Hello, I'm really hoping I can get help since it seems mechanics no longer like to work on these old trucks.
Vehicle - 1990 ford ranger xlt 4x4 with 4.0L V6
Problem - engine turns over but woin't start
possible clues - KOEO, fuel pump continues to run and won't shut off. Pulls one OBD code which is 16.
recent work - replaced PCM, EDIS module, CKS, fuel pump and EEC power relays, coil pack. recent work done because truck wouldn't start. finally solved with new EDIS module. ran great for a month or so and then this started up.
Any help or suggestions would be GREATLY appreciated.

 

Pull computer out and replace the 3 Blue(or black) capacitors, $5 fix

The EDIS replacement was a fluke, never even read of one failing unless rad support was hit in a front end crash, and EDIS has no bearing on Fuel pump 12volt power, only computer does

Code 16 may mean computer is not seeing engine RPMs when cranking
Watch CEL(check engine light)
It should come on with key on
Turn key to START
CEL should go off if computer is seeing Crank sensor RPMs while cranking, this is FROM the EDIS module
If CEL doesn't go off then No Fuel Injectors, because there is no timing pulse

Code 16 could have come during previous parts replacements

Simple test for "spark or fuel" issue is 50/50 test
Spray gasoline or ether into the engine and try to start it
If it starts and then dies you have a fuel delivery issue
If it doesn't start then you have a spark(or compression) issue
50/50 instant results

 

CEL does not go off when cranking but tach does climb.

 

Thanks for responding and please know that I'm pretty challenged with electronics. Everything I read about the EDIS system said that the truck should be able to at least start without the ECM even being hooked up if everything else is in working condition.

 

Tach's a different wire

So crank sensor is working but computer is not getting RPM timing pulse

I think if you re-read that article or post about EDIS, it will say SPARK will still work without computer hooked up, which is true, but no fuel injectors without computer getting timing pulse from EDIS
Try 50/50 test to confirm working spark, engine will start and then die when it runs out of the added fuel, confirms no injectors

I would pull the computer and have a look inside, unless you think the connector on the EDIS-6 module had a problem?

 

Again, thanks so much Ron. This time around things seem different. believe it or not last time the truck would start with ether even though the problem was actually spark. sprayed it 3 or 4 times and it won't start with the ether this time. Also, now the fuel pump is cutting off after 2 seconds as it should but still no start. I have always had a suspicion that its the connector or wiring harness from the CKS to the EDIS Not sure how to test that the EDIS is getting the signal. Am not oppossed to pulling the computer, just not sure whaqt I am looking for. I know what a blown capacitor looks like, is that what I am looking for?

 

Yes, after 20+ years the electrolyte capacitors will leak their fluid which is a problem, the key words are WILL LEAK, so when it's out you replace them regardless
Also a general look at the circuit board for corrosion

EDIS-6 wiring seen here: https://forums.hybridz.org/applicati...0655222062f3d4

The smaller oval connector is the Coil Pack

The VR sensor is the Crank Sensor, it's the Big Kahuna of sensors, when starter motor turns the crank the crank sensor sends a timing pulse to EDIS and that starts SPARK
The EDIS then sends that timing pulse(PIP and SAW) to the computer to start the injectors

There is no connection between EDIS or computer and the Starter motor, the ONLY WAY EDIS or Computer knows you want to start the engine is when Crank sensor starts sending EDIS a timing pulse

Crank sensor is a VR(variable reluctance) sensor, it generates its own AC Voltage when a "tone wheel's" teeth spins passed it, .5-.1.0vAC cranking speed, up to 8vAC at 5,000pms

 

Thanks Ron. I tried spraying ether into the air intake and still got no start. I checked and I do have spark, got an awfully good jolt I am confused as to why it won't start with ether but for some reason I do believe the problem is not on the spark side. Is there a way to test an injector for pulse without a noid light? Do I need a meter to check these things? I have no diagnostic tools but will get some if someone can tell me what I need. I tossed parts at it last time and would rather not do that this time.

