94 4L no start
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Joined: May 2004
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94 4L no start
I've finally registered in this group after lurking for a while as I have this problem with my '94 Ranger 4x4(?) with a 4L V6 auto which I got off the show room floor almost 10 years ago and the gauge now stands at 186K mostly commute interstate. I have only had two problems in the past, -the intake manifold gasket went at 120K and the front brakes have warped twice.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>
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About a month ago, it failed to start after a 25 minute drive and I put a "Sunpro" "Scanner"(not really, just pulls out the codes to a beeper but it works). It indicated 543, open power to the fuel pump. It started about 2 minutes later so I assumed that running the scan cleared the alarm. Well, was I wrong? 10 days ago it did it again so I took it to a local garage and asked them to look at it. They came back with no trouble found!! The fuel pressure was within correct limits. Butter wouldn't melt in its mouth for about 5 days. I went out and the thing was again dead, turned over briskly but no fire. I checked the spark and saw spark both with an old timing light and a clipwire. After swearing for about 10 minutes, I got out the scanner and found good old "543" again. Only this time it didn't start after scanning it. <o:p></o:p>
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I then went to the local Library and got the wiring diagram and other info from a copy of "Mitchell’s Manuals" to try to troubleshoot the thing, along with my trusty volt-ohm meter. Several questions come to mind that you old hands at this will probably say is this guy stupid or what. I listen for the fuel pump and when I turn the key on I hear the pump operate and then shut off. So the first question is -- what tells the pump to shut off with no motor run, the computer or some back pressure switch in the pump assembly?<o:p></o:p>
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If it is the computer where does it get its signal from, a timer loop? or what? I have added wire stubs wrapped around the terminals of the fuel pump relay so I can measure both voltage and continuity there but as it hasn't failed since the last time ----? Another question-- I think I always get the 543 code Switch-on-Engine-Off after the 111 code, is this normal? I look at the fuel pump solenoid and wonder if the contacts could be singed so that some carbon or what ever occasionally prevents the thing from making contact. As it is sealed you can't see.<o:p></o:p>
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And finally the mechanic at the local garage said that there was a lead from a solenoid in the tranny that often gummed up but is a pain to change. I see nothing that I can identify as that kind of thing on the wiring diagram? Am I missing something? <o:p></o:p>
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I would appreciate any feedback you can give as I really like this truck and other than this it runs great and uses less than a pint of oil in 3K miles on the road it gets 21mpg.<o:p></o:p>
The question mark after the 4x4 above is because I have the suspicion that the front drive isn't working but am unsure how to test it.<o:p></o:p>
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About a month ago, it failed to start after a 25 minute drive and I put a "Sunpro" "Scanner"(not really, just pulls out the codes to a beeper but it works). It indicated 543, open power to the fuel pump. It started about 2 minutes later so I assumed that running the scan cleared the alarm. Well, was I wrong? 10 days ago it did it again so I took it to a local garage and asked them to look at it. They came back with no trouble found!! The fuel pressure was within correct limits. Butter wouldn't melt in its mouth for about 5 days. I went out and the thing was again dead, turned over briskly but no fire. I checked the spark and saw spark both with an old timing light and a clipwire. After swearing for about 10 minutes, I got out the scanner and found good old "543" again. Only this time it didn't start after scanning it. <o:p></o:p>
<o:p></o:p>
I then went to the local Library and got the wiring diagram and other info from a copy of "Mitchell’s Manuals" to try to troubleshoot the thing, along with my trusty volt-ohm meter. Several questions come to mind that you old hands at this will probably say is this guy stupid or what. I listen for the fuel pump and when I turn the key on I hear the pump operate and then shut off. So the first question is -- what tells the pump to shut off with no motor run, the computer or some back pressure switch in the pump assembly?<o:p></o:p>
<o:p></o:p>
If it is the computer where does it get its signal from, a timer loop? or what? I have added wire stubs wrapped around the terminals of the fuel pump relay so I can measure both voltage and continuity there but as it hasn't failed since the last time ----? Another question-- I think I always get the 543 code Switch-on-Engine-Off after the 111 code, is this normal? I look at the fuel pump solenoid and wonder if the contacts could be singed so that some carbon or what ever occasionally prevents the thing from making contact. As it is sealed you can't see.<o:p></o:p>
<o:p></o:p>
And finally the mechanic at the local garage said that there was a lead from a solenoid in the tranny that often gummed up but is a pain to change. I see nothing that I can identify as that kind of thing on the wiring diagram? Am I missing something? <o:p></o:p>
<o:p></o:p>
I would appreciate any feedback you can give as I really like this truck and other than this it runs great and uses less than a pint of oil in 3K miles on the road it gets 21mpg.<o:p></o:p>
The question mark after the 4x4 above is because I have the suspicion that the front drive isn't working but am unsure how to test it.<o:p></o:p>
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Elder User
Joined: Feb 2004
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From: Rosebud
The next time it does'nt start, try tapping on the fuel pump relay a couple of times,sometimes they stick,this is a common problem.From the front, its the second one back on the left.They are only $10.
