Thread: Isuzu 2.8 4J stalls at higher revs, idles fine

Sounds like an air leak in the fuel system. Check all hoses and joins from the fuel tank.

There are lots of places for blockages in the fuel system. Drain the tank to see if there's any gunk in there. Clean the fuel sedimenter. Check lift pump (if there is one) and fuel injection pump for gauze filters that block easily. Blow out fuel lines with air.

Cheers guys, I've checked the unions in the pipes in the engine bay on the ip, fuel filter, and lift pump and they all seem to have good seals and the clamps are tight. I'm going to clean the sedimenter and if that doesn't sort it I'll drain the tank. Cleaning the fuel pipes with air isn't an option as I don't have a compressor but I thought I might try disconnecting the pipe on the input side of the lift pump and putting it into a can of diesel, then I can rule out the fuel lines from the tank up to the lift pump in the engine bay.

I'll let you know how I get on.

Also check the breather in the fuel cap isn't blocked.

Not sure on the 2.8, but could it have the small gauze filter in the banjo fitting on the inlet side of the pump like the 3.9,s have.

Have you tried to google a workshop manual and have a look at the fuel system.

By the way how does the 2.8 push the RRC along.

Justin

Originally Posted by abaddonxi

There are lots of places for blockages in the fuel system. Drain the tank to see if there's any gunk in there. Clean the fuel sedimenter. Check lift pump (if there is one) and fuel injection pump for gauze filters that block easily. Blow out fuel lines with air.

I'm not sure the 4J engine has a gauze filter at supply (pump) or not either.

If the car ran ok for that two hours getting it home then this is a good sign (!?)

I have had good results from a diesel purge (Liqui-Moly) product available from supercr@p auto (has a small red funnel hanging off the side of the lid)- it costs $15.75 or so and its a can- take it home, pull supply and return pipes at the pump pickup and put these in the can- Or use a glass jar like i do and put product in this, place a fair sized rag underneath and put bottle in engine bay and place (cleaned) supply and return pipes in fluid in can/jar.
Allow to run using accerator actuation at the pump to vary/sustain the revs- use all of the can- perhaps even put diesel fuel additive+diesel in the jar afterward (a strong mix- longer application the better- put through it perhaps do it two separate occasions though it may hasten a dying injector pump on it's way) .
This should 'help' clear up some of the junk (contaminant solids, gelly and gum and varnish) inside the pump- it's going to be a rotary pump with some sort arrangement for electronic actuators or solenoids for pump fuel flow and volume relative to revs and temp.

Later style rotary pumps take these measures (eg 'drive by wire') as well as air inlet temp, fuel temp, crank & throttle position sensors etc etc including strange solenoids inside a cam that adjusts for the pump's primary output timing- relative to information from all of those sensors (ie early 2000 transit vans- engine families that now power the 'Land Rover Puma' "but does it really jump and pounce & ponce about though?"

They (later injection systems) do get kinda complex (perverse) right up until the common rail setups where they get sensible but even more delicate (and you can sort of begin to start trusting some of the diagnostic information coming from the ECU).

Not sure what pump you have there. These solenoids and various galleries can gum-up with the garbage diesel they sell here in Oz. Use additive and fuel from one good location (in future) if possible.

This purge product should help the situation. Remember to watch fuel quality at the tank when you buy a diesel car that has been sitting for a bit- but most people around here have a 4BD1 or 4BD1-T and these leave the 4J motor for dead in terms of outright toughness- but they are heavy too- around just under one half a metric ton minus 50Kg or so.

Anyway, I like the Isuzu engines- have respect for the factory engineering and design principles. They are not all the same 'Isuzu tough' and some of the smaller domestic diesels have similar issues to other mortals (ie- Mitsubishi, Land Rover 200/300 engines, various toyota and nissan offerings, and my new Personal favourite 'Great-Wall': Heads, electronics and pumps tend to provide interesting feedback to the poor bastard that owns it- And such like.
Perhaps give the liqui-moly product a try and see what happens. Perhaps drain that damned tank put fresh fuel in and replace all filters including the one you just put on. Put a proper fuel cleaning system in later- this is not at all hard.
Use a fuel additive and service the thing.. Are there white metal and bronze shavings at the sump plug? Whats the gearbox oil look like? Is the box an LT77??? or did they put R380 in.
Still- a high speed turbo diesel in an R/R should be nice. I reckon you wiould need to be vigilant though.

Cheers mate

Originally Posted by isuzurover

Also check the breather in the fuel cap isn't blocked.

Will do. Thanks.

Originally Posted by DRanged

Not sure on the 2.8, but could it have the small gauze filter in the banjo fitting on the inlet side of the pump like the 3.9,s have.

Will check this.

Originally Posted by DRanged

Have you tried to google a workshop manual and have a look at the fuel system.

Yep, got one from here Isuzu4J - similar arrangement of fuel system elements as the original VM 2.4

Originally Posted by DRanged

By the way how does the 2.8 push the RRC along.

It's got good torque and power when it gets enough fuel, looking forward to getting this problem sorted so I can take it out and see what it can do. It seems similar to my 300tdi but hard to say if its better or not until its running right. Massive improvement on the old 2.4 VM I had a few years ago though.

@Svengali0 - I may give the diesel purge a go. Its an old truck and it needs a good service so this seems like a good idea to me. There's no doubt a load of gunk all the way through the fuel system. Oil and air filters are to be done over the weekend as well, and lubricant changes for engine, gearbox and diffs. It has the original LT77 with the typical clunk you get when they have done over 150k or so. Not as bad as my 110 though and that has only 180k miles on it, this one has almost 220k miles on. I'm keeping my eyes open for a disco1 with an r380, should be able to get a rotten one for cheap with a decent gearbox and tbox.

Thanks all.

Well I think I've fixed it. I found this little inline fuel filter tucked away and removed it and it seems to have sorted the problem out.



I can get it to full throttle for a few mins now without it running rough or stalling like it did before. I've also cleaned out the sedimentor and drained the fuel tank - the filth that was in there was so bad I had to poke a stick through the drain hole and wiggle it around before anything would come out.

I'm going to give it a good long run tomorrow and see if this has really sorted it. Sadly I have to spend the rest of the day drinking in pubs in the sunshine. Never mind, I'll just have to try and put a brave face on it.

Thanks for all your advice.