Thread: 3.9i, starting issues, please help!

The petrol ECU gets its RPM signal from the negative side of the ignition coil. The amount of times I have seen loose terminals around the coil and electronics, I suggest you pull each connector off the coil, squeeze it gently and refit. Also I often have to upgrade the Lucas ignition amp because they fail regularly. I use a Bosch ignition module instead.

If you figure out what brand of vapour injection you have I might have the software to get into it.

Originally Posted by Que

heyas... i've had my 97 disco for a few years now without a problem in the world... until now...

1) about a month ago i was driving home from work and she kept stalling. next morning i checked under the hood and noticed the big airhose from the MAF to the plenumn was all but right off. put it back on, she started fine, i thought problem solved. wrong.

2) about 5 min into the drive it felt like i ran out of fuel... pulled over, no luck getting started again, so got towed to a local mechanic. he's decided its the fuel pump, had a look and its a commodore pump (a common thing i've heard?) and where the wiring has been chopped to fit it the earth has come out of its poorly twisted and taped connection. he's sourced a 2nd hand origional pump that 'aparently' has been kept lubricated and is in full working order. once that's in she starts fine, runs around 20min then the tacho drops to zero then she stalls. takes ages to start (he says he's had to jump start a few times when he's run the batteries flat) then will only run 5 min at the most... i get it towed home.

3) i can hear the fuel pump run, and pressurise. he checked the pressure at the rail and it was apparently fine. could the problem still be with the pump? or i keep coming back to the MAF... is there something there that could of been knocked out of sorts when the big air hose came away? checking the throttle butterfly i noticed far more black oil in there than i would expect... could this be related to something? i have spark, and can at least smell fuel. on the rare occasions it does run its as smooth as ever, so i doubt its a major engine problem relating to compression etc. i have a dual battery system with two deep cycle batteries... how to these handle being run flat as often as this mechanic seems to have done?

4) lastly, the car IS on gas, with a vapor injection system that i know nothing about. however it will only start on petrol and switch to gas at the right temp, there is no over-ride switch to force it to start on gas. as the car hasnt run in weeks and we're middle of winter on the south coast of SA its most definately trying to start on petrol, which makes me tend to think the problem isnt related to the lpg system. although i dont hear any solenoids click when i turn the ignition on.

Quote: " i have a dual battery system with two deep cycle batteries... how to these handle being run flat as often as this mechanic seems to have done?:

Deep Cycle Batteries are not designed to be Starting (Cranking) batteries, you also said that the Tacho needle drops to Zero and the engine stops, the Tacho reads it's signal from the Alternator, so it seems to me that you have an electrical problem. Have the main starting Battery tested and make sure it's functioning properly, true Deep Cycle batteries can be ruined by using as a cranking battery, Regards Frank.

*bump*
ok, tried bee utey's suggestions, cleaned up all the terminals around the coil. everything was pretty grimy, but didnt make a difference. how can i check that ignition amp? i'd drag the car up your way bee utey, but if you're who i think you are your driveway would be a bitch to get a dead disco on a trailer into if you happen to be down victor harbor way tho...

talking to the dodgy bloke who installed the battery set-up (my dad) he reckons they're not true deep cycle batteries and are fine as they are, set up as a cranking battery etc. i take his word for it...

the car turns over really strong, and even sounds like its trying to fire. i keep thinking it must be fuel related and given i just had the fuel pump replaced i cant convince myself its an unrelated coincidence. the car has been dyno tuned last service, could changing from the poorly wired commodore pump to the 2nd hand origional pump cause a problem with the tuning? standard pumps on the 3.9i discos are a variable speed according to the guy who tuned it, which was apparently why he had problems getting it right? i'm completely out of my depth working on anything more complicated than my old 202 kingswood (which wont go either *sigh*) but cant get this thing to anyone at the moment... the only local bloke who seemed to know his way around a landy is stumped and doesnt want to know about it anymore... seems unless i can get it worked out at home i'm going to have to fork out to have it towed a long way to get it anyone who knows anything about the thing... which financially just isnt an option right now. but neither is no car...

*bump*
ok, tried bee utey's suggestions, cleaned up all the terminals around the coil. everything was pretty grimy, but didnt make a difference. how can i check that ignition amp? i'd drag the car up your way bee utey, but if you're who i think you are your driveway would be a bitch to get a dead disco on a trailer into if you happen to be down victor harbor way tho...

talking to the dodgy bloke who installed the battery set-up (my dad) he reckons they're not true deep cycle batteries and are fine as they are, set up as a cranking battery etc. i take his word for it...

the car turns over really strong, and even sounds like its trying to fire. i keep thinking it must be fuel related and given i just had the fuel pump replaced i cant convince myself its an unrelated coincidence. the car has been dyno tuned last service, could changing from the poorly wired commodore pump to the 2nd hand origional pump cause a problem with the tuning? standard pumps on the 3.9i discos are a variable speed according to the guy who tuned it, which was apparently why he had problems getting it right? i'm completely out of my depth working on anything more complicated than my old 202 kingswood (which wont go either *sigh*) but cant get this thing to anyone at the moment... the only local bloke who seemed to know his way around a landy is stumped and doesnt want to know about it anymore... seems unless i can get it worked out at home i'm going to have to fork out to have it towed a long way to get it anyone who knows anything about the thing... which financially just isnt an option right now. but neither is no car...

gah, sorry for the double post, kept asking me to log in to post, although i was already... only one seemed to work, seems two did.

My guess is the guy that replaced the pump didn't use the correct pressure hose, or the clamp has come off. Getting the pump assembly out isn't rocket science, its just under the load area carpet, then inspect the outlet hose from the pump to the housing top. The Commodore pump is fine if properly fitted, there's nothing variable speed about it. Unless the pump was refitted with the original hose and clamps, or special submersible fuel hose, there's a likelihood of standard fuel hose being used. It bursts when immersed in fuel within a couple of weeks.

Been there, done that, learnt from experience.