I've read several threads that seem to be similar to my problem. The latest of which seems to be:https://www.ford-trucks.com/forums/register.php?a=act&u=186388&i=99732710

My Explorer runs fine for extended periods of time and then just won't start. When it doesn't start, the fuel pump relay "clicks" but the fuel pump doesn't pump up when the key is turned on. It seems to be worse in warmer weather. I have read the threads relating to the IAC replacement. There have been a few(very few) occaisions when actual loss of power has occured during driving, but mostly the problem happens as a won't start after trouble free operation. It would seem that the fuel pump is OK...but I don't know. Two different dealerships and a couple of mechanics can't find anything wrong due to the fact it hasn't been malfunctioning when I have managed to get it to the repair facilities. Arrgh!!! I am ready to just "try" something...like tell them to replace either the fuel pump, or IAC, whichever is the most likely to fix it....unless somebody else has a better suggestion??? Please help!!!

Thank you in advance for your response to my desparate plea!!!

 

Sounds to me like you are possibly having a problem with either the wiring to the fuel pump,or the pump itself may be going bad,when you first turn the key on the fuel pump is supposed to come on for a few seconds to pressurize the fuel rail,if indeed you are hearing the relay click,then I would try having somebody get in the truck while you listen at the tank,have them turn the key to on,they dont have to start it,just turn it to on,if you dont hear the pump kick on,bang on the tank,sometimes this vibrates the tank enough to jar the pump,if the pump does kick on,then you know it is either the connections on the sending unit or the pump itself,although this doesn`t always work,sometimes it does and helps save time by not having to check all the connections and circuits to the pump.The reason you need two people is that the system is designed to only come on long enough to pressurize the fuel rail then the fuel pump will shut back off until the computer sees a crank signal,once the computer sees that the engine is turning over it the tells the pump to come back on.

BTW>Welcome to FTE

 

Thanks for the welcome. I can tell when the pump kicks on. And all connections are good....I'm pretty sure. The pump "usually" comes on as it's supposed to and pressurizes the fuel rail then shuts off prior to starting most times. When in the "no start" mode, the pump will not go through that sequence. And none of the mechanics have been able to diagnose the problem....as I stated. So back to my original question. If I were to just try to guess at fixing it by replacing something by chance...I know, I know, not the best approach but looks like my only option at this point, what would you recommend? Or what diagnostic procedure to really find and fix the problem???

Many thanks!

 

The first thing I would replace would be the relay,I have had them test out just fine and then went back and had them fail,but I hate to tell you to just start swapping things,seems to me,the way you state that it trys to die while driving it,could be monitored with a fuel pressure guage on a road test,that and having a scanner hooked up while trying to duplicate the problem,was this a Ford shop?The reason I ask is Ford scanners have a record feature that can record the vital info when this is occuring,granted it might not say what the problem is,but will verify important stats such as fuel trim,o2 readings.

 

Yes, two different Ford shops have tried to diagnose it. But as stated, it wasn't acting up at the time. Thanx for the pointers....still think the relays are likely to be working though...but what do I know? Would think more likely to be either a sensor, or the fuel pump...still just a guess on my part. The AIC (IAC?) also sounds like a possible culprit...geez, so many possibilities. It really needs to be properly diagnosed!! Oh well.

What or how many systems or sensors have the ability to keep the fuel pump from going through the initial pressure ramp-up when the key is turned on, assuming the relay is operational? Just grasping at straws, I guess..

 

sometimes and i mean sometimes a problem can be solved with milage and previous repairs. how many miles on the truck and have you ever replaced the fuel pump, if you got over 100,000 miles lets say and have never replaced the fuel pump. maybe it wouldn't hurt. or do the simple things first relays, inertia switch, fuses, blah blah blah.

most times its the most exspensive way to do it, but you eventually get it fixed.

oh and other questions to ask yourself is how often have you changed the fuel filter and what grade of gas you use

just some ideas to throw out there.

when my pump went all it took was loading the truck up with guys to go golfing and going up a big hill it studdered and shuddered. I said thats the pump and changed it out and problem solved

 

Your IAC is Idle Air Control valve,and no it has nothing to do with initial rail priming

 

Thank you guys for all this very helpful input. The truck is an weary old workhorse with ahem, 175,000 miles. Pretty well maintained and primarily "highway" miles. No major repairs to speak of. One owner prior to me and I haven't owned it very long. I agree on the fuel pump thing....usually it either works or it doesn't. But they can have a faulty diaphragm or pump mechanism that will give lower than needed pressures..but that doesn't seem to be the problem here. Oh well. I will try some of your suggestions and let you know what I find out. Again I really do appreciate your interest in helping me out. Thank you very much!!

 

does it always start when cold then wont restart after running a while?? if this is the case it most likely has nothing at all to do with your fuel system...its more likely a faulty ignition part....

 

No, I wish it were as simple as that. And besides, the issue of the fuel pump not initiating after the key is turned on when I have the no start problem wouldn't be explained by an ignition problem, would it? The two Ford shops said my ignition system was OK. I would tend to take their word on that before taking their word on any other of their diagnostic abilities. Incidentally, I tried switching around or changing out the relays for the fuel pump...they all appear to be the same part...ie., EEC, ABS, Air Bags, etc., and that didn't work either. I'm thinking perhaps I may just try to put in an aftermarket, inline electric fuel pump, replace the filters, and hope for the best. I'm about at my wits end.

 

Relay Connections
All automotive relays have a schematic printed on them and the pins are numbered on the base. It may require a magnifier and optimal lighting to see them. When the relay is powered, the (87) NO or Normally Open relay contact connects with the (30) C or Common contact. Some relays do not have the center pin (87a) NC or Normally Closed contact since this has no use in many applications, Pins are designated by the state when no power is applied. The coil of the relay are pins (85) and (86). These are on the outside edge of the case and face in the same direction. Coil resistance is typically about 70 ohms.

To jumper out a relay, look for the two outside pin sockets that are in opposite directions to each other. The socket accepts the common male 1/4" spade pins used to make electrical wire connections. Female 1/4" connectors will also press onto the relay pins. This will allow you to make a four wire adaptor and extend the relay out of the distribution box for testing. Adding small indicator lamps to the pins is very helpful in diagnosing an electrical problem.

Use a 1/4 inch male wire connector to probe each socket connector. A socket may have a loose contact or may not be seated properly in the plastic. This allows the connector to be pushed out when the relay is inserted. Compare the force required to insert and remove the pin in each socket.

Check the two opposite facing fuel pump switched sockets. One will have 12V on it all the time. Check the other for resistance to ground, should be less than 5 ohms. By jumpering those two with a voltmeter in the amps position, you should get about 5A. The flow of current is battery, to fuse, to relay, to inertia switch, to tank electrical connector, to pump, and back to ground. I haven't seen that you have done any real testing. You do not really know if the relay is turning on. Something as simple as splicing a small lamp into the circuit just before the tank will tell you that voltage is getting there. I have pulled the fuel pump fuse, run wires into the cab, and put a meter on for a week to monitor current to determine fuel related problems.

 

Sounds like a really good plan to me!!! And makes sense. I thank you very much for the advice and will give it a shot. I'll let you know if I have any luck. Again, many thanks!!