Hi. I need help with a problem that I have yet to diagnose.

1997 Ranger
4.0L V6
217k miles

The truck cannot be started by simply turning the ignition switch. When the switch is turned to the on position, the fuel pump starts humming. This hum can last for anywhere from 15 seconds to 15 minutes depending on the temperature (cool weather = longer wait). If I attempt to start the truck before the hum stops, it will only crank and not start. As soon as the fuel pump (and IAC valve) stop humming, the truck can be started and it runs great.


I should also point out that the check engine light stays on for the entire humming process, and only momentarily blinks as the fuel pump stops running. Once the truck is started the CEL goes out.

A few days ago I took it to a local dealership for codes....none. Today I took it to an Autozone just to make sure....no codes.

Today I also tested the rail pressure. It immediately jumps to 40psi when the ignition is turned on. Once started it drops to 30 psi. I've been told that is normal.

I just bought this truck from a friend for my son. He has had this issue for several years now. He has changed the fuel pump twice, and fuel pump relay. I've got spare relays and swapped the fuel pump relay again as well as the pcm relay. I was changed the crackshaft sensor. The fuel filter has been changed many times over the last few years.

I've also cleaned every ground i could find under the hood (I think I found 5 of them).


Any ideas?

Thanks in advance for any assistance!

 

Sorry to bump my own thread....but I need help.

 

think you need to some further diagnostics
did you check for spark when cranking? are the plugs wet after cranking?

 

You've been busy on this one & done some good trouble shooting on the usual suspects.

Maybe an ECM/Computer problem, as at KOEO before we crank the engine, it times the fuel pump prime run time & arms the ignition system & fuel injectors with B+, then when we crank the engine, it ground switches the fuel injectors & coils & for the start, then when it looks for & detects crank & cam shaft movement from the crank & cam sensors signal, it'll continue to run the engine.

Make sure at KOEO, before cranking the engine for a start, that the computer is arming the injectors & coilpack with B+. If not, thats another reason to suspect an internal ECM problem.
If the fuel pump prime run time is acting out, suspect internal ECM problems.

If you can find a like ECM to try out, maybe from a salvage yard donor vehicle, that might be a quick way to trouble shoot if its an ECM problem.

Had a similar fuel pump run time & a random stall problem, in which I finally found spark also randomly going missing on my 94 Taurus last year. Opened that computer up, looking for over heated components, cracked/broken race, solder splashes, or cold solder connections & found about 75% of the solder connections to be suspect & lots of solder splashes under the circuit board conformal coating.

I picked out as many suspect solder splashes as I could without joy, but it was an impossible trouble shooting task to try & reheat that many suspect cold solder joints, so I bit the bullet & replaced the ECM/computer & all has been well since. No more fuel pump chatter, or running on for long periods on a start, or random stalls from lack of spark. All of the components looked ok, just really poor workmanship on the component circuit board soldering.

Some thoughts for consideration, let us know how it goes.

 

Thanks for the responses guys. I really appreciate it.

Update:

Knowing that warmer weather greatly reduced the wait to start time, I did a little experiment. I removed the pcm and warmed it with a hair dryer for about 20 minutes. Got it good and warm. I re-installed the pcm, re-connected the battery, and she fired up in only about 5 seconds. I allowed it to cool for about 20 minutes and tried again. This time it took much much longer (didn't time it). Failing components?

So I guess I'm on the hunt for a new pcm. How closely do the numbers on the pcm have to match? Are there only certain numbers that are important?

Also, the pcm sits on two flat plates. There was evidence of water on one of the plates (white discoloration) as well as the bottom of the pcm itself. If I do install a new pcm, can I wrap it in plastic to protect it from future water intrusions?

 

Good trouble shooting idea with the hair dryer, looks like you got a positive on the warm up/heat test.

If you suspect a water leak has damaged the computer, remove it & use a water hose around the suspect area & inspect the computer mounting area for signs of a water leak. Do this before replacing the computer.

It is important to match the computers numbers with the one in there now.

For the Taurus I chose a reman one from Advance Auto & crossed checked their number with their vendors number, to make sure what I was ordering would work with my Taurus.

They had my computer at a discount on line & I also found an on line discount promo code link, so I ordered it on line & picked it up in the store without shipping charges. It had a one year warranty. Ended up costing me $15 out of pocket when all was said & done, so it was less expensive than a salvage yard part for me. Take the time to look around for the best deal. I have a link to a bunch of Advance discount codes in Favorites somewhere, if I can locate it I'll post the link. Edit found it http://www.cheaperseeker.com/sem/Adv...0promo%20codes If none of them work, try P20, it'll take off 20% on anything you order online.

Let us know how it goes.

Edit: I wouldn't wrap the ECM, as it needs to breathe to cool itself & prevent moisture from collecting inside.

 

Excellent trouble shooting and advice. Take a look on Craigslist. Where I live there are always a few trucks being parted out.

 

Thanks for all the input guys. I was getting really frustrated and greatly appreciate the advice.

Just to satisfy myself that it wasn't a fluke I did the hair dryer test again this moring. It fired up in about 5 seconds like it had been sitting in the sun all day in the middle of July.

I found a replacement PCM from autozone that match the numbers on my current pcm. The calibration code also matches the one found in the door jamb.

So my question is this.....since even the calibration code matches, this unit should be a plug and play right? No flashing or anything required?

I will update you guys when I get and install the pcm. Fingers crossed!

 

First remove the battery B- cable, then the old computer, then install the new computer, reattach the battery B- cable & take the time to go through the cold & warm idle relearn routine outlined here, to prevent possible driveability problems & it should be a plug & play deal. Ford Truck Enthusiasts Forums - View Single Post - high idle problem

Let us know how it goes.

 

Update:

I am happy to report that the installation of the new pcm completely solved the issue. I followed the idle relearn process outlined by pawpaw and she's back on top of the world.

To those of you that took the time to respond.....I really appreciate the help. Seriously!

 

great job.....glad you got it fixed.....future members want to know ....how much was the <acronym title="Powertrain Control Module">pcm</acronym>? was it a plug and play deal? where did you buy it?

 

I found matching numbers (including calibration code) through AutoZone. After I turn in the core it'll end up costing me about $160. It was completely plug and play...I just followed the idle relearn process suggested by pawpaw.

Thanks again for the help!

 

Good find, fix, feedback & to hear all seems well & your "on the road again"!!!! Thanks & Reps to you for the feedback & closing out your thread.