 

Not possible to get a no start with added fuel and spark......................unless you also have no compression

Gasoline engines as very simple to diagnose, doesn't matter what "they" add to the outside, they all still work the same way
Fuel
Spark
Compression

If you are missing 1 or all 3 you have a no start

If you add fuel manually and have a no start, that leaves spark or compression
Pull a spark plug and crank engine, you should hear whoooosh of escaping air on compression stroke, if you have a compression gauge use it to see
Engine needs above 100psi compression to start cold, 4.0l runs 150-160psi
If you have a vacuum gauge you should see 2" of vacuum while cranking with throttle closed

Are you sure the ether is OK?
Should have a VERY strong odor

Never heard of a 4.0l OHV losing compression, its possible just not very likely

Spark also has to be at the right time
Coil pack wiring is like this
3 4
2 6
1 5
front

The 5 6 4 side can be miswired, but engine should still fire

 

Thanks Ron. I think I need to start at the beginning. I had a no start problem about 4 months back. I changed out the crankshaft sensor, both the EEC poower relay and fuel pump relay, the coil, the computer and finally the EDIS module. The Edis module seemed to fix the problem as after that it started just fine. Then, last week, after runnin g and starting just fine every time, I went out one morning and it wouldn't start. It has been very foggy the past month or so. I will check the spark again tonight after it gets dark but although I didn't see the spark I could hear it using a spark tester and when I touched it with the engine cranking I got a pretty good shock. That is what makes me think I am getting spark. All of the coil wires and the spark plug wires are correct as I haven't done anything other than to take off the #1 plug wire to test for spark. I wouldn't think that the truck would be running fine when parked and then lose all compression but I could easily be worng I guess. I am wondering if somehow the moisture in the air is causing my fit? Thanks again for hanging in there with me. I realize I'm not real savy on this stuff.

 

Ok, finally was able to check the spark and there is none. I'm fairly sure I know how to trouble shoot the EDIS system. Fortunately I have spare parts for all the components. Waiting now for a multimeter I just ordered. Hope that someone can help me if I have questions.

 

checked the spark in complete darkness and I have a very weak spark. checked the leads to the coil pack with a test light and all show as they should. Power lead shows good with key on only and switching leads show flashing when cranking the engin. I'm thinking bad coil pack or bad plug wires?

 

So, The CEL remains on while cranking means that the Computer is not getting the signal from the EDIS module. Have confirmed that the switching signal is present at the coil pack connector. Can you tell me the procedure to check the connector at the computer fdr the signal please.

 

There are 4 wires from EDIS to Computer
EDIS....................................Computer
Pin 1 PIP, grey/orange wire, .....pin 56 <<< crank signal out
Pin 2 IDM/Tach, tan/yellow, ......pin 4 <<< coil pulse timing out
Pin 3 SAW/SPOUT, pink, .........pin 36 <<< return spark advance signal from computer
Pin 4 IGN Ground, orange/red, pin 16 <<< makes sure computer and EDIS have common reference ground

I would first check continuity on all 4 wires
Pin 1 and 4 on EDIS 6 should show 0v/12v off/on when engine is cranking

Engine should start if you add fuel manually to the engine, 50/50 test, only that test confirms spark is OK(strong) and is timed correctly, and crank sensor/EDIS-6 is working

This is a 1994 EDIS-6 4.0l diagram but same for 1990 4.0l, just easier to read wiring on this one

 

The ether I used is good. Is there somewhere that I should spray it other than into the throttle body? BTW, it did not even cough with it.
Thanks Ron. I also want to do integrity check on the wires from the EDIS to the computer. Is there a specific ohms value I should be looking for on these wires. Much interested in the IDM also as that is mentioned in the OBD code 16. I found this on the web, does it sound correct?

"disconnect PCM connector and EDIS connector. measure resistance between Pin 4 on PCM connector and Pin 2 on EDIS connector. should be LESS than 5 ohms.

if so, check resistance between Pin 4 and Pins 40, 46, and 60 on PCM connector. each resistance should be OVER 10,000 ohms."

