Need Help - Intermittent Fuel Pump at Start Up. '99 SOHC

[KC]

Greetings and Happy Holidays to All! Here is my problem - My '99 4.0 SOHC AWD EB X is having some intermittent problems starting. Seems like it's not necessarily temperature sensative, as it happened during the summer months as well. But always only when starting. The initial symptom was that it would start, but not idle. Once it would start to idle it would run for days without problems. The problem would only happen randomly every few weeks. Recently, however it began not starting at all - it would crank over just fine but no sputters or anything. A no-spark or no fuel situation, for sure. Of course this would only happen to my wife and by the time I could get to her it would usually start right up. So we traded cars and since I've been driving it the problem has expressed itself several times. Same thing. Cranks but no fire. I realized that whenever it would not start I would not hear the hum of the fuel pump. Cycling the key from off to on anywhere from 3 to maybe 10 times would usually get the pump running. As soon as I hear the hum of the pump it will start right up without problems then run without problems.

After searching the forum I have cleaned the IAC valve (not too dirty) and inspected the MAF sensor. Still no help (I really only did the IAC because of the previous idle problem and didn't expect it would help any with the fuel pump running or not!) and the problem was becoming more and more frequent, like every other day. I have checked the fuel pump relay for clean connections, checked the fuses for the FP, ECU and PCM(?) after looking at wiring diagrams and I checked the inertia switch. I crawled under and took a look at the harness connector back by the fuel tank, although I did not actually take it apart and look. At one point I noticed the engine was cranking somewhat sluggishly during an episode of not starting. It was an older battery, so I hooked up my charger to it and as soon as I tried it after connecting the charger the fuel pump hummed and it started right up. I thought maybe there was a voltage sensor within the ECU that might prevent the pump from running if it sensed battery voltage was too low, so I replaced the battery. Since replacing the battery over two weeks ago I hadn't had a problem until yesterday afternoon when I went to start the X during my luch break. No hum, no start. Turn key off/on times 3 and it hummed. Cranked it and it started right up again, and of course it has been fine since.

BTW - during all of this I have never seen the Check Engine Light even flicker. (It does illuminate at key-on-engine-off...)

Can anyone give me some ideas here? What, if any sensor/ecu conditions might intermittently cause a fuel pump to not start running when you turn the key? If not something like that, what else should I look at? I know from past experience that fuel pumps generally either work or they don't, although they may go intermitent once or twice before givnig up altogether but I really don't think it would behave like this if it was going south (although I guess anything is possible!).

Thanks in advance!!

 

[CDW6212R]

Two things, first be sure that the PATS is not disabling the FP. Watch the "THEFT" light each time you turn the ignition on. That light must not flash, if it does, the engine will not start. The key code is verified every time the ignition is turned on. My 98 truck used to randomly not start, and the theft light was always flashing when that happened.

Last, check the fuel pressure, you need 62psi at least, all of the time. I had only 50-55psi in my 99 truck, it took me five months to get around to checking that. My issue wasn;t starting though, the power and mileage were just down. Good luck,

 

[KC]

Thanks Don, I wasn't aware that the keys were encoded that way on the '99 and that is something I haven't looked for, so thanks for that info.

On that note, there is one other thing going that's been going on for awhile now - the left turn signal lights come on when you press the brakes. The turn signal light works normally by itself, but it also comes on (front & rear) with the brake lights. This all started when the fuse blew for that circuit, so obviously something shorted. I have removed the affected lights one-by-one to try to isolate a bad socket or whatever as well as changed the flasher relay to no avail. It has been suggested to replace the multi-function switch, which I have not done, but I wonder if the two issues are related???

I don't think it would be a pressure prob since when it doesn't start, there is no "hum-O-the-pump", and when it does start you can hear the pump run for a moment in the key on/engine off position.

Thanks, and please keep the ideas coming!

