1988 S4 problem starting (devek 6 litre stroker car)
04-11-2015, 04:37 PM
#61
Rennlist Member
Thread Starter
ok, the ECU's (both ezk and LH as well as MAF) checked out fine from Rich.
so, im still trying to get the owner to get the darn ohm meter out and test Temp II at the harness and at the sensor itself. not thinking that could be the issue, as usually that means there is not enough fuel at start up , but there is too much. so much fuel when we were starting up, that it was leaking out the CAT. we always thought there was one injector that might be hanging open, but is that enough to lower fuel pressure to almost zero?l how does it barely run, with 0 fuel pressure. (ran for about 3 mins, horribly , like 3 cylinders, but ran).... then when the fuel pump jumper is connected, the pressure goes to 45psi but it doesn't run. then there is the TACH signal to the dash, that is not working. I don't understand how it can be running at 0 psi and wont even catch when fuel pump is jumpered.
vacuum lines are all off the regulator and dampers.
I think it has to be something related to the injectors being turned all the way on at start up, by some kind of bad ground.
Ill have to visit the patient and do some more tests. temp II, harness ground verification, etc.
then, I guess we just start pulling things off and replacing.
so, im still trying to get the owner to get the darn ohm meter out and test Temp II at the harness and at the sensor itself. not thinking that could be the issue, as usually that means there is not enough fuel at start up , but there is too much. so much fuel when we were starting up, that it was leaking out the CAT. we always thought there was one injector that might be hanging open, but is that enough to lower fuel pressure to almost zero?l how does it barely run, with 0 fuel pressure. (ran for about 3 mins, horribly , like 3 cylinders, but ran).... then when the fuel pump jumper is connected, the pressure goes to 45psi but it doesn't run. then there is the TACH signal to the dash, that is not working. I don't understand how it can be running at 0 psi and wont even catch when fuel pump is jumpered.
vacuum lines are all off the regulator and dampers.
I think it has to be something related to the injectors being turned all the way on at start up, by some kind of bad ground.
Ill have to visit the patient and do some more tests. temp II, harness ground verification, etc.
then, I guess we just start pulling things off and replacing.
04-11-2015, 09:58 PM
#62
Nordschleife Master
One obvious failure which didn't occur to me until now as a possibility.. If there's that much fuel flowing off the cats: if a fuel hose at the back of the valley under the airbox has failed (cracked), then it would explain lots of fuel by the cats, the lack of fuel pressure initially, and the drop in pressure when the engine's turned off.
My advice is to direct the owner to a 928-qualified shop to get the car fixed.. before this story ends up with a car (or worse) going up in smoke.
It sounds like the owner doesn't know enough about cars to be troubleshooting this himself, which given its a fuel leak issue, is a huge risk. If there's raw fuel pouring onto the floor, then the chances of the car or garage going up in flames is too great.
My advice is to direct the owner to a 928-qualified shop to get the car fixed.. before this story ends up with a car (or worse) going up in smoke.
It sounds like the owner doesn't know enough about cars to be troubleshooting this himself, which given its a fuel leak issue, is a huge risk. If there's raw fuel pouring onto the floor, then the chances of the car or garage going up in flames is too great.
04-12-2015, 03:21 AM
#63
Rennlist Member
Thread Starter
One obvious failure which didn't occur to me until now as a possibility.. If there's that much fuel flowing off the cats: if a fuel hose at the back of the valley under the airbox has failed (cracked), then it would explain lots of fuel by the cats, the lack of fuel pressure initially, and the drop in pressure when the engine's turned off.
My advice is to direct the owner to a 928-qualified shop to get the car fixed.. before this story ends up with a car (or worse) going up in smoke.
It sounds like the owner doesn't know enough about cars to be troubleshooting this himself, which given its a fuel leak issue, is a huge risk. If there's raw fuel pouring onto the floor, then the chances of the car or garage going up in flames is too great.
My advice is to direct the owner to a 928-qualified shop to get the car fixed.. before this story ends up with a car (or worse) going up in smoke.
