Turbotubbs

Turbotubbs

New Member
Evening all!
I'm (hopefully) coming to the end of my 3.9 v8 EFI conversion, but I can't get the damn thing to start! It turns over fine and I get a spark alright but the injectors aren't firing. I've tested at the ECU connector for all the sensors etc and everything seems good - even went as far as to buy a new (scrappy) ECU, but still dry plugs!
Is there a way to test if the ECU is getting a correct signal from the coil to trigger the injectors?
I've got a shiny new powerspark dizzy to fit as the current one is looking tired and battered (still get an acceptable spark), just wanted to have it running before I play with that.

Any help greatly appreciated...
 
Yeah that's all fine. Like I said, tested at the ecu plug and earth is fine, getting the correct voltages/ohmages at all the other pins. One thing that came to mind - I had to make up a couple of wires to bridge the amplifier to the coil. The current one is the two lead amp - could I have got the polarity wrong? As I said before - it's got an average spark...
 
Just be reading elsewhere, the pump should prime for a couple of seconds (which mine does) but should come on as soon as the engine is cracked... that'd explain it - the ecu is not getting a signal from the coil so doesn't know the engine is cranking.
Question is: how come? There's voltage getting to the ecu from the coil. Coil is brand new. Amp is old but with average, not perfect spark.
 
Turbotubbs said:
Just be reading elsewhere, the pump should prime for a couple of seconds (which mine does) but should come on as soon as the engine is cracked... that'd explain it - the ecu is not getting a signal from the coil so doesn't know the engine is cranking.
Question is: how come? There's voltage getting to the ecu from the coil. Coil is brand new. Amp is old but with average, not perfect spark.
Click to expand...

would be a pulse not stable voltage
 
Yeah. Think it must be time for the new dizzy, rather than fitting it to a proven running engine I'll bite the bullet and do it.
 
Check the fuel pump relay , you can bridge the switched live to power the fuel pump,but first
check for 12v at switched live also relay should click when the ignition is switched on.
 
Both relays click as they should. Fuel pump comes on to prime but doesn't run at any other time. I assumed it would come on when it sparked. Ecu relay comes on when I turn the key and stays on for 5 seconds afterwards
 
Turbotubbs said:
Both relays click as they should. Fuel pump comes on to prime but doesn't run at any other time. I assumed it would come on when it sparked. Ecu relay comes on when I turn the key and stays on for 5 seconds afterwards
Click to expand...

yes as they should then switch on when you crank
 
Good question boycie! The guy who sold it said 92...

Got the dizzy in now. Still no luck. I've found LT checks on another post and according to that, I should be getting 0v between battery +ve and coil -ve with ignition off. I'm getting 12.8v! How can this be with brand new lucas coil and powerspark dizzy/ign amp?
 
You could try bridging the relay to bring on the pump , I had to do that when I bought a non runner it started and then I worked my way back with a volt meter and found a damaged fuse holder fixed that and bingo, that was with the help of the folks on here over 2 years ago.
 
The reason I asked the year is there are 2 types of distributor serpentine and pre serpentine.
You probably know they will interchange but the motor will run badly with the wrong one fitted.
 
I think tomorrow I'll try and bridge the relay and see if it'll run. Surely the fact that the fuel pump primes on ignition means that is working though?

Mine is non-serpentine btw
 
Been thinking about it. I'm at home now so can't check, but I think I wired the switched live for the ecu to the ignition switch where it's dead whilst cranking! Coil is connected to the old stop solenoid so that's why I've got good voltage and spark on that side.
*Fingers crossed*
 
I think the pump primes for 5/7 seconds when the ignition is turned on then off ,runs again when the engine is cranked I think the signal wire is the white one on the coil,if I am wrong someone will let us know in a little while .
 
Last edited:
Signal wire is black/white. I'll know for definite tomorrow morning, but I'm convinced the issue is that it thinks the ignition is off when I crank it. It was a schoolboy error after working a night shift and not thinking!
 
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