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Author
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Topic: Fuel pump power source?
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Stimson
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Member # 51
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posted
 
 
Anyone know where the fuel pump gets its power from? I'm purely guessing somewhere around the ignition/steering wheel area, but would like to know for sure. I'm trying to trace a faulty connection... so far I believe it is upstream of the fuel pump relay.
Posts: 2373 | Registered: Jun 2000
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93PONY
Mr. Valve Events
Member # 60
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posted
How about the relay under the drivers seat? Connectivity from there to the inertia switch?
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www.advancedenginedevelopment.com
SCT dealer
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(916)715-7569
Posts: 4265 | From: Fair Oaks, CA | Registered: Nov 2000
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Stimson
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Member # 51
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posted
I believe my problem is where the relay gets its power from to send to the fuel pump.
I thought the inertia switch was placed in series right before the fuel pump, thus being downstream from the relay? I'm pretty sure my problem is upstread from the relay, but its intermittant and hard to trace ![[Mad]](mad.gif)
Posts: 2373 | Registered: Jun 2000
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JohnB
Tech Moderator
Member # 969
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posted
It all goes through your ignition switch. I had a similiar problem a while back with a 91 LX....sometimes you'd hear the pump, other times it wouldn't work. I fought that thing for months...nothing like driving somewhere and coming back out to a dead car. I, of course, did everything in reverse...changed the pump, then the relay, then shot the wiring... ![[Roll Eyes]](rolleyes.gif) Turned out the connections in the switch were corroded.
The newer Chilton's manual has a pretty good diagram on this.
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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JoeT
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Member # 298
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posted
did you get hit in the rear? there's a reset switch in the trunk.
Posts: 6785 | From: San Jose | Registered: Jun 2001
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Stimson
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Member # 51
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posted
Thanks JohnB, I'm an electrical engineering major with a fair amount of hands on experience so I quickly figured out chances are the problem is upstream of the pump. How did you fix this... new ignition switch from Ford? God knows how many times my ignition switch has been turned in the past 15 years/230,000 miles ![[Eek!]](eek.gif)
Also- how new do you mean when you talk about the new chiltons... 2-3 years new?
Posts: 2373 | Registered: Jun 2000
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JohnB
Tech Moderator
Member # 969
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posted
Ya, I changed the ignition switch out with one directly from the dealer. Seems the ones they sell over the counter at Kragen, etc have aluminum contacts, the factory ones are brass.
While you've got it all apart...might I suggest changing out the mechanical linkage in your lock mechanism (has the gear on it that meshes with your key tumbler). I tore my column apart in my Cobra last week the change the ignition switch (one of the mounting ears was cracked)...only to have that part fail...and tear it all apart again. Part is like $11 from the dealer...and makes the tumbler/key tumbler turn ALOT smoother.
The Chiltons is a 1999 print, it's one of the "larger" books....with the old ones being around a 5x7 size. The schematics in those really sucked.
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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Stimson
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Member # 51
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posted
My key turns just fine, but I'll keep that in mind. So from the dealer, a new switch and two new ignition keys is only $11??? I'm surprised something on my car rusted...even though it has a lot of miles on it, everything has a nice film of oil on it preventing rust and corrosion ![[Big Grin]](biggrin.gif)
ps-when your switch was bad and the fuel pump didn't start, did wiggling the ignition key help at all? Wiggling the key doesn't do anything for me... it seems to be 100% random. If anything, it is sensative to big temprature changes.
Posts: 2373 | Registered: Jun 2000
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JohnB
Tech Moderator
Member # 969
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posted
The $11 was for the mechanical linkage part. The linkage will work just fine until a tooth or two breaks off the gear (happened to me!)
The ignition switch was somewhere around $25. Wiggling the key did nothing for me either, as the key portion is just a mechanical tumbler...there are no electrical contacts in the key.
What's happening is you are losing the "key on" power from your ignition switch, in turn, shutting off the fuel pump relay under the drivers seat (if it's a 5 liter car, 4cyl's don't have this).
