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Intermittent crank no start issue

Tiny
OLLEIA56
  • MEMBER
  • 2001 FORD MUSTANG
  • 4.6L
  • V8
  • 2WD
  • MANUAL
  • 68,000 MILES
My car listed above GT model, is having an intermittent crank no start problem. (0 PSI fuel pressure) Sometimes it will start up and run fine. Here is what I checked: 12V into and out of the inertia switch, on the fuel pump driver module the white/red wire has 12V at key on, will drop to 1.6V while cranking but never come up to 12V koeo like I think it should. The next time it feels like running, I would like to scope the fuel pump waveforms to see if there are bad spots on the pump. Can you tell me what wires to hook my scope to on the fuel pump driver module? Thumping the tank does nothing. Any advice as to where to go next would be appreciated. Thank you.
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Saturday, January 23rd, 2021 AT 1:25 PM

31 Replies

Tiny
BMDOUBLE
  • MECHANIC
  • 1,139 POSTS
The brown with pink wire is the actual power to the pump wire. The white with red wire is the duty-cycle wire between the powertrain control module (PCM) and the fuel pump control module. I attached a quick test that will rule out the fuel pump module by putting direct power and ground to the pump. If you want to scope the pump all you would need to do is put an clamp on amp lead onto the fused jumper between terminals nine and ten.
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Monday, January 25th, 2021 AT 11:10 AM
Tiny
OLLEIA56
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Update: I have not been able to conduct the test you gave as the car has been starting. While running the fuel pressure went to 0 PSI it wanted to stall I blipped the gas and it ran fine.
The next time it doesn't start I will conduct your test. Would I disconnect the fpdm for the test, hook up wires then turn on key? Also I have a Kenne Bell supercharger with a Boost a Pump installed will that interfere with the test? Thank you
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Tuesday, January 26th, 2021 AT 6:34 PM
Tiny
KASEKENNY
  • MECHANIC
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Just to jump in, yes you would disconnect the module. What he has you doing is just bypassing the module by putting those wires in place.

However, if you have confirmed the pressure is going to 0 then you know the pump is not supplying pressure. Which means we can just go to the pump and monitor the voltage. If it has 12 volts then you know the module is good and the pump needs replaced. Basically you are doing the same thing by bypassing the module but I always find it easier to leave everything hooked up and just monitor the voltage.

Let us know what you find or what questions you have. Thanks
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Saturday, January 30th, 2021 AT 1:15 PM
Tiny
OLLEIA56
  • MEMBER
  • 23 POSTS
Thank you Kasekenny, was going to do the bypass test today upon disconnecting the fpdm connector, every pin had green corrosion on them, cleaned with electrical connector cleaner. Went one step further and disconnected the fuel tank connector, only to find green corrosion on every pin, cleaned and blew compressed air on every connector. Put it all back and the beast started up. Going to let it sit until tomorrow and see if she starts up. Thanks for your input, I will let you know how it goes. This has been an intermittent problem I am hoping the corrosion on the pins was causing this problem. So the wire to monitor for pump voltage is the BN/PK right on the fpdm connector? Thank you.
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Saturday, January 30th, 2021 AT 3:34 PM
Tiny
KASEKENNY
  • MECHANIC
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That is great news. The dreaded green corrosion is the worst because we don't always find it and it can cause all sorts of odd issues. I would put dielectric grease in each of those connectors as that will help keep the water out.

Yes, that is the power wire to the pump so that is what you would need to monitor but the fact that you found that, I suspect all the components are fine and that corrosion is the issue.
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Saturday, January 30th, 2021 AT 5:25 PM
Tiny
OLLEIA56
  • MEMBER
  • 23 POSTS
Thank you Kasekenny, it's a load off my mind, was hating the thought of replacing the fuel pump. I am going to put dielectric grease in those connectors as per your suggestion. I have a good mind to go over all connections and check their condition, because since that corrosion was there it might be other places. Thank you for taking time to write, I will let you know if the beast starts up tomorrow.
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Saturday, January 30th, 2021 AT 7:23 PM
Tiny
OLLEIA56
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  • 23 POSTS
Kasekenny,

