need some help please
08-02-2009, 10:40 AM
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need some help please
87 with twin 454s when i get above 3000 rpms both motors fall on there face,like its not getting enough fuel but i have been through the fuel system from tank to carbs so im thinking its electric,any help would be appreciated. thanks in advance
08-02-2009, 05:35 PM
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Three main things to check:
1) Alternator output. Are you only runnning one alt? If so, it's probably losing juice (not charging) above 2000 and when you hit 3000, the motor is draining volts. From memory, the TBIV system doesn't like any less than about 11v but won't run with less than 9.3v or something. Intermittent failure of elec supply would cause both engines to play up due to lack of sparky juice. Belt slipping? Bearing shot? Have a spare alt you can try?
2) Coils. but seeing as how both motors fall over at the same revs I doubt it. You never know until you check though. Replace one, try it out and if it solves the problem, buy another. If it doesn't, it's good to have a spare anyway!
3) Distributor Advance / Timing. If you've lost your curve (springs broken or plate stuck) you'll get stuck. Again, unlikely to happen on both at the same time but worth checking.
The Alt would be my first place to check unless you just also happen to have a dead battery that won't hold a charge? Check that too. Start with the battery, then test the alt for charge under load.
Good luck!
1) Alternator output. Are you only runnning one alt? If so, it's probably losing juice (not charging) above 2000 and when you hit 3000, the motor is draining volts. From memory, the TBIV system doesn't like any less than about 11v but won't run with less than 9.3v or something. Intermittent failure of elec supply would cause both engines to play up due to lack of sparky juice. Belt slipping? Bearing shot? Have a spare alt you can try?
2) Coils. but seeing as how both motors fall over at the same revs I doubt it. You never know until you check though. Replace one, try it out and if it solves the problem, buy another. If it doesn't, it's good to have a spare anyway!
3) Distributor Advance / Timing. If you've lost your curve (springs broken or plate stuck) you'll get stuck. Again, unlikely to happen on both at the same time but worth checking.
The Alt would be my first place to check unless you just also happen to have a dead battery that won't hold a charge? Check that too. Start with the battery, then test the alt for charge under load.
Good luck!
08-02-2009, 07:45 PM
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i helped a friend on his 93 fleetwood motor home (454)recently that was doing the same thing. i ended up finding a bent fuel line. onece i fixed that the problem was solved. i know you said you went through all that however just be certain.
john
ps maybe put a fuel pressure gauge on one engine anyway.
john
ps maybe put a fuel pressure gauge on one engine anyway.
08-02-2009, 09:25 PM
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Three main things to check:
1) Alternator output. Are you only runnning one alt? If so, it's probably losing juice (not charging) above 2000 and when you hit 3000, the motor is draining volts. From memory, the TBIV system doesn't like any less than about 11v but won't run with less than 9.3v or something. Intermittent failure of elec supply would cause both engines to play up due to lack of sparky juice. Belt slipping? Bearing shot? Have a spare alt you can try?
2) Coils. but seeing as how both motors fall over at the same revs I doubt it. You never know until you check though. Replace one, try it out and if it solves the problem, buy another. If it doesn't, it's good to have a spare anyway!
3) Distributor Advance / Timing. If you've lost your curve (springs broken or plate stuck) you'll get stuck. Again, unlikely to happen on both at the same time but worth checking.
The Alt would be my first place to check unless you just also happen to have a dead battery that won't hold a charge? Check that too. Start with the battery, then test the alt for charge under load.
Good luck!
1) Alternator output. Are you only runnning one alt? If so, it's probably losing juice (not charging) above 2000 and when you hit 3000, the motor is draining volts. From memory, the TBIV system doesn't like any less than about 11v but won't run with less than 9.3v or something. Intermittent failure of elec supply would cause both engines to play up due to lack of sparky juice. Belt slipping? Bearing shot? Have a spare alt you can try?
2) Coils. but seeing as how both motors fall over at the same revs I doubt it. You never know until you check though. Replace one, try it out and if it solves the problem, buy another. If it doesn't, it's good to have a spare anyway!
3) Distributor Advance / Timing. If you've lost your curve (springs broken or plate stuck) you'll get stuck. Again, unlikely to happen on both at the same time but worth checking.
The Alt would be my first place to check unless you just also happen to have a dead battery that won't hold a charge? Check that too. Start with the battery, then test the alt for charge under load.
Good luck!
08-02-2009, 09:27 PM
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i helped a friend on his 93 fleetwood motor home (454)recently that was doing the same thing. i ended up finding a bent fuel line. onece i fixed that the problem was solved. i know you said you went through all that however just be certain.
john
ps maybe put a fuel pressure gauge on one engine anyway.
john
ps maybe put a fuel pressure gauge on one engine anyway.
08-03-2009, 03:27 AM
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Strange that it happens to both engines though. Have you put a vacum gauge on the motors to make sure they pull enough for the secondaries? Check the vacum lines too.
Still can't get around both motors stumbling at the same revs though. Smells like bty / alt issue that's made you check other areas that have now been highlighted. I just don't like the chances of two motors suffering the same fate at the same time!
Keep on keepin' on.
