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new engine in XT, won't start *SOLVED* Bad ECU


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SO close!!! i'm excited, that digi-dash i cool stuff, i like it!

put a new motor in it, this car has never run since i've owned it.

 

this is a Turbo to NON-TURBO conversion so i don't know if there are any vaccuum lines or things that can keep it from starting? are the Turbo and non-turbo ECU's compatible?

 

with the stock ECU the car doesn't get any fuel. when i crank it, the fuel pump does nothing. swapped in another fuel pump, same thing. when i plug the green connectors in for TEST mode the fuel pump does not cycle.

 

if i plug in an RX ECU the fuel pump cycles like it's supposed to with the green connector plugged in and fuel comes out the engine lines. but i get a code 44 with the RX ECU (but not with the XT Turbo ECU). i'm wondering if this is EGR related because it's not in my 88 FSM and the turbo motor had an EGR system, the new motor does not.

 

but...the car still doesn't start on the RX ECU. should it work okay for the XT engine non-turbo? i'm thinking the stock XT Turbo ECU is shot - it doesn't pump any fuel and it doesn't show the 44 code the RX ECU shows.

 

No trouble codes (except a 44 with the RX ECU), got spark, compression excellent, timing belts dead on, fuel injectors all have good resistance. continuity from all injector harnesses, the dropping resistor tests within spec.

 

there is a device that bolts to the dropping resistor and has some vacuum lines on it....what is this, because i don't have it hooked up to anything? i took a picture and left my camera at home (GRRRR, at my parents now).

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did you put the coil back in and hook the 2 wires up on that bracket that the coil is on?

 

If you can't get the fuel pump to run why don't you hot wire it so you can atleast make sure everything works properly and come back to that problem later.

 

I don't think the ecu is bad. The car ran when the motor got borked.

 

Good luck

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did you put the coil back in and hook the 2 wires up on that bracket that the coil is on?
yep, it's all good.

 

If you can't get the fuel pump to run why don't you hot wire it .
was thinking about that, but that it runs fine with the RX ECU really has me baffled?

 

what is the thing bolted to the dropping resistor on the passengers side? has an elecrical plug, two vacuum attachments and two other hose fittings and i have no clue what they are for? i assumed this was a turbo gizmo....

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44 Wastegate Duty Solenoid (Turbo Models)

45 Pressure Sensor Duty Solenoid (Turbo Models)

 

could either of these turbo items cause a non-turbo motor to not get fuel? anyone know where these items are located?

 

will an NA car run fine on a non-turbo ECU?

i think they will.

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44 Wastegate Duty Solenoid (Turbo Models)

45 Pressure Sensor Duty Solenoid (Turbo Models)

 

could either of these turbo items cause a non-turbo motor to not get fuel? anyone know where these items are located?

 

will an NA car run fine on a non-turbo ECU?

i think they will.

 

Wastegate duy solenoid is on the turbo itself.

Dunno what the Pressure sensor duty solenoid is though?

 

An NA car should run on a non-turbo ECU. NA is non-turbo ;)

 

[edit] here's a thought. Have you checked that the disty in the right position? I don't know if your JDM motor came with the disty on it already or not, but it might be good to check. If that's good, have you checked that the disty cap isn't 180 degrees out of rotation? On mine, the #1 spot on the cap is pointing north (up)

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EDIT - will an NA motor run fine on a turbo ECU. car was originally turbo, i put in a non turbo motor.

 

well crap...what is this thing bolted to the dropping resistor on the passengers side right behind the air box? i don't have it plugged in? maybe that's my issue.

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The wastegate duty solenoid is mounted to the passenger fender, at least it is in my 87 RX.
thanks boosted balls, looked at the RX at my place and it's the same. so i'm assuming same part, been searching for a pic.

 

DANG IT - i was hoping this was my issue.

 

that would explain the code 44 i'm getting. why do i get the 44 code on the RX ECU but not the XT Turbo ECU?

 

RX gives a code 44 and primes the fuel pump.

XT Turbo ECU does neither one of these....sounds bad but i'm confused at the moment.

 

got compression. got spark. got air. seems like i get fuel on the RX ECU...but who knows.

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what is the thing bolted to the dropping resistor on the passengers side? has an elecrical plug, two vacuum attachments and two other hose fittings and i have no clue what they are for? i assumed this was a turbo gizmo....

 

Ok.. left side of pic.. just in front of the strut tower....

 

http://usmb.net/albums/albuo11/Picture_057.jpg

 

silver box with pressure switch attached to it.

 

Is that the part you are referring to?

 

Do you have all the wiring hooked up to that box?.. The vacum lines are not important(as long as they aren't hooked to any vacuum lines on the motor, but it is vital that all the wiring that goes to that box is hooked up.

