Thread: HELP!!! V8 Won't Fire After Head Rebuild

Okay, the plot thickens. Dropped $$$$ on a proper fuel pressure gauge and the pressure with the ignition switched on is 0, zilch, nada.

Crank the starter and the fuel pressure climbs to 40psi and then immediately falls to zero once cranking stops.

Sprayed in easy start and cranked - engine doesn't fire.

Pulled fuse to kill the fuel pump and sprayed in some more easy start and engine starts to fire.

So answer is the engine is flooding, but now it begs the question is it the fuel pressure regulator or an issue with the injectors or is there something else that I'm missing; like a split vacuum hose????

To answer a couple of other questions - the engine is only being cranked in short bursts, just over a long period of time. Yes, the hose from the regulator to the stepper motor is connected.

This is really testing my diagnostic skills so why isn't there a Gregory House in the real world for rover V8s; Rave and Haynes are just not cutting the mustard. In all my years of working on vehicles I have never had such a massive problem from what is described as old-school technology. I guess it's like Millionaire - the answers are easy so long as you know them!

there is but so far you're only up to the first comercial break.

Youve got to wait for something unrelated to occur in real life that will spark the required knowledge to the front.

give it 30-40 more posts to banter around some ideas based on some seemingly relevent new piece of diagnosticary symptom and then I'll be having a problem with a chainsaw in townsville that will turnout to be a paperclip stuck in the ignition switch shorting out the motor and I'll have an epiphany pronounce all the others wrong post a simple "replace relay thus and so" and the engine will be fixed.

Here’s a link to the readings I got :

http://www.aulro.com/afvb/technical-...ecs-rev-3.html

As you’ll see, mine went to 40 psi on prime then 37 once prime completed, once motor was running it jumped to 50-55 psi. as the regulator is meant to keep pressure around 32-35 psi and you are getting 40 psi, by rights if you take the fuel return line off you should have fuel coming out past the regulator. If not, it sounds like the reg is shot like mine was. I’ve no experience in this but it is fresh in my mind from doing this exact same thing last week. I would look on it positively as you have probably found your problem.

Originally Posted by Tyresqueal

Pulled fuse to kill the fuel pump and sprayed in some more easy start and engine starts to fire.

Catch 22 .... can only try 1 thing at a time ...

... Now try again ....

Pull the fuse on the pump
Get it to fire up on "easy start" ...

NOW ... Put the fuse back in ... and this time, unplug the MAF
Cycle key turn starts


Does it fire?

Originally Posted by Tyresqueal

Okay, the plot thickens. Dropped $$$$ on a proper fuel pressure gauge and the pressure with the ignition switched on is 0, zilch, nada.

Crank the starter and the fuel pressure climbs to 40psi and then immediately falls to zero once cranking stops.

Sounds like either 1. your fuel pump non-return valve is failed or 2. during your head swap you got crud into an injector which is blocked open and spraying madly into the intake while you crank. It really means lift the plenum, unscrew the fuel rail and injectors, lift them up, check for leakage. It should also appear as a drowned spark plug, so do the priming/cranking thing and find the fuel-wet spark plug.

The ECU operates the Fuel Pump relay for 3 seconds when you turn on the ignition.
Then it turns the pump off while cranking until the coil provides a signal that the engine has revs over 450RPM, then the pump is turned back on.
I suspect it is doing that, but I suggest that you turn on the ign and check that this sequence is followed.

If it is immediately dropping pressure , then I suspect either the fuel pressure regulator has failed, the non return valve in the fuel pump has failed, or some injectors are jammed open.
Regards Philip A

Originally Posted by Tyresqueal

Crank the starter and the fuel pressure climbs to 40psi and then immediately falls to zero once cranking stops.

geez, it's much less frustrating when someone else has the problem. (says me after the bearing in my water pump got ground up and spat out two days ago when i was down the bush and took me an hour and a half to file/hacksaw the head off one of the seized bolts as with no spanner to take off fan there was no room to move...)

anyway, your quote above reminds me the pressure in mine immediately went back to zero a few times. it sounded like there was air in the system as i could hear a different sound from the fuel tank. it was like air was being expelled back down the return line and someone was blowing bubbles in the petrol in the tank. it was after a few goes priming that the sound disapperared and all things quietened down and the fuel pressure stabilised.

It's alive! After some painful forum searching I came across a post on landrovernet.com by "Odyssey" who suggested drying the plugs, turning the engine over once, then pulling the fuel pump fuse, cranking again until it starts to fire, and then putting the fuel pump fuse back in whilst it's still cranking.

After a couple of attempts the old girl fired up and only required a slight twist of the dizzy to run as sweet as a nut and the original tappet noise that started this whole strip down has disappeared too.

Apparently "the theory is that the ECU needs to 'relearn' the correct settings". Who am I to argue with this - it worked for me.

Thanks to everyone who has provided advice, laughter and encouragement throughout this thread and hopefully it might just help another poor soul avoid days of torment, sleepless nights, and hours and hours of painful diagnosing. Now I'm off to enjoy my D1 again!