Good news, car started right up this morning, going to try it throughout the day to see if it's consistent. I believe it will be!
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Sunday, January 31st, 2021 AT 7:06 AM
Tiny
OLLEIA56
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  • 23 POSTS
Kasekenny, car has been starting up all day at different times. One thing I noticed after prime pressure at 30 PSI when cranking pressure drops to 20 PSI until it starts don't know if that's normal, never really noticed if it did that all along.
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Sunday, January 31st, 2021 AT 3:49 PM
Tiny
KASEKENNY
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That is good news that it is starting however, that pressure does sound slightly low. It is normal for it to drop when you are cranking the engine as the injectors are opening and that is relieving the pressure. However, you will just need to keep an eye on it if this issue starts coming back as your minimum spec for pressure is 35 PSI. Again, not cause for alarm but I don't imagine it will get better over time.
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Monday, February 1st, 2021 AT 3:47 PM
Tiny
OLLEIA56
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  • 23 POSTS
Thank you for your input, I will keep an eye on the pressure, the car is supercharged along with a boost a pump installed, I would hate to lose pressure under boost and send my supercharger through the hood. I will not go into boost until I am satisfied things are normal. If the problem comes back would you put blame on the fuel pump or the FPDM? I plan on checking the connectors on the ccrm, crank position sensor and the fuel rail pressure sensor for corrosion. Again, thank you
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Monday, February 1st, 2021 AT 5:42 PM
Tiny
KASEKENNY
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The most likely cause would be the pump as the module should just be supplying a steady 12 volts. So if the pump is getting the proper voltage which you can check, then the pump is the issue.
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Monday, February 1st, 2021 AT 8:06 PM
Tiny
OLLEIA56
  • MEMBER
  • 23 POSTS
Thank you Kasekenny, I will keep an eye on things. For the record the fuel pressure has always been 30 PSI since I got the car just the nature of the beast I guess.
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Tuesday, February 2nd, 2021 AT 5:00 AM
Tiny
KASEKENNY
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Yep. That is fine. It is only slightly low. That could be a combination of things as it is only about 15% low which is nothing to worry about.

Thanks again. Talk to you next time.
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Tuesday, February 2nd, 2021 AT 6:41 PM
Tiny
OLLEIA56
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Thank you Kasekenny for all your help, I really appreciate it.
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Tuesday, February 2nd, 2021 AT 7:28 PM
Tiny
OLLEIA56
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Kasekenny, I am disappointed to report this morning was testing start up. The car does one of three things.

1. Will prime to 30 PSI upon cranking will go to zero PSI no start.
2. Will prime to 30 PSI and start up like normal.
3. Will not prime at all.

I want to read the voltage to the fuel pump like you suggested, what wire on the FPDM would I monitor to check for momentary voltage?
If it gets momentary 12V for prime and doesn't prime would that mean the pump is bad? Thank you
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Wednesday, February 3rd, 2021 AT 1:36 PM
Tiny
KASEKENNY
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Sorry to hear it. You are correct. If the pressure is dropping to 0 then I suspect the pump is the issue. If the module was the issue then when it primes, it would not bleed the pressure. Granted when you crank the engine the injectors are opening and the pressure will bleed off but it should fire for at least a few seconds before it sputters out if the pump was holding pressure but just not continuing to run.

However, your approach is the correct way to figure it out. You should have 12 volts on pin 10 at the module brown/pink wire. Then when you crank the engine it should bring the voltage back. The red/black wire is the return or ground for the pump so you can check that as well if you want to.
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Wednesday, February 3rd, 2021 AT 6:42 PM
Tiny
OLLEIA56
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Kasekenny, once again thank you. I am beginning to suspect the pump.
Going to check the voltages just for good measure.
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Friday, February 5th, 2021 AT 4:02 PM
Tiny
OLLEIA56
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  • 23 POSTS
Hi Kasekenny, since the car has be starting and running consistently, I would like to know if I can hook up a bench oscilloscope (not an automotive tool) just an oscilloscope I use for TV repair? I'd like to see the pump waveform if so, which wire would I hook it up to? I'd like to send you a photo of the waveform. Thanks.
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Monday, February 15th, 2021 AT 10:33 AM
Tiny
KASEKENNY
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You can hook it up but this is DC current so it will most likely be a flat line. I see any circuits that would be AC to give you an alternating wave form. So basically the scope will tell you the same thing a meter does which is what the constant voltage supplied is.
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Monday, February 15th, 2021 AT 6:28 PM
Tiny
OLLEIA56
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Kasekenny, thank you for answering. I was hoping my scope would show the waveform. Guess that's where the automotive scope comes in.
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Monday, February 15th, 2021 AT 8:07 PM

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