3.9 EFI: No power

lollorock · Post by **lollorock** » Wed Mar 12, 2014 7:16 pm

Hi everyone,
I'm an Italian owner of a Range Rover MY1990 3.9 V8 EFI (+LPG).

Since last year I have lots of problem when the car is running with petrol.
With LPG everything is ok, but when i switch to petrol the sound of the engine becomes not like a V8, the car has no power (i have to use 1st low gear for road where usually i use 3th high gear). The engine idling is non regular and from the exhaust comes out drop end black smoke…

In this year i have done:

- Check timing (with strobe lamp)
- new stepper motor
- new fuel pump
- new MAF (used but working)
- new fuel pressure regulator
- new sparks
- new wires
- new ignition coil
- new injectors
- new petrol temperature sensor
- new water temperature sensor
- new vacuum, rotor and cap of distributor

I have no more ideas about how i can fix this problem

with LPG the car is very good, with petrol…sucks!

I'm waiting for the cable to use rover gauge, but I do not have much hope…

ChrisJC · Post by **ChrisJC** » Wed Mar 12, 2014 9:43 pm

If it is OK on LPG, then the ignition system must be OK.

So it is fuelling.

Roverguage is a good way to proceed.

Chris.

Captainbeaky · Post by **Captainbeaky** » Wed Mar 12, 2014 11:42 pm

It sounds like you have a petrol injector stuck open ( or more correctly, being commanded open permanently)

I have had reliability issues with the injector emulators before on my 1991 RRC on LPG - they use relays that can stick - and short out a bank of injectors. Also prone to water ingress.

You may well have a problem with these emulators, or their wiring.

Put an injector test lamp - often called a noid lamp ( any small 12 v bulb will do) on each injector, and see if any injector is staying on ( rather than pulsing)

Also, you can use a long screwdriver to listen to the injector.
Put the metal end of the screwdriver onto the injector, and put the screwdriver handle to your ear, you should hear the injector making noise as it works. No noise - injector not switching and off..

Hope this helps.

Mike

DaveEFI · Post by **DaveEFI** » Wed Mar 12, 2014 11:44 pm

Most common reason for over fuelling is a failed coolant temperature sensor or wiring. If you unplug it with the engine idling and hot, does it make a difference?

I dunno LPG - does it share the coolant sensor?

Captainbeaky · Post by **Captainbeaky** » Wed Mar 12, 2014 11:58 pm

You might well be right there... I hadn't thought of that.

LPG does not need cold start enrichment like petrol does - so there is no mechanism to increase fuelling on LPG when cold.

So it could well be the coolant sensor forcing a rich mixture - definitely worth checking.

lollorock · Post by **lollorock** » Thu Mar 13, 2014 5:41 am

thank you very much guys, today i'm gonna do these tests

About the noid lamp, is it ok use two tiny wires to connect the injectos plug and the bulb?

something like this:

with 12V bulb

DaveEFI · Post by **DaveEFI** » Thu Mar 13, 2014 8:58 am

The factory trick if a coolant sensor is suspect is to replace it with a 175 ohm resistor. This mimics a fully hot engine without having to drain down the system and replace the sensor.

However, this doesn't check the wiring to it. You'd need to unplug the ECU and measure the resistance of the sensor there, against a temperature/resistance table for the sensor.

But if there was a break in the wiring etc, simply unplugging it with the engine idling and hot should show this - if nothing changes. With it working correctly, the engine should go very rich and stall.

lollorock · Post by **lollorock** » Thu Mar 13, 2014 11:17 am

I am so confused

With new hose from MAF to plenuum, the old MAF and temperature sensor not connected the car is a little bit better.

ChrisJC · Post by **ChrisJC** » Thu Mar 13, 2014 6:09 pm

The Rovergauge gives you all the sensor readouts as seen by the ECU. This will instantly confirm which sensor is at fault, without any guesswork!!

Chris.

lollorock · Post by **lollorock** » Fri Mar 14, 2014 7:49 pm

Next monday I will order the USB cable

lollorock · Post by **lollorock** » Sun Mar 16, 2014 7:51 pm

Cable ordered…i hope it comes soon

A question: if the problem is about injectors, in example like this:

Captainbeaky wrote:It sounds like you have a petrol injector stuck open ( or more correctly, being commanded open permanently)

Can I see it with rover gauge?

lollorock · Post by **lollorock** » Sat Mar 22, 2014 6:19 pm

Hi everyone,

I'm still waiting the cable for rover gauge.

Meanwhile i was thinking: Can the inlet manifold gasket damage be the reason of my problems?

Thank you lot

jenand40 · Post by **jenand40** » Sat Mar 22, 2014 9:36 pm

Please enlighten me.
What is a Rover gauge?

ChrisJC · Post by **ChrisJC** » Sat Mar 22, 2014 9:47 pm

Rovergauge is some software that talks to the ECU and gives a ton of useful diagnostic info.

http://alum.wpi.edu/~colinb/14cux_software.html

Chris.

lollorock · Post by **lollorock** » Sun Mar 23, 2014 12:42 pm

what is this? strobe?