S8 dies at 60mph. Coughs a little but no start.
09-29-2017, 10:52 AM
#1
AudiWorld Member
Thread Starter
S8 dies at 60mph. Coughs a little but no start.
My daughter was cruising along around 60mph when the engine stumbled and died. The car wouldn't start again. It makes an attempt, with a few coughs.
After I had it towed home, it started for a couple of seconds then immediately died.
Codes are P1128. P1130 banks 1 and 2, System too lean, and random cylinder misfires P0301, p0305, p0306, p0302.
Under the hood the only obvious problem was one of the two vacuum operated manifold flaps had a broken plastic connector, so one of the flaps is not operating, but this shouldn't be enough to stop the car in full flight. There's no obvious vacuum lines broken.
Any thoughts on first places to start anyone?
After I had it towed home, it started for a couple of seconds then immediately died.
Codes are P1128. P1130 banks 1 and 2, System too lean, and random cylinder misfires P0301, p0305, p0306, p0302.
Under the hood the only obvious problem was one of the two vacuum operated manifold flaps had a broken plastic connector, so one of the flaps is not operating, but this shouldn't be enough to stop the car in full flight. There's no obvious vacuum lines broken.
Any thoughts on first places to start anyone?
09-29-2017, 10:55 AM
#2
AudiWorld Super User
My daughter was cruising along around 60mph when the engine stumbled and died. The car wouldn't start again. It makes an attempt, with a few coughs.
After I had it towed home, it started for a couple of seconds then immediately died.
Codes are P1128. P1130 banks 1 and 2, System too lean, and random cylinder misfires P0301, p0305, p0306, p0302.
Under the hood the only obvious problem was one of the two vacuum operated manifold flaps had a broken plastic connector, so one of the flaps is not operating, but this shouldn't be enough to stop the car in full flight. There's no obvious vacuum lines broken.
Any thoughts on first places to start anyone?
After I had it towed home, it started for a couple of seconds then immediately died.
Codes are P1128. P1130 banks 1 and 2, System too lean, and random cylinder misfires P0301, p0305, p0306, p0302.
Under the hood the only obvious problem was one of the two vacuum operated manifold flaps had a broken plastic connector, so one of the flaps is not operating, but this shouldn't be enough to stop the car in full flight. There's no obvious vacuum lines broken.
Any thoughts on first places to start anyone?
10-01-2017, 06:09 PM
#6
AudiWorld Member
Thread Starter
Just a little update:
Yesterday I disconnected the pressure fuel line where it joins the fuel rail on top of the manifold.
I pulled the fuel pump fuse in the passenger footwell and then sent 12v to the fuel pump for about 15 secs. Small amounts of fuel pumped lamely into my catchment jar. Obviously fuel was not being delivered properly.
I then extracted the fuel pump and ordered a new one.
With the old pump on the bench, I fed it 12v and the pump span just fine with no strange noises.
So I'm a little confused as to why the pump appears OK on the bench. I realize that normally it operates submerged and I understand that I might have jogged it into life by extracting it, but it's still not convincing.
RE: Checking the filter. I haven't done this yet, because I reasoned that if a filter was slowly clogging up, it would hardly suddenly completely cut-off the engine - or would it? Wouldn't a clogging filter show itself in a slow build up of a problems? and not a sudden cut off?
Yesterday I disconnected the pressure fuel line where it joins the fuel rail on top of the manifold.
I pulled the fuel pump fuse in the passenger footwell and then sent 12v to the fuel pump for about 15 secs. Small amounts of fuel pumped lamely into my catchment jar. Obviously fuel was not being delivered properly.
I then extracted the fuel pump and ordered a new one.
With the old pump on the bench, I fed it 12v and the pump span just fine with no strange noises.
So I'm a little confused as to why the pump appears OK on the bench. I realize that normally it operates submerged and I understand that I might have jogged it into life by extracting it, but it's still not convincing.
RE: Checking the filter. I haven't done this yet, because I reasoned that if a filter was slowly clogging up, it would hardly suddenly completely cut-off the engine - or would it? Wouldn't a clogging filter show itself in a slow build up of a problems? and not a sudden cut off?
10-02-2017, 04:33 AM
#7
If you google around you can find teardowns of these pumps, often when they fail chunks of the commutator break off and wedge the pump. A good trick to get home is to reverse the power to the pump to temporarily unjam them.
When you get the pump make sure it has the extra port on the bottom, common pumps fit but lack this port for the (scavenge pumps in the far reaches of the tank).
When you get the pump make sure it has the extra port on the bottom, common pumps fit but lack this port for the (scavenge pumps in the far reaches of the tank).
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10-03-2017, 05:56 AM
#8
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When I replaced my pump due to the car not starting I had the same bench test results as you. Seemed to work every time I applied power to it. Finally it did not respond to power, tapped it about a dozen times and it took off again. Point being replace the pump as it has given up it useful life. Not a fun job to replace, but worth the effort.
10-06-2017, 05:44 AM
#9
AudiWorld Member
Thread Starter
Car running again
Car is running again with one potential worry.
Here's what happened:
While waiting for the new pump I replaced the fuel filter. The old filter didn't appear to be clogged - I tested it with a jet of water and it passed thru just fine.
I then assembled and installed the new pump. Getting the housing back into the tank was a pain until I realized that the rubber grommet ring around the top opening should be installed on the tank first and not on the housing first. If you put it on the pump housing then the whole unit sits in the right place but can't be pushed down that last inch and won't sit flush on the tank rim opening. I was trying to get the large locking ring to thread so it would draw it down but it wouldn't take. Placing the rubber ring on the tank first solved the problem.
OK, the potential worry is the long rod bolt. I tightened it up while the pump housing wasn't quite all the way in. When I had to back the housing out a little to put the rubber ring on the tank opening, I tried to undo the bolt but it wouldn't undo. It just rotated with no effect. So I assume that at the other end the nut was rotating in its plastic housing. I tightened it back up, but I suspect that it probably wouldn't tighten fully for the same reason.
Anyway, the car started right up and it's gone off on a long trip, but my daughter filled it up before it dropped below half a tank, so I'm not sure if it's good or not.
In conclusion, the pump may look good on the bench but still be bad.
Here's what happened:
While waiting for the new pump I replaced the fuel filter. The old filter didn't appear to be clogged - I tested it with a jet of water and it passed thru just fine.
I then assembled and installed the new pump. Getting the housing back into the tank was a pain until I realized that the rubber grommet ring around the top opening should be installed on the tank first and not on the housing first. If you put it on the pump housing then the whole unit sits in the right place but can't be pushed down that last inch and won't sit flush on the tank rim opening. I was trying to get the large locking ring to thread so it would draw it down but it wouldn't take. Placing the rubber ring on the tank first solved the problem.
OK, the potential worry is the long rod bolt. I tightened it up while the pump housing wasn't quite all the way in. When I had to back the housing out a little to put the rubber ring on the tank opening, I tried to undo the bolt but it wouldn't undo. It just rotated with no effect. So I assume that at the other end the nut was rotating in its plastic housing. I tightened it back up, but I suspect that it probably wouldn't tighten fully for the same reason.
Anyway, the car started right up and it's gone off on a long trip, but my daughter filled it up before it dropped below half a tank, so I'm not sure if it's good or not.
In conclusion, the pump may look good on the bench but still be bad.
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