Has anyone experienced a problem with the engine dieing and not restarting unless you swap the fuel relay with another?
The engine gets spark but no gas. The problem seamed like the relay was overheating and most times the relay was hot to the touch until recently. Replacement did not cure the problem. The next logical step would be to replace the fuel filter. If anyone knows where its located and what if any special tools are required that would be helpful. If anyone has experienced and cured this seamingly random fuel intruption problem, the help would be greatly appreciated.

 

Look to see if the connectors in the socket are in place. Relay has diagram on it. One relay contact pin should have 12V on it all the time. Use a wire and jumper it over to the other contact to run the pump. Key doesn't have to be on. Sequence is fusew, relay, inertia switch, tank connector, pump.

 

Thanks for the reply. Not too sure what you are getting at here ... but your suggestion is appreciated.

Any thoughts are welcome.

 

My interpretation of Opera House's comment: Make sure the connections at the relay are good. When it fails, you can ground the relay to see if that gets the fuel pump working, which can indicate on which side (circuit) of the relay the fault lies.

While you're at it, make sure there isn't some other loose connection in the wiring to the fuel pump.

 

Relays get warm because they normally dissipate about 5-7 watts of power. Won't heat your house but it should feel warm to the touch. Remember the relay is on all the time the engine runs. If the vehicle won't start, it won't get warm.

When you first turn the key on, the relay turns on for about 5 seconds then shuts off until the engine starts. This makes it hard to diagnose what is happening.

The computer shorts one side of the relay coil to ground. The other side of the coil goes to the switched 12V power.

Thr relay coil operates a switch inside the relay package. A box figure on the relay indicates the coil. The other two pins of the relay are the switched contact. If you jumper those two pins, the pump should operate if the key is on or not.

If this doesn't make it run, you keep going down the circuit till you find a bad connection where the voltage stops.

Switching the relay has a chance of making it work. It sounds like you have switched it a few times. Are you sure you have switched the correct relay? If this doesn't make sense it is time for a mechanic.

 

Thanks for clarifying, Opera House Works. Thanks to mrshorty, as well. This makes more sense. I was hoping this Forum would give me some ideas for troubleshooting this problem. This is a great vehicle other than this periodic failure.

I have had 4 different mechanics/shops look at the problem over the course of a year with no resolution. It even died on a dealer's lot but they could not diagnose the cause. I understand how tough it is to find an intermittent problem.

The truck dies a couple of times a week and then is fine for a few months, but it is becoming more frequent. After it dies, it always starts back up after letting it sit for 5 minutes. Weather conditions (hot, cold, dry, rain) do not seem to impact the problem. The amount of time the car has been running does not seem to impact it either ... drove it round trip from St. Louis, MO to New York without a problem.

When switching the relays, I always put them back the way the were. They are more than warm after the truck has been running. In fact, the heater blower relay has become discolored (brownish around one prong) from, what I guess is, heat. The mechanic said it wasn't a problem.

Again, I appreciate everyone that replies and offers assistance. You have been more helpful than any of the 4 shops that have looked into this problem.

 

Those relay pins are definitely a problem. Even though it is a heater relay, it indicates to me that you hare having a problem with the relay block. Many of the power wires are jumpered in this block and a connection at a different relay can cause a problem. When these pins overheat, the spring contact force of the connector decreases. This causes even more heating. This starts off often because of corrosion because of airborne salt. I would check the fuse for the pump first for any signs. The pump is actually fairly low current, 5A. You may have a wiring problem which is shutting off more than the pump. It is obvious that this mechanic doesn't understand electrical.

 

Through the month of December, my Explorer has died only twice. Both times I used your suggestion to unplug the relay and use a wire jumper it over to the other contact. Each time, the fuel pump kicks on. Plug the relay back in and I'm back on the road.

If the wire jumper always engages the fuel pump, it seems the relays are bad. Would you agree with that?

I purchased new relays about two years ago when the problem started. I am wondering if there is another electrical problem that causes the relays to over heat or just go bad.

Again, thanks for taking the time to reply to this topic. This forum is great!

All thoughts and comments are welcome.

