HELP - really techy - sorry folks!
04-16-2002, 05:39 AM
#1
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HELP - really techy - sorry folks!
1984 4.7L 16V Euro (twin Dizzies) LH Jetronic (No Cats, No Oxygen Sensors) wheel in each corner.
on going problem:
car starts fine...warms up fine, idles fine...cannot be driven....no power, back fires, falters etc etc. eventually dies after about 2 minutes of attempted driving...does not over heat.
mixture at idle 0.1% (wrong!) can only be set at 1.5% by raising fuel pressure to 3.7 bar. then runs very very rich above idle.(to be expected)
fuel pressure at idle 2.0 bar. fuel pump checked for flow and pressure - well within spec.
all new plugs, all new filters, injectors serviced and balanced.
valve timing checked, all ok
ignition timing checked, statically, dymanically at idle, and checked for advance...all seems ok.
inlet tract checked for air leaks - none - all vacuum hoses checked, all oil filler/breather hoses and gaskets checked - no air leaks. (checked with butane lance)
hot wire air mass meter checked - no air flow ~1.8VDC full flow 4.85VDC
throttle switch checked, all temperature sensors checked. all switch and sensor connections/function checked back to ecu connector.
all earths undone, cleaned and refitted.
injection ecu replaced, refurbished unit rechecked by manufacturers, unit from another running vehicle also used. no difference.
has anyone got any ideas? 'cos i have run out!
regards
johnb <img src="graemlins/c.gif" border="0" alt="[ouch]" /> <img src="graemlins/crying.gif" border="0" alt="[crying]" />
on going problem:
car starts fine...warms up fine, idles fine...cannot be driven....no power, back fires, falters etc etc. eventually dies after about 2 minutes of attempted driving...does not over heat.
mixture at idle 0.1% (wrong!) can only be set at 1.5% by raising fuel pressure to 3.7 bar. then runs very very rich above idle.(to be expected)
fuel pressure at idle 2.0 bar. fuel pump checked for flow and pressure - well within spec.
all new plugs, all new filters, injectors serviced and balanced.
valve timing checked, all ok
ignition timing checked, statically, dymanically at idle, and checked for advance...all seems ok.
inlet tract checked for air leaks - none - all vacuum hoses checked, all oil filler/breather hoses and gaskets checked - no air leaks. (checked with butane lance)
hot wire air mass meter checked - no air flow ~1.8VDC full flow 4.85VDC
throttle switch checked, all temperature sensors checked. all switch and sensor connections/function checked back to ecu connector.
all earths undone, cleaned and refitted.
injection ecu replaced, refurbished unit rechecked by manufacturers, unit from another running vehicle also used. no difference.
has anyone got any ideas? 'cos i have run out!
regards
johnb <img src="graemlins/c.gif" border="0" alt="[ouch]" /> <img src="graemlins/crying.gif" border="0" alt="[crying]" />
04-16-2002, 12:41 PM
#2
Racer
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Have you checked fuel pressure (dynamic or residual) right after an episode happens?
I had a similar problem a few months back with similar symptoms. I installed a fuel pressure guage on the rail and found that I was loosing fuel pressure. In my case, I was not able to isolate the cause to one component but after a new pump, filter, pick-up screen and regulaters, The problem is fixed.
Could you be loosing the signal that keeps the fuel pump relay energized... maybe under load ?
I had a similar problem a few months back with similar symptoms. I installed a fuel pressure guage on the rail and found that I was loosing fuel pressure. In my case, I was not able to isolate the cause to one component but after a new pump, filter, pick-up screen and regulaters, The problem is fixed.
Could you be loosing the signal that keeps the fuel pump relay energized... maybe under load ?
04-16-2002, 05:24 PM
#3
Burning Brakes
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John, dude I think your car is just cursed.
I've still got my intake apart - plenum to air filter is off the car. I'm waiting for a new throttlebody to elbow seal, and one for the fitting on the front of the plenum that goes to the AC idle bump valve.
