Thread: 3.9 no Power. Please help

Have you checked the fuel pressure regulator on the end of the fuel log, make sure it is connected to the IAC on the back of the plenum, also make sure the IAC is not loose, there are 3 allen bolts, check for tightness, does the Mallory have a vacuum advance unit and is it working, Regards Frank.

Similar story if your vacuum advance diaphragm is perforated. Try sucking on the vacuum hose to the distributor to make sure it holds vacuum - whilie you're at it check the vacuum advance is actually moving the plate round in the distributor to give you advance - probably it's ok if you're getting good initial throttle response - but the mechanical advance might be inoperative and not giving advance at higher revs.
......just read Tank's response and didn't know you had a Mallory - still check your advnce with a timing light.

Originally Posted by aRRon

Similar story if your vacuum advance diaphragm is perforated. Try sucking on the vacuum hose to the distributor to make sure it holds vacuum - whilie you're at it check the vacuum advance is actually moving the plate round in the distributor to give you advance - probably it's ok if you're getting good initial throttle response - but the mechanical advance might be inoperative and not giving advance at higher revs.
......just read Tank's response and didn't know you had a Mallory - still check your advnce with a timing light.

At one stage we thought we had solved it when we found that the advance was jammed. Fixed it, not really any better and if you disconnect the advance from a good motor it goes worse but not like this.

This has basically no response to throttle input from about half to full throttle or about three inches or so. There is a very subtle almost inaudible change in engine note and it will kick down but in essence it does nothing.

Originally Posted by Tank

Have you checked the fuel pressure regulator on the end of the fuel log, make sure it is connected to the IAC on the back of the plenum, also make sure the IAC is not loose, there are 3 allen bolts, check for tightness, does the Mallory have a vacuum advance unit and is it working, Regards Frank.

Yes we have, cheers

Originally Posted by Freestyler

How good is you high pressure pump? Mine after 6 years and a dirty load of fuel is failing to maintain good pressure on full flow and is leaning out. I have an O2 sensor and the jaycar kit that tells you the mixture ratio.
Tim

One of the next things to do is check this better. We did have full flow from the pump but we are going to check the flow at the injectors as well. All injectors have been flow tested on the bench and one needed replacing which improved things but was not the problem. cheers

Originally Posted by nzlandies

Yes we have, cheers

What pressure did you get at the Fuel pressure regulator, is it up to factory specs, there were no fuel leaks from the reg., Regards Frank.

G`day ,

have you tried taking it for a drive at full throttle or when ever it`s not doing what you want .

Turn it off and pull the plugs , from their colour you should have more of a clue where you should be looking .

When i say turn it off i mean at full throttle or whenever , let the throttle go as soon or at the same time as you turn it off .

There is no reason it has to be done in a high gear or high speed you should be able to duplicate in a lower gear , just do it a bit longer .

Mostly remember you only need to turn the engine off you don`t need LOCK the steering and have brakes with good boost assist .

This may help - it's a great read from the British V8 site re 14 CUX

Rover 14CUX Hot Wire Mass Flow EFI: Service and Troubleshooting

The article notes that the ECU has a safety mode. Basically if the VSS (vehicle speed sensor) shows an overspeed it will prevent acceleration..

AFAIK if you disconnect it, the ECU will default to the idle fuel map (which although will give odd fuelling) will also establish if the VSS is stuffed.

Chris
p.s Don't forget to clear fault codes on the ECU by a battery disconnect so the problem doesn't carry over