 

We have to be concerned with theories when there isn't evidence to match. If there is heating on the pins then there is a problem with the connection in the socket. The relay armature contacts only wear and heat up when a connection is made or broken. Highest current is when the pump first starts. Normal pump current is about 5A. At instantanious startup this would probably go to about 15A. This relay should be rated at 30A. A 10A relay would have a shorter life. Most pump relay failures are from welded contacts that keep the motor running. I get the feeling that if you plugged the same relay back in again that it would probably work. That would lead me to suspect socket contact problems. This relay is turned on by the 12V power from the ECM relay and the other side of the coil goes to the ECM which switches it to ground. If the socket is bad it may be easier to wire in an external relay, example fog light relay, on the fender and splice in to the socket wires.

 

Probably the fuel pump. I've put 5 or 6 fuel pumps in my 92 Explorer. I drive the truck for work in a large terriorty.Have to get gas every day. The fuel pump is cooled and lubricated by the gas. They tell me not to run the tank down past a quarter full. Right

 

Hello!

I have this exact problem with my 1995 Explorer 4.0:

Observations:

Each time this happens the engine has recently been warmed up or is at operating temp.

Each time, I jump out and put in a spare relay, try to start it, if it does not start I switch the relay around again, and repeat until it starts. Then it is fine for who knows how long.

Last night is happened again after the car sat for only 2 hours (sometimes this happens when I just turn off the car at the filling station). Anyway, I swapped relays around as usual about three times with no luck and then took the "bad" relay and swapped it with my PCM relay (so the PCM relay had the bad fuel pump relay and the fuel pump was using the PCM relay). It fired up immediately and has started three time since with no problem.

I read somewhere that the three relays in that box are all identical so I figured "what the heck".

ALSO: when it WON'T start I do NOT hear the fuel pump when I turn the key. When it WILL start I hear it do it's little motor thing. Thus, I can now tell before I try ignition if it's going to start.

NOTE: Letting the car sit for anywhere from 20 minutes to 8 hours still seems to remedy the no start problem without changing any relays.

I am out of ideas. Please email me at rrd@redriverdgn.com if anyone has any suggestions.

Opera House Works: are you suggesting (above) that the block needs to be replaced as the contacts are wearing out? Your theory makes the most sense but I have seen no consistency in when this happens...the engine having been run is the only consistent event I can see. Also, to jumper/bypass the relay, which two legs of the relay are you referring to? My relay has no diagram on it.

Also, since the relay's legs are not making contact, could I try thickening their mass with a dot or two of solder? If I tinned them they may go in a little harder but keep contact...just a thought.

 

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 sockets that are in opposite directions to each other. The socket accepts the common male1/4" 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. Generally, thickening of the pin is not a good idea. Nothing has been said so far that indicates this relay or contacts are the source of the problem. I would like to see some supportive evidence before we discuss this any further. This should set an engine code.

 

ScoutTheDog ... a few questions, since we are experiencing what seems to be the same problem.

- How long has the condition existed?
- Has it become more frequent?
- Has the engine ever quit when you were driving, or does the vehicle just not start intermittently?

 

Redeye,

Here is the info:

1) We bought the car used in April, 2003 with 110,000 miles on it
2) This started with us in August
3) It has been VERY random
4) It is not more or less frequent...goes in spurts...three weeks with nothing wrong and then a solid week with three occurances
5) The car has never stopped while driving or while the engine is running...this ONLY happens when we go to start it.
6) The car now has 133,000 on it
7) I have used several different relays in this position. All work or fail at the same rate. One is (still) the original, one is new the other is used.

Thanks brother! I thought it was only me but am glad to hear I am not alone (but not glad for you that you are experiencing this too).

-Dean

 

Hi,

I came to these forums in hopes of finding a solution to this very problem. First time was a hot day, I drove my 94 a couple of miles, parked for about 10 min. and could not get it to start. When the towtruck got there about an hour later, it started right up. The last time it happened I drove to work, and it would not start 4 hours later at lunch, it was 40 degrees out. It started later when it was time to go home.

I am not sure I hear the fuel pump noise talked about here, but on the times when it does try to kick over it just bearly runs (as if not firing on all cylinders, or starved for gas).

I talked to a guy who said he had the same problem. The dealer replaced the computer...but it had been only a few weeks, so he could not tell if it was fixed. Mine has gone months with no problem, then no start until it sits for 30 min or an hour. Seems very random to me.