1999 F150 (5.4) bad engine computer???
Thread Starter
|
Tuned
Joined: Jul 2006
Posts: 284
Likes: 6
From: Clover, SC
1999 F150 (5.4) bad engine computer???
I have a '99 F150 4x4 with the 5.4 in it. It has been sitting for approximately 5 months. Prior to being parked 5 months ago it was running, albeit rough. Had a dead miss(es) at idle and would only run on all 8 at a specific unloaded speed going down the road. This is the reason the truck was parked. Today was the first time I messed with it in 5 months and it would not start at all. The fuel pump does not appear to be running and it also does not seem to have any spark. (Wont fire with fuel or starting fluid sprayed in the throttle body, etc). I am wondering now if perhaps the ECM is the root problem. How common are ECM/PCM failures on these trucks? If I determine the ECM/PCM is the problem, can I simply replace it with a like ECM/PCM from another truck or does it have to be programmed to match this particular truck? Any comments or suggestions are much appreciated.
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
It's not the PCM from just setting.
First thing is to drain the tank and put fresh gas in and hope the pum is not stuck.
Make sure the crash sensor is not tripped.
Next, is to get the fuel pump running.
Turn the key to run and listen for the pump to run about 3 seconds than shut off.
If yes, put a gage on the test port.
Cycle the key to run several times to build pressure. It should go to about 35 psi.
Next re-seat the crank position sensor to be sure it's not the problem for starting.
If you have the Theft system what does the lamp do?
After you get it to start, ID the cylinder that is out and don't drive it until repaired.
There is no room for guessing. Do the trouble shooting to find the issues same as a shop would do or you will be in confusion.
Good luck.
First thing is to drain the tank and put fresh gas in and hope the pum is not stuck.
Make sure the crash sensor is not tripped.
Next, is to get the fuel pump running.
Turn the key to run and listen for the pump to run about 3 seconds than shut off.
If yes, put a gage on the test port.
Cycle the key to run several times to build pressure. It should go to about 35 psi.
Next re-seat the crank position sensor to be sure it's not the problem for starting.
If you have the Theft system what does the lamp do?
After you get it to start, ID the cylinder that is out and don't drive it until repaired.
There is no room for guessing. Do the trouble shooting to find the issues same as a shop would do or you will be in confusion.
Good luck.
Thread Starter
|
Tuned
Joined: Jul 2006
Posts: 284
Likes: 6
From: Clover, SC
Thanks for the reply - here's an update on my troubleshooting....
I removed the battery and the battery box so that I could gain access to the PCM bulkhead connector. I unplugged that and inspected it. Some of the pins looked a little dirty so I cleaned it the best that I could. I also unplugged the larger bolt-together connector on the engine harness. That connector is attached to a bracket that is mounted to the firewall on the passenger's side. There was also some dirty looking pins in that connector as well. After cleaning both of those connectors I was able to get it to run on raw fuel that I squirted into the throttle body. However the fuel pump is indeed stuck. The circuit does draw current, however its not quite enough to pop the fuse. The fuel pump is definitely not running and there is no pressure on the rail. The truck was parked on an empty tank. I figure the pump just got stuck as a result.
This is not my truck, I am working on it for a friend. I am suspecting the fuel pump was probably the root of the original problem. We'll see.
I removed the battery and the battery box so that I could gain access to the PCM bulkhead connector. I unplugged that and inspected it. Some of the pins looked a little dirty so I cleaned it the best that I could. I also unplugged the larger bolt-together connector on the engine harness. That connector is attached to a bracket that is mounted to the firewall on the passenger's side. There was also some dirty looking pins in that connector as well. After cleaning both of those connectors I was able to get it to run on raw fuel that I squirted into the throttle body. However the fuel pump is indeed stuck. The circuit does draw current, however its not quite enough to pop the fuse. The fuel pump is definitely not running and there is no pressure on the rail. The truck was parked on an empty tank. I figure the pump just got stuck as a result.
This is not my truck, I am working on it for a friend. I am suspecting the fuel pump was probably the root of the original problem. We'll see.
Thread
Thread Starter
Forum
Replies
Last Post
medic10928
1987 - 1996 F150 & Larger F-Series Trucks
52
Aug 1, 2025 03:36 PM
jwandell
1997 - 2003 F150
6
Apr 25, 2018 08:18 PM
