%*&$*&^%# !!! Thoughts (& Help) Requested
05-10-2011, 07:31 AM
#46
Captain Obvious
Super User
Super User
Thanks!
That's tomorrow after work then!
Will report back.
"Good Attitude" is about right. Spins up on the starter and will catch for a sec, but not enough to actually run for more than a second or two. Certainly no revs or power.
Where is the external high pressure pump located?
That's tomorrow after work then!
Will report back.
"Good Attitude" is about right. Spins up on the starter and will catch for a sec, but not enough to actually run for more than a second or two. Certainly no revs or power.
Where is the external high pressure pump located?
05-10-2011, 07:46 AM
#47
Three Wheelin'
Rob I also have a working external fuel pump for you to try if you need it. I carry it around as a spare after I changed to the single GTS pump. Good luck dude!
05-10-2011, 08:52 AM
#48
Rennlist Member
Having read the latest posts I would think the problem almost certainly reduces to lack of fuel delivery. If you are seeing 28 psig briefly that explains the engines ability to fire initially. That you only see 28 psig suggests that either your delivery system is blocked/not working correctly or the FPR is not working correctly.
The first test you should carry out is the standard fuel delivery test. You take the nut [or pressure gauge] off the end of the fuel rail, connect a hose and time how long it takes to deliver a specified amount of fuel into a measuring cylinder of the requisite volume. This is best done by firing the fuel pump but not the injectors. If the system cannot deliver the requisite amount of fuel in the specified time then the problem has to lie with the pump/plumbing system as the FPR is out of the loop [filter blockage, crap in the system, whatever]. The WS manual specifies this test but I cannot remember the exact numbers off hand [I seem to remember either 800cc or 1 litre in something like 30 seconds]. I’ll post the numbers later this evening for you if I can think on.
The main pump must be firing or you would not even see 28 psig however brief. If there is a blockage in the system, then when shutdown, fuel will most likely still flood through the system until it reaches the height of fuel in the gas tank. If your tank is well and truly full this may be enough to flood the fuel rail or come close to it. When you attempt a start some static pressurization will occur briefly [would explain the 28 psg?], the injectors fire, system pressure is then lost [insufficient delivery] - engine dies.
If the fuel delivery test is positive then the only thing I can conclude is that the spring in the FPR has failed and as the pressure pulse hits the FPR it immediately pushes the control plunger full open and the pump cannot supply enough fuel to maintain pressure- system dies immediately.
If the secondary board on the LH unit that controls the fuel pump is failing, I suppose it is possible that the pump is briefly cutting in and then out [unlikely I suspect] however, when my LH unit failed on my late S4 it did show similar erratic behaviour very briefly before it packed up altogether. Not sure if you have tried fitting another LH unit as yet.
Regards
Fred R
The first test you should carry out is the standard fuel delivery test. You take the nut [or pressure gauge] off the end of the fuel rail, connect a hose and time how long it takes to deliver a specified amount of fuel into a measuring cylinder of the requisite volume. This is best done by firing the fuel pump but not the injectors. If the system cannot deliver the requisite amount of fuel in the specified time then the problem has to lie with the pump/plumbing system as the FPR is out of the loop [filter blockage, crap in the system, whatever]. The WS manual specifies this test but I cannot remember the exact numbers off hand [I seem to remember either 800cc or 1 litre in something like 30 seconds]. I’ll post the numbers later this evening for you if I can think on.
The main pump must be firing or you would not even see 28 psig however brief. If there is a blockage in the system, then when shutdown, fuel will most likely still flood through the system until it reaches the height of fuel in the gas tank. If your tank is well and truly full this may be enough to flood the fuel rail or come close to it. When you attempt a start some static pressurization will occur briefly [would explain the 28 psg?], the injectors fire, system pressure is then lost [insufficient delivery] - engine dies.
If the fuel delivery test is positive then the only thing I can conclude is that the spring in the FPR has failed and as the pressure pulse hits the FPR it immediately pushes the control plunger full open and the pump cannot supply enough fuel to maintain pressure- system dies immediately.
If the secondary board on the LH unit that controls the fuel pump is failing, I suppose it is possible that the pump is briefly cutting in and then out [unlikely I suspect] however, when my LH unit failed on my late S4 it did show similar erratic behaviour very briefly before it packed up altogether. Not sure if you have tried fitting another LH unit as yet.
