Engine flooding - causes?
02-05-2006, 03:45 PM
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Track Day
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Engine flooding - causes?
I've posted a few other threads about my '89 S4 (UK model) - it was laid up for a couple of months and now won't start.
I have tested the leads with a timing gun and found that it does have spark. I have cleaned the ground points and run most of the appropriate tests on the LH & EZK (incl. thermo II & unplugging the MAF) with the following exceptions:
- cleaning the ground point X as I can't find it ('upper crankcase rear left' my a**e)
- engine speed reference signal (I don't have an oscilloscope)
- fuel pressure in the rail (don't have the necessary adapter, but am ordering one)
- injector valve operation
It's definately flooding - after just a couple of attempts to start I found fuel seeping through the exhaust/header joints (and also seeping through a welded repair to the center exhaust box). I pulled the plugs to find them soaked. Yes, I will be careful! No, my car does not have cats.
Suspects are:
- LH gone bad and injectors stuck open (unlikely? is this type of failure common?)
- Diaphragms in one or more of the three regulators have split, and intake vacuum is sucking fuel into the intake
- Dodgy engine harness connector (the rectangular 14-pin connecter next to the jump start post)
Engine harness connector: while inspecting the wiring I found that the blue wire in the top half of the plug was broken. I repaired it but still no start. I could have broken this wire as I was moving the loom around when it was laid up (replaced front shocks). I can't work out what this wire is for so can't discount it - can anyone help? Can't find it on the wiring diagrams.
Diaphrams in fuel regulators:
I have read in past posts that the diaphragms can split and cause fuel to be sucked into the intake. This is my prime suspect!
It was at or around 0 degrees C when I first cranked that car after its lay-up - as we know from the Challenger disaster rubber doesn't like to stretch when it's cold. So old rubber could have given way...
Is there a way to reliably test these? Suck on a vacuum hose and see if I get a mouthful of fuel? I have pulled the vacuum lines off all three, they all smell a bit of petrol but there are no obvious signs of leaking.
LH control unit:
I have not been able to check that the injector valves are operating correctly - I was going to stick my ear on a screwdriver pressed against each injector, but I don't have a helper on hand to crank the engine (I have no friends as I spend all of my time on my car).
Is there another way to test for operation? Can I rig up a test light using battery +ve and the ground from an injector or will this fry the brain?
I have yet to do the injector voltage and coil resistance checks under 'test point 16' of the LH diagnostics, however this won't confirm whether or not the injectors are stuck open.
The car has been running faultlessly for the last six months that I have owned it (following engine rebuild by a respected local 928 expert).
Can anything else cause flooding like this?
Sorry for the looong post, but cheers as always for your help!
Barry
'89 S4 (UK model)
I have tested the leads with a timing gun and found that it does have spark. I have cleaned the ground points and run most of the appropriate tests on the LH & EZK (incl. thermo II & unplugging the MAF) with the following exceptions:
- cleaning the ground point X as I can't find it ('upper crankcase rear left' my a**e)
- engine speed reference signal (I don't have an oscilloscope)
- fuel pressure in the rail (don't have the necessary adapter, but am ordering one)
- injector valve operation
It's definately flooding - after just a couple of attempts to start I found fuel seeping through the exhaust/header joints (and also seeping through a welded repair to the center exhaust box). I pulled the plugs to find them soaked. Yes, I will be careful! No, my car does not have cats.
Suspects are:
- LH gone bad and injectors stuck open (unlikely? is this type of failure common?)
- Diaphragms in one or more of the three regulators have split, and intake vacuum is sucking fuel into the intake
- Dodgy engine harness connector (the rectangular 14-pin connecter next to the jump start post)
Engine harness connector: while inspecting the wiring I found that the blue wire in the top half of the plug was broken. I repaired it but still no start. I could have broken this wire as I was moving the loom around when it was laid up (replaced front shocks). I can't work out what this wire is for so can't discount it - can anyone help? Can't find it on the wiring diagrams.
Diaphrams in fuel regulators:
I have read in past posts that the diaphragms can split and cause fuel to be sucked into the intake. This is my prime suspect!
