I have looked through thread and can't find answer. I have a rebuilt 4.2 injected engine. I have good spark and fuel from rail when starting and activating flapper door in Air flow unit. No fuel going through injectors . Starter motor cranking well

 

Some free-n-easy checks to begin with:

- There is (or should be!) a white/black wire from the coil "-" post running aft along the water rail. Is it there, connected, and in good shape? This is the trigger wire that wakes up the ECU, so to speak

- At the rear of the water rail is a bundle of ground wires under bolt head. These are the grounds/earths for the entire F.I. system. Make sure they're all attached and the connection is tight and clean

- Use a test light or meter to see if the injectors are getting 12 volt supply voltage. With the key on, engine off you should see B+ voltage on both sides of the injectors

Post back if these don't pan out

Cheers
DD

 

I have 12.5 volt on both terminals of injector. White and black trigger line in good shape. Only have braided earth and earth from injector loom on that bolt. Can't see any others. How many should there be? Where are other earths going so I can locate any missing. Can't see any more

 

There are 4 or 5 wires earth wires plus that small braided strap. As I recall they go to the large (1.25" diameter?) loom that enters the cabin and goes clear back to the ECU

Unless someone cut 'em off, there'll dangling down there somewhere. Keep looking!

Cheers
DD

 

In simple terms the fuel injection ECU relies on a pulse from the coil to fire the injectors. It is very simple, as all the injectors are fired together once per engine revolution. The ECU actually switches the injectors to earth, they having a constant 12 volts at the injector.

So, no pulse to the ECU = no pulse to the injectors.Simple !

Have a read here: -

Fuel injection and the Jaguar XJ6 4.2 Series 3 / AJ6 Engineering

The whole system is analogue and there are no complex programmable logic controller chips or memories anywhere. A bit different to today, but it worked very well on my XJ6 that I had for 14 years !

 

Can someone please chime in and advise where the earth wires at the rear manifold mount bolt come from. I can only see the braided earth strap and one earth wire that goes into the loom running forward towards the coil. I recall there being more but cant find any others and engine wont start. It is a 4.2 injected series 3 with the loop fuel rail

 

Have you found the main fuel injection loom that goes thru the bulkhead into the cabin? On a RHD car this would be (approximately)under the brake booster, towards the transmission 'tunnel'.. The wires are probably dangling in that area

Cheers
DD

 

Shall take a look in there when home tomorrow. Thank Doug. You are very generous with your time and experience. Would love it if people always posted the fixes on their thread so it can be used by the rest of us

 

Here's a pic of the main fuel injection harness

At the top you'll see the ring connector with 5 ground wires. That's what you are looking for. The bundle of ground/earth wires enters the main loom just below my thumb.

To give you a frame of reference, just below the little bundle of ground wires you'll see the connectors for the relays and diode pack that are mounted on the bulkhead. You also see the harness connectors for the wiring that runs along the water rail

Cheers
DD

 

Thanks Doug. Found them. They were bolted onto the full load vacuum switch bracket. Put them on manifold bolt.
Still no start. Before I removed the engine it was cutting out and wouldn't start intermittently. The only time it would start was when I could hear a relay cutting in and out. If that noise was not there it would not start.

 

Anyone suggest next move from my last post

 

I can think of 3 relays that would be involved

- Fuel pump relay....but you say that you have fuel flowing so the relay must be OK

- Main relay....which gives supply voltage to the injectors ...but you have voltage to the relay

- Starter relay...which operates the starter, obviously, but also powers up the fuel pump circuit while the engine is cranking.


Try this, just for giggles....

Put the gearshift in "D" (or any position except "P" or "N") and turn the key to the "start" position. The starter will not operate BUT you should hear the fuel pump run. If you don't, post back

Cheers
DD

 

Put into drive and starter engaged when I turned key???

 

The neutral safety switch isn't working. That can be addressed later.

Open the trunk so you can listen for the fuel pump humming while a helper turns the key

Cheers
DD

 

Fuel pump is working in start while in drive

 

Let's go a back a bit. You say the engine was rebuilt.

Are you sure the spark plug wires are in the correct order and distributor properly installed?

Cheers
DD

 

Timing apears correct. Leads are correct. Have swapped ECU and resistor relay on front RH fender. Still no start.

 

Wild way out guess.


Look up the S57 schematics. The starter relay ground leg goes back to a micro switch on the shift tower. Fault here as the engine cranks in drive! Wrong. It should only crank in P or N !


So, it just might be that although the starter cranks, the fuel pump is not.


So, use a very long wire and jump 12v directly to the pump to assure FP in crank.
A spare battery can do that.


And, yes, in the lower right corner of the engine bay, there is a large grommet. A big bundle of wires enters the cabin there. Dropping the right scuttle and feeling up and high, you will find the bundle coming in to the cabin. It continues along cosole to floor joining on to the boot!!! A break any where along there can mess things up big time.


Carl

 

I had a similar problem as you described on my Sovereign. The intake hose where the air flow meter sensor is located was disconnected and air was not flowing through it. The car would not start under this condition (do not know whether the fuel or ignition was cut off). Once I connected the hose, it started right up.

So, have a looksy at the air flow sensor.

 

Are the injectors clicking when you crank the engine? And/or do you have a 'noid light' to check them. We know from previous posts that you have voltage to the injectors but I don't think we've confirmed that they are actually operating.

Also, we know you have fuel flow....but have you checked actual *pressure*? it's important.

Another freebie idea: remove the plug to the coolant temp sensor and jump the contacts with a small paperclip or wire. Any change?

Cheers
DD