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Hey guys. Got a 1993 4.9 that has had an intermittent no start for years. So intermittent that I couldn't figure it out. Lately it has become much worse and started stalling. I replaced the ignition module and the truck ran fine for about 2 weeks and started stalling again. Went out to move it to work on it and it won't start at all now.
No spark. Fuel pumps both cut on at "on".
Advance replaced the module again. Still no start
New coil (was original) . Still no start.
No change with SPOUT removed.
Read up on the distributor module and found a good video to test. That top wire in the ignition module harness that is supposed to have 10 volts on it with the key on has .03v. Verified good grounds etc. Pretty sure that points me in the right direction of what is wrong. Maybe a wiring issue? Or do you guys think that pickup in the distributor would cause that? Tired of throwing parts at it.
Exactly what step in the starting process failed? The key wouldn't turn? The engine wouldn't idle? Or somewhere in between? BE SPECIFIC.
Originally Posted by jimmykicker
...started stalling.
Under exactly what conditions? A slow stall, like running out of gas? Or quick, like turning the key off?
Originally Posted by jimmykicker
I replaced the ignition module...
Why? With what (brand, PN, source)?
Originally Posted by jimmykicker
No spark.
How exactly are you checking?
Originally Posted by jimmykicker
Fuel pumps both cut on at "on".
Does that mean BOTH? Only 1 should run, depending which tank is selected. Or did you mean EACH? Does it run for ~1sec and shut off? Or does it run for >5sec without cranking the engine? Read this caption:
That's one guess, but until you do some real diagnosis, it's no more-likely than any of the thousands of other possible guesses.
Originally Posted by jimmykicker
Or do you guys think that pickup in the distributor would cause that?
It's hard to say with so little description of what's happening.
Originally Posted by jimmykicker
Tired of throwing parts at it.
You should never have started that.
Originally Posted by jimmykicker
Anybody got a GOOD wiring diagram for 93?
http://www.bbbind.com/free_tsb.html
You don't have to give your real e-mail, but click WIRING DIAGRAMS when you see that button. But you should follow the ignition diagnostic procedure in Ch.5 (usually Sec.5 or 7, depending which edition you get) in:
Exactly what step in the starting process failed? The key wouldn't turn? The engine wouldn't idle? Or somewhere in between? BE SPECIFIC.
Quote:
Originally Posted by jimmykicker
...started stalling.
Truck initially would not start on occasion. No spark. Fuel pump comes on. Starter spins. No spark. Eventually would start and run fine. May not do it again for months. No missing. No stalling while driving it. Eventually would turn off as if key was being turned off while driving after just a few minutes. Leave it alone for 30 and cranks right up. Replaced module (tested bad) and truck ran fine for a couple weeks.
Under exactly what conditions? A slow stall, like running out of gas? Or quick, like turning the key off?
Like turning the key off.
Originally Posted by jimmykicker
I replaced the ignition module...
Why? With what (brand, PN, source)?
Because it tested faulty. Advance auto parts. Carquest I believe. It has another new one as I noted. No change.
Originally Posted by jimmykicker
No spark.
How exactly are you checking?
Inline spark tester. Verified on another vehicle it works.
Quote:
Originally Posted by jimmykicker
Fuel pumps both cut on at "on".
Does that mean BOTH? Only 1 should run, depending which tank is selected. Or did you mean EACH? Does it run for ~1sec and shut off? Or does it run for >5sec without cranking the engine? Read this caption:
No that means that they individually come on. It's NOT a fuel problem. It runs for a few seconds as it always does when it runs. I've been through this and THOROUGHLY tested the fuel situation. Without question 1000% not fuel related. No spark at plugs.
(phone app link)
Quote:
Originally Posted by jimmykicker
Maybe a wiring issue?
That's one guess, but until you do some real diagnosis, it's no more-likely than any of the thousands of other possible guesses.
What I noted was that there is .03v on a wire that is supposed to have 10 volts. It does not change when cranking. That is the "PIP" wire I believe. From what I saw it is supposed to have 10v on it at key on and around 4-5 while cranking. Forgive me, I am new to Ford trucks. If this was a Chevy S-10 1st gen I could teach a class on that. In that light, what "real" diagnosis-es should I be doing?
