Thread: 3.9 V8 Injectors

1. Have you checked the vacuum hose to the fuel pressure regulator? A holed reg will let fuel into the inlet manifold and lead to flooding.

2. Have you tried adjusting the idle mixture screw on the MAF?

Plugs are set differently to manufacturers spec ,, also a different heat range is preferred, please check posts in our LPG forum,,
Bee utey probably has this info on speed dial

It has a new set of Platinum plugs, the same type that I have used for the last 100,000 Kms. It goes like the proverbial once started, both on petrol and LPG. It cranks over normally and I have tried it with 2 batteries, but the same result. If it was a carby engine I would say it was flooding, as it does object with knocking for a couple of seconds once it does start and spews out unburnt exhaust fuel. All cylinders are around 160 psi and the fuel rail is 2.5 Bar.

The shop want me to buy a set of injectors, but I am not convinced that they are the problem. He has sent a photo of the spray pattern taken via a bore scope, but I do not know if what it shows is good or bad.

If either the fuel pressure regulator or an injector was leaking slowly, you would get a similar result. One way to ascertain that there is indeed fuel leakage is to turn off the fuel pump with a dash mounted switch (or remove the fuse) and run the engine until it stalls on petrol before parking it over night. Without pressure it shouldn't flood so after turning on the pump switch in the morning it should start as normal.

If you decide the injectors do need replacing, remanufactured Holden VN V8 injector sets are readily available and should cost you less than $A200 including postage from ebay. Example:

Holden Commodore, Fuel injectors, VR,VS,V8. Remanufactured, Genuine Bosch. | eBay

I've swapped a few sets of injectors around before, there are lots of different vehicles with compatible Bosch injectors. It doesn't have to be a perfect match to suit your needs.

Thanks very much, bee utey. I have tracked down the various injectors on the Internet. Can you confirm that the OEM are 24 lb / 252 cc Bosch?
I have read that these things are not "serviceable", except for cleaning and replacing the filters and seals. Is that correct?

It is a big problem here for me with so-called mechanics, and the language. The dealer that has it now has a young Brit mechanic, and although he obviously knows what he is doing, the first thing that he asked me was: "where is the OBD socket"? I believe that he served his time on Land Rovers, but he seems to be better versed in diesels, and probably not on older Land Rovers. In fact, he worked in Oz with a trucking company for awhile on Cummins.

Although I originally served my time as an electrical fitter, I have marine tickets and have worked on diesels from single cylinder up to walk in sized ships engines. Cheers

Originally Posted by Old Farang

Can you confirm that the OEM are 24 lb / 252 cc Bosch?
I have read that these things are not "serviceable", except for cleaning and replacing the filters and seals. Is that correct?

Sorry, with LRV8's I've only ever gone to a wreckers and knocked off whatever looked similar. One time I had a plenum off a blown up 3.9 and fitted six of those injectors to a Ford Falcon and they ran perfectly. So later I took 8 injectors off a couple of wrecked Falcons and fitted them to a different 3.9. It is a common problem with LPG conversions for injectors to fail and many people are too short of cash to fit new ones. Other vehicles here have been fitted with sets purchased off ebay or trade suppliers. Nowadays I prefer to fit vapour injection LPG kits programmed to run a small percentage of petrol under full load so the fuel does get used up and replaced more quickly.

Try cleaning you current injectors as per a miriad of vids on Youtube - I followed one in cleaning 16 Thor injectors and 12 came up good - a bit messy but if the injector is basically OK electrically the cleaning process may work.

In working on mine I just used Supercrap carby cleaner rigged to provide pressured fuel/cleaner for the injector and connected it to a 12v battery to fire the injector - as I indicated out of the 16 I had I managed to get 12 to squirt correctly and provide consistent an equal spray patterns.

I was quoted $25-$30 to get each injector professionally sonic cleaned and tested - so I saved a bit of money cleaning myself.

Garry

It is a BRC system that has to start on petrol. I now only use straight 95 octane and only keep a small amount in the tank. However, for awhile here there was no straight 95 so I had to use Gasohol, not sure what the percentage was. But, I have had the "O" rings replaced twice because of it, and no longer use it, so I suppose it is well within the realms of possibility that the Gasohol has affected them.

Thanks for the link. I have sent them an email as it states "may not post to Thailand".