Need some diagnostic help...

[Scott Douglas]

My wife's '04 Mustang 3.8l wouldn't start for her today.
It ran fine as recently as Monday.
I checked the battery voltage first thing as it was suspect a few weeks ago when she said it wouldn't start for her then. It measured 12.3v.
When I went to start it this afternoon, it cranked just fine. It wouldn't crank for her at all this morning when she wanted to go to the store.
I pulled a plug and had her crank it while I checked for spark. It has a nice spark, nice and blue.
Will an OBD reader tell me if the fuel pump is having a problem?
I checked the fuel pump switch in the trunk and it was/is fine, ie not tripped.
I'm stumped as I'm old school (or should that be electronically challenged?), Chrysler Trouble Shooting Contest trained from high school. This new EFI stuff is great when it works but...
Any ideas from the trusted brain trust here would be appreciated.
Thanks.

[john70t]

Sounds like you used a good systematic process and narrowed it down to the pump or the fuel electronic system.

The spark plugs are firing, so the crank/cam sensor is good.(btw there is a clip-on-fake-plug tool which makes removing a plug not necessary.)

A "noid light" will show a quick check if the injectors are firing(or being told to).
There should be a shraeder valve on the fuel rail to check pressure.

There could be a bad ground connector on the electronic side.
Checking voltage at the pump might be the last step.
I'd think a weak pump would be problematic with loss of power for a while first, but it could just croak.

[john70t]

btw, saw a guy holding onto the plug technique.
Looked down, and there was a spark jumping to the bumper from his jeans!

[Scott R]

There is a fuel pump driver module in the trunk, on the drivers side. Looks like a small brick, half black and half silver colored. You have to check for power coming out of the module to the fuel pump.



These modules are prone to failure. In the occasions I've seen these fail it was after the car had been sitting for a while. It may be pure coincidence, I have no idea. I do know that a lot of the issue is the lack of relay for the module and it's not uncommon to find an aftermarket relay added in to cure the failures.

[Scott R]

wow, I have the bosch part number still on my notepad. "67170'

[Scott Douglas]

Thanks Scott!
That is the kind of help I was looking for.
I'll check it out when I get home this afternoon.
Is the module located near the switch by chance? I found it right behind the left tail light assembly, right where the owners manual said it would be.
By the way, the car has been sitting a while, other than being driven on Monday. It was probably sitting for a week or so before that and it's been super hot in our garage with the weather we've been having lately, if that makes any difference.
I'll report back with any findings.
Thanks again for the help.

[kaisen]

Originally Posted by Scott Douglas

When I went to start it this afternoon, it cranked just fine. It wouldn't crank for her at all this morning when she wanted to go to the store.

The fuel system and ignition system has nothing to with it cranking over.

If it doesn't crank, it's the starter (bad spot, solenoid), wiring (corroded, fatigued, loose/intermittent connection), or switch (physical contacts, wiring, anti-theft). It could also be an interlock that doesn't allow the starter to engage, like the gear position switch.

If you stated it incorrectly and the engine/starter is turning over (cranking) but not firing, then look at the fuel system, including Ford's fuel pump cut-off switch located on the driver's LH kickpanel.

[1990C4S]

Since you have a spark I will assume it is turning over but not starting.

I would spray some quick-start into the intake and make sure it fires, if it does you likely have a fuel problem. But it certainly sounds like you don't have fuel.

Get a cheap noid lights to check if your injectors are firing.

But to answer your question, it is unlikely OBD II will diagnose your 'no start'. The 'check engine' light turns on with the ignition (this indicates the ECU is running), and then it should turn off after a few seconds. I don;t think you can tell if you have stored fault until the car starts and runs.

This could be hard to diagnose, from you description it is intermittent?

[Scott R]

Originally Posted by kaisen

The fuel system and ignition system has nothing to with it cranking over.

If it doesn't crank, it's the starter (bad spot, solenoid), wiring (corroded, fatigued, loose/intermittent connection), or switch (physical contacts, wiring, anti-theft). It could also be an interlock that doesn't allow the starter to engage, like the gear position switch.

If you stated it incorrectly and the engine/starter is turning over (cranking) but not firing, then look at the fuel system, including Ford's fuel pump cut-off switch located on the driver's LH kickpanel.

