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'94 Explorer won't start...

irrig8r

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'94 XLT
You know I Googled " '94 Explorer won't start " and a lot of websites came up.

There were a few links that took me to this site.

I'm hoping for some advice from someone with more mechanical experience than I have.

I posted the following in a reply to another thread in another section of this forum yesterday. I probably should have started another thread here.


Thanks for any helpful suggestions.

Hi. I'm a Newbie here.

Got my '94 Explorer (112K miles) back from the mechanic about 3 weeks ago, and it only acted up twice more before today. The problem is recurring, intermittent and driving me and my mechanic nuts.

I've been stranded a few times, sometimes just temporarily, where it will start again after sitting a while. Other time have had it towed.

Looked at the inertial cutoff switch (an AAA driver showed it to me once.) Seemed to be OK, not tripped. Haven't tested it with my mulimeter yet and wondering how.

Both times before today removing and re-installing the fuel pump relay "fixed" it, just as has sometimes worked in the past.

First replacement was from Kragen's. Bought two more from the Ford dealer and installed one and have a spare.

Can I use my multimeter to test the relay? Any idea what kind of resistance readings I should get or should I just be checking continuity?

Fuel pump was replaced a couple of months ago and seemed to fix it... but only temporarily. Returned the vehicle to the mechanic where he said his assistant cleaned all the electrical contacts in the fuses and relays, then kept it for a few days and started it several times.

I do not hear the whine of the fuel pump priming when I turn the key (as I do in my '91 Sonoma P/U).

I was thinking maybe a loose wire connection under the fuses/ relays box...or between the relay and ignition switch, or the relay and the pump...?​

Thanks,
Gregg
 


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Anime

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Try replacing the ECU relay in the fuse box in addition to the fuel pump relay. Sometimes that does it.

Could also be a bad fuel pump but those don't usually just stop working.

It's also possible your ECU is damaged. The capacitors on the ECU board go bad over time and eventually leak, which damages the connections on the ECU board and often breaks the connections which deal with starting the engine. You can get refurb replacements at auto parts stores.
 




MrShorty

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Can I use my multimeter to test the relay? Any idea what kind of resistance readings I should get or should I just be checking continuity?
You can, I'm not sure what the "best" way is to test. A relay is basically a switch. When I do it, I tend to test for voltage (or maybe voltage drop across the switch) to see if the switch is closing when commanded or not. If the relay is not closing when commanded (by the PCM or grounding the fuel pump test lead in the self-test connector), then you can further inspect to see why the relay is not closing. If the relay does close, then you can move further down the circuit to see if there is a break elsewhere in the circuit.
 




irrig8r

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Try replacing the ECU relay in the fuse box in addition to the fuel pump relay. Sometimes that does it.

Could also be a bad fuel pump but those don't usually just stop working.

It's also possible your ECU is damaged. The capacitors on the ECU board go bad over time and eventually leak, which damages the connections on the ECU board and often breaks the connections which deal with starting the engine. You can get refurb replacements at auto parts stores.

Google took me here:
http://autocomputerexchange.net/1994-ford-explorer.html

Haven't entered a VIN number yet, jus trying to get an idea of costs. My mechanic said it's an expensive "throw at".

Lots of things have been replaced already, some related to this some probably not. (There's also a pinging under load that I was trying to get rid of.)

-Fuel pump relay replaced and switched with other relays out of desperation a few times. Worked like magic half a dozen times.
-Spark plugs and wires were replaced.
-There was either a cam sensor or crank sensor replaced... can't remember which he called it.
-Temp sensor was replaced.
-Fuel pump was replaced.
-MAP air sensor was cleaned
-Various electrical contacts were cleaned

No CEL while driving anymore... that was intermittent but I think had to do with the pinging that is mostly gone.

A former mechanic said something about how the '94 Explorer was a "transition year" and that he needed to separate devices working in tandem to read the computer codes.
 




irrig8r

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You can, I'm not sure what the "best" way is to test. A relay is basically a switch. When I do it, I tend to test for voltage (or maybe voltage drop across the switch) to see if the switch is closing when commanded or not. If the relay is not closing when commanded (by the PCM or grounding the fuel pump test lead in the self-test connector), then you can further inspect to see why the relay is not closing. If the relay does close, then you can move further down the circuit to see if there is a break elsewhere in the circuit.

I know my way around a multimeter troubleshooting AC low voltage circuits mostly. Resistance, continuity, volts and amp readings are all important in trouibleshooting and repairing irrigation and LV lighting systems, which is how I earn my bread.

However, I am a total novice working on vehicle electrical issues. I've replaced batteries, headlights, etc. on my own, but I've never been schooled in the rest. Sounds like it's similar though, looking for breaks or "opens"...
 




MrShorty

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I'm not real familiar with AC electricity, but it always seemed to me that the theory behind DC electricity and understanding DC circuits was simpler than AC. The fuel pump circuit is a fairly simple DC circuit (the only "complication" is that the switch is a relay controlled by another DC circuit).
 




Anime

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Haven't entered a VIN number yet, jus trying to get an idea of costs. My mechanic said it's an expensive "throw at".

A former mechanic said something about how the '94 Explorer was a "transition year" and that he needed to separate devices working in tandem to read the computer codes.

