Injectors not firing

[360beast]

Here's one for you boffins.

I've converted a 1991 940GL from an LH2.4 B200F &M47 to a 1995 B230FK with M90 gearbox.

The car was running when it came in and I drove it around the block so I know it was all okay.

I have fitted T5 blue injectors (no ballast resistor as the loom is N/A).

I have cut the MAF plug and extended the loom to the other side of the car so it can go in the original turbo position.

It cranks happily but the injectors will not fire!!! It is doing my head in now.

If I run a wire from the grey terminal of an injector across to the strut tower, crank the car and make and break the earth connection it runs. However the moment I stop earthing the injectors it stops running.

There is 12V at the green and grey terminals on the injectors when the plug is connected to the injector.

I have 12V at the blue yellow feed wire for the suppression relay and the relay works fine, I even fitted a known working relay just to make sure and it still doesn't start.

The fuel pumps prime once ignition is turned on and after "running" the engine they prime again.

I have checked the loom from the grey wire to ECU pin 18 and there is continuity with no resistance.

So what on earth should I be checking? It is like the ECU isn't earthing the injectors, I have tried two different ECU's and it won't start on either one unless I manually make and break the earth.

[Laird Scooby]

Originally Posted by 360beast

It is like the ECU isn't earthing the injectors.

I think thats the problem - the question is why?

[TonyS9]

I assume you are getting rpm needle movement during cranking?

I'm thinking about the CPS but you should not get fuel pressure, unless its residual. Do you know if the pump is running during cranking?

I have 95 B230FT which is basically the same electroncally, very hard to see why injectors would not fire if you are getting crank data to the fuel ECU.

Can you get a scope on the grey wire?

What did you pull over on the conversion?

I assume it wasn't the full loom? You swapped fuel+ignition ECU? Could the wiring be different?

[Laird Scooby]

Originally Posted by TonyS9

I assume you are getting rpm needle movement during cranking?

I'm thinking about the CPS but you should not get fuel pressure, unless its residual. Do you know if the pump is running during cranking?

I have 95 B230FT which is basically the same electroncally, very hard to see why injectors would not fire if you are getting crank data to the fuel ECU.

Can you get a scope on the grey wire?

What did you pull over on the conversion?

I assume it wasn't the full loom? You swapped fuel+ignition ECU? Could the wiring be different?

Yes, and a good spark to the (dry) plugs.

Multimeter on the grey wire reveals no voltage drop when the injectors should fire, remains at near enough the same potential as the green wire.

Fuel ECU pinouts are the same (all LH-2.4), although the grey wire checks out with a multimeter for continuity between ECU and injectors, it could still be broken and that only shows under load - i.e. when the injectors should be firing.

As it stands at the moment, weather permitting, Luke is going to run a slave wire from pin 18 on the ECU to the injector -ve (grey) terminal and see if that brings about a start. Then check the ECUs by substitution to confirm operation, assuming the slave wire permits an unaided start. From Lukes post :

"The fuel pumps prime once ignition is turned on and after "running" the engine they prime again."

All conditions are present and correct except signal to fire the injectors so it either means 2 duff ECUs or the grey wire has a break in it that only shows under load. Not sure on the exact resistance of the injectors he's got but generally injectors designed for use without an injector resistor pack are 12-16 Ohms each - as it's full group injection/batch-fire, that gives 3-4 Ohms total resistance and by inference, 3-4A current, a lot more than the mA or so from the multimeter to test continuity.

You now know as much as we know - any suggestions?

[360beast]

Originally Posted by TonyS9

I assume you are getting rpm needle movement during cranking?

I'm thinking about the CPS but you should not get fuel pressure, unless its residual. Do you know if the pump is running during cranking?

I have 95 B230FT which is basically the same electroncally, very hard to see why injectors would not fire if you are getting crank data to the fuel ECU.

Can you get a scope on the grey wire?

What did you pull over on the conversion?

I assume it wasn't the full loom? You swapped fuel+ignition ECU? Could the wiring be different?

No rpm needle movement, I swapped in a known good one and it still doesn’t move during cranking.

I know the pump primes and if I flick the key to crank and instantly let go then it will prime again, I can disconnect the fuel line though and test it is pumping during cranking tomorrow.

Sorry Tony wiring is not my strong point, what is a scope?

I swapped in a 1995 B230FK & M90 with solid flywheel, extended pivot ball, support bearing adaptor etc. Wiring loom is the original 1991 loom and I’m using the EZK from a 1998 940 turbo as the 1995 one is a gold one so I have kept that for my 940 and the ECU is from the 1995 donor, I’ve tried the 98 ECU and no difference.

Me and Dave have gone through wiring diagrams, I’ve used my official volvo green books and on paper it looks like the ECU one bout is the same across the lh2.4 7/900 range. However tomorrow I will be plugging in the N/A ECU just to prove it. I will also be running a slave wire from pin 18 to an injector grey terminal to bypass the loom and see if it works then.

Edit: Dave beat me to it haha

[Laird Scooby]

Originally Posted by 360beast

Edit: Dave beat me to it haha

That's because i thought you were catching ZZZZZZZZZZZZZZZZZZzs!

[360beast]

Originally Posted by Laird Scooby

That's because i thought you were catching ZZZZZZZZZZZZZZZZZZzs!

couldn’t stop thinking about this after I phoned you!

[Pete940]

There are some ecu's and ezk's that aren't compatible with each other. Not exactly sure which but I ran into that problem with my engine swap.
When you said about it priming again when you let the key return, I wondered if the ecu is losing power during cranking. But that seems unlikely if your loom is original. That was another problem I ran into with my swap, since the loom came from a newer model.

[Laird Scooby]

Originally Posted by Pete940

When you said about it priming again when you let the key return, I wondered if the ecu is losing power during cranking.

It's meant to!

The pumps run during cranking and keep running for another 1-2s after. Turn your key to position 2 (just warning lights) and wait until the fuel pumps finish priming. Now "flick" the key onto position 3 (start) so the starter just starts turning and release - you will hear the pumps run for 1-2s after.

Handy to know if you ever run out of petrol and for diagnostic purposes to make the pumps run.

[Bugjam1999]

It’s the immobiliser. Chip the ecu with a chip that removes the immobiliser function and it’ll work.

All the ‘upgraded’ chips you’ll find online will have the immobiliser function turned off.

Cheers