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Old 07-20-2018, 10:06 AM   #1
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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.
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Old 07-22-2018, 02:15 PM   #2
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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.

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Instruction manuals.
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This is how it came packed.
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This is the fuel flow sensor.
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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.
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Old 07-22-2018, 02:21 PM   #3
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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.
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Old 07-22-2018, 02:22 PM   #4
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Contents of the box...
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Old 07-22-2018, 02:29 PM   #5
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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.
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Old 07-26-2018, 05:14 PM   #6
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Zemco Fuel Computers

Unit arrived, and I wasted no time to examine the EFI box.

Note the date code!
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I知 glad I知 staying period correct!

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

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I have no idea what I知 looking at, but it痴 1983 technology, so.....
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Old 07-26-2018, 06:33 PM   #7
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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...
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Old 07-27-2018, 05:58 AM   #8
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Originally Posted by Keyair View Post
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.
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Old 07-27-2018, 08:08 AM   #9
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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!
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Old 07-27-2018, 08:44 AM   #10
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Originally Posted by bkahler View Post
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
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Old 07-27-2018, 09:22 AM   #11
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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
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Old 07-27-2018, 10:51 AM   #12
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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
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Old 07-27-2018, 10:58 AM   #13
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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
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Old 07-27-2018, 09:05 PM   #14
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Zemco Fuel Computers

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.

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