3.9v8 not starting then not drivable

**GuyG** · 14th April 2011, 10:30 AM

Hi folks, chasing some assistance here. My 3.9v8 RRC died at the servo a couple of weeks ago. It was running fine, filled up with fuel, and yes it was the correct fuel, and it wouldn't re start. Sometimes, it would fire, there was good spark, sort of weakly run then die. Others times it would only turn over. Had to get the car towed home.

On checking that there was power to the fuel pump I managed to break the terminal off the pump

, so have replaced the pump with a known running pump. The other pump was only a couple of years old. Now the car will start, idle and rev but only while stationary. If I try to drive it I only make it about 50m up the road before it starts to die, that is, it dies under load. I haven't checked the fuel pressure as I don't have the required gauge - and will more than likely have to send the car to the mechanics.

One odd thing that did happen, while it was sitting at idle the temp gauge flicked back to the off position, then slowly came good - I have had the gauge checked not that long ago and it was operating correctly - what else could cause this?

Couple of side things; from about mid November when I cleaned the engine following time at Fraser Island the fuel economy went from bad to worse. from about 18-19L/100 to 24-26L/100km - I was only getting about 260km per tank

. Tuning made no difference, replacing faulty TPS made no difference. Then after I chained the engine mounts for a club trip the economy drastically improved, by about 100km/tank, so I'm assuming a dodgy earth that chaining overcame.

So could other bad earths be causing the running issues and where are all the earth connections on a 1990 V8 Range Rover, both wiring and others?

**Ye Olde Rangie** · 14th April 2011, 10:35 AM

just a thought have you checked the air mass meter?

**PhilipA** · 14th April 2011, 10:43 AM

Sounds like low fuel pressure to me.

Check the connector sitting on the LH chassis rail behind the LH rear wheel ( if it is like my 92)

Check the fuel relay under the drivers seat ( blue one?) and maybe change for another one. Make sure it is diode or the narva protected one.

I suggest that maybe temporarily hot wire the fuel pump from the battery , and if that doesn't work , run another earth and see if that works.
Double check your fixed connection at the tank.

You can follow the main earths from the battery, but pay attention to the earth from the body to the engine behind the starter motor. But if your main earths are bad , you should have a dull red light on the dash.
Regards Philip A
Regards Philip A

**GuyG** · 14th April 2011, 11:02 AM

Thanks Philip

The motor is higher than normal compression with a torque cam fitted if that would contribute to the fuel issues.

The fuel replay under the seat is silver with a red line across it - I swapped it with another I had, but made no difference.

I had to remove the tank to swap the pump, due to no access panel in the rear floor and having drawers fitted. Then fitted a different plug/wire due to modifications when the previous pump was fitted.

We have tried to run the pump from an external power source, the pump worked but the car did not start.

It is plugged in near the LH chassis rail, I can hear the pump start up when I turn the ignition on. Parked in the driveway, you can run the car at 1800rpm without issue - its just not drivable.

There are no lights on the dash coming on.

I haven't as yet, swapped the AFM or computer, but I do have spares to give it a try.

**PhilipA** · 14th April 2011, 11:11 AM

What about the earth from the fuel pump? changed that?

Once you have done the obvious, It's time to do a diagnostic on the 14CUX. The steps are in the manual.

Regards Philip A

**GuyG** · 14th April 2011, 11:26 AM

Might sound like a silly question, but where is the earth for the petrol pump? There are the 2 wires in the plug but that is all.

The pump is screwed into the tank with rubber gasket and the tank is bolted to the chassis, so I imagine that would be the earthing points.

**isuzurover** · 14th April 2011, 11:34 AM

Originally Posted by GuyG

Might sound like a silly question, but where is the earth for the petrol pump? There are the 2 wires in the plug but that is all.

On the carb versions the earth ran to one of the mounting bolts.

**PhilipA** · 14th April 2011, 07:05 PM

On my 92 which had a plastic tank, there is a separate spade connector on the top plate of the fuel pump/gauge unit.

Regards Philip A

**GuyG** · 14th April 2011, 07:49 PM

Thanks Ben. With the efi - hotwire injection - the pump is in the tank and I think it earths through the screws holding it in and where its bolted to the chassis.

Mines the metal tank, and the plug is part of the pump which connects to the harness down near the chassis at the rear.

I replaced the filter today and it may have helped a little but still not enough to be safe to drive.

A few people have mentioned checking the valve on the fuel rail - do they all have this as I had a look but couldn't see it?

**PhilipA** · 15th April 2011, 08:18 AM

A few people have mentioned checking the valve on the fuel rail - do they all have this as I had a look but couldn't see it?

Earlier 3.9s do not have a schrader valve, eg my 92 RRC doesn't.

When I was fitting the Thor manifold I borrowed a Disco 1 rail which had the valve, but also has the fuel pressure regulator on the LH instead of the RH, and the fuel temp sensor half way along the LH side. This makes it unsuitable to use with a Thor, as there is not enough room.
Regards Philip A

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