tach and eec

whitebroncoii87 · Jun 27, 2015

hi, getting around to trying to get my tachometer to work, never did since purchase. which wire from behind the instrument cluster is responsible for tach and is it fed from eec or the coil itself or tfi? where do i get a pinout of my eec, i can't seem to find an 87 pinout? i took it out and found these serial numbers: efi-sd22a and e7tf-12a650-be1a, what do they mean? is this an 87 eec? Thank you!

adsm08 · Jun 27, 2015

The tach itself is probably bad.

And yes, that is an 87 computer.

whitebroncoii87 · Jun 29, 2015

Cleaned out bunch of contacts behind the cluster and the green cable at the coil so they are free from rust and tach is working now. However when I turn off the car the needle still remains at 750 rpm from idle. Is it suppose to point to zero?

adsm08 · Jun 29, 2015

I want you to tell me what you think the answer to that question is.

RonD · Jun 29, 2015

Pin out for EEC-IV here: http://www.auto-diagnostics.info/ford_eec_iv

Yes, tach signal comes from Coil "-" terminal or TFI coil wire, they are the same
Yes it should be 0 if engine is at 0 RPMs.

e7tf-12a650-be1a
e7 = 1987, e =1980(decade), 7 = 7(year in that decade)
t = not sure, I thought 7 here meant Ranger, so if this is a BII then t = BII
f = engine accessory

12a650 = Ford part number for all EEC-IV, not model or year specific

be1a is the firmware and revision

There should be a large 3 or 4 letter code on that label as well
Read here for what that means: http://oldfuelinjection.packrad.net/page17.html

whitebroncoii87 · Jun 29, 2015

ha, i guess that means it should be at 0. the needle does seem very stiff, doesn't jump the slightest, just moves really steady. maybe some wd40 will do the trick.. sigh, don't really feel like opening up the cluster again

whitebroncoii87 · Jun 29, 2015

RonD said:
e7tf-12a650-be1a
e7 = 1987, e =1980(decade), 7 = 7(year in that decade)
t = not sure, I thought 7 here meant Ranger, so if this is a BII then t = BII
f = engine accessory

12a650 = Ford part number for all EEC-IV, not model or year specific

be1a is the firmware and revision

There should be a large 3 or 4 letter code on that label as well
Read here for what that means: http://oldfuelinjection.packrad.net/page17.html

Awesome information! thank you very much!

Does efi-sd22a means tfi iv? I think I have an 88 engine with an 87 computer. Why did they remove egr from 88 engines? Can I keep my 87 computer or will it give inferior calculations due to missing egr. Thank you!

RonD · Jun 30, 2015

efi-sd22a
I am guessing but EFI would be electronic fuel injection and sd22a would be the "type/revision"

In the above link the pictured EEC-IV label has SFI-SD1 which would make me think sequential fuel injection "type SD1"

EGR system is used to lower NOx emission
NOx emissions go way up when cylinder temps go up, like when engine is under load.
If you mix exhaust gases with air/fuel it causes a slower burn so lowers the peak cylinder temps, so lowers NOx production

You can also do this by retarding spark timing, but it does reduce power.
Running slightly richer mix under load would lower temps
These can be done by changing computer software

Or change the cam, lowering compression a bit.

whitebroncoii87 · Jun 30, 2015

yeah, my engine knocks a lot under load, especially when warmed up. I think my compression might be too much, i remember when I took out the heads and put them back and starter cranked each cylinder for about 1 second and they were already at 150 psi, maybe under normal load with spark and fuel they go up even higher? Any idea how much pressure the cylinder should have when you crank dry from the starter? I'm going to readjust my valve lashes again based on these cylinder pressure readings, maybe tighten them to see 130 psi on compressor test. Just pulled that number randomly less than 150..

RonD · Jun 30, 2015

I use the number 18.3 along with compression ratio number to get approx. expected compression for an engine
2.9l is 9.0:1 ratio

9 x 18.3 = 164.7psi

So the 150 would be OK dry, I would expect closer to or just above 160 adding oil, with no spark plugs in and a fresh battery.

Many set TFI base spark timing back to 12deg BTDC instead of 10deg BTDC, this retards spark under load to help prevent pinging/knocking.

whitebroncoii87 · Jun 30, 2015

where is 9.0:1 coming from, what does it mean?

you mean to 8* btdc instead of 10*? that that would retard the timing right? (12* would advance the timing?) i was thinking of setting it to tdc (0 degrees) and let the computer handle the rest.

I should really put this in another thread but what is the correct procedure for resetting the eec after you have unplug the battery for a while. I usually just let it sit/idle/no messing with throttle for 5 minutes then turn it off for 5 minutes. Is that all? Thank you.

adsm08 · Jun 30, 2015

whitebroncoii87 said:
ha, i guess that means it should be at 0. the needle does seem very stiff, doesn't jump the slightest, just moves really steady. maybe some wd40 will do the trick.. sigh, don't really feel like opening up the cluster again

If you have the needle off try zeroing it as well. With the needle off plug everything in, turn the key on, and then put the needle on facing 0.

adsm08 · Jun 30, 2015

whitebroncoii87 said:
where is 9.0:1 coming from, what does it mean?

you mean to 8* btdc instead of 10*? that that would retard the timing right? (12* would advance the timing?) i was thinking of setting it to tdc (0 degrees) and let the computer handle the rest.

I should really put this in another thread but what is the correct procedure for resetting the eec after you have unplug the battery for a while. I usually just let it sit/idle/no messing with throttle for 5 minutes then turn it off for 5 minutes. Is that all? Thank you.

9.0:1 is the rated compression ratio of the 2.9. It has about nothing to do with timing.

Setting the timing to 0* will probably stop the knock, but it will also stop the power. The computer only has the ability to vary the timing in an limited arc, idle should be near 10 or 12, running it can get close to 20, which is outside the computer's range if you set the base timing to zero.

I have my base set at 15* and no knock. I think your issue may be something other than timing.

whitebroncoii87 · Jun 30, 2015

adsm08 said:
I have my base set at 15* and no knock. I think your issue may be something other than timing.

what are some possibilities. I lopped the knock sensor in half when I pulled the y-pipe out to replace the catalytic converter (it was totally hollowed inside, hoping that would reduce the knocking noise, it didn't). But the knock was there before that. I'm waiting on ebay to send me another knock sensor my first time buying on ebay seems to take forever to ship, no where else has it.. Do you think I should readjust my valve lashes to read less than 150 psi on each cylinder to lower the compression? (sure hope I have egr in this situation.. maybe I have to get an 88 computer to match with lack of... not really wanting to..)

adsm08 · Jun 30, 2015

Have you tried running a tank of 89 through it?

tach and eec

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