It sounds like the owner doesn't know enough about cars to be troubleshooting this himself, which given its a fuel leak issue, is a huge risk. If there's raw fuel pouring onto the floor, then the chances of the car or garage going up in flames is too great.
the tests we did were with the air box removed...... so we could see that area of the fuel lines. If there is no leak, what are the possibilities... the rapid decay of fuel pressure, could that be due to fuel pump check valve, or the injectors being stuck on ?
It sounds like the fuel is coming out of the engine and into the cat. if so, that's not a safe situation too. actually not a cat, but that bypass muffler.
04-12-2015, 02:32 PM
#64
Rennlist Member
Thread Starter
I very much doubt that a diaphragm failure [and the resulting side stream flow] will be such that the pressure delivery can collapse to the point where the system will not fire up- I do not think the vacuum line will allow sufficent flow to do that but it may reduce the fuel rail pressure a little.
so, where is the fuel going? back to the tank, or into the engine?
all this coupled with the fact that the tach doesn't work either.
04-12-2015, 02:40 PM
#65
I very much doubt that a diaphragm failure [and the resulting side stream flow] will be such that the pressure delivery can collapse to the point where the system will not fire up- I do not think the vacuum line will allow sufficent flow to do that but it may reduce the fuel rail pressure a little.
04-12-2015, 03:55 PM
#66
Rennlist Member
Thread Starter
04-12-2015, 04:54 PM
#67
Archive Gatekeeper
Rennlist Member
Rennlist Member
Do you (still) have compression in all 8 cylinders? I'd be worried about a stuck injector filling a cylinder.
04-13-2015, 01:36 PM
#68
Rennlist Member
Thread Starter
wonder if there is a possiblity that the pump can deliver static pressure as tested, and flow with no pressure as measured, but cant deliver pressure and flow.
04-13-2015, 03:28 PM
#69
The jumpered fuel pump circuit provides full voltage to the fuel pump, but the relayed circuit doesn't. Why?
Alan or other electrical gurus may want to check me, but looking at the wiring diagrams there seem to be some possibilities....
1. The relay contacts are burnt causing high resistance/low voltage to the fuel pump.
2. The relay coil is faulty and doesn't make enough magnetism to pull the relay armature to completely close the contacts, the poor connection can't carry the FP current without excessive heat, burnt contacts, and low voltage to the fuel pump.
Nos. 1 and 2 are fixed with a known good relay.
3. The voltage on the circuit serving the relay coil is too low to completely close the contacts as above, causing low voltage to the fuel pump.
One side of the FP relay coil is connected to the LH, pin 20. This should be at ground potential when the LH wants the FP to run. If the LH is too hot, maybe there's a bad connection/broken wire in this circuit near the LH making heat.
The power side of the coil is fed from the 15 bus (ignition switch) in the CE panel, anything connected to that bus could pull down the voltage. These are:
a) T22 plug for alarm system connections (under CE Panel) and on to EZK relay coil. If there's an alarm system connected, disconnect it and jumper pins 1 and 4 to energize the EZK.
b) ignition circuits to distributors
c) kickdown switch relay (contacts and coil). If you pull the KD relay XV with the FP relay in place and you get full fuel pressure, the problem is either the KD relay itself or somewhere in the KD circuit.
If any of these areas have been recently 'touched', that might be the place to start.
Alan or other electrical gurus may want to check me, but looking at the wiring diagrams there seem to be some possibilities....
1. The relay contacts are burnt causing high resistance/low voltage to the fuel pump.
2. The relay coil is faulty and doesn't make enough magnetism to pull the relay armature to completely close the contacts, the poor connection can't carry the FP current without excessive heat, burnt contacts, and low voltage to the fuel pump.
Nos. 1 and 2 are fixed with a known good relay.
3. The voltage on the circuit serving the relay coil is too low to completely close the contacts as above, causing low voltage to the fuel pump.
One side of the FP relay coil is connected to the LH, pin 20. This should be at ground potential when the LH wants the FP to run. If the LH is too hot, maybe there's a bad connection/broken wire in this circuit near the LH making heat.
