have an intermittent problem. I started the car about once a week and it ran fine at idle all winter. There was roughly 1/2 tank of super in it this spring left over from the winter. First time this year (May) I drove to work and after about 30min the car started to sputter in parking lot when I pulled in. It died and would not restart. I did not hear the whine of the fuel pump pressurizing when I turned the key forward. Checked the Shrader valve and just got a dribble with key on. Left car overnight, called for a tow the next AM and it started right up. Had it brought to dealer - said FP was fine and sent me on my way with a $100 diagnostics fee. Said it was due to the additives in the winter gas and it was causing a possible vapor lock. Said to refill, add a bottle of FI cleaner and it should be ok. Took it out second time (June) and once again it started and drove fine - took it up to 90 without hesitation or roughness at all. About 30 minutes later I pulled off to get a soda and it started to sputter in the lot and died. Once again no pressure in the Shrader valve. Waited about 1 hour and it started up again and ran perfectly. Same issue - no fuel pump hum with key on initially but after 1 hour I heard it come on and I knew it would start and it did. Now I'm afraid to drive it cause I don't want to get stuck anywhere. Any chance this is at bad CCRM or would that not be an intermittent problem as I described. To me the FP sounds the same as it always did since I've owned the car - high pitch hum and not rough or louder than normal. I did notice a check engine light on now so I will look into that as well. Trying to diagnose this more closely without just random part swapping. I will also check for a bad ground as this seemed to be a concern in some threads. I appreciate any help. This car has 50,000 miles. Its had a fuel filter, wires, new battery this year, but original coil packs and plugs that are probably due to be replaced soon I imagine. Has run perfect since new without any issues. Thanks in advance. I'm missing my top down cruises this summer so I appreciate any help in getting back on the road.
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  2. COramprat

    COramprat Drone Driver Mod Dude

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    If it was stored maybe a mouse or something chewed on a wire? Sounds like a light short somewhere but get the code checked and check back.
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  3. triplblk98

    triplblk98 New Member

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    Happened again tonight - this is getting to be a pain in the #@$. On the bright side it was the exact same circumstance so at least its consistently the same scenario. Again it was a warm day about 80. Drove the car for approximately 1/2 hour without any issues up on the highway and city driving. Knowing the problem usually occurs about 30 minutes in I was on my way home when it happened. Basically the car just sputtered and ran out of fuel. I pulled it over and noticed the fuel pump again would not cycle on. After about 2 hours when the weather cooled down it started again. I tried about every 20 minutes to turn the key forward and listen for the Fuel pump. My question is I can hear the relay in the fender clicking but I'm not sure if it's the fuel pump relay or one of the others. I was suspecting this was my problem to begin with. Would it be possible to have a bad relay in the CCRM that is effected by the heat? I'm thinking its running fine for a while and somehow heats up and stops turning on the fuel pump after a while and thats when the car dies. This is the 3rd time with the same scenario. I'm going to try to check codes with a multimeter or similar. I'd take it to Autozone but I'm afraid to get stuck their if I have to turn the car off. Can I use a digital multimeter to check codes or does it need to be an analog voltmeter ? I have a friend helping me out and just need to know what to use. Thanks again !
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  4. blubullett

    blubullett Member

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    You could take a multimeter with you and when it happens again check for power at all the connectors in the fuel circut. That will show you if you have a bad wire somewhere. You didn't say if you had refilled the tank yet? It does sound like it is vapor locking, possibly from some water left in the tank.
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  5. PANAKSA

    PANAKSA New Member

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    98 GT

    Hi, I also have a black 98 Mustang GT 5spd w/ blk leather & 100% stock. Mine has 195,000 miles and up until two years ago, it use to be my daily driver. I bought it brand new an would put 120 miles on it every day M-F, lived 60 miles from my job. Always kept up the maintenance on it specially the oil, mobile 1 synthetic only and never had a problem with it. Everything changed when I got married and had two kids and gas prices went up. It just became very difficult with two kids in the back as they got older. Now I drive a 2000 Honda Accord EX-L sedan 5 spd. 4 cyl. I have not sold the mustang because it's really not worth that much and since it's been such a good car to me, I keep it in the garage nice and clean and polished and drive it to work once every two weeks if its not forcasted to rain or snow. I try to at least start it on sundays and warm it up to keep the battery charged. For the past month, I have been very busy and just forgot all about the mustang. I had not driven or started it up for about four weeks. The car has a brand new battery and yesterday I tried to start it and it wouldn't. It has less than 1/4 tank of gas. I am thinking that it might be the fuel pump since I don't hear it. I'll try to fill the tank to see if it helps. Any sugestions?
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  6. wmburns

    wmburns SN Certified Technician

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    I see a few problems here. IMO, there is limited usefulness of a volt ohm meter on the side of the road. Accessing pins off of the CCRM and FPRM is a hugely frustrating task. Especially if you are not really certain what you are looking for.

    IMO, a better idea is to get an ODB2 scanner monitor fuel pressure as reported by the PCM. Optionally, since the OP’s car has a Schrader valve, an after market fuel pressure gauge can be used.

    The OP stated that the fuel pressure drops after the motor has been turned off for a very short time. Obviously, the 1st thing to do is to confirm if the fuel pump is running just before it dies.

    If the pump is running right up until the car is turned off, then the problem is pressure leak down. Try this, turn the key on/off several times and see if the fuel pump will run. The pump should run for a few seconds with each key on/off cycle. Let us know if the car will start then.

    If the pump is failing while the car is running, then it is not likely to be a relay problem. IMO, it is more likely to be a heat related problem in the fuel pump motor itself. The fact that it is somewhat predictable in the run time before it happens (coupled with the cool down) adds credence to the theory.

    For a long shot, consider either a gas tank venting problem or evaporative purge problem. For example, if the evaporative purge solenoid is stuck open, this will draw excessively rich vapors in to the intake. Creating vapor lock.

    I could see a case where the constant vacuum from a stuck open evaporative purge creates a vacuum in the gas tank. This vacuum could cause the pump to cavitate and starve for fuel.

    Similarly, if the gas tank venting system is not working, this could create a partial vacuum in the gas tank causing the pump to be starved for fuel. Might try opening the gas cap and see if you hear air enter.

    From the age of the car, consider replacing the EVAP solenoid. The part has a fairly high failure rate in older cars. The part itself is not $$ and it is easy to change.

    Again, having an ODB2 scanner would allow us to monitor the fuel pressure, evaporative purge solenoid position and anything else this may lead to.

    Please post the DTC codes. This could provide an important clue as to the direction to head.
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  7. wmburns

    wmburns SN Certified Technician

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    At the risk of high jacking someone's thread, I am assuming that the starter turns the engine but the engine does not start.

    Try turning the key on/off several times and see if you car hear the pump run. If it starts after serveral key on/off cycles, your problem is pressure leak down.

    Check the IFS switch in the trunk.

    I am assuming the anti-theft is not active.
    #7

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