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-   -   Zemco Fuel Computers (https://www.airforums.com/forums/f159/zemco-fuel-computers-184587.html)

Keyair 07-20-2018 11:06 AM

Zemco Fuel Computers
 
Wanted to start a discussion, and resource page for these cool little units.

Long been a fan of these, and had one on my Mini in the mid 80s and loved it.

I have bought a bunch of them over the years(maybe 5 or 6 of em!).
I have begun to set up a ZT4 unit in the Motorhome, and installed the fuel flow sensor in the carb feed line.
They came in a variety of units, from a dash top mounted unit(ZT1 and 4), to a DIN style(DCS).

As stock, they are only suitable for carburetored vehicles.
The fuel flow sensor installs in the feed line to the carb.
The unit senses speed and distance by some magnets and a sensor on the driveshaft.
Some units have a cruise control integrated.

However, I knew that Zemco built a optional add on box that replaced the flow sensor for Fuel injection vehicles, but they are rare and have proved elusive for years.

That changed this week, because a Zemco unit (DCS 310 EFI) that is a DIN style head unit, popped up on Ebay this week. I didnt hesitate, and bought it.

It has the EFI box.... and whilst it has not arrived yet, just looking at the box there is more info there than I have ever been able to glean before!

I will begin adding more info, and pics of the units I soon.

Keyair 07-22-2018 03:15 PM

7 Attachment(s)
So, this is a ZT4.
This one is mine and it’s an unmolested, NOS unit.
Box.
You can still find these, like this, on Ebay and the like.

Attachment 317759Attachment 317760Attachment 317761Attachment 317762

Instruction manuals.
Attachment 317763

This is how it came packed.
Attachment 317764

This is the fuel flow sensor.
Attachment 317765

I have several of these.
I have a later unit, looks like the ZT4, but has an LCD display, and that is the one I am planning on installing in the MH.

Keyair 07-22-2018 03:21 PM

4 Attachment(s)
This is a DCS 310 EFI unit.
This one has the EFI add-on box, and the cruise control module which is vacuum powered.
I also have a DCS 310 without it.

Keyair 07-22-2018 03:22 PM

2 Attachment(s)
Contents of the box...

Keyair 07-22-2018 03:29 PM

What intrigues me is this elusive "EFI box".
I have been looking for one, for years!

This info says that the box connects to "TBI and Bosch Electronic" injector with two wires, that sense the fuel injection pulses and provide accurate fuel consumption readings.

There was a guy on another forum, years ago that replicated this box and had a diagram.... but its a long dead trail, and his email address is dead too.

Keyair 07-26-2018 06:14 PM

Zemco Fuel Computers
 
4 Attachment(s)
Unit arrived, and I wasted no time to examine the EFI box.

Note the date code!
Attachment 318106

I知 glad I知 staying period correct! [emoji3]

So, I examined the box, and it seemed to be held together by a strip of electrical tape....
Attachment 318107

And so, throwing caution to the wind, and without a care about voiding the warrantee, I pulled off the tape to find it痴 secrets......

Attachment 318108
Attachment 318109

I have no idea what I知 looking at, but it痴 1983 technology, so..... [emoji16]

Keyair 07-26-2018 07:33 PM

1 Attachment(s)
And so, im digging around today and I find this thread from 2008...

https://ecomodder.com/forum/showthre...-box-5369.html

And there is a diagram, Post #18, by Racprops...

Apparently it has some errors, but this is what he posted...

bkahler 07-27-2018 06:58 AM

Quote:

Originally Posted by Keyair (Post 2134508)
And so, im digging around today and I find this thread from 2008...

https://ecomodder.com/forum/showthre...-box-5369.html

And there is a diagram, Post #18, by Racprops...

Apparently it has some errors, but this is what he posted...

Makes me think you should have a conversation with Wayne about reverse engineering the board and then having him make some new ones.

One of the reasons I gave up on using a Zemco was the scarce availability of the EFI support module. I've got either four or five of the Zemco units sitting on the shelf and can't use them. At one time I was going to use one in my Argosy and one in my TR6. Now that the Argosy is fuel injected and my TR6 is getting the same treatment the Zemco units are useless to me.

Keyair 07-27-2018 09:08 AM

I知 sure Wayne will pipe in when he gets a minute. Magnet18 was interested too, and I sent him some pics of the board yesterday and he seemed to think it was pretty straightforward.
Me, I知 clueless on electronics, and not ashamed to admit it!

Magnet18 07-27-2018 09:44 AM

Quote:

Originally Posted by bkahler (Post 2134667)
Makes me think you should have a conversation with Wayne about reverse engineering the board and then having him make some new ones.

One of the reasons I gave up on using a Zemco was the scarce availability of the EFI support module. I've got either four or five of the Zemco units sitting on the shelf and can't use them. At one time I was going to use one in my Argosy and one in my TR6. Now that the Argosy is fuel injected and my TR6 is getting the same treatment the Zemco units are useless to me.


I'm already halfway done reverse engineering it!

