Disco 1 V8 3.9 V8 1997 Weird Fuelling Issues
Discussion
Hey everyone!
Long time lurker on the forums.
Bit of background - I own a Disco 1 3.9 V8 EFI. When I got it it a few years ago, it started developing a head gasket exhaust noise. I ended up replacing the head gaskets, water pump, and all other perishables on the way. After that was fixed and running really smooth, I tuned the MAF, checked all the vacuum hoses and made sure everything else was good.
The car ran well for about 1500km, albeit still with higher than normal consumption (25+l/100km) even on the open road with aircon off. After this time period we started experiencing some unusual things.
Initially, the car would start fine, drive for about an hour on the highway really well until you would come to a stop. At this point the car would loose ability to idle and stall. After this, it would take a long time (5+ crank attempts) to get started again. Once it was up and running it would be hit and miss if it would run smoothly or would stall again.
This now happens pretty much every time without fail. A few weeks ago it stopped again at a stop street - luckily i was able to push it inside a driveway. It sat for about a week before we were able to get it running again. We checked the spark, fuel, air and timing and all was good. We even replaced the idle air control valve, even though the old one was fine. Eventually what worked was taking a cloth, soaking it in thinners, and putting it on the intake. When we did that, it started up, albeit on 5 cylinders, but eventually the others fired up too. We think it flooded and the spark wasn't strong enough to ignite with the plugs being so wet.
About 3 weeks after that, the car was driving perfectly fine until we got back from a weekend away and same story - at slower speeds the engine would cut out. Managed to get it running again shortly after and has been fine until last weekend. Now the car will not start properly even though it has fuel, spark and air. When it does start, it runs really rough and smells really rich. The only driving it will do is in idle, as soon as I try and accelerate, the engine starts to die. When I let go, it catches again but only idles. Does not let me accelerate at all almost as if it's being starved of fuel.
We now can't get it to run smooth at all, almost as if it's running without the MAF plugged in. The majority of times this has happened has been when the car has been low on fuel (light is on). Not sure if this is related or coincidence.
Have any of you experienced these symptoms before?
TLDR; Can will start fine, run smoothly on the open road, and will cut out when coming to a stop. Will not start again after that.
Will appreciate any form of advice!
Long time lurker on the forums.
Bit of background - I own a Disco 1 3.9 V8 EFI. When I got it it a few years ago, it started developing a head gasket exhaust noise. I ended up replacing the head gaskets, water pump, and all other perishables on the way. After that was fixed and running really smooth, I tuned the MAF, checked all the vacuum hoses and made sure everything else was good.
The car ran well for about 1500km, albeit still with higher than normal consumption (25+l/100km) even on the open road with aircon off. After this time period we started experiencing some unusual things.
Initially, the car would start fine, drive for about an hour on the highway really well until you would come to a stop. At this point the car would loose ability to idle and stall. After this, it would take a long time (5+ crank attempts) to get started again. Once it was up and running it would be hit and miss if it would run smoothly or would stall again.
This now happens pretty much every time without fail. A few weeks ago it stopped again at a stop street - luckily i was able to push it inside a driveway. It sat for about a week before we were able to get it running again. We checked the spark, fuel, air and timing and all was good. We even replaced the idle air control valve, even though the old one was fine. Eventually what worked was taking a cloth, soaking it in thinners, and putting it on the intake. When we did that, it started up, albeit on 5 cylinders, but eventually the others fired up too. We think it flooded and the spark wasn't strong enough to ignite with the plugs being so wet.
About 3 weeks after that, the car was driving perfectly fine until we got back from a weekend away and same story - at slower speeds the engine would cut out. Managed to get it running again shortly after and has been fine until last weekend. Now the car will not start properly even though it has fuel, spark and air. When it does start, it runs really rough and smells really rich. The only driving it will do is in idle, as soon as I try and accelerate, the engine starts to die. When I let go, it catches again but only idles. Does not let me accelerate at all almost as if it's being starved of fuel.
We now can't get it to run smooth at all, almost as if it's running without the MAF plugged in. The majority of times this has happened has been when the car has been low on fuel (light is on). Not sure if this is related or coincidence.
Have any of you experienced these symptoms before?
TLDR; Can will start fine, run smoothly on the open road, and will cut out when coming to a stop. Will not start again after that.
Will appreciate any form of advice!
Check the fuel pressure when it is running normally, and when the problem happens.
Check the ECU coolant temp sender circuit resistance at the ECU plug.
Check the throttle pot circuit resistance at the ECU plug.
Remove and clean the idle control stepper motor.
Check the throttle butterfly is clean.
The smell of fuel is probably just due to the misfire and doesn't necessarily imply that the misfire is caused by overfuelling. The fact it started with extra fuel added suggests it may be under fuelling.
Check the ECU coolant temp sender circuit resistance at the ECU plug.
Check the throttle pot circuit resistance at the ECU plug.
Remove and clean the idle control stepper motor.
Check the throttle butterfly is clean.
The smell of fuel is probably just due to the misfire and doesn't necessarily imply that the misfire is caused by overfuelling. The fact it started with extra fuel added suggests it may be under fuelling.
GreenV8S said:
Check the fuel pressure when it is running normally, and when the problem happens.
^^^This, I had an XR4i years ago that had symptoms almost exactly as you describe, upon investigation I found that it had been fitted with a fuel pump which was too small and on it's last legs, the fuel pressure was less than half what it should have been.Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff