I've got a 1991 Automatic with a 3.0. I've owned it for 10 years. For over a month now, I've been having problems with an intermittent crank no start condition. Seems to be a real ghost in the machine.

After sitting without being started for a day or two (over the weekend), the engine will crank strong, but won't start. If I spray a little ether into the intake, it stumbles on the first try, then starts up. It'll run, like crap with CEL on, for about 5-10 minutes then *click* and runs "fine" (sometimes a little stumble/hesitation). Then, it'll start up and run fine until I leave it sit for a couple days. Rinse and repeat. It never stalls or shuts off while I'm driving, and it hasn't left me stranded as long as I got my trusty can of ether.

When I try to read the codes, it won't go into read mode unless it's running well, then it shows no codes. I did have two codes the first time I checked them for the intake air temp sensor and the coolant temp sensor. I changed them, and the codes went away, but the problem didn't.

Makes me think it might be the EEC, maybe camshaft or crankshaft position sensor, but I don't want to guess.

Things I've checked:
Fuel pressure sits rock solid at 40 PSI and fuel pump is about 2 years old
Battery is at 12.6 V
No codes when running fine
All plugs are firing, but they're a few years old
Fuses all look good (haven't checked them with a meter)
EEC and Fuel pump relay seem to be fine (fp relay is about a year old)
Filled up at a couple different stations since the problem started, tried a bottle of HEET

I appreciate any help, thanks.

 

Welcome to the forum

Good testing

The 1991-1994 3.0l Ranger uses a distributor and TFI ignition, so no crank sensor
You have a remote mounted TFI Module, its on the Rad support in front of battery

Video here shows location:


The TFI Modules on the 3.0l lasted longer than the ones mounted on the distributors(2.9l engines) but could still start to fail, but usually this would be a heat issue so seen on warm start, not cold start

The pre-"crank sensor" was the hall effect sensor inside an electronic distributor, it sends a pulse(PIP) to the TFI module that starts the Spark, and then the TFI Module sends that same pulse(PIP) to the EEC(computer) so it can time and start the fuel injectors
The EEC then sends TFI module Spark Advance suggestions, after startup, on the SPOUT wire

TFI Module's spark is autonomous on startup, because computer doesn't even know the driver wants to start engine until it gets the PIP signal from the TFI, there is no connection between starter motor and EEC or TFI, it all comes down to both seeing that pulse(PIP)

No Pulse would be no start, not stumbling start, so hall effect sensor is working
I would check the wiring at TFI module, it is 28 years old, unplug connector and make sure contacts are clean and wires are not frayed
Also the SPOUT Connector as seen in video



What my best guess is:
I would change. just on speculation, the ECT(engine coolant temp) sensor, this is a 2 wire 5 VOLT sensor on the top front of the engine
The GREY 2 wire connector in this picture: https://www.ranger-forums.com/attach...ant-sensor.jpg

The RED 1 wire connector is the 12 VOLT sender for the dash board temp gauge, so not interchangeable

The ECT sensor tells the EEC when to CHOKE the cold engine and how much choke to apply, so if ECT sensor was telling EEC that engine was already warmed up, 120+degF, then engine would be hard to start and would run like crap until it did warm up, then it would be fine

Its not an expensive sensor, but you can test it if you want, use a sewing pin to pierce wires while they are hooked up to sensor
Key on:
1 wire will show 5volts, from EEC, most sensors use this same 5volts, grey/red stripe wire
Other wire will show 2.5-3.5volts depending on how cold it is outside
After warm up this other wire will show under 1 volt, .5-.8v is spec

So if there is corrosion on either of these wires voltage will be lower, so warmed up engine regardless of actual temp
Or if ECT sensor has failed


If you have already changed the ECT sensor, or you do and cold start is still an issue then I would pull out the EEC and open the top

Should look like this inside: http://www.auto-diagnostics.info/ford_eec_iv

The 3 BLUE capacitors can leak after 20+ years and will cause odd problems, like no communications and startup issues, and while its not always intermittent, no reason it can't be depending on what circuits are effected
$5 fix

 

Thanks, that's a lot of really good info. I did change the ECT sensor because I had a code that called for it, but I didn't check the voltages and can't rule out a corrosion issue. I was thinking that the issue seems more digital than analog to me because of the sudden *click* that makes the engine run fine, but I don't really know. I'll take a look at the TFI module and the caps on the EEC, and be sure to post an update.

 

Is the ECT code gone now?
And how long has it been since it was changed

Only reason I am asking is because the symptoms fit an ECT issue, and if it wasn't the sensor then maybe it is the wiring or that circuit in the EEC

 

It's gone when the CEL is off, but I actually did see the code once since I changed the sensor now that you mention it. The engine was cold, though.

I thought I might clarify that when it runs like crap after I first get it started with ether, the CEL is on. Then after about 5-10 minutes of running, it suddenly clicks and the CEL goes off and everything runs fine. I'm having problems extracting the codes when the CEL is on or when it won't start, though. It just won't kick into the test mode. So, it's hard for me to pin down.

 

Well a code should be stored in memory unless you unhook the battery longer than 5 minutes

So just a CEL with no codes may indicate misfires, which is what you describe

One other thing to test is at the inertia switch, fuel pump voltage
Inertia switch is under glove box and screwed to the firewall
When you turn on the key you should see 12.6v(battery voltage) for 2 seconds, then it will drop to 5-8volts, this is from EEC monitor circuit, no amps just volts

When engine starts you should see 13.5-14.8volts, alternator voltage
If its lower than "system voltage" computer can "see" that and will turn on CEL until it comes up
All lower voltage would mean margin fuel pressure at that time, not sure if that was part of the fuel pressure test
The "click" could be fuel pump relay resetting and voltage coming back up

 

Update:
After running fine for a several days, I just had the crank, no-start issue this morning. Since the last post I have:
-Inspected the TFI module and SPOUT connector. Everything is clean and dry and shows no signs of corrosion.
-Measured the voltages on the ECT sensor (replaced the sensor before starting thread). They seem to be fine.
-Replaced distributor cap, rotor, plug wires, and spark plugs. (Probably not the problem, but it was overdue)
-Cracked the case on the EEC, and inspected the PCB. Everything was clean and dry, no corrosion. Blue capacitors weren't swollen or leaking (mine only had two).

The procedure this morning was the same as always:
-Crank, no start
-Spray ether into intake
-Starts and runs after a couple of tries
-Runs in safe-mode with CEL on (unplugged MAF and saw no change to confirm safe-mode) for 5-10 minutes
-Sudden *click*, CEL goes off, runs great.

As before, I could not extract the codes while in this mode. I tried, they just wouldn't come up.

I'm thinking about rolling the dice and buying a new EEC, they're only about 90 bucks. Hate to do it if that's not the problem, though.

 

You can pull the computer and open it up, pull the top off

You should see this with cover off: Ford EEC-IV

There are 3 blue capacitors that can leak after 20+ years and cause odd issues
Under $5 to replace them and clean off residue

Pictures here of that issue: Capacitor Repair: Ford A9L ECM « Moates Support

Inspect the circuit board for damage before ordering a new one

 

I opened up the case on the EEC last week, and didn't see any signs of burning or corrosion on the PCB. I only saw two blue capacitors, though. Are there always three? The two I saw didn't look swollen or seem to be leaking. One of the bolts on the EEC case was corroded, but everything looked okay inside.

I didn't look at the caps as closely as shown in the link. I think I'll take another look when I get the chance. Might just swap them out anyway, just as a Hail Mary.