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Fuel pump woes

seibertjd

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I have been searching for a solution to this for quite a while, and I am still kinda stumped...

One day, I was driving (only made it to the end of the block) and I lost fuel. I swapped relays, verified I had fuel in the tank, and went to go try to start it back up. The fuel pump didn't prime when I turned the key. I pulled it back to the house and checked all my fuses, and tested my inertia switch. Still no luck.

I cut a hole in the floor and put in a new pump/strainer/float assembly, got it all installed, plugged in, etc. Went to go turn the key, and the pump still doesn't prime. It cranks nice and fast, healthy spark, but that doesn't get me anywhere if the pump doesn't kick on...

What should I be looking for here? Brand new pump, relay/inertia switch are good, no bad fuses... but still no luck?
 



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MrShorty

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Starting in the "middle" of the circuit -- how did you test the inertia switch? continuity only? Was there 12 V at the inertia switch with the relay closed?

A systematic approach to this circuit would suggest that you start at the battery and test convenient locations along the circuit until the voltage drops significantly below 12 V. The problem will be the point where the voltage drops.

Do you have a wiring diagram? Even the one in Chilton's is pretty good for the fuel pump circuit.
 






seibertjd

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I have a Chilton's... and the way I tested the inertia switch isn't exactly the 'right' way... I unplugged the connector and just put a jumper wire in it to bypass the switch, just to see if that was my problem. I don't have a multimeter at the moment, but am considering purchasing one when I get paid next. Is this an uncommon problem? I have visually inspected the wiring and didn't see anything out of the ordinary, but what else could go wrong in kicking the fuel pump on?
 






MrShorty

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Is this an uncommon problem? I have visually inspected the wiring and didn't see anything out of the ordinary, but what else could go wrong in kicking the fuel pump on?
I don't have statistics to prove it, but gut feel is that the fuel pump relay is probably the most common cause of fuel pump circuit problems, followed closely by problems with the PCM power circuit/EEC relay (the PCM is responsible for telling the fuel pump relay to close, so when the PCM doesn't have power, the fuel pump doesn't get power). It should only take a few minutes with a voltmeter to verify that the fuel pump relay is closing or not.
 






seibertjd

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Not really asking for statistics, just want an opinion from someone more experienced in Fords. I will pick up a multimeter when I get paid and start doing some nitty gritty wiring diagnostics. I was hoping to avoid that, but I guess it is my only option at this point unless I want to drag it to a shop (which I don't). I will throw out an update by the 22nd or so if no one else posts back... thanks for your help.
 






prince402

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I'm on my first full day of maybe solving my full pump cutting off problem. I'm just back from an early morning round trip of about 45 miles (about 35 miles on I-95 at 65 mph) and so far so good.

I think that my recent finding and acting upon it may have solved it; there are two (not one) relays regarding the fuel pump : 1. fuel pump relay (naturally!) and 2. eec relay (my recent finding). Previously I changed only the fuel pump relay.

Try replacing them both with genuine Ford (not aftermarket) relays. Not wanting to go to the dealership (stealership?), I went to my local, favorite salvage yard and salvaged from the latest model Ford, Mercury, or Lincoln that I could find there.. The part numbers matched. I got eight nice (clean, bright white bottoms) for $5 from 1999 models. I would have preferred later models but.... Also some other car makes also use this popular, common relay. You can sometimes find the other makes on parts sites. If you get good ones it beats $25 each at the dealer, but of course even at the dealer price, if it solves the problem, it's worth it!

I always burnish the contact spades with with a #2 pencil. The clay used for hardening the lead does the polishing and the graphite deposit is a terrific conductor that also transfers to the female spade connector part. The graphite is also a great lubricant that makes the relays slide in and out nicely. The goal is an optimum electrical contact. I had to use my channel-lock pliers to remove the 1999 relays and this is evidence of some surface corrosion.

Another way to condition the terminals is to apply a gaphite lubricant (LockEase) with a small artist paint brush.

In the past few weeks my fuel pump cut out at high speed on I-95, after fueling at the gas stations along I-95 after hours of high speed driving and upon trying to leave the I-95 Rest Areas after a restroom stop. It would also cut out during local driving in the parking lot after going into Walgreens for about ten minutes.

I'm keeping my fingers crossed. Currently I have too much anxiety worrying about it cutting off in traffic and it took all the courage I could muster to take this morning's trip on I-95. So now it is one trip at a time and time will tell. It's scary sitting in that left breakdown lane on the Interstate!
 