Raw costs should be about $8 per board plus a couple bucks in parts, whoever has a TBI unit and volunteers first to test it gets a free one

Magnet18 07-27-2018 10:22 AM

One of the mistakes the other guy made was that those 1Megs from the injectors pull up, not down

Maybe Wayne can chime in with how he thinks the injector sense lines are wired. I can't decide if it's one line to ground at an injector, and one to the coil, or one line to each of the 2 injector coils.

The signal is measured differentially, and it's intentionally designed to be bipolar, but I can't tell if that's for counting both injectors with just 2 wires, or if it's just to idiot-proof it and make it less prone to noise

bkahler 07-27-2018 11:51 AM

Quote:

Originally Posted by Keyair (Post 2134722)
I知 sure Wayne will pipe in when he gets a minute. Magnet18 was interested too, and I sent him some pics of the board yesterday and he seemed to think it was pretty straightforward.
Me, I知 clueless on electronics, and not ashamed to admit it!

Myself, I know just enough to be really dangerous :lol:

bkahler 07-27-2018 11:58 AM

Quote:

Originally Posted by Magnet18 (Post 2134732)
I'm already halfway done reverse engineering it!

Raw costs should be about $8 per board plus a couple bucks in parts, whoever has a TBI unit and volunteers first to test it gets a free one

I don't mind volunteering. It looks like in about 2 maybe 3 weeks I'll be able to drive mine out of the shop for the first time under it's own power :)

Steve, can you post a complete list of components (with pics!) used in an EFI version of the Zemco ZT-4? I have several NOS ZT-4 units but I don't know what extra bits and pieces are needed for the EFI version.

Brad

Keyair 07-27-2018 10:05 PM

Zemco Fuel Computers
 
5 Attachment(s)
Brad, my understanding is that this EFI module replaces the Fuel Flow Sensor, as it plugs into the same wires, and replicates the input to the Head unit.
I did not receive a manual with this unit.

There are 5 wires coming out of the EFI unit.
They are labeled on the circuit board as follows:
Orange, Labeled ACS.
Grey, Labeled OUT.
Grey/Black, Labeled GND.
Two Black wires Labeled IN, which I assume means Injector.

My research tells me that TBI and Bosch EFI injectors run on two wires: A battery + wire, and another wire that goes to the ECU/PCM, which is a Ground.
We believe the two black wires go to one injector only.
I believe that this feedback is then calibrated like the fuel flow unit via the Head Unit. I have added the fuel calibration page from a ZT4.
See the attached pics.

Attachment 318214Attachment 318215
Attachment 318216
Attachment 318217
Attachment 318218

bkahler 07-28-2018 06:32 PM

I tend to agree that the two wires go to one injector only. If it was one wire per injector then it would only be good for throttle body injection and not multi port injection.

What I believe happens is the system counts the number of pulses and uses that to help determine fuel usage. Kinda of a crude way to to it but it should be in the ball park.

Do you have any instructions on what settings and/or parameters that you have to enter when you set things up? I.e. number of injectors, etc.

Brad

Keyair 07-28-2018 08:19 PM

Brad,
I have no info, but, my guess is:
1/ The EFI unit is set up to replicate the input from the flow meter that you normally get in the kits.
2/ The Head unit has the logic capability to be adjusted/calibrated for fuel discrepancies.
3/ So, my assumption is that the the EFI module converts the Injector pulses, and pulse widths, into a simple analog signal, that roughly replicated the fuel flow sensor, and the Head unit is calibrated by the user to smooth and refine the differences.
4/ The Head unit wiring incorporates a simple battery backup that retains the calibration in case of power loss.

bkahler 07-29-2018 06:30 AM

Converting the injector signal to replicate the flow meter does make sense and would explain why you don't need any changes in the head unit.

The one thing I didn't like about the flow unit was the ports were 5/16" when 3/8" was really needed. This EFI unit eliminates that issue completely.

Keyair 07-29-2018 02:17 PM

1 Attachment(s)
Scanned a copy of the ZT4 Instalation Manual...

Took it apart and tried to get the scanner to do it so it would print as a 2 sided doc... not sure if I was successful, but its all there!

See Attached.

Keyair 07-29-2018 02:24 PM

1 Attachment(s)
And the Zemco ZT4 Operation Manual.

See attached.

Keyair 08-04-2018 04:54 PM

2 Attachment(s)
Wow, its been strange... the Zemco godfather must be smiling at me!

Picked up a used ZT4 a while back for $20, and it was just the head unit and fuel flow sensor... Figured it might work for an idea I had to watch the fuel consumption of the onboard genset... or dissection or something...

Anyway, with Magnet18 working on duplicating the EFI Module, I figured I would mail it to him to mess with, test or something... but there was no wiring harness or speed sensor, etc. He said cool, he could figure it out.

Then another popped up... used but looked complete.
Made the guy a cheap offer which he accepted.
Attachment 318879

That is heading your way next week Magnet18.

The surprise was hiding in the box...
An opened, but seemingly unused "P/N 4792 Fuel Return Kit".
Probably means nothing to 99.999% of people... but to me, having seen it mentioned in the install manual, I always wondered what it was, how it worked, and if I needed it... :blink:

Drum roll.....:D

Attachment 318878


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