Intermittent and numerous starting problems

[jman101]

I have a 99 Explorer (v6 SOHC) that's having intermittent starting problems. It will always crank but sometimes (i'd say 50/50 chance) not start. I think it may be the fuel pump since i'll turn the key and sometimes hear the pump prime and the car will fire up. Other times I won't hear the pump prime and the car won't start. I've replaced the relay and the fuel pump reset switch but it hasn't fixed anything. Should I look into getting a new pump? I've also noticed that a couple times when I've started the car it takes a minute for the radio to turn on like it's not getting any power immediately so i'm wondering if I might have an electrical problem somewhere?

Also, last couple days I've gone to start my car and it'll start and then immediately die, once I get the fuel pump running and car started I have to hold the throttle for a bit before it'll hold idle on it's own. Not sure how it's related to the previous problems though.

 

[imp]

When it DOES start, will it keep running satisfactorily to be driven, then the no-start happens again later?

If something like that, I would start to suspect an intermittent connection in the wiring to the pump. This would most likely be at one of the connectors, but I did hear of one where the wires feeding back to the fuel tank had worn through rubbing on a sharp part, causing intermittent power to the pump.

I would run a length of wire temporarily from a convenient place, best would be the pump relay terminal which feeds the pump, back to the wiring at the tank, thereby simply paralleling the factory wire in the harness. If that gets rid of the intermittent problem, put the new wire in permanently. Just a thought. imp

 

[2000StreetRod]

possibly bad fuel pump

The fuel pump should run for a couple seconds each time the ignition is switched from off to on and continuously when the starter motor is cranking the engine. If you have the original pump in your 1999 then there's a good possibility that your pump is going bad. Your vehicle has a returnless fuel system and the pressure should be about 60 psi for all engine conditions. I suggest that you measure the pressure. You might increase the chance of the engine starting by cycling the key from off to on a few times before cranking the starter. If that helps then that increases the probability that your pump is failing.

 

[imp]

The fuel pump should run for a couple seconds each time the ignition is switched from off to on and continuously when the starter motor is cranking the engine. If you have the original pump in your 1999 then there's a good possibility that your pump is going bad. Your vehicle has a returnless fuel system and the pressure should be about 60 psi for all engine conditions. I suggest that you measure the pressure. You might increase the chance of the engine starting by cycling the key from off to on a few times before cranking the starter. If that helps then that increases the probability that your pump is failing.

Agreed and understood! However, have you seen pumps which would run acceptably one minute, and fail to start running the next, if no electrical problem existed? I have not. imp

 

[koda2000]

Agreed and understood! However, have you seen pumps which would run acceptably one minute, and fail to start running the next, if no electrical problem existed? I have not. imp

fuel pumps will absolutely behave in this manner. as said, you should hear it prime each time the key is turned to ON. my money is on a worn out pump. I replaced 2 in two 2000's last month. I've had them work intermittently for 6-9 months, usually failing during the winter, and I've also had them fail without warning. change your pump.

 

[2000StreetRod]

internal electrical problem

I agree there is probably an electrical problem but it may be internal to the pump. The older conventional fuel pumps incorporate brushes that utilize coil springs to maintain electrical contact with the rotating armature. The springs soften with age and the brushes wear (shorten) with use. The result is a less reliable contact that inhibits current flow. More current is required to start the motor rotating than to keep it rotating. That's why a fuel pump is less likely to start than to stop while running. Some newer design fuel pumps use brushless motors increasing their reliability.

 

[imp]

I agree there is probably an electrical problem but it may be internal to the pump. The older conventional fuel pumps incorporate brushes that utilize coil springs to maintain electrical contact with the rotating armature. The springs soften with age and the brushes wear (shorten) with use. The result is a less reliable contact that inhibits current flow. More current is required to start the motor rotating than to keep it rotating. That's why a fuel pump is less likely to start than to stop while running. Some newer design fuel pumps use brushless motors increasing their reliability.

I expect that going to the returnless fuel system has resulted in much longer pump life. In the old system, the pump ran at full speed, full output volume all the time. Now, it pumps only as much fuel as the engine is using, regardless of engine speed or load. imp

 

[drdoom]

I am fairly certain the pump in my 97 was failing, and I can tell you that not knowing when or where I would be stranded was a horrible feeling. Hearing a satisfying whine every time I hit the key is a great feeling. Totally worth the sixty bucks. YMMV

 

[2000StreetRod]

only since 2004

I expect that going to the returnless fuel system has resulted in much longer pump life. In the old system, the pump ran at full speed, full output volume all the time. Now, it pumps only as much fuel as the engine is using, regardless of engine speed or load. imp

For the returnless fuel systems from 1999 thru 2003 the fuel pump still runs at full speed. The fuel pressure regulator is part of the intank fuel pump assembly. When the pressure exceeds the regulator setting the excess is bypassed back into the tank. On your 2004 and later models the rail mounted fuel pressure sensor allows the PCM to control the pump speed to maintain the desired rail pressure.

 

[Runnin'OnEmpty]

I agree Jman's problem is most likely a bad fuel pump.
I chased the same symptoms last winter with an 04
Ranger, which was indeed the pump. After cutting the
pump open, I found the brushes had worn valleys in the
commutator which gave a poor electrical contact.

This truck had only 60K miles on the odometer. That's why
it was so hard to believe the pump was worn out. I think
Motorcraft installed a batch of bad brushes in these pumps
around 2004. Since then I have heard of several
pumps failing at relatively low mileage...

 

[imp]

For the returnless fuel systems from 1999 thru 2003 the fuel pump still runs at full speed. The fuel pressure regulator is part of the intank fuel pump assembly. When the pressure exceeds the regulator setting the excess is bypassed back into the tank. On your 2004 and later models the rail mounted fuel pressure sensor allows the PCM to control the pump speed to maintain the desired rail pressure.

Thank you for revealing this. I have a 2004, and do know the pump speed is regulated, but thought from reading very early reviews of the idea of returnless, that ALL of them functioned thusly. imp