The only other thing to check is the power supply to the injectors. As load and rpm increase, the injectors use more power. So if the power supply can't keep up, you'd get a lean condition that worsens as rpm and load increase. So starting and idling are OK, but driving is not. The suspects here would be whatever relay powers up the engine management computers, and checking for battery voltage at the ECUs. And your battery and alternator should be in good shape too. This would explain why your car ran the same way with another computer, why your computer eventally blew (it was bad, right?), why you can start and idle OK but not drive, and why nothing you've mentioned so far (which is a lot) has solved it.
Good luck and let us know what you find.
Bryan
I've still got my intake apart - plenum to air filter is off the car. I'm waiting for a new throttlebody to elbow seal, and one for the fitting on the front of the plenum that goes to the AC idle bump valve.
The only other thing to check is the power supply to the injectors. As load and rpm increase, the injectors use more power. So if the power supply can't keep up, you'd get a lean condition that worsens as rpm and load increase. So starting and idling are OK, but driving is not. The suspects here would be whatever relay powers up the engine management computers, and checking for battery voltage at the ECUs. And your battery and alternator should be in good shape too. This would explain why your car ran the same way with another computer, why your computer eventally blew (it was bad, right?), why you can start and idle OK but not drive, and why nothing you've mentioned so far (which is a lot) has solved it.
Good luck and let us know what you find.
Bryan
04-16-2002, 10:20 PM
#5
Three Wheelin'
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High combustion chamber pressure can cause a lean condition, do a compression test. If the reading is higher then specification, it may indicate a buildup of carbon on the pistons or valves. A worn exhaust cam lobe or weak valve springs can also raise compression (lean condition)
If you have a functional air pump, disconnect the drive belt. Unmetered air can enter the engine by a fault system.
Voltage spikes from a bad alternator (diodes, regulator) can alter fuel injector pulse time.
The most over looked area of unmetered air, are vacuum leaks below the throttle plate, throttle plate housing gasket, intake manifold gasket, oil dipstick seal, oil filler neck gasket, valve cover gasket.
Good luck
Steve C
The Great White
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If you have a functional air pump, disconnect the drive belt. Unmetered air can enter the engine by a fault system.
Voltage spikes from a bad alternator (diodes, regulator) can alter fuel injector pulse time.
The most over looked area of unmetered air, are vacuum leaks below the throttle plate, throttle plate housing gasket, intake manifold gasket, oil dipstick seal, oil filler neck gasket, valve cover gasket.
Good luck
Steve C
The Great White
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
04-17-2002, 04:48 AM
#6
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hi guys
many thanks for all the suggestions.
we have checked the compression...all ok.
i have booked this afternoon off work, my bosch guy and i are going to go right thro' every system again.
i am going to make a 'breakout' box for all the connections on the ecu headers. that way i can check exactly what is going on with voltage levels, pulse timing etc as the car is driven.
i'm fairly certain it will turn out to be something very trivial...a sometimes/maybe connection.....dodgy earth or power feed.
today is the day...the car will run, one way or another!......now, where did i put those Carburettors and points..........
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" /> guys
johnb
many thanks for all the suggestions.
we have checked the compression...all ok.
i have booked this afternoon off work, my bosch guy and i are going to go right thro' every system again.
i am going to make a 'breakout' box for all the connections on the ecu headers. that way i can check exactly what is going on with voltage levels, pulse timing etc as the car is driven.
i'm fairly certain it will turn out to be something very trivial...a sometimes/maybe connection.....dodgy earth or power feed.
today is the day...the car will run, one way or another!......now, where did i put those Carburettors and points..........
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" /> guys
johnb
04-17-2002, 05:29 AM
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John,
I think this last post is on the right track- check what the ECU is seeing. You may be getting signal to the back of the connector, but you MAY have a bad connection into the ECU. Having swapped ECUs, this less likely, but still possible - eg temp sensor signal (low ohms) not getting through will keep it rich. I can think of much else?
jp
I think this last post is on the right track- check what the ECU is seeing. You may be getting signal to the back of the connector, but you MAY have a bad connection into the ECU. Having swapped ECUs, this less likely, but still possible - eg temp sensor signal (low ohms) not getting through will keep it rich. I can think of much else?
jp