'94XLT Cranks, No spark, intermittent

[George Scott]

V6, 4.0L, 4WD, Auto. 168K miles.Infrequently and unexpectedly engine will crank but not start. When this happens, there is fuel pressure, but no spark. I have used a spray bottle and wet down selected areas (wires, connectors, modules) which did not help the diagnosis. It has happened in hot weather and cold, after sitting overnight and after a quick stop in the gas station when it's up to temperature. Problem does not appear to be related to temperature, moisture, altitude. When it starts everything runs fine. When it doesn't, it's like in the old days when you pulled the coil wire out of the distributor. Check engine light comes on at key-on but does not display when engine is running, and I have used a code reader and there are no codes in the memory. My Honda car had an intermittent ignitor once. Is this probably the same sort of failure ? I have a Chilton and a Haynes manual but they are both woefully inadequate regarding troubleshooting. I checked the Stickies and about 30 pages of posts after doing a search but most starting problems seem to be fuel related. Are my symptoms a commonly known problem with this year/model ? Can you provide a series of things to investigate. Thanks.

 

[MrShorty]

A few things I might look at:
1) Verify that the ICM has power and ground. Bad wiring to the ICM will often trigger trouble codes, but EEC-IV isn't perfect at detecting them. make sure the wiring to the ICM seems good.

2) Check wiring to CKP and/or CMP, to be sure the PCM/ICM can see when that the engine is turning over.

3) Check for power to the coil.

 

[dogfriend]

I had similar intermittent no start with my 89 Ranger that I used to own. It turned out to the ignition coil. The resistance went up so much that it wouldn't fire at all, but it took several months for it to get that bad.

I would suggest testing the coil pack secondary resistance. There is a good description with specs in the Haynes manual if you have it.

Another possibility is the TFI ignition module. They are notorious on older Ford EEC IV because they were mounted to the distributor body and would get hot. On the Explorer, the TFI module is mounted to the radiator support, so they don't get as much heat, but you can have this tested at some of the better auto parts places (Napa, possibly Autozone).

 

[BrooklynBay]

Welcome to this forum! It might be the crankshaft, or camshaft position sensors.

 

[George Scott]

Thanks for your help

Thanks guys for your suggestions. That is exactly why I joined this forum, to benefit from another set of opinions and to get input from guys who had gone through these things before. Looks like it's time to schedule some "under hood with a meter" sessions. Fortunately the weather here is very cooperative. And I've picked up some other good tips in some of the other forums here for example, replacing the plastic thingy that makes the rear hatch lock respond to the key and not just to the electric operation. Now I know what to expect when I pull the inside panel off for a look-see. Thanks again for taking the time to make your suggestions.

 

[George Scott]

Just a quick follow-up: First of all the problem went from intermittent to permanent failure. Yayy ! It's tough to fix something when it's working. It's easier to diagnose when it's out and out failed. I did the checks of primary and secondary resistance on the coil pack including the presence of B+ voltage and everything seemed to be okay. Also, I did the test using a test light to watch for the timing signals from the ICM and it was okay as well. Since nothing seemed to make sense, I reconnected the connector to the coil pack, hit the key and it fired right up ! So I took the connector apart, cleaned the contacts and blew everything out with canned air. That was 5 days ago and it's been running fine in daily use since then. The connector looked fine from the outside so there's proof that looks can be deceiving. Thanks for the help, guys.

 

[Burns]

Good to know you figured this out.

 

[dogfriend]

First of all the problem went from intermittent to permanent failure. Yayy ! It's tough to fix something when it's working. It's easier to diagnose when it's out and out failed.

Yep, that's how I finally found out what was wrong with the 89 Ranger. Intermittent problems are a *****.

Glad you figured it out.