Yea, this was the confusing statement for me as well, but I figured unless he was triggering a spark event without cranking it had to be a typo?

When I went to start it this afternoon, it cranked just fine. It wouldn't crank for her at all this morning when she wanted to go to the store.
I pulled a plug and had her crank it while I checked for spark. It has a nice spark, nice and blue.

[john70t]

I've had an experience with Bosche + Fuel.
An 87 Golf wouldn't start again after running a bit.
Intermittent.
I thought it was vapor lock or a head temp sensor or something along those lines.
It was overheating due to another problem(radiator core rusted shut and popped), and there was lack of cooling fan due to some source(thinking ecu after throwing sensors and thermostats at it).
Then it quit while driving. Hmmm, something's hot on the fusebox.

Turned out to be the fuel pump relay.

[Scott Douglas]

First, thanks for the help guys.
There is a bit of confusion now on my wife's part as to whether or not it was cranking when she went to start it the yesterday. That is why I checked the battery voltage first.
Since it is cranking (yesterday, I haven't tried it today yet) and it does have a nice blue spark (at least on the plug I pulled) I think it's the fuel system. I've never heard this fuel pump, unlike our Taurus which was noisy as all get out, and I don't hear it now. I'm going to look for the module in the trunk and see if it's getting power.
I have some starting fluid I use on my lawn mower and will try some of that if I can't find the module.
What is a 'noid light'?
I've never heard of one before.

[john70t]

Noid light: Unplug the injector(s) and attach a light.
It flashes when the injector is pulsed by the computer to open(squirt fuel).

It means the electronics from the crank/cam sensor to computer to driver to injector is working.
(but remember signal not voltage/timing/dwell/etc....It only indicates some sort of signal is being sent).

Here's one place, but a specific search gave crap results though. I don't have time to go through them all. A universal kit will probably work.
noid lights - BuyCheapr.com

[Scott Douglas]

OK, making some progress here.
FOUND the module on the pass side inner fender in the trunk.
Took it out, unplugged it, hooked my VOM red lead up to #9 term of the connector in the car and touched the black lead to ground with the key in the 'on' position and got a reading or 11+/- volts. I think the module is indeed kaput.

[Scott R]

What is the output of pin #3 when the car is cranking? I don't think 11v at pin #9 is an issue, the battery may just be a little low. Pin #3 is actual power supply for the pump and the module is not working it tends to not drive pin #3.

You should get a priming pulse to #3 when you first turn the key on, then it should be hot while cranking and running.

[rick-l]

We still don't know what your definition of cranking is.


Cranking is something you would do with a crank at the front of a model T regardless of whether or not it starts.

[Scott Douglas]

OK, thanks for that. At $163 quoted price I need to make doubly sure it's the module.
I'll go run that test now.

Cranking = turn the key and the engine turns over (ie starter is working fine) but it doesn't fire. It's the kind of thing that wears batteries down in a hurry if you're not careful.

[Scott Douglas]

I THINK I may be doing this wrong...
I put the red lead of the VOM into pin 3 on the connector in the car and had my wife crank the engine over, got nothing. Should I be hooking the module up and piercing the wire from pin three instead?

[john70t]

11V? Put a charger on it asap.
That's starting to sound like dead mode.

The electronics might not function if they get <9V while in crank/start mode.

[Scott Douglas]

Re-ran the test with the module plugged in.
Red lead piercing the wire from #3 and black lead on ground, engine cranking, got a reading of .7v. Point 7 volts is not going to run the fuel pump I don't think.

john70t - it may look low voltage wise but it's cranking over same as it always has, with lots of vigor. It could have been my um, less than perfect connections that gave the 11v reading.
I really think the module is shot.
Now to find one...

[Scott R]

Originally Posted by Scott Douglas

Re-ran the test with the module plugged in.
Red lead piercing the wire from #3 and black lead on ground, engine cranking, got a reading of .7v. Point 7 volts is not going to run the fuel pump I don't think.

john70t - it may look low voltage wise but it's cranking over same as it always has, with lots of vigor. It could have been my um, less than perfect connections that gave the 11v reading.
I really think the module is shot.
Now to find one...

That's what they read when they die. The last thing I check for my own sanity is to borrow 12V from a nearby source and jump pin #2 and listen for the pump.