The power side of the coil is fed from the 15 bus (ignition switch) in the CE panel, anything connected to that bus could pull down the voltage. These are:
a) T22 plug for alarm system connections (under CE Panel) and on to EZK relay coil. If there's an alarm system connected, disconnect it and jumper pins 1 and 4 to energize the EZK.
b) ignition circuits to distributors
c) kickdown switch relay (contacts and coil). If you pull the KD relay XV with the FP relay in place and you get full fuel pressure, the problem is either the KD relay itself or somewhere in the KD circuit.
If any of these areas have been recently 'touched', that might be the place to start.
04-13-2015, 04:02 PM
#70
Rennlist Member
Thread Starter
The jumpered fuel pump circuit provides full voltage to the fuel pump, but the relayed circuit doesn't. Why?
Alan or other electrical gurus may want to check me, but looking at the wiring diagrams there seem to be some possibilities....
1. The relay contacts are burnt causing high resistance/low voltage to the fuel pump.
2. The relay coil is faulty and doesn't make enough magnetism to pull the relay armature to completely close the contacts, the poor connection can't carry the FP current without excessive heat, burnt contacts, and low voltage to the fuel pump.
Nos. 1 and 2 are fixed with a known good relay.
3. The voltage on the circuit serving the relay coil is too low to completely close the contacts as above, causing low voltage to the fuel pump.
One side of the FP relay coil is connected to the LH, pin 20. This should be at ground potential when the LH wants the FP to run. If the LH is too hot, maybe there's a bad connection/broken wire in this circuit near the LH making heat.
The power side of the coil is fed from the 15 bus (ignition switch) in the CE panel, anything connected to that bus could pull down the voltage. These are:
a) T22 plug for alarm system connections (under CE Panel) and on to EZK relay coil. If there's an alarm system connected, disconnect it and jumper pins 1 and 4 to energize the EZK.
b) ignition circuits to distributors
c) kickdown switch relay (contacts and coil). If you pull the KD relay XV with the FP relay in place and you get full fuel pressure, the problem is either the KD relay itself or somewhere in the KD circuit.
If any of these areas have been recently 'touched', that might be the place to start.
Alan or other electrical gurus may want to check me, but looking at the wiring diagrams there seem to be some possibilities....
1. The relay contacts are burnt causing high resistance/low voltage to the fuel pump.
2. The relay coil is faulty and doesn't make enough magnetism to pull the relay armature to completely close the contacts, the poor connection can't carry the FP current without excessive heat, burnt contacts, and low voltage to the fuel pump.
Nos. 1 and 2 are fixed with a known good relay.
3. The voltage on the circuit serving the relay coil is too low to completely close the contacts as above, causing low voltage to the fuel pump.
One side of the FP relay coil is connected to the LH, pin 20. This should be at ground potential when the LH wants the FP to run. If the LH is too hot, maybe there's a bad connection/broken wire in this circuit near the LH making heat.
The power side of the coil is fed from the 15 bus (ignition switch) in the CE panel, anything connected to that bus could pull down the voltage. These are:
a) T22 plug for alarm system connections (under CE Panel) and on to EZK relay coil. If there's an alarm system connected, disconnect it and jumper pins 1 and 4 to energize the EZK.
b) ignition circuits to distributors
c) kickdown switch relay (contacts and coil). If you pull the KD relay XV with the FP relay in place and you get full fuel pressure, the problem is either the KD relay itself or somewhere in the KD circuit.
If any of these areas have been recently 'touched', that might be the place to start.
fuel is being bled off at a high rate, as to show pressure decay in a matter of seconds, not the 30mins of a normal system. Is the check valve in the pump? if not that, then the only other possibility is going to be the injectors leaking fuel.
I think that the fuel pump is not being told to run, by the ecu for some reason. also , there is no Tach signal to the dash... related? I dont know.
there is spark.... and the ECUs have been tested to be good. MAF?? could the maf cause this kind of issue? it will be tested shortly as well.
the crazy thing is that it was hobbling along running, and there was no tach signal, AND no fuel pressure shown on the guage....... when i put the jumper on the fuel pump, it wouldnt come close to starting with full line pressure at rated levels. again, then lots of fuel found dripping out the exhuast.
one time, as it was trying to start with fuel pump relay in, it would start to catch and the pressure did work up to 5-10psi, but when it started , it started and ran horribly with 0psi.