 

[CDW6212R]

BTW, when my 98 Mountaineer did have that issue, the pump didn't always make noise, but most of the time it did. Most of the time, when the "THEFT" light flashed, the pump would turn on for about 1/2 of a second. That time period was about 1/3 of normal, I could tell by listening to it if the engine would start. It took me many weeks to learn about the theft light and the PATS system. Knowing about the theft light made it much easier to start, I just turned on the key while watching the light. By listening you have to have complete silence to hear the pump well. Good luck,

 

[Lloyd10977]

Thanks Don, I wasn't aware that the keys were encoded that way on the '99 and that is something I haven't looked for, so thanks for that info.

On that note, there is one other thing going that's been going on for awhile now - the left turn signal lights come on when you press the brakes. The turn signal light works normally by itself, but it also comes on (front & rear) with the brake lights. This all started when the fuse blew for that circuit, so obviously something shorted. I have removed the affected lights one-by-one to try to isolate a bad socket or whatever as well as changed the flasher relay to no avail. It has been suggested to replace the multi-function switch, which I have not done, but I wonder if the two issues are related???

I don't think it would be a pressure prob since when it doesn't start, there is no "hum-O-the-pump", and when it does start you can hear the pump run for a moment in the key on/engine off position.

Thanks, and please keep the ideas coming!

Despite all your work, it still sounds EXACTLY like a problem I had that was eventually resolved when I replaced the fuel pump relay with a new one. I too checked for a bad connection at the relay, but once I replaced the relay, all my problems disappeared. What gave me the hint was that I switched the relay with the one for the A/C.

 

[CDW6212R]

Swapping the relays is easy, and easier is watching the dash "THEFT" light. Rule things out one at a time.

It is also possible to have a loose connector on any of the relays, underneath. Start with the easy stuff. The turn signals sound like either a wire has come completely loose(unlikely), or somehow a couple of wires have been crushed together. Swapping out those electrical components is easier, but of course they cost money. Regards,

 

[KC]

Good Info! Thanks! Still haven't had the problem show itself again, though...

 

[KC]

OK, so this morning it acted up again. I looked at the "Theft" light on the dash and it went solid red as soon as I turned the key to the ON position. But I did not hear the fuel pump. Lo and behold, no start. I turned the key off/on a couple of times and I thought I heard it run momentarily so I tried starting - the engine started just briefly, then stopped again. Turn key and no pump noise. Tried it like 8 times with no luck, then thinking of the "key-reading" issue I pulled the key out, re-insert, turn it on and I heard the pump run. The engine started and ran fine all the way to work... The entire time I never saw the Theft light blink as long as the key was inserted.

 

[Lloyd10977]

OK, so this morning it acted up again. I looked at the "Theft" light on the dash and it went solid red as soon as I turned the key to the ON position. But I did not hear the fuel pump. Lo and behold, no start. I turned the key off/on a couple of times and I thought I heard it run momentarily so I tried starting - the engine started just briefly, then stopped again. Turn key and no pump noise. Tried it like 8 times with no luck, then thinking of the "key-reading" issue I pulled the key out, re-insert, turn it on and I heard the pump run. The engine started and ran fine all the way to work... The entire time I never saw the Theft light blink as long as the key was inserted.

Another thing to try which would pinpoint the problem area, instead of fiddling with the key and attempting to restart a dozen times is:

If no start, pop the hood and tap the fuel pump relay with a screwdriver. It will almost always start. Bottom line is REPLACE THAT RELAY!

 

[Turdle]

To answer you earlier question-yes. when the key is switched on the check engine light should come on-this tells you rthe PCM has powered up-
If the pcm has no power (PCM relay and fuses) the fuel pump circuit will not be switched on.
I had a loose connector to my PCM relay causing this type of intermittent problem.
http://www.explorerforum.com/forums/showthread.php?t=180814&highlight=power+layout

 

[CDW6212R]

Good, progress, now check the inertia switch connector. Go in the passenger floor board and disconnect it. Look at it carefully when you start, imagine if something has bumped it, where it is at the feet, that connector or the wires get damaged sometimes. Connect it back securely.

