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Discussion Starter · #1 ·
Hey guys my 89 f350 with the 460 has an issue, usually it runs really well, but after idle for 15 mins, I put my foot down hard and the engine just fell on its face, no power barely accelerating, fuel filter is changed, regulator is changed, fuel psi is about 30 at idle gets up to about 36, does not increase much with acceleration never gets up to 40 psi. Makes no difference what tank i am on, any ideas ? Thanks.
 

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Did you check fuel pressure while driving at WOT (38 lbs + or - 1) or at a stand still. Checking fuel pressure at a stand still does not tell you if the fuel pump is putting out the correct volume.
I really suspect your high pressure fuel pump (on the frame rail) is faulty. Do the correct fuel pressure test. It's all a process of elimination.
If your fuel pressure is good, I would then suspect the Ignition Control Module, on the distributor. The distributor mounted ICMs are world famous for heat failure. That's why Ford moved them to a heat sink on the fender well in later years.

Causticuc, I would really be interested in the science of why piston ring wear, on a running engine, would cause the OPs problem. Help me learn more.

Richard
 

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Did you check fuel pressure while driving at WOT (38 lbs + or - 1) or at a stand still. Checking fuel pressure at a stand still does not tell you if the fuel pump is putting out the correct volume.
I really suspect your high pressure fuel pump (on the frame rail) is faulty. Do the correct fuel pressure test. It's all a process of elimination.
If your fuel pressure is good, I would then suspect the Ignition Control Module, on the distributor. The distributor mounted ICMs are world famous for heat failure. That's why Ford moved them to a heat sink on the fender well in later years.

Causticuc, I would really be interested in the science of why piston ring wear, on a running engine, would cause the OPs problem. Help me learn more.

Richard
Fluid viscosity cold vs warm, at 15min he would be at 30W. If his pistions or rings are worn below spec he will start loosing power.

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Discussion Starter · #7 ·
Did you check fuel pressure while driving at WOT (38 lbs + or - 1) or at a stand still. Checking fuel pressure at a stand still does not tell you if the fuel pump is putting out the correct volume.
I really suspect your high pressure fuel pump (on the frame rail) is faulty. Do the correct fuel pressure test. It's all a process of elimination.
If your fuel pressure is good, I would then suspect the Ignition Control Module, on the distributor. The distributor mounted ICMs are world famous for heat failure. That's why Ford moved them to a heat sink on the fender well in later years.

Causticuc, I would really be interested in the science of why piston ring wear, on a running engine, would cause the OPs problem. Help me learn more.

Richard
Ok thanks I did wonder if i needed to do it on the go, I will do that then, gonna be hard to rig it right lol, this almost certainly is a fuel issue i'm sure, I really dont think piston ring wear has anything to do with it. As a machinist I have seen people run engines with the most loose tolerances going and they dont do what this truck is doing. OK will let you know, so 38 psi at WOT right? minimum? cheers.
 

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Your issue, as described is temperature related.

Many of the other ideas would be constant or randomly intermittent. I am still of the mind it is either a compression issue (it is highly likely that in 31 years they have never been looked at, ethanol in fuel is also not helpful) or that your altitude/barometric sensor is experiencing thermo-failure and messing up the Speed Density values.



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Discussion Starter · #12 ·
Your issue, as described is temperature related.

Many of the other ideas would be constant or randomly intermittent. I am still of the mind it is either a compression issue (it is highly likely that in 31 years they have never been looked at, ethanol in fuel is also not helpful) or that your altitude/barometric sensor is experiencing thermo-failure and messing up the Speed Density values.



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This is when warm, and it is random
 

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Does your check engine light work?
Has is ever lit up even temporarily?
Are you getting a pip sensor code?

OEM distributor or an aftermarket replacement?

This may be ignition related. Problem with hall effect sensor / profile ignition pick up or ignition coil. Perhaps the TFI module. Yours should be grey.

Baro sensor possible I suppose.


SJ
used 2b RHP
 

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Discussion Starter · #14 ·
Does your check engine light work?
Has is ever lit up even temporarily?
Are you getting a pip sensor code?

OEM distributor or an aftermarket replacement?

This may be ignition related. Problem with hall effect sensor / profile ignition pick up or ignition coil. Perhaps the TFI module. Yours should be grey.

Baro sensor possible I suppose.


SJ
used 2b RHP
No engline light has never come on it was just once under hard accleration it just did not accelerate was just flat, does not do it all the time
 

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No engline light has never come on it was just once under hard accleration it just did not accelerate was just flat, does not do it all the time
That is a very different description than what you started this thread with.

This is normal behavior for a 460 with SD when you go through elevation changes. So the question is were you going through an area where you were either going down or up 1500+ feet from your normal altitude?

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No engline light has never come on it was just once under hard accleration it just did not accelerate was just flat, does not do it all the time

Does the check engine light come on when you turn on the ignition switch to run but not start?
Sometimes the bulb burns out.

Ever pulled codes?

KOEO / KOER



SJ
used 2b RHP


.
 

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Discussion Starter · #18 ·
That is a very different description than what you started this thread with.

This is normal behavior for a 460 with SD when you go through elevation changes. So the question is were you going through an area where you were either going down or up 1500+ feet from your normal altitude?

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its not different, i never said an engine light came on, I never said it was all the time, I said usually its fine and after letting idle it just fell on its face, there was no change in elevation whatsoever
 
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