He does have an alarm system, but seems to know how to jumper and disable that circuit. but, all this happened when he was chasing a interior light repair (above rear view mirror) and pulled the fuse panel out to see if the wires were burned all the way to the panel, which they were not. he fixed the light issue, but now the car wont start. im thinking something got damaged or disconnected when he pulled the fuse panel back off the attachment points.
04-13-2015, 07:06 PM
#71
Team Owner
pull the plugs and spin the engine see what cylinder sprays fuel,
disconnect the computers first
disconnect the computers first
04-13-2015, 07:51 PM
#72
Rennlist Member
Thread Starter
if it doesnt, then its due to the injectors being forced open for all injectors.
but why does the fuel pressure decay so fast. has to be the pump or an injector. your test should be a good first step in figuring it out. thanks
04-13-2015, 08:28 PM
#73
Rennlist Member
Thread Starter
If the temp II is infinte resistance, that means real rich, right? his harbor frieght meter is flakey and im about to stick needles in my eyes trying to help him over the phone.
spec is 1500ohms and he is getting that only if he touches both of contacts together , not individually. individitually, he is getting one ohm.... ill have to visit with my Fluke.
spec is 1500ohms and he is getting that only if he touches both of contacts together , not individually. individitually, he is getting one ohm.... ill have to visit with my Fluke.
04-13-2015, 08:31 PM
#74
Rennlist Member
Thread Starter
The jumpered fuel pump circuit provides full voltage to the fuel pump, but the relayed circuit doesn't. Why?
Alan or other electrical gurus may want to check me, but looking at the wiring diagrams there seem to be some possibilities....
1. The relay contacts are burnt causing high resistance/low voltage to the fuel pump.
2. The relay coil is faulty and doesn't make enough magnetism to pull the relay armature to completely close the contacts, the poor connection can't carry the FP current without excessive heat, burnt contacts, and low voltage to the fuel pump.
Nos. 1 and 2 are fixed with a known good relay.
3. The voltage on the circuit serving the relay coil is too low to completely close the contacts as above, causing low voltage to the fuel pump.
One side of the FP relay coil is connected to the LH, pin 20. This should be at ground potential when the LH wants the FP to run. If the LH is too hot, maybe there's a bad connection/broken wire in this circuit near the LH making heat.
The power side of the coil is fed from the 15 bus (ignition switch) in the CE panel, anything connected to that bus could pull down the voltage. These are:
a) T22 plug for alarm system connections (under CE Panel) and on to EZK relay coil. If there's an alarm system connected, disconnect it and jumper pins 1 and 4 to energize the EZK.
b) ignition circuits to distributors
c) kickdown switch relay (contacts and coil). If you pull the KD relay XV with the FP relay in place and you get full fuel pressure, the problem is either the KD relay itself or somewhere in the KD circuit.
If any of these areas have been recently 'touched', that might be the place to start.
Alan or other electrical gurus may want to check me, but looking at the wiring diagrams there seem to be some possibilities....
1. The relay contacts are burnt causing high resistance/low voltage to the fuel pump.
2. The relay coil is faulty and doesn't make enough magnetism to pull the relay armature to completely close the contacts, the poor connection can't carry the FP current without excessive heat, burnt contacts, and low voltage to the fuel pump.
Nos. 1 and 2 are fixed with a known good relay.
3. The voltage on the circuit serving the relay coil is too low to completely close the contacts as above, causing low voltage to the fuel pump.
One side of the FP relay coil is connected to the LH, pin 20. This should be at ground potential when the LH wants the FP to run. If the LH is too hot, maybe there's a bad connection/broken wire in this circuit near the LH making heat.
The power side of the coil is fed from the 15 bus (ignition switch) in the CE panel, anything connected to that bus could pull down the voltage. These are:
a) T22 plug for alarm system connections (under CE Panel) and on to EZK relay coil. If there's an alarm system connected, disconnect it and jumper pins 1 and 4 to energize the EZK.
b) ignition circuits to distributors
c) kickdown switch relay (contacts and coil). If you pull the KD relay XV with the FP relay in place and you get full fuel pressure, the problem is either the KD relay itself or somewhere in the KD circuit.
If any of these areas have been recently 'touched', that might be the place to start.
