1998 Ford Taurus Won't always start-Engine races now &

Tiny
KIRBYMURPHY
  • MEMBER
  • 1998 FORD TAURUS
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 110,000 MILES
It started with the 30 degree weather, but maybe it's a coincidence. Hot or cold, sometimes the car won't start. Cranks fast, no battery problem.

This morning it wouldn't start. Ambient temp about 25 degrees in the garage, but it failed last week after it was warmed up and about 40 degrees.

Couldn't hear the fuel pump when I turned on the ignition. Swapped the AC clutch relay with the fuel pump relay (same Part#) and it started. Maybe another coincidence? Replaced the relay and it still starts OK.

After reading many forums, the IAC (Idle Air Control)sounds suspicious. It has an occasional problem with the engine racing, about once a month.

Other forums mentioned the Mass Air Sensor as a possibility. Would that or the IAC prevent the fuel pump from getting energized?

EDIT: Just tried to start it again and couldn't hear the fuel pump and it wouldn't start. :(
Never got a check engine light, no codes.
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Monday, January 4th, 2010 AT 1:53 PM

13 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
IF you don't hear the fuel pump again, something tells me the relay is bad and working when it wants. Try switching them again and let me know if it starts. Also, make sure the connections are clean and tight when you put the relay in place.

AS far as the IAC and the MAF, neither one would cause the fuel pump not to work. Something tells me you either have a bad relay, connection, or the pump is going bad.

Let me know about the relay.

Joe
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Monday, January 4th, 2010 AT 3:46 PM
Tiny
KIRBYMURPHY
  • MEMBER
Already swapped in the AC clutch relay as a check and there is a new relay in place.
Engine started after I temporarily replaced the relay with the AC clutch relay, so I went ahead and bought a new relay.

Looks like it is something else and the starting was a coincidence. :(

Checked the collision switch and it's reset.

I suppose it "could" be the pump, but I would expect it to work or have total failure.

I'm looking for things that would cause the relay not to energize the pump before I undertake a tank drop and pump replacement.

Thanks!

EDIT"
Looks like the pump relay + side is in series with the PCM relay, so if the PCM relay isn't closed the pump relay gets no power.
The ground side of the pump relay is connected through the PCM module.


http://www.2carpros.com/forum/automotive_pictures/458250_pump_1.jpg

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Monday, January 4th, 2010 AT 4:01 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Let me know what you find.
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Monday, January 4th, 2010 AT 6:00 PM
Tiny
KIRBYMURPHY
  • MEMBER
Yesterday I swapped in a new PCM relay in the relay/fuse box. Car started right up and I thought it was fixed.

10 degrees. It failed at the grocery store this morning.

I knew when I didn't hear the pump when I turned on the key that there was a problem, and of course it didn't start. Sat there for about 15 minutes, trying it every couple of minutes. Then I heard the pump and it fired right up.

Summary
If the pump won't run, it won't start. (Obviously)
When it does start, the pump never fails to run. Never shuts off while driving.
While I can't say for sure, I think the pump is fine based upon those observations.

Guess next I'll meter at the inertia switch and make sure there is power back to it. If there is, the pump (or wiring harness) must be bad. If not, it must be ahead of the inertia switch.

I'm leaning to the PCM or a sensor that sends a needed command to it. I wish I knew what sensor could send or not send the needed signal to the PCM. Anyone know where I can find a diagram of the wiring to the PCM and sensors? Maybe I'll unplug/plug-in the connectors on the relay box and PCM
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Wednesday, January 6th, 2010 AT 8:51 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
From what I remember, the inertia switch will also shut down the power to the ignition. Do you have spark when this happens?
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Wednesday, January 6th, 2010 AT 6:42 PM
Tiny
KIRBYMURPHY
  • MEMBER
If you look at the schematic above you can see that the "Pinto" intertia switch cuts power to the pump. It doersn't show up in the ignition circuit, and in fact has just 2 wires, one in and one out of the switch. One from the relay and one to the motor. I even jumpered it out for testing.

Problem is, it hasn't failed since yesterday morning so further testing is moot. God and bad I suppose. :()
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Thursday, January 7th, 2010 AT 8:36 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
I looked at the schematic and see what you mean. Do you still have it bypassed?
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Thursday, January 7th, 2010 AT 8:56 PM
Tiny
KIRBYMURPHY
  • MEMBER
No. But it had failed while bypassed.
2 days later, no failure, so no chance to troubleshoot.

My gut tells me it's in the relay panel assembly or another relay. When I had my wife switch the key to ON, there would be no pump sound. When I swapped the relays around again, and had her try, I heard the pump and told her to try and start it. It fired right up.

The relay panel was the only area I was moving things around and presumably the only place to have any physical movement. Maybe it spontaneously decided to work, or maybe my removing and swapping relays caused an intermittent connection to make the proper contact.

I'm going to buy another new relay so BOTH the Fuel Pump relay and the PCM relay are new. Right now the AC Clutch relay is in one of the slots.

I'd like to yank the entire relay panel and check the connections but it's 5 degrees and it looks like a lot of labor. :) Anyone ever pull the assembly?

Of course I can't rule out the PCM itself. It is an odd setup the way the PCM completes the ground for the Fuel Pump relay on the LB/O wire.

Thanks.
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Friday, January 8th, 2010 AT 8:40 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
The relay does seem to be the only thing that has made the change. And, I don't blame you for not working on it with that temp. It could be something as simple as a loose connection in the relay block.

Regardless, let me know what you find.
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Saturday, January 9th, 2010 AT 1:32 AM
Tiny
KIRBYMURPHY
  • MEMBER
No start yesterday morning.
No pump, no start.

Semi-permanently bypassed intertia switch. While the wires were apart and not connected to the pump, I only measured 6.8 volts on the DG/Y wire from the Fuel Pump relay.

The only path is through the Fuel Pumo relay, through the PCM relay and direct to the 30A fuse link. Guess I need to find that fuse link and work my way back to the pump.

The relay panel looks like a bugger to get out and apart.

The perplexing thing is that it runs fine after starting. Makes me wonder about that little diode right after the 10A fuse in the start portion of the scematic. It's the only thing not in the circuit during run condition. Maybe it's gone high resistance and won't fully pull-in the PCM relay, dropping my voltage to 6.8v.
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Saturday, January 9th, 2010 AT 11:26 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
I was wondering if you have had the chance to check things out and what you found.

Joe
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Wednesday, January 13th, 2010 AT 8:52 PM
Tiny
KIRBYMURPHY
  • MEMBER
Sorry not to update sooner.

In desperation I replaced the fuel pump and haven't missed a lick.
Must have been a bad spot on the armature or something similar.

Just a recap, on the 1998 there is the relay box next to the battery.

Fashioned a jumper out of 2 spade connectors to bypass the TWO relays that are in the circuit. Yanked them out and used the jumper to bypass the relays, one at a time or both together. Just remember the pump will possibly be running and will continue to do so.

Also bypassed the fuel inertia switch.

Didn't leave much else but the pump, but the way it started sometimes made me hesitant to tackle the pump until all else was eliminated.
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Tuesday, April 27th, 2010 AT 1:51 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
I'm glad you got it fixed. Let us know if you have questions in the future.

Thanks for using 2carpros. Com.
Joe
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Tuesday, April 27th, 2010 AT 2:05 PM

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