The no spark mystery continues

[Kmcbride3956]

I thought I should start a new thread on my truck because the one I had started before was about a separate issue. So I have an 88 4 cylinder 5 speed ranger that was given to me because it wasn’t getting spark and the previous owner gave up on it. I had to replace the coil because the tip of it was broken off. After replacing that I started checking the ignition control module and found that it had a bad ground. I fixed the ground but still no spark. I also found a few other wires that were cut or otherwise messed up. The wires going to the MAP were cut so I fixed them, still no spark. Then I found the wire going to the oil pressure sensor was cut. I decided to test this wire by putting my test light on the positive side of the battery and touching the wire with the test light. It didn’t light up, leading me to believe that there is a problem in that wire somewhere. I traced that wire to the large wiring bundle that also connects to the ICM. I then traced all that back to the computer. I took off the passenger side kick panel and found the casing around the computer to be wet. So I pulled the computer and opened it up. It looks dry and I don’t physically see anything wrong in there but I don’t know how to tell just by looking at it. So now I don’t know if I should replace the computer or not. Obviously it’s been getting wet every time it rains, but I don’t know how wet, and if it’s just the case, or if water has gotten inside. The truck seems to have some wiring issues at the very least because I have found 2 different areas that didn’t have continuity. I don’t really know what to do next. Replace the computer? Attempt to trace every single wire? I am not a professional mechanic, and have a limited amount of knowledge when it comes to wiring and electrical components. Any suggestions?

 

[RonD]

1988 Ranger with 2.3l was the last year 2.3l Ranger with a Distributor and it used TFI module on the side of distributor as the ICM

This is a self contained Spark system with only the Coil as a separate part

It needs 12volts and a ground to make spark, no other wiring is needed

The wires to the computer are for "vacuum advance" advice, not needed for start up or making spark, computer issue can cause sluggish engine response but not "no spark"

First thing to check is if the distributor is actually turning when engine is being cranked , take off cap and crank engine, make sure rotor is turning
If its not then no spark of course, could be broken distributor shaft gear or timing belt is broken, or has come off

Coil gets 8-9volts with key on, thru a resistor, then should have 10volts while cranking(resistor by passed), you do need to test if coil is getting the 10volts while cranking, it is two separate power pathways, so it can have voltage with key on but no voltage cranking, so needs to be tested

TFI module testing here: https://therangerstation.com/tech_library/TFI_Diagnostic.shtml

There are two different TFI modules for distributors, a grey one and a black one they are NOT interchangeable, different wiring hook ups

So if tracing no spark stick to the distributor and coil, that all there is for the spark system on your 1988 2.3l

 

[Kmcbride3956]

Thank you for that information! Yeah, I have the gray TFI and will check the things you mentioned. I am thinking it’s the TFI just because the one on it is an older aftermarket part and I know they are know to fail pretty regularly.

 

[RonD]

No spark for the TFI module is unusual, weak spark when its hot was the often seen failure

 

[Kmcbride3956]

How can I test the pip sensor? Or the whole distributor?

 

[RonD]

Did you download the test sheet, here: https://therangerstation.com/tech_library/images/tfi_worksheet.jpg

Use a sewing needle to tap SPOUT or PIP wire, so TFI stays connected, turn key on
You can turn engine manually and should see 12v then 0v as distributor sensor opens and closes or if you crank engine with starter motor you should see 5-7volt average as sensor opens and closes at 200rpm speed

 

[Kmcbride3956]

Got it. Thank you for that. I’ll try that to and let you know how it goes.

 

[Kmcbride3956]

Hey Mr. RonD, can you explain to me how to do test number 4? I’m not sure how to test resistance. I put my meter on 20 ohms but what do I touch the leads to? And the key is supposed to be off for this test right? How do I know which is the primary coil, secondary, and is the path to ground the thing on the side of the coil that has a ground wire attached to it?

 

[RonD]

An ignition Coil should have 2 wire connectors(+ and -) and then a single spark plug wire type connection on the top

Unplug 2 wire connector and spark plug wire to distributor

Primary Coil is the two wires, they would have 12v and Ground with key on, ohms are low on Primary so 20 ohm scale is correct, .5-1.5 ohm between the 2 wire connectors

Switch ohm meter to 20,000(20k) scale to test Secondary coil, put probe on Spark plug connector and other probe either wire connection you just tested, 7-15k is expected
Secondary is actually only connected to the Ground side of Primary coil, but since its only 1 ohm difference between + and - it doesn't matter which one you use for the Secondary coil test


Not that it matters but Ignition coils work like this
Primary is a coil of wire wrapped around a metal core, for simplicity lets says there are 100 loops/coils on this wire between + and - connections
When voltage is applied to this coil it becomes an electro-magnet, so a magnetic field is generated around it

The Secondary is another coil of wire wrapped around the Primary coil of wire, insulated so they don't touch
The Secondary has more loops/coils, say 100,000, 1,000 times more than Primary
The magnetic field causes a charge to build up in the Secondary coil, charge is multiplied by the number of coils, so 1,000 times more than Primary volts, but very low AMPs

If Primary has 12volts then Secondary has 12,000volts
To release this 12,000volts the power to the Primary coil is cut, this collapses the magnetic field

In the old days the Points in the distributor were hooked to a Ground and then the "-" terminal on the Primary Coil
The Primary coil got 12volts with key on
When Points were closed the Primary was grounded so powered up, when Points were Opened power is cut and spark is released

Now a days a transistor is used inplace of the Points to power up and cut power to the Primary coil, but the coil itself is exactly the same and still uses "-" terminal to power up and cut power
Even Coil Packs are the same, they just have 2 or 3 coils inside instead of 1

 

[Kmcbride3956]

I’m getting 0.00 when I do test both the primary and secondary.

 

[Kmcbride3956]

I’m getting 0.00 when I test the primary, and secondary, however, if I plug the primary back onto the coil then I get 8.53 when I test the secondary.

 

[RonD]

Take your meter with you to get a new coil and test it before you buy it, to make sure meter is working correctly

 

[Kmcbride3956]

Okay new coil is testing correct. Moved onto next tests. In test number 6, coil voltage is 12, start voltage is 9, but run voltage is 0. I also went ahead and tested the Hall effect at the spout connector. It was really hard for me to know if I was on the spout connector or not, so I ran a wire to the pin on the TCM for the spout connector and put my probe on the other end of the wire. It was only reading .20 volts while cranking. So I was going to test it at pin 56 of the ECA but I don’t have a clue which one is pin 56.

 

[Kmcbride3956]

Correction again! I am getting 12 volts on the run circuit. I guess I didn’t have my test pin in good enough at first. So I suppose the Hall effect test is the only one it’s failing at this point.

 

[Kmcbride3956]

Does that mean I need a new distributor? I also just found a giant hole in the radiator... I really want to make this truck run, and I can change out the radiator no problem, but I’m getting frustrated with this no spark condition because honestly I don’t know what I am doing! I can change out parts all day, but when it comes to diagnosing the ignition system I don’t know what I am doing. I appreciate your help, it’s gotten me further than I would have ever gotten on my own. I’m just wondering if I just went ahead and replaced the distributor and the ignition control module shouldn’t it run then? If I replaced those two items, it already has a new coil, shouldn’t it get spark then? What else could be causing the problem besides these 3 things? I’m guessing a problem in the wiring harness somewhere?