1990 f250 Won't start, fuel pump doesn't shutoff

[F 150Cobra]

Over oktober it took longer and longer for the fuel pump to shutoff.
As long as the fuel pump is running the truck won't start. If it does happen
to start it runs rough then smoothens oout

http://s198.photobucket.com/albums/aa217/demon6696/?action=view&current=STARTINGPROBLEMS.flv
this video was just when it startet to do it..now if i start immeditly it wont start... i have to wait a minute for the fuel pump stops priming

 

[blacksnapon]

Over oktober it took longer and longer for the fuel pump to shutoff.
As long as the fuel pump is running the truck won't start. If it does happen
to start it runs rough then smoothens oout

http://s198.photobucket.com/albums/aa217/demon6696/?action=view&current=STARTINGPROBLEMS.flv
this video was just when it startet to do it..now if i start immeditly it wont start... i have to wait a minute for the fuel pump stops priming

A fuel pressure test is in order. The fuel pump running would suggest to me that it is having trouble building sufficient pressure to run (like a fuel leak, regulator bypassing, fuel pump issue).

 

[F 150Cobra]

i tought of that but on anothr furom they said.. bad computer sympton


reply 1. Replace the computer.
The fuel pumps are timed, they do not shut off by pressure.

reply 2. classic symptom of a bad computer

is this a posebelity?

 

[blacksnapon]

i tought of that but on anothr furom they said.. bad computer sympton


reply 1. Replace the computer.
The fuel pumps are timed, they do not shut off by pressure.

reply 2. classic symptom of a bad computer

is this a posebelity?

Think about it...Fuel pump,running, no start. Fuel pump deals with what........fuel. If the fuel pump is running, it should be pumping fuel, the computer commands the fuel pump to run, its running. If it constantly runs, its not pumping anything. Do a fuel pressure test........much cheaper than replacing the pcm, then finding out the fuel line on the fuel pump was leaking.

 

[CaFordDude]

I don't know the answer but if I am lookin for one.

I am gonna have to go with the man with the "ase master tech--fmc master tech" after his name.

 

[F 150Cobra]

ok.. i will.. and i Do get a fuel smell while its priming for a while..

 

[bowtiehatr]

try a new fuel pump relay. the relays can hang up even with no power there for them to switch. also you may want to take the shell off and look inside. i have seen several instances where ants get inside relays and cause them to malfunction. if ants are the cause, try a new pcm relay as well because they are probably there as well.

if you have a fuel smell, i would look for a leak somewhere. leaks can cause low fuel pressure which can lead to running issues.

 

[F 150Cobra]

ok im going to chek pressure , leaks and relays for ants. or something this weekend ( i have testweek this week ) i will letyou guys know when im finished cheking.

 

[Bob Ayers]

When you say your fuel pump continues to run, is this with the key in the "run" position? If you are cranking your engine "start" position, then
it's normal for the fuel pump to continue to run. When you turn the key to
the "run" position, the pump should run for a few seconds, and then shut off.
It shuts off from a timer circuit in the PCM, NOT ON FUEL PRESSURE!!
A bad PCM or fuel pump relay will cause the pump to run continuously with the key in the "run" position.

 

[F 150Cobra]

ok here i get this message again about

a bad PCM so now who is right?

i dont mind cheking them both but it would save me alot less time to only do one

 

[blackhat620]

ok here i get this message again about

a bad PCM so now who is right?

i dont mind cheking them both but it would save me alot less time to only do one

Start with the easiest thing for you to test and work your way to the end of the list until you find the cause.

 

[Bob Ayers]

ok here i get this message again about

a bad PCM so now who is right?

i dont mind cheking them both but it would save me alot less time to only do one

Check the voltage across the fuel pump relay coil. If the voltage is 0V, then the relay is bad. If the voltage is 11V or higher, the PCM is bad.

 

[blacksnapon]

Don't make things more complicated than they need to be. From the very first no start diagnostic to now, the procedure hasn't changed. If its getting fuel, if its getting spark, if its in time, it should start. Step one: IS IT GETTING FUEL?

 

[F 150Cobra]

Check the voltage across the fuel pump relay coil. If the voltage is 0V, then the relay is bad. If the voltage is 11V or higher, the PCM is bad.

how to do this? where to set the V meter? on the relay itself? while its running or on run ?

 

[F 150Cobra]

Don't make things more complicated than they need to be. From the very first no start diagnostic to now, the procedure hasn't changed. If its getting fuel, if its getting spark, if its in time, it should start. Step one: IS IT GETTING FUEL?

but it does start just takes to long to prime like 1 or 2 minutes and will only start after it primes..

 

[bowtiehatr]

if you are saying the fuel system takes a while to prime, them you are looking at a pump or pumps. does it only do it on one take or both?

lets do this....
you get in the truck and try to crank it. what happens?
if you switch the truck on. what happens?
if you shut the truck off. what happens?

 

[F 150Cobra]

i dont know the rear thank hasnt work since foreever

1. if i do it instantly just get in and crank it wont start..
2. the fuel pump primes for a while like 45 secs to 1 minute or longer when it clicks ( stops priming i can start the truck just fine )
3.shuts off normal

i will begin by changing the relay becuase if it turns over just fine and runs fine after it starts the pump is ok i guess

 

[Bob Ayers]

Don't make things more complicated than they need to be. From the very first no start diagnostic to now, the procedure hasn't changed. If its getting fuel, if its getting spark, if its in time, it should start. Step one: IS IT GETTING FUEL?

The one voltage measurement will determine if it is the PCM, or fuel pump relay causing the fuel pump to continuously run. Can you suggest a more simple procedure for determining what is at fault?

Your voltmeter needs to be set on DC VOLTS mode, and either AUTO range, or a range high enough for about 12V. The measurement should be made with the ignition switch in the "RUN" mode.

 

[Bob Ayers]

try a new fuel pump relay. the relays can hang up even with no power there for them to switch. also you may want to take the shell off and look inside. i have seen several instances where ants get inside relays and cause them to malfunction. if ants are the cause, try a new pcm relay as well because they are probably there as well.

if you have a fuel smell, i would look for a leak somewhere. leaks can cause low fuel pressure which can lead to running issues.

I just checked, and the fuel pump relay is fed from UN-SWITCHED 12V. If the relay contacts were fused closed, then the fuel pump would continue to run even with the ignition switch in the "OFF" position.....

 

[F 150Cobra]

thank you allot.. i will get a new relay tomorrow thanks..