I have a 03 Expy that has been intermittently shutting down, sometimes it restarts right away, sometime it doesn't. The fuel pump is fairly new and it has a new fuel filter. I am being told that it is the fuel pump relay that is part of the PCM, and that it is unserviceable and I must replace the entire module. I believe it is the R303 relay in question, but not sure.

My question is where should I be testing for voltage and amperage to determine if the relay is working or not? I have a good meter (Fluke87) just need to know what to connect to in some detail.

Thanks

Joel

 

The fuel pump relay is integral to the CJB and is not an individually serviceable component. You either have to replaced the complete CJB or you'll have to McGyver it with an external relay should the relay be defective.

You can check its output at the inertia switch (DK GN/YE wire).

Personally, I'd replace the PCM Power Relay as an inexpensive first step. While I rarely advocate "throwing parts" at a problem, I do make exceptions for intermittent problems that are otherwise difficult to trace down.

 

projectSHO89--

Thanks for your response. My situation has changed a bit. Now it is dead and wont restart, so at least its not intermittent

I took out relay 203 (PCM) and exchanged it with another one already in the panel. I checked them closely before I did this and they appear to be the same #, etc. This did not hep my problem, so if I am understanding you correctly this probably rules out the PCM Power relay. ??

I have checked to be sure the inertia switch is not tripped but have not gone any further yet. Next step is to get to the inertia switch and check for power there. If this isn't the problem I guess I am looking at Relay 303? Any tips on the McGiver approach? I am somewhat technical, have access to lots of "stuff" and have access to an eletrician/electronics guy to help me out if necessary. Thankfully there is Dairy Queen and he has a fondness for Blizzards!!!

Thanks

Joel

 

Now that it's dead, it will be easier to diagnose.

Does the PATS system prove out at key-on? No use wasting time elsewhere if the security system has disabled the engine.

Does the fuel pump run for 1-3 seconds at key-on? Listed at the fuel filler opening with the cap off. If the fuel pup runs, do you have adequate fuel pressure at the rail? Use a fuel pressure gauge to measure.

Do you have a "No Crank" or a "Crank but does not start" condition?

Make your voltage check as I prescribed. You should see that wire go hot during the initial pump priming time.

 

OK--that was fun

PATS system is good--flashes every 2 seconds in off--turns on for about 3 seconds when turned to run/start. then goes out while cranking. I think thats how its supposed to be?

I have a crank but no start condiditon. Do not hear the pump running.

Finally dug deep enough to get to the inertia switch. (that was the fun part) It is functioning properly--have continuity, shake it a bit, lose continuity, then reset it and it works.

Do not have voltage at the DK GN/YE wire when the key is cycled. Is this supposed to have voltage anytime the key is on, or just when fuel pressure in the rail is down? I do not have a fuel pressure tester, so I am unable to test that at this time.

 

UPDATE!!!!!

I finally got it! Ended up pulling the fuse box (central juction box) and decided to disect it. Found relay 303 melted and smoked.

Now just to figure out if I am smart enough to cross rference the relay and solder in a new one or bite the bullet and buy a whole new fuse box.

 

You can probably splice in a generic relay that piggybacks the bad R303. That's what is sometimes done when the trailer running lamp relay goes out in the SD trucks.

 

I have been doing some looking for a replacemetn relay that I can put in place---what I dont know is the wiring layout, control voltage, etc to make sue I dont get the wrong one.

Any suggestions for the "right" one??

Thanks

 

I was told my fuel pump relay switch needs to be replaced as I am experiencing the same issues, it will intermittenlty shut off while driving, sometimes start right a way or takes about 10-15 minutes to start back up. Was this easy to fix or replace.

 

I was told my fuel pump relay switch needs to be replaced as I am experiencing the same issues, it will intermittenlty shut off while driving, sometimes start right a way or takes about 10-15 minutes to start back up. Was this easy to fix or replace.

 

I was told that my fuel-pump control module need to be replaced but then found that the alarm system (smart key) went dead in my 2000 Ford F150 and would not let my fuel pump turn on. After switching to my second key I have never had the problem again.

 

I get low voltage to the inertia switch with key on. I notice that it has 12 volts initially then drops down. Is this normal? I suspect a bad fuel pump but want to verify before I drop the tank.

 

If you turn the ignition key to "ON" and don't crank the engine the fuel pump only recieves power for about two seconds.

 

Yes that seems to be the case. I am checking it at the output on the CJB. According to a schematic I found the only thing between this and the pump is the inertia switch.
Frankly I was hoping it would be the fusebox as I am not looking forward to dropping the tank.

 

Update:
Was able to confirm no voltage to the inertia switch. Swapped pump and running again. Thanks for the help.