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1987 - 1996 F150 & Larger F-Series Trucks 1987 - 1996 Ford F-150, F-250, F-350 and larger pickups - including the 1997 heavy-duty F250/F350+ trucks

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Old 03-09-2014, 11:35 AM
Magnum199944 Magnum199944 is offline
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Won't start injectors not firing, runs rich when started

1995 5.8, all stock 224000 miles need help, when the truck sits for a couple hours it usually won't start cranks great but injectors are not firing. I have 35 psi on the fuel rail when cranking, I have spark, 3 codes in comp 116 114 636.
I replaced both temp sensors, injectors, o2, battery

Some times it will start, when it does now it runs very rich, high idle no power, was able to do a switch test when running and it idle down and ran great at 700 rpm, no engine light. Also tried to unplug the temp sendors did the same thing just ran rich with high idle

Right before this when we got it started it would sometimes run rich until temp gage went 1/2 way, (warmed up )

Also am having trouble scanning codes, sometimes I can get it to work.

Any help would be great sorry for the long wording just trying to get the info out ther
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Old 03-09-2014, 11:44 AM
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Sounds like classic PCM failure.

#1 reason - sometimes can pull codes, sometimes not.

ECT and IAT sensor codes you pulled would have shown up if engine wasn't up to operating temp.

I would pull PCM, and open it up and look for burnt traces, bulging, leaking capacitors. 30 min job if you want to eliminate it.

Also, could be crud, poor, corroded connections at PCM connector. It happens and PCM is thought to be at fault. Also make sure that when you check for codes, that you use a good ground and the DLC connector where you jumper isn't corroded.
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Old 03-09-2014, 11:49 AM
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Ok thanks I will inspect the PCM now
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Old 03-09-2014, 11:58 AM
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The self test on these OBD1 systems was designed to be executed on a powertrain at operating temp so you will always get temp sensor codes on a cold motor and they can be safely ignored.
Spark originates with the PIP module in the distributor so that is the place to start when you have a no spark condition, the next part in line after that is the TFI module and these are known to develop intermittent problems and are easy to change so maybe try that to see if it makes any difference before you swap out the PIP or the whole distributor.
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Old 03-09-2014, 12:16 PM
Magnum199944 Magnum199944 is offline
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Quote:
Originally Posted by Magnum199944 View Post
Ok thanks I will inspect the PCM now
Ok inspected the PCM looks good, all connectors good no burnt spots or bulges
Took pics but don't know how to post them on here.

By the way also tested tps it's in the limits, cleaned all grounds too
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Old 03-09-2014, 12:19 PM
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Originally Posted by Conanski View Post
The self test on these OBD1 systems was designed to be executed on a powertrain at operating temp so you will always get temp sensor codes on a cold motor and they can be safely ignored.
Spark originates with the PIP module in the distributor so that is the place to start when you have a no spark condition, the next part in line after that is the TFI module and these are known to develop intermittent problems and are easy to change so maybe try that to see if it makes any difference before you swap out the PIP or the whole distributor.

I have spark, the injectors are not firing
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Old 03-09-2014, 12:26 PM
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Oh... I misread that. In any case the ignition pulse that is used to generate spark is also used by the computer to time injector firing, so try swapping the TFI module.
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Old 03-09-2014, 12:48 PM
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Ok I reinstalled PCM, cranked over but would not start, sprayed carb cleaner in throttle body, started and ran fine, scanned with kore test, codes 116 172 632
Cleared codes, shut off truck, restarted fine no codes, ran other test with scanner all came back fine. This is driving me crazy, has to be something not telling the injectors to fire when it's cold. What does that?
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Old 03-09-2014, 04:36 PM
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Did you not read the my last post?
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Old 03-09-2014, 07:32 PM
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Ok replaced the tfi, will see how it starts in the morning, thanks
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Old 03-09-2014, 08:02 PM
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Note that the TFI is Black in color. If they try to sell you a Gray one it is the wrong one.
Yes I know what their computer says but their computer is wrong.
By the way the TFI is called an ICM (Ignition Control Module).

Quote:
Originally Posted by Magnum199944 View Post
This is driving me crazy, has to be something not telling the injectors to fire when it's cold. What does that?
It does sound like you have a bad PCM Computer.
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Old 03-09-2014, 08:02 PM
 
 
 
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