OK, so you have B+ to the DLC, but no communication with the computer, so you'll need to ring out the other wires between the DLC & ECm's firewall electrical connector. Maybe using a wooden dowell, push on all of it's pins/sockets to make sure they're fully seated & locked into place & inspect the wiring for cuts/breaks between the two connectors.

Yah the DLC connector gets it's B+ feed to power the scantool, through the cigar lighter fuse, kinda weird but thats how Ford does it. lol

So it now seems that something is taking out the computer fuel pump & fuel injector drivers for some reason. So you might consider doing a current draw test on the fuel pump & measuring the fuel injectors resistance to make sure there isn't a short causing excessive current draw that takes the ground switching drivers out. The injectors should be closely matched for resistance & measure between 12-16 ohms.

 

Hi PawPaw,
Thanks for the thoughts. I will test the fuel pump for draw, I believe I can do that by taking a jumper wire from the battery positive and run it to the pink/black at the inertia switch and put a VOM in there and measure amps. Today I got the used ECM and even though I did not have a chance to get the new DPFE and relays, I installed it, went to KOEO and checked for codes. The OBD connected just perfect and there were no codes. I started the truck and it fired right up. I let it run for a minute at most, and then got my VOM, and connected it to the battery. I started the truck and measured 14.28 volts at the battery. I shut the truck off and have not done anything else. Life gets in the way. Tomorrow I do hope to get the DPFE sensor, and ECM and fuel pump relays. After that, I am just not sure. I also spoke with Cardone tech help line, but although he did his best, his advice was to check for sensor draws as well. This is where I am right now. More to follow and thanks again,
Tony

 

I have been advised that while a faulty DPFE sensor can cause a vehicle to stutter, or even stop, unplugging it will restore ECM and engine function, and they do NOT bring down ECM's terminally. So I am once again wondering what to do, how to proceed. I feel that I will measure amp draw of the fuel pump. I do not recall if the fuel pump runs full time or is intermittant in normal operation. I am going to proceed cautiously. Thanks again to all for your help,
Tony

 

We have a returnless fuel system, that has the fuel pressure regulator in the tank with the fuel pump. So once the engine is running, the ECM uses PWM to control the fuel pump, so it's duty cycle will vary with engine load demand.

 

PawPaw,
Thank you for the clarification, concise and complete as always. I'm still doing more checking,
More Soon,
Tony

 

After reading through the original thread btw Antiquey and Pawpaw, I continued on to this one hoping to find a resolution at the end. Yikes, its not here.

So, Antiquey if you're still around, do you have your vehicle back in working order yet?

Your story is very similar to that of my wife's truck. For about three years now we have fought a completely random and intermittent crank, no start condition. Prior to me putting my foot down, she spent $2k at a dealer who looked through everything, replaced the ECM, reprogrammed keys, removed remote start, had it start and sent her on her way. One year later, the same problem happened (random no start for a day or two, then no problem). Through another series of months with a dealer they could not find anything wrong with it. They would make a change, no start then mysteriously start 100 times in a row. They gave it back with a "can't figure it out". I went ahead and replaced the ECM, reprogrammed yet another set of keys and it was fine for a couple weeks. Then bam, its back again. I'm going to throw a cam synchronizer at it and see if that will do anything. The biggest problem through this all is there haven't been any codes, through the OBD or TECH1 scanners.

I hope you have a solution you can post up. My trials have been mind boggling too.

 

Dear ado2b1,
My problem turned out to be chewed wires at the top of the gas tank, either mice or squirrels. The wire to the fuel pressure sensor was touching the 12 volt power supply wire to the pump and 12 volts where there should be a 5 volt reference signal caused repetitive ECM failure. Wires are repaired and, so far, knock on wood, all is cool. Have you figured out whether you are losing fuel or spark when the truck won't start? I knew I had spark by spraying ether into the intake horn and after reconnecting the intake pipe, when I cranked I got a bit of firing. The injectors are hot all the time and are triggered by a completed ground at the ECM, at least on my '98, 4.0 OHV. The injectors also "click" when they inject and with a stethscope you should be able to hear them when someone else cranks, if they are working. Does your truck have the PATS system for the igition key? Do you carry a lot of keys on your keyring that hangs from the ignition key? This can cause intermittant ignition problems. I hope I have given you somethings to think about. I just thought, did you check the "Inertia Switch" at the passengers feet? Jumping power to the pink/black wire at this switch should cause the fuel pump to run, again, at least on my '98. Hope this helps.

 

Antiquey,

Thanks for the reply. I read about the frayed wires, but hoped the solution was something else (no frayed wires on mine). Other than that though, I have checked pretty much everything you've listed. The terrible design known as PATS was replaced by the dealer in throwing parts at the problem 2+ years ago. Fuel pump, I replaced (mistakenly) when the problem first occurred, though we had appropriate pressure at the rail. I've pulled the spark plugs and can view spark as well as using an inductive timing light. I haven't checked injectors or inertia switch, but will do so tonight. In my mind fuel, air, spark = running vehicle, but with ECM issues, sensor malfunctions, etc. in modern vehicles, apparently that is no longer the case.

This is a '99 B4000, BTW. I'll post back when I look at injectors, inertia switch, and replace the cam synchro and crank position sensor.

 

ado2b1,
I actually did forget to mention something (hard to believe!), on the Fords at least, there is a TSB for faults at the electrical connector at the fuel pump. Connectors can look OK but be failing. Give this the wiggle test. A friend of mine replaced 3 pumps on a customer truck before he discovered the fault was in the wiring connector. By the way, I also had a Door Ajar light and alarm going off at odd times, I fixed this by spraying WD40 into the door latch assembly on the body, it was just hanging up. I hope any of this is a help,
Tony AKA Antiqueynot

 

Tony & others possibly searching the thread

Update time,

After finally getting around to part replacement time, I tried the crankshaft position sensor first (easiest). Decided to give it a try and voila, engine fired up immediately. Took the opportunity to listen to the injectors with a "homemade" scope, they are all ticking merrily away. The cam synch will go in eventually, but as of right now, I think my troubles are over. Its been running great for several days with no signs of even an extended crank period before start.

Also took the opportunity to try the WD-40 in the latch mechanism. I SOAKED it 'cause I had plenty of WD-40. The door ajar problem has gone away too.

For new searchers: I had a no start condition, continuous crank, no fire. Problem was intermittent at first, sometimes several days between the no start times. Then it became permanent. There were never and OBD codes, nor did the dealer(s) computers detect any issues. The CPK appeared fairly clean, no built-up gunk. Replaced as part of a multiple-pronged approach and it worked.

 

ado2b1,
Congratulations on getting your truck going. let us know how the cam synch goes, as I too need to do this. Glad the WD40 worked, I like JB, it tastes better :-] Good diagnosis and repair, thanks for sharing,
Ynot