Intermittent Start Problem

Tiny
CARHELP2
  • MEMBER
  • 2001 MERCURY SABLE
  • 3.0L
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 20,000 MILES
LS model with a 3.0 Duratec Engine.
Intermittent start problem no codes generated and no other drivability problems

So Far I:
• Checked inertia switch (in trunk) with meter.
• Supplied twelve volts power to down-stream side of inertia switch – fuel pump runs.
• Replaced fuel filter
• Replaced power control module (PCM) relay.
• Replaced Fuel Pump Relay

When car starts – turning ignition key just before start position – fuel pump runs (can be heard running) – car starts.

When car will not start – turning ignition key just before start position – fuel pump does not run (can not be heard running) – car does not start.

When car will not start – switching the ignition key on/off several times (removing the key from the ignition switch each time) will eventually get the fuel pump to run – and the car will start.

I believe this problem is either a bad fuel pump or power control module (PCM).

How can I determine which component is faulty and causing the problem?

If you feel it may be a different problem – please let me know what it might be.

Thank You.

John Lipps
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Friday, February 3rd, 2017 AT 9:52 AM

4 Replies

Tiny
HMAC300
  • EXPERT
Check fuel pressure with a gauge may be to low, auto parts rent it. See link. pump is probably weak.
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
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Friday, February 3rd, 2017 AT 12:16 PM
Tiny
CARHELP2
  • MEMBER
I will rent the guage to check pressure. Is it common for a failing fuel pump to be intermittent at start up and also have insufficient pressure output?
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Friday, February 3rd, 2017 AT 2:44 PM
Tiny
CARHELP2
  • MEMBER
Checked fuel pressure: 48 to 50 PSI
Pressure while car is running and with ignition key just before start position is 48-50 psi.
When switching the ignition key on/off several times fuel pump can be heard running prior to car starting when pump is heard. Car starts runs fine and fuel pressure reads 50 psi. When pump isn't heard car starts runs a few seconds and stalls, fuel pressure reads 0 psi. Switching ignition key on/off several times until pump is heard again pressure reads 50 psi car then starts runs fine.

I read a common problem with this sable and Ford Taurus is pinched fuel pump wires (on top of fuel tank) and or corroded fuel pump ground wire.

Which fuel pump relay pins are (positive twelve plus) power and (negative) going to the fuel pump so I can check for power to pump and voltage drop.
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Monday, February 6th, 2017 AT 12:42 PM
Tiny
HMAC300
  • EXPERT
See picture for power and ground. Also, check relay for corrosion on prongs if any clean it and use dielectric grease on them for better contact.
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Monday, February 6th, 2017 AT 3:23 PM

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