Robex94

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I'm curious if that has still proved to be the solution? I have had the exact same problem and I went about replacing the fuel pump, filter, and relay all to no avail. The inertia switch has power and all, I am stumped. It's a great car otherwise and I am anxious to get back in the driver's seat.
 






Anime

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Mine turned out to be the ECU. The capacitors leak after their expected life of 10-15 years, corrode the motherboard, and make for a flaky connection on the traces.

You can get a new ECU for ~$100 (or try to get a used one for use in the meantime). Sad thing is it's an easy fix to replace the caps, all of a few bucks and time to remove the old ones and solder in new ones.

If the fuel pump doesn't prime, even though the relays and pump are known to be good, it's likely the ECU. Mine had the strange symptom of cranking at wamer temps, but not cranking if it was cold.
 






prince402

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:)Follow-Up on my Mar 6 post above and Happy to report::)
Regarding my post above on 6 Mar 12 on the first day of my replacing the two relays (fuel pump and eec).

In the week and a half since that post my EB EX is still running fine without the starting problem. :) A neighbor was complaining to me about her 93 EX having starting problems. I gave here two Ford relays for her fuel pump and eec. She told me yesterday that her problem is solved too.

I had a the problem of sometimes not starting on my previous Ford product, a 93 Mercury Cougar. It was the ECU (PCM). So I can give thumbs up on those who posted here citing the ECU (PCM).
 






Anime

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Replacing the fuel pump relay and EEC relay worked for me the first few times it happened years ago. But as the age and mileage creep on, eventually those capacitors leak and it will be the ECM.

My suggestion is to pull the ECM now, before it's ruined, and have those capacitors replaced. It's a lot easier to just do it without having to clean up a corrosion mess. There's a good chance there is still some corrosion though, just not enough yet to inhibit it from functioning.

http://www.explorerforum.com/forums/showthread.php?t=189504
 






Robex94

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Ok, great! One last question, I plan on just going ahead and replacing the pcm and the relays just to be sure and because it is relatively cheap, but I have been told by a couple people that if I replace the pcm I would have to get it programmed. Is this true or not? I don't particularly want to pay to have it programmed at a shop. Thanks for everyone's help so far!
 






prince402

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My EX is still starting and running good with the two new relays, but I just wanted to add, in support of this discussion, that the PCM in my Mercury Cougar V6 died at 17 years (1993 to 2010). I was just thinking yesterday that my ECM may be on the brink and now I know it is time to look it over. Thanks for the info.
 






Anime

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You don't need to get anything reprogrammed if you just have the capacitors replaced on your original ECU.

Reprogramming is what they do at companies that refurb used ECU's, they change the program on the less sellable ECUs to that of the ones that are in highest demand. This is why when you buy a refurb, they usually have the wrong factory code stickers on them (if it's not just painted over), but the program should be correct.

I don't like refurbs though, I bought one just to get back on the road while I fix the original, and not all of the capacitors on the refurb were replaced.
 






prince402

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I just checked my Haynes manual for the exact location of the ECU which I guess Haynes calls the PCM (powertrain control module) and it does not give the exact location in the 1st gen Ex's. Where, exactly, is it? I want to get it out and check the capacitors.

I've already removed and repaired the Cruise Control Module by removing the glove box drawer and looking up above it. Now I need to know how to find the ECU (PCM?) to do the same thing as suggested in this thread.
 






MrShorty

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On the 1st gen Explorers, the PCM is behind the kick panel, in front of the passenger door, below the glove box.
 






rlcmec2

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94 Explorer / intermittant "wont start"

Not really asking for statistics, just want an opinion from someone more experienced in Fords. I will pick up a multimeter when I get paid and start doing some nitty gritty wiring diagnostics. I was hoping to avoid that, but I guess it is my only option at this point unless I want to drag it to a shop (which I don't). I will throw out an update by the 22nd or so if no one else posts back... thanks for your help.

My 94 has one of the mystery problems of not starting when it cranks fine. Mine is related to the fuel pump not turning on. Through these Explorer blogs I hope we can sneak up on the problem and find out all of the various causes, (that Ford is already aware of) which contributes to which make of car I replace the FORD with. Helpful ??? the only almost certainty is when I apply a little more voltage it fires right up. AS soon as a jump or a charger is placed on the car the fuel pump comes right on. The new battery worked for a few short weeks. No ground to the system has been detected. No known drain on the battery. Come back the next day,"VROOM".... (?) sometimes it fires right up, like this morning after hiking back to the car.
 






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