The V8 Owners Forum -

I recently swapped a 90' 3.9 into my 72' series 3 88" The motor was running fine before when I pulled it from the range rover.

I have the 4 main wires connected, 12V, ignition, fuel pump, and 510ohm ground (auto to manual trans).

The motor turns over, there is spark and I have approx. 37lbs fuel pressure at the rail.

My problem is the injectors are not opening. I pulled the fuel rail with the injectors attached and grounded pins 11,13, and 16 with the ignition on and the injectors open but they are not opening under normal circumstances.

What could be causing this? Im stumped and would like to get this thing going! Thanks for any help

Follwing are a few pics of the swap.

Cheers -Donovan

Hi Doni,
welcome to the forum,

is the trigger for the ecu wire conected to the coil?
has the resistor in the trigger wire loom (near ecu) come apart?
have you conected the erth rings to a good eaerth for the ecu, (back of passengers head usually)

Yes, the trigger wire (white, black) is connected to the - coil.

Ive checked the inline resistor and it is fine.

The group of grounds from the wiring harness were all attached right to the engine block. Is there more grounds I dont know about?

Thanks for the welcome and the help!

on the seperate efi loom in the engine bay should also be some earth tags, (if i remember correctly) around the back of the passengers cylinder head,

Doni wrote:Yes, the trigger wire (white, black) is connected to the - coil.
Ive checked the inline resistor and it is fine.

Hello Doni,

I'm fishing around here, only being au fe with the earlier flapper system, but does your trigger wire go via an overrun vacuum relay that cuts the trigger signal on overrun?

Have you verified the signal wire integrity all the way from coil neg all the way to the pin (1 ?) on the ECU multiplug?

Failing that, could the ECU output transistors have croaked?

Ramon, the trigger signal goes to the ECU via a 6k8 ohm resistor only, it is not switched in any way.

Doni, two checks for this trigger signal:

Do a continuity check from coil negative to pin 39 of the ECU, should show 6.8k ohms for the resistor and wire.

Crank the engine over for 10 secs, check for fuel pump operating. The fuel pump primes at ignition switch-on. It will remain off until it senses the engine turning over ( as in starting) via the trigger signal and then turn on and remain on until engine rotation ceasing is sensed, again via the trigger wire.

jw

Right now I have my fuel pump wired to a switch, so I can turn it on or off. When connecting the pump using the white/purple wire from the pump relay it does not come on or "prime" at all
-not sure what's going on here, will it cause me issues to run the pump separately? It's an aftermarket external pump that will only hold pressure in the fuel system when it is on.

Ive done the continuity check from coil - to pin 39 and it's what it should be.

Im not sure if my system is the 'hotwire' or flapper style ecu. From the harness I have the 12v, ignition, and grounded via 510ohm wires, and im not using the pump wire. Should this work?

cheers.

From my limited experience it looks like hotwire

When you turn on the ignition you should get a click (or 3) which are the relays clicking in and activating the various circuits

One of these relays shouid feed the fuel pump whick will run approx 3 secs to prime the system then turn off

If it is not doing this then I would suspect tyour relays are loose or no longer operating

So listen for the click of relays when you turn on the ignition

Ian

Hi Doni, looks a tidy landy, and conversion. It appears to me to be hotwire also, you could check your wiring from the sticky thread at the top of this section.

Just another thought, have you got the relays in the correct sockets, they are not all the same and it wont run with them incorrectly installed.

I reckon you may be a wire(s) short on your installation.

Check the following ECU pins with the connector plugged into the ECU:

15. I/P. Permanent battery supply to ECU, used to retain memory contents.
12. O/P. Switches Engine Load relay on when ign switched on.
2. I/P. Switched battery supply to ECU from load relay.
19. I/P. Ign switched supply, wakes ECU.
16. O/P. Will supply earth to operate fuel pump relay when ign switches on.
14. Battery ground.
40. Battery ground.
27. Battery ground.
39. I/P. Engine speed signal from coil negative.

The I/Ps and battery grounds are mandatory for ECU to work. Check that the load relay operates at ign switch-on and supplies power where it should.
Check pin 16 with a test bulb to batt pos, should prime at switch-on, and if ECU recognises the ign pulses when engine cranking will turn on for as long as engine turns.
When ECU recognises engine turning will fire injectors.


The inability of the fuel pump to hold pressure while off will delay engine starts while pump primes the fuel system, hence the initial switch-on prime pulse.


Enjoy,
jw

Heres where I am at now, it still WONT START. I have pin pointed the problem, when i turn the key to ignition the pump primes for 3 seconds, when it starts to crank the injectors all fire once, then nothing while the engine is cranking. when I stop cranking they fire once more.

So, why aren't the injectors firing?

I've checked my wire and resistor from -ve coil to pin 39, and Ive tried plugging my ecu into another range rover and it ran fine (computer working fine) what else could cause this?

Im so close to having this thing running, I know my issue is probably something silly, any ideas?

Have a check of your igntion feeds to the ECU, make sure that they stay live when the key goes to poss 3.

Some Ign fed circuits will cut out in poss 3 to ease battery load on start up.

Doni wrote: turn the key to ignition the pump primes for 3 seconds, when it starts to crank the injectors all fire once, then nothing while the engine is cranking. when I stop cranking they fire once more.

So, why aren't the injectors firing?

Hello Doni, Just thinking out loud here, based upon the reported symptoms.

# You have not indicated whether the engine tries to fire or if it simply remains dead?

# The pump primes and runs briefly so you have fuel pressure? Yes? Have you measured it?

# You say the injectors fire once at cranking and again at stop cranking.

# If you have fuel pressure then fuel is being injected into the combustion chambers during those two injector blips,

# But the engine will not try to catch, fire up and run? Yes?

# If the engine will not fire up, then it indicates that either

. o You dont have any sparks. or alternatively

. o The combustion chambers are totally flooded quenching any available sparks.

# Check for smell of unburned fuel in the engine bay and wet spark plugs.

# If you dont have any sparks, that may also explain why your injectors do not operate, because, despite the wiring from coil to ECU apparantly being OK, there is no signal from coil negative.

Lets have some more info on the unanswered questions above.

Sorry, I forgot to mention I have spark, I have pulled each plug and laid it on top of the engine and they all have a good strong spark.

-engine turns over nice and strong but wont catch

-I have an inline pressure gauge installed and my fuel pressure is at the recommended ~37lbs

-I have the fuel rail with injectors installed sitting on a baking tray above the manifold so I can observe the injectors (how I know they fire once before and after). But the engine will not try to catch when the fuel rail is installed.