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I think I need a new EEC - Any input??

3631 Views 7 Replies 4 Participants Last post by  GeoffSmith54
Hey! –I just found you while trying to research the first major problem with my Bronco. – Great site.
I think I need a new EEC but I would be grateful if anyone has any input.
I have a California Spec. ’96 351 E40D that I’ve had from new. It has 138,000 miles, about half of which was towing a trailer. The drivetrain is standard and it has been great (except for the front hubs) until about 3,000 miles ago. Sometimes it would crank but not start (no splutter – nothing) - always when cold. Then it would start and run fine until it decided to do it again. It’s gradually got worse until now it usually won’t start – but if it does, it runs great. I checked all the usual stuff (listed below) and the only thing I can find is that there is no pulse to the injectors (tested with a known to be good noid light). I unplugged the multi- pin plug to the EEC and there is continuity from one side of the injector plug to one pin on the EEC and from the other side of the injector plug to four pins, so I think the harness is ok. Before I buy a new EEC…

Is there anything else I should check? I found a comment on that said, “ECM failures are most likely caused by a shorted solenoid” Yikes – but what solenoid affects the injectors?
If I need a new EEC, does anyone have any recommendations about the best place to get one? Any experience with one of the rebuilds that several places offer?

Other info.
When I try to start it, as I stop cranking (let go the key), the noid light will, very occasionally, give one flash. This corresponds with something else I noticed - when it won’t start but then does, it is usually as I release the key that it would catch and start.
There are no codes. It did throw a 1401 in the middle of this but the DPFE tested bad and I replaced it without any noticeable difference.
The fuel pump runs for a couple of seconds when the ignition is turned on. The pressure at the rail was low but I replaced the filter and now there is 38 psi at the rail (without the engine running).
There is a good spark (tested with a spark tester) and, as a precaution, I replaced the plugs, wires, distributor cap and rotor, and the coil early on in this process when I wasn’t sure what was going on.
I completely uninstalled the alarm to make sure it wasn’t interfering with anything.

Any input at all would be truly appreciated.
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Sounds like your truck is OBD-II (EEC-V). Not sure if it still uses the IDM signal to tell the PCM The coil is firing. Midway down the page on this link: shows the diagram of the IDM signal. If the PCM does not see the coil firing one would assume it would not fire the injectors? I am no expert on the EEC-V, but I do understand electronics. You might need to invest in Service and EVTM manuals. I am away from mine until this weekend. This may sound like a stupid question, but are there any codes now?
I bet you don't. Do a search on here and the net for EEC diagnosis or words to that effect. I bet though that you need a new EEC relay
Thanks for the input, I truly appreciate it.

Rla2005 - Yes, it is OBD-II and no, there are no codes currently. I certainly see the logic in not firing the injectors if there appears to be no ignition and I’ll try to use the Haynes manual and follow that train of thought tomorrow. I’m struggling a bit because most of the information I can find, including the Haynes manual, focuses on EEC-IV, while the EEC-V is certainly different in wiring and layout if not in function. I bought the EVTM manual off of ebay yesterday and I’m crossing my fingers it arrives for this weekend.

Waltman – Yes I search for EEC here and on the web and found lots of interesting stuff but nothing that really helped.A lot related to EEC-IV diagnostics which is one of the biggest difference between IV and V. 'Wish I’d got that pristine ’95 instead of the new ’96 but the discontinuation had been announced and I got a deal I couldn’t refuse. I’ll certainly check out the EEC relay which I assume is the one marked “Powertrain Control System” in the Power Distribution Box. If that failed though, wouldn’t the EEC just stop working completely?

Thanks again for the help – I’ll keep you posted.
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As far as the signals in/out for spark and fuel between the EEC-IV/V they are basicly the same. Yes I know there is a makeshift crankshaft positioner for mis-fire detection, but that is probably not the issue here. I looked some info on one of my Service cds to compare the EEC-IV and EEC-V signals. Both use the PIP, SPOUT and IDM signals. According to the manual the PCM uses the PIP signal to trigger the injectors. So I would suspect a possible missing PIP signal. I am not 100% clear what the IDM signal does.

I did have one other thought around midnight last night: Both systems will shut off the injectors if the TPS signal indicates full throttle when in the Start mode. What if the OPs TPS was shorted? This would send the +5V reference signal directly through to the feedback signal. Easy check: disconnect the TPS, then try to start.

Next I would start verifying the PIP and possibly the IDM signals are getting back to the PCM.
Sorry for the slow response – life and weather slowed me down.

The relay is fine.
Unplugged the TPS – no change.
The PIP has continuity between the distributor connector, the ICM connector and the PCM (EEC) connector BUT with the distributor connected (and only with the distributor connected), shows battery voltage with the ignition on (12.9V DC) and cranking (10.7 DC). This remains the same with the ICM and PCM disconnected, therefore I must conclude that the DC voltage comes from the distributor. If I understand correctly the PIP circuit should be zero voltage until cranking/running when it should show 3.0 – 8.5V A/C so I assume that there is a short to the 12V DC supply in the distributor, or at least on the distibutor side of the connector. [ I now know this logic is flawed - see my next post in this thread] The thing that I find strange is that I would have thought that this would have thrown a code (P0320??).

I have a few more checks to run but I suspect that I’m off to NAPA for a new distributor – I’ll let you know how it works out.

Thanks again.
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Usually if the eec goes bad it will have corrosion. I'm not sure if the 96s have a TFI (thick film ignition), but that might be something to search on also.
She Lives Again.

Picked up a rebuilt distributor from NAPA today. Before I installed it I grounded it (probably not necessary), plugged it into the Bronco harness, turned the ignition on and spun the distributor by hand… and the noid light flashed away, Yeah! Swapped out the distributor and it fired right up. My logic was flawed though, because the new PIP signal is still 12V DC with the ignition on – having now read up on how hall effect sensors actually work, that makes sense. BIG, BIG “Thank You” to rla2005 for pointing me in the right direction and saving me from buying an EEC that I didn’t need.

Need4racin – Thanks for contributing. As far as I can figure out, TFI(Thick Film Ignition), Ignition module and ICM (Ignition Control Module) all refer to the same module which can be black or gray (not interchangeable) and can be mounted to the distributor or, on later model years, remote mounted on a heat sink. I’d be curious if anyone knows different.
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