sible88

sible88

New Member
I have put a 3.9 efi hot-wire in my defender 90 and everything NOW works but it struggles to start when cold and when it does start it runs like **** and really under powered it almost cuts out when u put your foot down anything passed quarter throttle?? It has got me stunned I have changed the coil and hot wire? It fun perfect in the disco??? It has a vac pipe from the left hand top casing next to the brake servo that I don't know what it goes to??? Will this go to (air con?/ fuel?/ air filter?) only ask this as I had put air con on the hose when taking off but can't remember taking it off? Fuel because it cuts out when blocked off? Or air as it constantly sucks air???
 
No it's a 2-3mm pipe really small? And the disco didn't have cruise control but did have air con?
 
Got it sorted now it was the AFM, it was sending wrong signals I knew it was something simple as it run perfect when I first started it in the defender but over night just stopped?
 
I have a similar problem with a 3.9 in a Classic - starts first time when stone cold - runs for 5 minutes or so and then dies and will not start again until cold. Leave the MAF unplugged once started and it will continue to run but if you then stop it, it won't start again with or without the MAF connected.
 
Yeah I have still got this problem too, I put new MAF on and drove it round the block and it went much better but still not right and just got worse? It is really annoying I have checked everything I can think off but nothing? It will rev when cold but soon as it gets hot it backfires from the MAF I know this don't sound true but I double checked because I didn't believe this could happen? It has too kenlow fans and brand-new rad so I am sure it isn't over heating but the water pipes do get hot???
 
The temperature gauge is matched to the sender so if you've hooked up the 3.9 sender to your 90 gauge, you may be getting a false reading. The water pipes will get hot though. Backfiring sounds like either too much fuel or ignition too far advanced. Have a look at the plugs after it's run hot and see how black they are.
 
Didn't think it would get too much fuel as it has a regulator on the engine?? How do you adjust the timing?
 
sible88 said:
Yeah I have still got this problem too, I put new MAF on and drove it round the block and it went much better but still not right and just got worse? It is really annoying I have checked everything I can think off but nothing? It will rev when cold but soon as it gets hot it backfires from the MAF I know this don't sound true but I double checked because I didn't believe this could happen? It has too kenlow fans and brand-new rad so I am sure it isn't over heating but the water pipes do get hot???
Click to expand...

Check the coolant thermistor, values can be found in Haynes. If thermistor is on its' way out it will tell the ECU the wrong value and the injection pulse will therefore be wrong. If you suspec it is overfuelling then it is possible the thermistor is telling the ECU it is cold. I ama bit rusty on this but if you bridge the thermistor wires it will tell the ECU the engine is hot so try that and see if it makes any difference.

you should also check the fuel temperature thermistor (the expensive one!). If this is not reading right, the ECU may think a longer injection pulse is needed for cold start enrichment.
 
sible88 said:
Didn't think it would get too much fuel as it has a regulator on the engine?? How do you adjust the timing?
Click to expand...

The ECU can over-fuel the engine as Classic Kev says if it thinks the engine is cold etc. The fuel regulator regulates the pressure in the fuel rail. If this is too high, you could get over-fuelling although i've never heard of this happening. The timing can only be checked with a strobe light.
 
Thinking of putting a manual dissy on my 3.9 will the 3.5 carb one fit and be ok?? May put weebers on aswell??
 
you mean points?

dont do that the leccy dizzy is superior in every way and not hooked up to the engine management.

You could put carbs on and leave the dizzy the same if you want.

The best carbs are SU's me thinks but your efi can be good you just need and expert to set it up if its beyond you.

If you want the deatils of the best mobile one I know of then let me know, he has sorted mine twice and has all the toys to do it.
 
Yes please can u pm me his details? I have this week and next off to sort it out so he sounds like my night and shining armour lol.
 
I am getting a very weak spk is this normal for a v8?? Have tried it straight off the coil and the same so not the dissy? Have ordered new leads and going to get plugs 2day? Also tried diff coil and still the same so must be 2 above or bad earth???
 
I got told you only need the White to ign live and brown to per live and purple to fuel pump and from existing loom fuel cut off to coil and it will run?? Is there any other wires I need for a fully running vehicle? Will check the ign live wire may be a drain/ not enough power as I have gone off something else on the ign barrel as I only have four wires not five like a disco??

Put new plugs in 2day and it run alot better but not right for all of 10 mins and wiped plugs out again and black and sooty so is defently running rich but is this because it not lighting the fuel due to ign problem or because of something else? Also tried bridging the the fuel thermo but still the same? (done this to tell the ECU it was hot and should lean it off a bit) ordered new leads yesterday so should be here 2moz or sat but seem fine but trying to illimanite everything within reason starting with cheapest as running out of money :-( when engine is running and I pull any lead off it makes no difference to revs? And that's and lead??
 
Think I have found the problem when I take leads 2-6-1-3 off it makes no difference? Looked up the firing order and mine is wrong. It should be 1-8-4-3-6-5-7-2 but I know this may be a silly question but from the dissy left of the clip is no 4 but does it go anti- clock wise or clockwise? And is it every other you count or every1 I am new to v8's so don't have a clue how they work? With your help and patience I am willing to learn
 
The dizzy has 8 contact points 1 to 8 and as the rotorarm passes each contact point it send a spark up the cable attached to it. so once you've figured out which cable is for no 1 cylinder and where on the cap it goes working round the dizzy cap attach the cables in the required firing order in your case

1 then no8 then no4 then no3 etc etc.
 
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