How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask kalamykid Your Own Question
kalamykid, Shop Owner/ Tech
Category: Ford
Satisfied Customers: 3661
Type Your Ford Question Here...
kalamykid is online now
A new question is answered every 9 seconds

I checked the fuel pump switch under the passenger side and

This answer was rated:

I checked the fuel pump switch under the passenger side and it was not tripped. Looked at the Fuel Pump Relay and one of of the pins did not have power. As soon as I replaced Fuse 24, it would blow out the new fuse. Any suggestions on moving om from this step?

What is the year make and model of your car please, and what size engine does it have?

Customer: replied 15 days ago.
98 Ford F150 with a Spi4.2L engine.

And you are blowing the 30 amp maxi fuse?

Customer: replied 15 days ago.

What fuse box is this fuse in, the one under the dash or the one under the hood?

Customer: replied 15 days ago.
The one under the hood

Can you pull the pcm power relay and see if the fuse will blow again please?

Customer: replied 15 days ago.
Can you explain where is the pmc Power relay located?

It will be the relay two relays up from the fuel pump relay, next to fuse 28 and 29.

Customer: replied 15 days ago.
removing the pmc relay did not cause the fuse to blow.

Can you move the horn relay up to the pcm relays spot and see if the fuse blows?

The horn relay is just under the pcm relay.

Customer: replied 15 days ago.
When moving the horn relay to the pcm relay, it blew the fuse out

Can you unplug the pcm and see if the fuse still bloss?

Customer: replied 15 days ago.
I'm buying more fuses. Should be able to test that here in a few minutes.

ok Do you have a digital volt meter?

Customer: replied 15 days ago.
I do not have a digital volt meter

Set your meter to ohms and lets see if the wire to the pcm has a short in it. With the pcm unplugged, and the 24 fuse out, see if you have 0.0 reading on either of the two slots for the fuse with your red lead in the sluts, and the black lead on a good ground.

Customer: replied 15 days ago.
I do not have a digital Volt meter.

I am sorry i thought you said you did. Can you pick one up when you go to get more fuses?

Customer: replied 15 days ago.
With the digital volt meter on fuse 24 and the pcm fuse out, we are not getting a reading on out meter.

Is that with the pcm unplugged?

Customer: replied 15 days ago.

Just so we are clear, the meter reads OL correct?

Customer: replied 15 days ago.
What is Ol? We bought a Pt Digital Multi-tester

ol would be open loop.

What exactly does you meter read when you have the test lead on either of the two slots for the fuse, with the fuse out and the pcm unplugged?

Customer: replied 15 days ago.
Meter can read Dcv, acv, dca, 10A, hFE, and ohm. The meter is set to reading 200 ohms but not picking up anything on slot 24 with the pcm out and the fuse out. On a working fuse, it is reading 01.0 on the meter under the same settings.

Do you have the black lead on good ground such as the engine block or battery negative post and testing with the red test lead?

Customer: replied 15 days ago.
Putting in the new fuse on slot 24 with the pcm out, the meter reads 1.0 like all the other fuses.

And the fuse did not blow?

Customer: replied 15 days ago.
No. Not with the pcm out

Then I hate to say it but the pcm in your truck has a short in it and the pcm will have to be replaced.

Customer: replied 15 days ago.
not the pcm relay correct? The whole fuse box?

No the pcm itself is bad. the relay and fuse box are ok, if the fuse did not blow with the pcm unplugged. you need to replace the pcm.

Customer: replied 15 days ago.
How would one go about replacing the pcm?

You can go to your local auto parts store and get one, or you can go to an auto salvage yard and get a used one.

Customer: replied 15 days ago.
Alright. Well we will have to do that another time then. Thank you for your help

You are very welcome.

kalamykid and 5 other Ford Specialists are ready to help you