You could swap the fuel pump relay with another next to it. Do pull out the relay and see if the contacts down in the connector looked equally as high. Jon is right, it is possible for those terminal contacts to become unlocked and push out. That is very hard to locate if you aren't looking for it. Good luck,

 

[KC]

Well I don't think it's the relay - It acted up again this morning and I went out and swapped the relays. Since I was kinda late leaving for work I didn't get a chance to inspect the terminals inside the relay block... After the swap, it still would not run the pump. Unfortunately I forgot to look at the THEFT light or the CEL light on the dash D'OH!!! AS usual, the pump finally started after about 8 or 10 twists of the key. Tonight I will dig into the intertia switch and make sure nothing is goofed up there as well as inspect the relay terminals.

Can someone tell me the location of the PCM module? I want to check those connections as well. That's not the box above the rear wheel well is it?

 

[CDW6212R]

The PCM is in the firewall, outside above the engine. Hopefully you are going to find a problem with some wiring or connector.

 

[KC]

Even more weirdness this morning... Last night after a trip to the store, the computer display was reading 16.1 mpg average. This morning after I got it started it was reading 12.1 and dropping! Nobody ran it after I got home (that I know of, anyway?) and none of the other settings were changed, such as gallons used, miles driven or oil life. By the time I got to work it had worked it's way up to 14.5. I don't think I inadvertently pushed and held the reset button...????

 

[CDW6212R]

That's hard to guess about. If the PCM is running it in open loop, the fuel would be richer than ideal.

 

[KC]

Basically it was reading 16 something when I turned it off, and 12 something when I started it again - there wasn't any time for the mileag to drop like that!

 

[KC]

Still having the problem - can anyone tell me where I can access the wires (and the color coding) inside the car that feed power to the fuel pump? I'm thinking of connecting a "test lamp" to those wires so that I can tell if power is being sent to the pump. That will tell me at least which half of the system is causing the trouble...

 

[CDW6212R]

When I had my PATS issues, I was best able to test the pump circuit at the PDB(power distribution box). I used a jumper wire and made the fuel pump run at the fuel pump relay. That is how I eliminated the inertia switch and relay, plus wiring, from my search. Be careful with any terminals inside any connectors, they are fragile. The number 30 is the load side of a rely, it's a large 1/4" terminal, centered and across from a perpendicular terminal. The relays have a diagram on the side of them. Good luck,

 

[KC]

When I had my PATS issues, I was best able to test the pump circuit at the PDB(power distribution box). I used a jumper wire and made the fuel pump run at the fuel pump relay. That is how I eliminated the inertia switch and relay, plus wiring, from my search. Be careful with any terminals inside any connectors, they are fragile. The number 30 is the load side of a rely, it's a large 1/4" terminal, centered and across from a perpendicular terminal. The relays have a diagram on the side of them. Good luck,

Thanks for the help! So your saying that by using a jumper wire in place of the relay I will be bypassing the inertia switch and wiring? I was thinking that the relay fed the fuel pump through the inertia switch... Does the signal from the PCM(?) pass through the inertia switch to the relay then?
Unfortunately (or msybe not) it has been working flawlessly again now for a couple of weeks....

 

[CDW6212R]

The inertia switch is between the relay and the pump I believe. I never could find a problem with my inertia switch. That's where everyone told me to hunt for an issue. Really that's easy to check, the only issue there can be is a break in the wiring. Evidently some people have had the wiring or connector there kicked, damaged by foot. So inspect it carefully, once you know it isn't damaged in the area, forget about that.

Bypassing the fuel pump relay was helpful to troubleshoot, I never drove the car or ran it that way. I was able to check the fuel pump functioning by standing there at the PDB and jumping the circuit. Checking the circuit is hard to do when it only comes on for a second or so.

My PATS issue was like that, very rarely did it malfunction. I have not fixed anything, it simply didn't accept my key on very rare occasions. I carried two keys for a while, I think that the PATS is reliable. My case was/is rare, but others may have faulty key receivers.

If you have a problem again, and you get into the PDB, pull the FPR and first inspect the terminals in the PDB. Use a small screwdriver or pick etc, and very gently press down on the terminals in the relay connector. What you want to do is confirm that the terminals stay up in place, and not push down or deflect down. There are only very tiny plastic clips holding them in. They will either stay up, or deflect easily. If they don't move, they are great, and check them off the list of potential problems.