It was at or around 0 degrees C when I first cranked that car after its lay-up - as we know from the Challenger disaster rubber doesn't like to stretch when it's cold. So old rubber could have given way...
Is there a way to reliably test these? Suck on a vacuum hose and see if I get a mouthful of fuel? I have pulled the vacuum lines off all three, they all smell a bit of petrol but there are no obvious signs of leaking.
LH control unit:
I have not been able to check that the injector valves are operating correctly - I was going to stick my ear on a screwdriver pressed against each injector, but I don't have a helper on hand to crank the engine (I have no friends as I spend all of my time on my car).
Is there another way to test for operation? Can I rig up a test light using battery +ve and the ground from an injector or will this fry the brain?
I have yet to do the injector voltage and coil resistance checks under 'test point 16' of the LH diagnostics, however this won't confirm whether or not the injectors are stuck open.
The car has been running faultlessly for the last six months that I have owned it (following engine rebuild by a respected local 928 expert).
Can anything else cause flooding like this?
Sorry for the looong post, but cheers as always for your help!
Barry
'89 S4 (UK model)
02-05-2006, 04:00 PM
#2
Rennlist Member
Barry.............how much petrol is in the oil if any?
Take the spark plugs out, disconnect the ignition coils and crank the engine over to evacuate the cylinders. If you have the cylinders as full as you say there's a potential of hydraulic lock and may bend something...........I would NOT turn the engine until the plugs are removed.
Once the cylinders are clear check for good spark and then all the basics remembering all you need is compression, spark and fuel/air mixture all at the right time. By the sounds of it you've plenty of fuel!!!
Take the spark plugs out, disconnect the ignition coils and crank the engine over to evacuate the cylinders. If you have the cylinders as full as you say there's a potential of hydraulic lock and may bend something...........I would NOT turn the engine until the plugs are removed.
Once the cylinders are clear check for good spark and then all the basics remembering all you need is compression, spark and fuel/air mixture all at the right time. By the sounds of it you've plenty of fuel!!!
02-05-2006, 04:21 PM
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Track Day
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flyin' scotsman - yes that was my first thought when I saw the fuel seeping through the exhaust joints!
Luckily I am due for an oil change anyway - just need to warm it up first. I'll pull the dipstick and see it if smells of fuel. Hopefully no damage will result from oil washed out of rings or fuel in oil... (eek) ...??????
Barry
Luckily I am due for an oil change anyway - just need to warm it up first. I'll pull the dipstick and see it if smells of fuel. Hopefully no damage will result from oil washed out of rings or fuel in oil... (eek) ...??????
Barry
02-05-2006, 05:05 PM
#4
Rennlist Member
Hi Barry
If you just switch on the ignition, can you hear the ijectors clicking regularly ? If so, LH ECU problem.
They don't usually fail hard on due to LH failure.
I don't recommend try to wire any power to the injectors. You need to monitor the volatges on one of the injector plugs. They are two pin connectors. permanent 12v is supplied to one side. When the injecors is to be opened, the other connection is grounded by the LH ECU. Try to check this when ingition only is on, not cranking, first. Then try when cranking the engine.
But do as Malcom says, and try and get that fuel safely out of the engine first.
If you just switch on the ignition, can you hear the ijectors clicking regularly ? If so, LH ECU problem.
They don't usually fail hard on due to LH failure.
I don't recommend try to wire any power to the injectors. You need to monitor the volatges on one of the injector plugs. They are two pin connectors. permanent 12v is supplied to one side. When the injecors is to be opened, the other connection is grounded by the LH ECU. Try to check this when ingition only is on, not cranking, first. Then try when cranking the engine.
But do as Malcom says, and try and get that fuel safely out of the engine first.
02-05-2006, 05:17 PM
#5
Rennlist Member
Back in the old 2 stroke motorcycle days we'd take the plug(s) out, invert the bike, drain petrol, right the bike, insert new plug, start engine and ride away. Not as easy w/ a 928.
'Speake' of the devil and he shall appear............good evening John.
'Speake' of the devil and he shall appear............good evening John.
