Modded Mustang Forums banner

1 - 17 of 17 Posts

·
Registered
Joined
·
300 Posts
Discussion Starter #1
So a few weeks ago my fuel pump wouldnt prime. I replaced the CCRM and it fixed the problem. But last night the pump wouldnt prime and I traced it to the pump itself. Removed the pump and it was definitely bad so I replaced it. But the new one still wont prime. Im only getting 6 volts at the pump connector every now and then. I checked the connection coming from the PCM and its only 6 volts. I took off the CCRM and tested it and the relay is fine and I was getting 12 volts to the CCRM relay. Any ideas?
 

·
Billy Weston
Joined
·
5,076 Posts
In the CCRM pigtail check the voltage on the yellow wire and the dark green and yellow wire by back probing the harness with the fuel pump on. Let me know what you find.
 

·
Registered
Joined
·
300 Posts
Discussion Starter #3
That was the first thing I checked. I found the problem. In the fuel pump circuit after the power comes from the CCRM it goes to a connector by the PCM and splices. One wire goes to the PCM and the other goes to the Inertia Switch and eventually the pump. The PCM was creating resistance and bringing voltage down to 6 volts or less. So I removed the PCM from the circuit since it is not needed to run, it just gets power from the relay to see that it is working. I cut the wire and the car started. But now I have a short somewhere and keep blowing fuses, so its just gonna be an annoying little task until I have time to find the short.
 

·
Registered
Joined
·
69 Posts
Please let us know your findings on the cause of the short. I've been fighting the exact same symptoms on my 98gt for the past year and a half, and still haven't foound the cause.

I think I have a short as well, or a bad ground somewhere, just haven't found it yet, so your answers on where the short is can help the rest of us.

Thanks
 

·
Registered
Joined
·
300 Posts
Discussion Starter #5
Well Ive gone up and down the entire circuit and havent found the short. But I did check the resistance of the Fuel Level sender which I believe runs off of the same 20A fuse. Im pretty sure that the sender should show around 70-80 ohms when the tank is empty and around 10 ohms when full. I have an almost full tank and Im getting 130 ohms. So Im thinking the fuel level sender is whats blowing the fuse so Im gonna cut the wire to see if it runs tomorrow.
 

·
Registered
Joined
·
300 Posts
Discussion Starter #6
Nvm thats what its supposed to be showing. So now Im clueless
 

·
Registered
Joined
·
207 Posts
I would hook the wire back up to the PCM and see if it stops blowing the fuse...........
If you were accidentally checking the wire that the computer uses for checking fuel level then you would have only seen 6 volts. The 12v wire will only energize for a split second when the key it first turned to run, then again constantly when the engine is running or cranking. I've seen several other people make this mistake cause they are just checking wires for voltage with the key on and when the find that one they think its the problem. BUT you definitely have a problem, could be a driver in the PCM
 

·
Registered
Joined
·
300 Posts
Discussion Starter #8
Ill hook the PCM back up today. But a guy I was talking to at work said he had the same problem with his 4.6 and ended up being the Fuse block. At this point I think it could be anything in the fuel pump circuit since my pump was so bad for so long.
 

·
Registered
Joined
·
300 Posts
Discussion Starter #9 (Edited)
Fuse still blows with PCM in circuit. But my battery also goes dead overnight whenever my fuse it taken out. So I think I might have problems somewhere else too. Also my CD player wont turn on and I cant see any fuses that are blown. I think my new CCRM may have a short tho in the switch side. It would explain why my battery goes dead since the switch side is hot at all times.
 

·
Registered
Joined
·
207 Posts
That would def drain the battery, Not sure what to tell you on the fuel pump problem, wish I could take a look at it in person
 

·
Registered
Joined
·
300 Posts
Discussion Starter #11
Well my radio has no power now and I cant see any blown fuses. What does the wire in the corner of the inside fuse box go to? is it power or ground and for what. I had it off once when I was troubleshooting last week and I think I might have put it in the wrong place but Im not sure. Because my Battery keeps going dead overnight and I have the fuel pump fuse completely out. So where else should I check. I know it has to be a short somewhere before or around the fuse box but my brain is so fried from doing this for so long that I cant even think anymore.
 

·
Registered
Joined
·
207 Posts
I'll try to look at a diagram in the next day or two and give you some better advise based on that.
 

·
Registered
Joined
·
300 Posts
Discussion Starter #13
I think Ive finally got it. There was an aftermarket alarm system that I didnt know about and the ground was fried. I fixed it and the radio works now. Also I tested the ground for the pump for the 100th time and I think I found the short. I disconnected the round connector and put the positive lead on the ground wire and neg lead on a chassis ground. I got 10 ohms and it had continuity with the connector unhooked. So that should mean that it is shorted to ground correct?
 

·
Registered
Joined
·
300 Posts
Discussion Starter #14
I fixed it. Turns out one of my wires in the tank was rubbing a hose clamp and shorting it out :rolleyes: Thanks for the help tho:D
 

·
Registered
Joined
·
69 Posts
Thanks for the info, Looks like fuel pump is where I'll start maybe it'll be the same and I wont have to check the entire wiringcircuit from trunk to pcm to ccrm
 

·
Registered
Joined
·
207 Posts
Well done man, I hate aftermarket alarm systems. I've removed probably 20+ and only installed 1! My buddy was worried bout his truck getting stolen so I wired him a high amp hidden switch for the 'run' circut, if it's off nothing can get power that the truck needs to run. Made the loom look like it was never tapped too so that if someone thinks they can just bypass it they would have to know the exact wires and location or where the switch is...:D
 

·
Registered
Joined
·
1 Posts
What fuse was blowing? I have a similar problem. I traced everything and can't find one short outside of the fuel tank. So I put a 4th fuse in and the car started. I let it run till the fan kicked on to make sure it wasn't a fan relay drawing too much current and still no pop. I took it for about an hour drive. and nothing. Fuse still good. Pump working. Now I do have an issue with keeping fuel pressure either caused by the regulator or the pump going bad. I did just fill the tank before this happened as well. But this has only happened one time to 3 fuses. No problems since 2 days ago.

My fuse was the #18 fuse under the driver side dash. The ccrm fuse.
 
1 - 17 of 17 Posts
Top