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No injectors on 2/3.


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Ok so this weekend i bought a 93.5 se. And all was well until for some reason injectors 2/3 stopped working. I removed the injector harness went through it it was all good right back to the ecu. The injectors are fin as i swapped them with 1/4. And still 2/3 wernt working. Have i got a fried ecm.?

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First off - I do not know anything about the ECU fitted to the Esprits or how it works but I have work on stand alone EFI before (Megasquirt).

It sounds to me like an injector driver has given up, injectors are *Usually* batch fired (So on a 4 pot they are fired in pairs), so either 1&4 or 2&3 fired together.

One pulse when the valve is open and one when it's shut. Sounds daft but firing on a closed valve cools the valve, vaporises the fuel and reduces the required injector size by half.

If it is an injector driver then it could jsut be a transistor has given up, might be an easy fix - if you can diagnose which one!

Lotus Esprit S4 - Work in progress

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to i talked to a John at WC engeneering and he and i walked through the problem . the original injectors of that car we known to draw too much as the injectors aged and intern ruined the driver on the ecm so he gave me the numbers for the parts i needed from ac delco for a new ecm and rc for some injectors . all will be well as hew says this happens on them all the time ...

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Yes it could just be the transistor/driver in the ECU, so easy to fix probably.

However, looking at the ECU manual (see below) there might something more simple: for each injector pair, the earth is rerouted outside the ECU casing, via a jumper, then goes back into the ECU to be grounded with everything else. So, make sure these jumpers are OK, tight and clean connections etc.

However, what puzzles me is that whatever the reason for the injectors not to be powered, the sense line is there to detect a low current condition, and it should set an error code which should light the yellow Check Engine Light on your dashboard.... unless this light doesn't work on your car, in which case hook up Freescan or Espritmon to your ALDL plug to read error codes... there ought to be a code 65 in there !

At any rate, whatever the problem in the ECU, it looks like an easy one to fix: transistor, current sensing resistor... not the other end of the world...

the original injectors of that car we known to draw too much as the injectors aged and intern ruined the driver on the ecm

Ah ok, this would explain why it doesn' traise an error flag then, as the ECU only checks for low current, not excess current.

Replacing the ECM is a bit strange though ! Cost a fortune when there is only for a few penny worth of transistor !

If you bin your old ECU then I would lov eto have it ! Being an electronic guy it should not be too much trouble to fix it ! This would allow me to have a real ECU on my bench to help me develop my ECU reader (A king of bespoke "Tech 1" handheld device) .....

post-31-0-60509900-1309194412_thumb.png

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do you know what the values are for the drivers ?

Nope, I don't have the schematics of the ECU (would love to though!) so can't know what component reference they used. But it's probably stamped on it if the casing is large enough for that, which it must be given that it's sized for a fair amount of current , hence fairly large package. You have nothing to lose anyway, so just open it up and have a look !

But before you open anything, have you made sure that the ground jumpers are OK, as I suggested above from the ECU wiring diagram ?

Edited by Vince
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new ECU is ~$80

Eh ?! How comes Lotus sells them for so little these days ?! I am schocked ! Used to cost thousands or at least many many hundreds of bucks !

Actually, looking at SJ Sports Cars' website, a simple reconditionned ECM, not even a new one, costs already 715 USD Excluding VAT !

So I am lost...

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Ok so got a new ecu . some new rc injectors and yeeees it fired up runs fairly good , check engine light is on and so is fan fail however i can hear the fans working . so i drove it home so i could have my shop to work on it not a garage in a distant country .

The car ran good . (in limp mode ) but ran good . once and a while the engine would die and back fire and then just go again . but it got me the 1700 miles home . now when i try to connect my free scan it connects but has no data . i also cannot jumper the aldl to get a flashing code ... any ideas .

btw DPO BAD ON THIS ONE

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The memcal for your car is specific to that model, so you can not use one from just any other car. Is the memcal in the car a Lotus Esprit SE memcal?

Visit Sanj's Lotus Esprit Turbo SE pages

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http://www.rockauto.com/catalog/raframecatalog.php?a=G-GM12752-13501

http://www.autoecms.com/parts/Details.cfm?ProdID=1240815&ord=product_name

~$100

GM part # 1228708 for the ECU for SE-S4s &GT3 (all chargecooled cars after the 89 non-SE)

Travis

Vulcan Grey 89SE

My Lotus Photo and Projects Album

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http://www.autoecms.com/parts/Details.cfm?ProdID=1240815&ord=product_name

~$100

GM part # 1228708 for the ECU for SE-S4s &GT3 (all chargecooled cars after the 89 non-SE)

Thanks !

It's not really a Lotus one it's not really 100 bucks (200) and it's not really a new one (exchange/refurbished), but it's still very interesting given the low price !

The hardware/electronics is probably the same though, so that does interest me as knowing the GM part number might make it easier to find the electronic schematics ! I woud love to have them... since you live over there and know so much, maybe you are aware of a website wher eI could get the schematics for this particular part number ??

Sorry for hijacking the thread ! :whistle:

Edited by Vince
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  • 2 weeks later...

SOLVED......

So i had asumed that the original ecu was no good after it was only running two of the four inj. so along with new rc units i installed a new computer . turns out the new ecm was faulty the whole time . installed the old ecm and voilla awsome car .

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