It's about $100 as a "throw at" for a refurb ECU, but it is the last resort when it won't start and you've replaced everything else it could possibly be. A cheaper way to test would be to try to get one from the junkyard or get one from someone parting out on here for a lot less. Just be sure to get one with the same part number (ex. F47F-12A645-YB) and 4-digit ECM code (ex. ANY1).

Usually the ECM cause manifests itself as a fuel pump that won't shut off when the key is turned, preventing starting, but it does occasionally just give nothing. Switching out the fuel pump and ECU relays worked like a charm for me a few times, but when the fuel pump wouldn't shut off no matter what, that was it, the ECU was damaged badly enough nothing else would do it.

The late '92- early '93 was the transition year for a lot of stuff. By '94 all Explorers had EGR, R134a for A/C, and everything else.


Did you already replace the starter? When the brushes wear down it won't start and just gives a 'click'. Fix is a new brush assembly for $20, or a new starter for $100+. You can tell if it's the starter by giving the starter a whack or two, then trying to start it. If it starts, it's because the brushes are worn and whacking it freed them up to make just enough contact.

Could also be the fender or starter mounted solenoid, or even the basic cause of a bad battery, corroded battery cables, stuff like that.

The switching relays fixing the problem leads me to believe it's the ECU though.
 




irrig8r

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It's about $100 as a "throw at" for a refurb ECU, but it is the last resort when it won't start and you've replaced everything else it could possibly be. A cheaper way to test would be to try to get one from the junkyard or get one from someone parting out on here for a lot less. Just be sure to get one with the same part number (ex. F47F-12A645-YB) and 4-digit ECM code (ex. ANY1).

Usually the ECM cause manifests itself as a fuel pump that won't shut off when the key is turned, preventing starting, but it does occasionally just give nothing. Switching out the fuel pump and ECU relays worked like a charm for me a few times, but when the fuel pump wouldn't shut off no matter what, that was it, the ECU was damaged badly enough nothing else would do it.

The late '92- early '93 was the transition year for a lot of stuff. By '94 all Explorers had EGR, R134a for A/C, and everything else.


Did you already replace the starter? When the brushes wear down it won't start and just gives a 'click'. Fix is a new brush assembly for $20, or a new starter for $100+. You can tell if it's the starter by giving the starter a whack or two, then trying to start it. If it starts, it's because the brushes are worn and whacking it freed them up to make just enough contact.

Could also be the fender or starter mounted solenoid, or even the basic cause of a bad battery, corroded battery cables, stuff like that.

The switching relays fixing the problem leads me to believe it's the ECU though.

When the problem occurs, and it is intermittent, the engine turns over but acts like it's starved for fuel. I don't the think the starter is involved.

Battery was seven years old and was replaced 5 months ago. Battery cables are fine.

I started with the fuel pump relay, then the fuel filter and finally the fuel pump. Then about three months ago the problem came back. The mechanic dropped tested the fuel pump pressure and found it low. He dropped the tank ( said it looked pretty clean too) and changed out the fuel pump. He showed me the old one and how they work.

I never did change the ECU relay. Worth a shot? Still have a spare new one if it's the same relay as the fuel pump, heater, ABS, etc.

So, reading through the forums, it seems like this is a really common problem. Does anyone know if Ford ever issued any service bulletins regarding it? Or does it happen so long after the cars were sold that they just don't give a damn?

How about this? Anyone tried it?
http://www.explorerforum.com/forums/showpost.php?p=2933079&postcount=4
 








Anime

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When the problem occurs, and it is intermittent, the engine turns over but acts like it's starved for fuel. I don't the think the starter is involved.

I started with the fuel pump relay, then the fuel filter and finally the fuel pump. Then about three months ago the problem came back. The mechanic dropped tested the fuel pump pressure and found it low. He dropped the tank ( said it looked pretty clean too) and changed out the fuel pump. He showed me the old one and how they work.

Maybe the Fuel Pressure Regulator? Those do go bad or even just get weak, and like a few other things once replaced, a new one puts performance back to like new.

I never did change the ECU relay. Worth a shot? Still have a spare new one if it's the same relay as the fuel pump, heater, ABS, etc.

You should definitely try it. But just bear in mind, even if that fixes it, it might just be a symptom of the larger cause. The ECU going bad seems to cause the relay problems, it's not the other way around.

So, reading through the forums, it seems like this is a really common problem. Does anyone know if Ford ever issued any service bulletins regarding it? Or does it happen so long after the cars were sold that they just don't give a damn?

There are common problems with Explorers, but they happen well after the age and mileage most people no longer keep their vehicles, so it would be pretty unreasonable to blame Ford. If anything, it's great the stuff lasts as long as it does and that there aren't bigger problems.


Yeah, that's how I went about it after the fuel pump stayed on and let me know it was the ECU. There was obvious leakage from all 3 capactors on the board, and right on the traces of the CPU and critical components. Really the BEST thing to do is pull the ECU ASAP and just replace the caps BEFORE they leak, which will give it another 10-15 years or more if the replacement caps are high quality and the same 105 degree temp rating for automotive use.

I've got a refurb ECU on there in the meantime, but I plan to get the caps and repair the original ECU as well. The refurb is ok but it doesn't offer as smooth of performance or as good of mileage as the original ECU did.
 




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