Post Fiend
Joined: Jan 2003
Posts: 9,748
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From: Connecticut
Lurkers are always welcome to join up here at FTE, glad to have you aboard. 
Vin's tip is a good one. You can also further test the fuel pump circuit by checking for Battery voltage (greater then 10.5v) at the fuel cut-off switch (PK/BK wire) during the no-start condition. If no B+ at the cut-off switch, then it's quite possible the Relay is sticking open.
If no B+ at the cut-off switch, but the Relay checks out OK, then I think you'll have to consider some kind of intermittent open or short in the circuit between the Battery and the Relay.
And yes, it is the PCM's job to control the FP circuit, energizing it for a second or two in order to prime the system before starting. Then it shuts off power to the FP until it receives a constant signal from the crankshaft position sensor telling it that the engine is running, at which time power is restored and the pump runs until you shut off the engine (or the cut-off switch is tripped).
Vin's tip is a good one. You can also further test the fuel pump circuit by checking for Battery voltage (greater then 10.5v) at the fuel cut-off switch (PK/BK wire) during the no-start condition. If no B+ at the cut-off switch, then it's quite possible the Relay is sticking open.
If no B+ at the cut-off switch, but the Relay checks out OK, then I think you'll have to consider some kind of intermittent open or short in the circuit between the Battery and the Relay.
And yes, it is the PCM's job to control the FP circuit, energizing it for a second or two in order to prime the system before starting. Then it shuts off power to the FP until it receives a constant signal from the crankshaft position sensor telling it that the engine is running, at which time power is restored and the pump runs until you shut off the engine (or the cut-off switch is tripped).
Post Fiend
Joined: Feb 2003
Posts: 6,940
Likes: 2
From: Eastern WA
Welcome to FTE.
Good advice on the relay and FP wiring. For the 4x4 test, engage 4x on dry pavement and while driving slowly, steer slightly to the left or right. If the 4x4 is working, the truck will "buck". There is no mistaking the bucking feel. If it's not working, post your findings in a new thread; we'll get it taken care of.
Good advice on the relay and FP wiring. For the 4x4 test, engage 4x on dry pavement and while driving slowly, steer slightly to the left or right. If the 4x4 is working, the truck will "buck". There is no mistaking the bucking feel. If it's not working, post your findings in a new thread; we'll get it taken care of.
Last edited by CowboyBilly9Mile; May 25, 2004 at 12:22 PM.
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Excellent, thanks, I'll review all of the points, I didn't mention that I messed with the emergency switch (the thingy below the wiskey pocket)and didn't get any results during the longest problem interval. Thanks for the 4x4 tip too, I'll try it.
Senior User
Joined: Feb 2003
Posts: 395
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From: South Carolina
Piper - had a very similar problem with my 94 4.0. After running, it sometimes wouldn't start until after sitting for a while. Finally got to where it wouldn't start at all. No spark to the wires.
https://www.ford-trucks.com/forums/s...d.php?t=240368
You can read about it here if you like, but the short story is that I replaced two relays - EEC Power Relay and the Fuel Pump Relay, and so far so good.
https://www.ford-trucks.com/forums/s...d.php?t=240368
You can read about it here if you like, but the short story is that I replaced two relays - EEC Power Relay and the Fuel Pump Relay, and so far so good.
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I gotta feeling that your telling me --replace the fuel pump relay dummy--which I will toot sweet. This won't prove the case but??? A follow up question on the processor control of the fuel pump, it sounds like the 543 code is almost required during SOEO test???
Buy the way(sic) CowboyBilly I tried your diagnostic and I can hear a click like something is trying to engage but when I move, steering all the way from a few degrees right or left to a slow swerve, I don't feel nothin'??? like a buck and I presume you mean a lurch or something like that?
Buy the way(sic) CowboyBilly I tried your diagnostic and I can hear a click like something is trying to engage but when I move, steering all the way from a few degrees right or left to a slow swerve, I don't feel nothin'??? like a buck and I presume you mean a lurch or something like that?
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Post Fiend
Joined: Feb 2003
Posts: 6,940
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From: Eastern WA
A lurch would be another way to describe it. Assuming the 4hi light is on after you press the button, I would investigate the electric shift motor next. They are known to stick when the 4x is not used/engaged for extended periods. The common repair is to take them off and clean them well, looking for dirt accumulation. On occasion they must be replaced; if such is the case you may wish to visit a junkyard; they are rather spendy when bought from Ford. If you do a search you should find several threads on the subject. Last on the list, I would focus on the hubs. Do you have auto or manual hubs?
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The hubs are auto. Recall I said that the disks had warped twice and the same garage I mentioned above replaced them. Is it possible that a re-assembly fault could be the problem? But in any case I'll persue your suggestion, probably not today though. I got to go do some maintenance on a computer network I'm responsible for so probably will be out of commision for a day or so. Thanks for the info.