 

"Continuity" means to test if both ends of the one wire show that the wire itself is OK, so should be under 5 OHMs, or 0 OHMs meaning no resistance because its just a wire nothing in between
Test all 4 wires first

Pins 40 and 60 on PCM are grounds and pin 4 on EDIS is also a ground so should be close to 0 ohms, but never test it before
Pin 46 is a signal return so while it is "technically a Ground its also 5volt pull down so shouldn't be test that way and not part of the EDIS circuit in any case

EDIS plugged in test PCM pins 56(12v) and 16(gnd) with volt meter set to DC Volts
Crank engine and you should see up and down voltage pulse, 0 to 12v
Thats the timing pulse computer needs to start fuel injectors

Just just spray into throttle while holding it open then let it close and try to start

 

Thanks Ron. I can confirm then that it doesn't even cough with ether sprayed into the throttle body opening. Believe it or not I actually do understand the workings of an internal combustion engine. Electical on the other hand has always stumped me so I want you to know that you and others here provide a HUGE service for the rest of us that would otherwise be completely stumped as to where to even begin with these "modern" electronic systems. Thanks so much and I will come back with the results of my testing. I have a hunch that I am going to find that the problem lies not in the components that have all been replaced within the last 6 months, but with the wiring of them instead.

 

The EDIS system is self contained, doesn't need PCM for start up, just for fuel, so you have no spark

EDIS module
Crank sensor
Coil pack
Those are the 3 parts for EDIS spark
The 4 wires to PCM are not needed for spark

Add 12volts and a ground and you will have spark
The Crank sensor generates its own AC voltage when crank turns the "tone wheel", .5-1vAC at 200 rpm crank speed

Hotrodders often use the Ford EDIS system because its so simple to use to get distrubutorless spark, no computer needed

 

Ok. I think that you are telling me that the problem is more than likely somewhere between the crank sensor itself and the spark plugs. I should check that the EDIS module is in fact getting the voltage from the crank sensor, sending the signal to the coil, and the coil is getting the signal and a full 12 Volts. from the ignition switch, is that correct? If so, I still have the coil I replaced back when I was easter egging parts. I can try putting it back on in case the new coil is the problem. Does that sound like the correct plan of attack?

 

Sorry it took me so long, had an emergency out of town. measured voltage of crank sensor going into edis and I get 1.3 - 1.5 V. AC. Is that too high? I tested the power and both grounds at the EDIS, and they are all fine. Tested the switching signal at the coil connector while cranking and all three show pulse. Tested the power lead at the Coil connector and it shows 12.4 volts KOEO and 11.4 volts while cranking. Is there a way to check the PIP signal with a votmeter or test light?

 

If above is true then engine should start if you have compression and you add fuel manually

The crank sensor voltage is fine, its RPM based, so at 150rpm it would be lower AC volts than at 250rpm, cranking speed, so depends on starter motor cranking speed

Long shot is coil pack is reversed but at least 2 cylinders should fire, 2 and 6, if that was the case
3 4
2 6
1 5
Front

1 5
2 6
3 4
front

 

I have not yet placed the coil pack back on the truck, just checking wires and the crankshaft sensor and EDIS. I will replace the coil tomorrow with an old one that I replaced when the problem turned out to be the EDIS module, so I think that coil was good. It may very well turn out to be the new coil pack went bad on me. Plan to put new plug wires on tomorrow also. IS the voltage at the coil while cranking ok? It does drop some when the motor starts cranking.

 

Voltage in the whole vehicle drops up to 2volts when cranking, should stay above 10.0 volts, starter motor's draw a lot of AMPs, 60-75amps, so normal, spark will be fine down to 9.5volts

 

I think I may have found a problem. I verified that I have good spark. I was going to test for continuity between the ECM and the EDIS but after taking the ECM out I found a hole in the case at the back. Have had problems with critters getting into the cab before. The wiring and connector look to be good. Haven't been able to take the case off yet as I don't have a socket small enough. Questions I have are what size the screw heads are. And knowing that the weatherstripping is poor to non existent on my truck and weather has been exceptionally moist with 10 hours or so of very thick fog for the last month or so, could this hole let in enough moisture to cause a problem?

 

Probably not, look at the 2 corners of the case in your picture, they're not air/water tight either.