 

As faras why one ECU works and another doesn't, sounds like the XT ECU is bad. when my ECU fried, that was the first symptom. No fuel, no way no how.

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yes, the silver box bolted to the strut tower. i have two parts there - the dropping resistor which is fine and all plugged in (tested resistance and all, all good). the other thing connected to it, i believe is the waste gate controller, but i can't verify it and it's hard to see in the picture of the entire engine bay.

 

it has two vacuum lines and two other lines...i guess that go to the turbo, but i don't remember pulling it off. i don't have it plugged in.

 

do i need it for a non-turbo engine? do the lines need to be hooked up to anything? i'll play with it when i get home i suppose.

 

what does it do? can it affect starting/running?

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here's the part in question zoomed in. there's a dropping resistor here and i can't make out the picture too well as i zoomed in on his larger pic. but ther'es also something else here....waste gate controller. but i have a non turbo EA82 in it, so what do i do with this thing? plug it in or not? will it affect starting/running? i don't have any FSM with turbo stuff in it.

post-6800-13602760716_thumb.jpg

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There are 3 units on the strut tower:

 

Resistor pack for fuel injectors - only connection is a wire harness (about 5 wires, i don't remember exactly)

WGDS - one electrical, 3 vac hoses

boost pressure switch - turns on the TURBO light in dash gauges when boosting - electrical & vac connections

 

With a turbo ECU, the WGDS needs to be plugged in, but doesn't need vac connections (you can run a hose from turbo outlet to wastegate for reference).

 

Are you trying to make the NA motor run on a turbo ECU?

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Are you trying to make the NA motor run on a turbo ECU?

 

yes NA motor. turbo stuff all gone.

 

update - i solved the ECU issue. this is twice in a row that i've swapped motors (last time on my XT6) and had multiple parts failing...really pissing me off.

 

the RX ECU would not spark - but gave fuel???

the XT Turbo stock ECU would spark - but no fuel.

 

so i hard wired the pump with a switch inside the cabin that i can turn on/off for now. car started right up. i guess that ECU has issues of some sort with the fuel circuit cause the RX ECU worked fine with the pump.

 

i'll source another ECU for now.

 

new issue is that the car won't idle at all, i have to keep pushing the gas pedal in and out to keep it idling. intake/vaccum hoses maybe?

 

still not sure if the waste gate or turbo pressure device can cause any problems with the idling/running.

 

getting closer, thanks for the heads up.

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yes NA motor. turbo stuff all gone.

 

update - i solved the ECU issue. this is twice in a row that i've swapped motors (last time on my XT6) and had multiple parts failing...really pissing me off.

 

the RX ECU would not spark - but gave fuel???

the XT Turbo stock ECU would spark - but no fuel.

 

so i hard wired the pump with a switch inside the cabin that i can turn on/off for now. car started right up. i guess that ECU has issues of some sort with the fuel circuit cause the RX ECU worked fine with the pump.

 

i'll source another ECU for now.

 

new issue is that the car won't idle at all, i have to keep pushing the gas pedal in and out to keep it idling. intake/vaccum hoses maybe?

 

still not sure if the waste gate or turbo pressure device can cause any problems with the idling/running.

 

getting closer, thanks for the heads up.

My guess is you have a vacuum leak somewhere. When Jefffast thought he had a bad MAF (He could unplug the MAF and the engine would idle), it turned out to be a loose vacuum line.

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i believe the ECU is bad. it won't provide fuel (i have the fuel pump wired to a switch). it'll start that way, but runs bad. i disconnected the purge solenoid and AAV and the car runs the same (barely) and the ECu spits out no codes, i think it's bad.

 

i don't have a vaccuum leak but things could be hooked up wrong. i only have the 4WD solenoid hooked up right now. i'm trying to figure out the routing of all the vacuum lines but it's not in the FSM. there's limited info, for once it's not complete on what i need!

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I have opened and compared both the NA and turbo ecu. The circuit boards are exactly the same, except that the turbo ecu has an extra transistor (this is to drive the WGDS, .... which acts as a control to maintain max turbocharging pressure at higher altitudes, where air density/pressure is less)

The turbo ecu also has a 2nd circuit board mounted about 3/4 inch above the main board, this is the knock control unit.

They are the only 2 differences that i can see.

 

So i dont see why you couldnt run the na motor with the turbo ecu, the 87+ ecu doesnt have a boost switch to tell it is under boost condition like the 84-86 ecu does. So it should work just like the na ecu, but with KNOCK CONTROL!!!

 

Hope this helps

 

 

Gannon

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