The only difference between the problem you're having and the one I had was that mine went all at once.
One quick check you could do is pop the steering column cover off and see if you can wiggle the ignition switch (the electrical part). If it is loose in the case, that's most likely the cause.
Outside of the ignition switch or the relay being bad, it's wiring.. ![[Frown]](frown.gif)
The inertia switch is strictly pump related, it works just like a trunk-mounted battery cut-off switch does..cuts the power right at the pump.
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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Stimson
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Member # 51
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posted
Thanks for the info. I'll probably install a new ignition switch this weekend and see if my problem goes away. The sad thing is, this gremlin only shows itself once every three months, so it'll be a long time before I know it is fixed. Replacing the relay is the first thing I did. I have a 255lph pump in there which probably draws twice the current as the stock pump... mix that in with a high milage switch and its easy to see why it would fail. One last thing... the fuel pump relay was the only thing that didn't turn on, right? Every other electrical item in the car worked, correct?
Posts: 2373 | Registered: Jun 2000
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JohnB
Tech Moderator
Member # 969
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posted
Yup, fuel pump relay was the only thing that wasn't working, all other electrical items worked fine. I wouldn't worry too much about the pump causing any problems, as long as it's not poppin' fuses.
With the problem so intermittent, hopefully that's your fix! Would almost be better for it to completely fail, at least you'd have a hard fix. If you need any schematics (from the newer Chilton's) let me know. I could fax them to you or bring them to the meet on the 17th (I'm gonna try to make my first meet). Good luck!
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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Stimson
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Member # 51
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posted
Thanks a lot for your help John. It turns out my Chiltons is the newer one so I do have the schematic. I'm having a intermitten sputter above 3K RPM at times which I think may be related to this same dead pump/relay problem. I'll pick up a new switch this week and install it over the weekend. I remember years ago there was a recall on these ignition switches so it wouldn't hurt to replace it.
I think you'll like the meet. Many people incorrectly assume the atmoshpere of the meets will be similar to the childish stuff that goes on in the General Talk forum when in actuallity the real car guys on the site are in Tech, Road Racing, Drag Racing and Ford Sale. The car guys show up to the meets, cruises, races, ect, while the kids stay home double clicking away online ![[patriot]](graemlins/patriot.gif)
-Sawson
Posts: 2373 | Registered: Jun 2000
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JohnB
Tech Moderator
Member # 969
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posted
No problem Sawson, hope all works out. You're correct, there was a recall about 4 years ago for the cheaply made ignition switches. Ford electronics and wiring...gotta love it.
As for the meet, I've been trying my best to get out to one, but work hasn't been cooperating...hopefully next weekend will work out great for me. With a lil luck, my Cobra will at least be in primer/guidecoat and I'll be able to bring it. If not, I suppose the Lightning will have to do..
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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JohnB
Tech Moderator
Member # 969
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posted
Sawson- check your mail...I made a troubleshooting chart for the fuel pump system...if you've got somewhere here to post it for the rest of the members, be my guest!
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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Stimson
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Member # 51
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posted
Sonofabitch When it rains it pours!
Tonight, there was another big temprature change... warm in the afternoon, freezing at night.... guess what? Even with the new ignition switch installed..... damn fuel pump relay didn't kick on!!!!!! I'm starting to think my problem is EEC related.
Can anyone confirm this..... power goes to the EEC when the ignition is put in the ON position. In turn the EEC provides power to the fuel pump relay to turn the fuel pump on. On the flip side... anyone know where the coil to the fuel pump relay is grounded to? My relay is new as well.
Once this is done, I have to figure out why I have a mis/hesitation every other second in my power band at 3/4 to full throttle. New cap, rotor, plug wires, plugs, MAF, alternator and I forget what else hasn't change the problem, all though the car revs a tad bit smoother now thanks to the tuneup.
Posts: 2373 | Registered: Jun 2000
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