Thread: 92 Classic 3.9 Running Rough under load

Originally Posted by chang

Sounds like you have checked all the basics but have you checked the ignition module & pickup inside the dizzy? also could be the coil or a combination of both producing the exact same symptoms as my old Vogue 3.9. Basically was a VERY weak spark that sometimes could not detonate on some cylinders. would not start sometimes also

Ordered new ones an installed a Bosch GT40 coil & she purred after that

Talking of the pick-up inside the dizzy, before I dismantled (broke ) this, as I rotated the shaft I felt 8 interference clicks from the reluctor. Does this mean that there was no gap set on the pickup and this may have been contributing to my problems ? As there was no circlip, top washer or grommet in place, or no plastic cover over the module, I am guessing there has been a bit of a botch-job done on this before......

Originally Posted by bee utey

Busted clip repair process and pics here:

Lucas V8 dissy nylon clip repair method.

The lugged plastic bitsy is important, goes only one way and holds the alignment of the reluctor steady. Grommet or silicone any mouse-sized holes.

now that looks very familiar ...........thanks for the post.........I will give this a go at the weekend.

ok........finally got everything back together last night just before dark. Gave everything the once-over and tried to start the engine......and got an engine struggling to turnover, followed by a clicking solenoid.

Trickle charged the battery overnight and tried again this morning and the engine struggled to turnover again.

So the obvious things to look for tonight are......1) poor battery connections, or 2) dizzy is out by 180deg.........is that a fair analysis considering the engine had not been turned since the work started and the dizzy could only go in one of 2 ways ?

Yep double check the timing of the Dizzy.
Generally speaking if the Engine cranks over Ok then the running voltage would have to drop below 11 volts before you notice problems.

Sounds like you are getting close.

Nearly there.

Forgot to mention.......whilst I had the bonnet up I decided to remove a lot of the plumbing for a check and clean.

I took off the flame trap and underneath was a crust of black, oily, mess ! Just a small hole to let the pressure out. Crud extended through the flame trap and hoses, through the T connector and to the plenum. Spoke to a friend who said that this was not unusual so I cleaned everything and put it back together. However I didn't touch the crust in the rocker cover as I was worried that this would break up and drop inside and block the oil passages.

So, when the weather warms up and I have some free time I will remove the rocker covers and take a good look with a view to cleaning everything up.

Wow.....that was a bit of an epic journey but I got there in the end. She is running beautifully......more power than she as ever had. Took her for a spin up the F3 to get some heat through the engine bay and to blow the cobwebs away and I suddenly realised that I was nearly doing 130 where I would previously stuggle to better 110!!!

So, new plugs, points, leads, dizzy cap, rotor and a second hand (tested) MAF sensor later, not to mention numerous skinned nuckles.

Got it to fire (and backfire) last weekend so this weekend found some old hose and an airtight foam tube extension. Turned the engine to TDC with the plugs out and blew. Lots of backpressure therefore ignition stroke found on No 1. Removed the dizzy, found an old piece of dowl and cut a groove across the end to re-align the oil pumpdrive shaft. Dropped in the dizzy so that it pointed to No.1 lead. Tightened everything and turned the motor. Lots of gunfire....very loud

Leads 2 and 4 were transposed.....whoops.

Swapped these over and tried again. Barely caught but it ran....very roughly. So wired up the strobe and she was at about 25deg BTDC with the vacuum touching the thermo housing.

So, pen and paper came out and I worked out that by moving the leads 1 place clockwise aroung the dizzy, turning the dizzy back by 45deg so that Plug lead 1 was relatively positioned, and then advancing 20deg I should be fairly close to TDC.

And.... bingo....! but I am not sure why ??? How could the timing change by that much if no work was done on the engine ? (lead 1 is now immediately left of the front dizzy clip instead of immediately to the right). The vacuum advance wouldn't make that much difference surely ?

But she runs, and better than ever before. So thank you very much for all of your input and help. Now, next weekend i will start on the power steering pump

Cheers, Steve

So it apears I have a defunct coil as well....

Having run well for a week I began to get some intermittant missfiring. Under full throttle I would get some 'drops in power' but it would pick up again almost immediately off full throttle.

Put it into Reverse on Saturday and the smooth idle suddenly went away. Lumpy, irregular, almost stalling. Back into Drive and it was fine again.

Sunday, took it for a good run and after 20 minutes I suddenly lost all power. Lumpy, irregular tickover, cycling between 500 and 1500rpm at times. Backfiring and smelling of unburnt fuel. Crawled aroud the corner to a safe spot and left it whilst I walked my son the last 2kms to his Rugby game.

Called NRMA after the game, got to the car about 2 hours after it was parked and.....it was fine...? NRMA could not find anything obvious so suggested I take the back roads home to be safe and to call them again if the problem re-occured. Sure enough, 500metres later, backfiring and no power again.

So second time around after checking for vaccum problems, fuel-flow, plugs/leads etc he pulled the Bosch ignition coil and put in a Holden Commodore unit and it bingo ! His comment was 'it should blow a fuse before it causes any problems' ? However it got me home and the engine ran great.

So, do I pull the Commodore unit ASAP and get a Bee-Utey replacement, or is the Commodore unit ok ????? (don't know the part number)

What damage can an incorrect coil do to the Rangie ???

A Lucas ignition amplifier should run most electronic coils for a decent while, although I have seen enough fail to not want to guess how long it will go for. The Bosch 024 amp/module will run for longer with most available electronic coils.