Thread: 3.9 V8 won't run on petrol

Hi Guys,

Well I fitted up one of those AEB 549n dual ignition curve units. Very simple, I just flicked it over to 8cylinder, 9 degrees advance, no advance on idle or over-run. I reset the timing to 8 degrees and fired her up ............. It sounded absolutely spectacular. I took it for a spin up the court and it revs out much more cleaning, smoothly and quickly than having the timing set to ~12degree.

OK, that test is good, now what I wanted was it drivable on petrol ... 'cos it's downright bloody dangerous if you run out of gas........ Flicked it over to petrol and she died in the arse. Would rev ok in nuetral, but wouldn't run under load, certainly with the clutch out you can't rev it past 2000rpm ....................... Hmmm...

So I took it home and bypassed the AEB unit and had the same behaviour .... Well bugger it all, I sure did mis-read the symptoms, I thought it was breaking down and dying as the igntion was far to over-advanced to run on petrol. I whipped the lid off the dizzie and check the weights and 'vac advance...... But she runs so incredibly sweetly on gas it simply can't be ignition.

I struck something similar to this on an old Citroen CX before with a flapper type air flow meter...... Which on that car I verified by unplugging the air flow meter and seeing if it would run .. which it did but poorly (as they must use a default map).

Soooooooooooo, I unplugged the mass airflow meter, and the rangie will now run on petrol, kinda poorly but it will rev out and run on petrol. I swapped it with the mass air meter off the other car and had the same symptoms.

Does this sound familiar to anyone ?? Is it a sensor unplugged somewhere ? The fact it runs ok with the air meter unplugged says the injectors and fuel system is flowing adequate fuel. Maybe I have a wire chaffed through somewhere. So if no-one has any suggestions I'm about to waste many hours following wiring back into the cabin and checking all the connections and plugs

But hey, it's bloody lovely running on LPG

seeya,
Shane L.

I wonder if I'll ever get tired of saying this ................ "You guys were right .... again ".

I just had another looks. Runs ok'ish with the MAF sensor unplugged. Nothing I could see is really wrong anywhere. Then I compared the two MAF sensors.... The one of the other bloody car is a different number from what I can tell. So may well be wired differently ..... Two 3.9 '92 V8's here and there bloody different ( yes, yes I know .... life is meant to be "interesting" ). So I plugged the cars own MAF back onto it.... I could find any carby cleaner anywhere, so I sprayed gasket cleaner ( ) down the metering hole in the MAF and then chased that with some WD40.... and I'll be damned if the thing doesn't run now ...

Sure it's not 100% ... it leans out at wide open throttle.... but it's 500% better than it was before. Sooooooo..... I guess I'm chasing a MAF for it at some point.

seeya,
Shane L.