Originally Posted by jimmykicker
Or do you guys think that pickup in the distributor would cause that?
It's hard to say with so little description of what's happening.
No offense, but I thought that was pretty clear describing the voltage coming to the PIP wire and how that relates to the distributor module.
Quote:
Originally Posted by jimmykicker
Tired of throwing parts at it.
You should never have started that.
It definitely needed an ignition module as it was bad and it fixed the problem at the time. The coil I simply replaced due to age. I don't want to put a distributor in it if I can help it.
Quote:
Originally Posted by jimmykicker
Anybody got a GOOD wiring diagram for 93? http://www.bbbind.com/free_tsb.html
You don't have to give your real e-mail, but click WIRING DIAGRAMS
Well I figured it out. I took the wiring diagram and looked at the PIP wire. It terminates in three places. One is the ECM, one is the distributor, and one is the ignition module. I back probed all the wires and make sure that I had continuity so I knew it wasn’t a wiring issue. Since there wasn’t the 10v On the PIP wire with the key on i had to figure out where that voltage comes from. Apparently a switched 12v hits the distributor and with the key on it delivers 10v from the distributor to the ignition module and ECM. I checked the switched wire and verified 12v coming into the distributor. Since I knew my wiring was good then that only left the distributor. Note I did pull my ECM to take a peek. No leaky caps etc. it’s important to note too that I found out the ECM doesn’t really do sh*t when it comes to spark. It only adjusts the timing once it’s running. It in theory should start with a bad ECM but run like total crap. I had zero fire. I suppose in a catastrophic failure it “might” cause a problem to interfere with that, but most of my research found that people complained only running issues, not “no start” scenarios. Or fire. Anyway, since my wiring tested OK and I had a new module that really only left the Hall effect stator in the distributor as the culprit. I ordered a complete distributor from Rock Auto and paid $75 on my door. Considering a quality module costs $40 that seems like a bargain vs rebuilding it seeing that it also comes with a new cap and rotor. My distributor was pointing towards the firewall perfectly so I used that reference and eyeballed the body position. (Another note. I read some “fear mongering” posts where the oil pump drive could fall out into the oil pan if it didn’t come out with the distributor. I found a metal c clamp providing a tight fit. It wasn’t going anywhere.). Anyway. I digress. I put the new distributor in a couple times till I got it to fully mesh and hooked everything back up. The truck immediately fired up and ran just fine. I made a small adjustment to the timing and we were good. I then tested the PIP wire again. 10v with key on as spec’d. Not .03v.
Moral to the story is this. If you don’t have 10v on the top PIP wire at the ignition module something is wrong. Either the wiring or the distributor module has an issue. You can bet the ignition module isn’t a fault, nor the coil. In my case I had two component failures at two different times. We’re they related? Probably never know.
Last edited by jimmykicker; 10-26-2018 at 11:36 PM.
Hey guys. Got a 1993 4.9 that has had an intermittent no start for years. So intermittent that I couldn't figure it out. Lately it has become much worse and started stalling. I replaced the ignition module and the truck ran fine for about 2 weeks and started stalling again. Went out to move it to work on it and it won't start at all now.
No spark. Fuel pumps both cut on at "on".
Advance replaced the module again. Still no start
New coil (was original) . Still no start.
No change with SPOUT removed.
Read up on the distributor module and found a good video to test. That top wire in the ignition module harness that is supposed to have 10 volts on it with the key on has .03v. Verified good grounds etc. Pretty sure that points me in the right direction of what is wrong. Maybe a wiring issue? Or do you guys think that pickup in the distributor would cause that? Tired of throwing parts at it.
Anybody got a GOOD wiring diagram for 93?
Thanks so much guys
-j
CHeck the crank sensor make sure it's good if it's not the you won't get a break in the flow so no spark it's like having your points touching
10-02-2018, 11:07 AM
No Start Condition 1993 f150
http://www.bbbind.com/free_tsb.html