Regards
Fred R
05-10-2011, 10:24 AM
#49
Rennlist Member
Regards
Fred R
05-10-2011, 11:01 AM
#50
Supercharged
Rennlist Member
Rennlist Member
Join Date: May 2002
Location: Back in Michigan - Full time!
Posts: 18,925
Likes: 0
Received 59 Likes
on
33 Posts
I agree with Fred. The low fuel pressure is suspect. I would first check voltage at the pump and make sure its close to 12v. if not, clean gounds and maybe trace back to CE panel.
My guess is voltage is okay, but something like a hunk of rubber from the in-tank pump is clogging things up. I would get a new External fuel pump, in-tank strainer, and maybe new filter and replace.
My guess is voltage is okay, but something like a hunk of rubber from the in-tank pump is clogging things up. I would get a new External fuel pump, in-tank strainer, and maybe new filter and replace.
05-10-2011, 04:54 PM
#51
Race Car
Just my experience you may find useful. My external pump was jammed by crap entering the split in-tank pump hose. The car would try to start and sputter a little, then die. I took the pumps out and was able to bring the external pump back to life by running it backwards and tapping it on the ground. It spit out all the rubber bits that stopped it, and then worked fine for over a year/12k miles before I put the 044 pump in my car. So, just because the external pump is jammed, doesn't mean you can't revive it.
Dan
'91 928GT S/C
475hp/460lb.ft
Dan
'91 928GT S/C
475hp/460lb.ft
05-10-2011, 07:52 PM
#52
Rennlist Member
Thread Starter
Early Update.....
Pressure at rail - zero.
Pump jumpered, nothing initially, go to back of car and can hear pump running clearly with mechanic's stethescope.
After checking around a bit, say five minutes, go to front of car and pressure at rail is at ten pounds.
Cover off pump now, and will be checking voltages. Also will see if there's any activity inside the tank....
Pressure at rail - zero.
Pump jumpered, nothing initially, go to back of car and can hear pump running clearly with mechanic's stethescope.
After checking around a bit, say five minutes, go to front of car and pressure at rail is at ten pounds.
Cover off pump now, and will be checking voltages. Also will see if there's any activity inside the tank....
05-10-2011, 10:19 PM
#54
Rennlist Member
Thread Starter
And tonight's results.....
As above, and...
Both internal and external pumps are running. I disconnected the external and could still hear the internal. Sounds smooth and regular, (both).
Still, pressure at the rail is nominal, 8 - 10 lbs. and not immediate, it takes a while to build.
Voltage to the pumps is 11.89, a drop of about .45 from battery.
Checked vacuum on the FPR and dampers, and all hold 20 inches no problem. Slight smell of gas at the front damper line.
The pump and filter (external) seem to be virtually new, which would support the bill from the Porsche dealer from two seasons back....
Getting more curious as the testing progresses......
Is it possible that the external pump is only able to push like 10 lbs without the internal assist??
Didn't have time to do the "padded squeeze" test on the return line yet, or the flow test. (Not sure how to hook up a line to the rail to prevent hosing gas all over the place assuming it's got some pressure behind it), (But I doubt it at this point).
All input appreciated!
As above, and...
Both internal and external pumps are running. I disconnected the external and could still hear the internal. Sounds smooth and regular, (both).
Still, pressure at the rail is nominal, 8 - 10 lbs. and not immediate, it takes a while to build.
Voltage to the pumps is 11.89, a drop of about .45 from battery.
Checked vacuum on the FPR and dampers, and all hold 20 inches no problem. Slight smell of gas at the front damper line.
The pump and filter (external) seem to be virtually new, which would support the bill from the Porsche dealer from two seasons back....
Getting more curious as the testing progresses......
Is it possible that the external pump is only able to push like 10 lbs without the internal assist??
Didn't have time to do the "padded squeeze" test on the return line yet, or the flow test. (Not sure how to hook up a line to the rail to prevent hosing gas all over the place assuming it's got some pressure behind it), (But I doubt it at this point).
All input appreciated!
05-10-2011, 10:29 PM
#55
Rennlist Member
Thread Starter
If I go in,
Hey Fred,
If I go in, I'll be replacing everything that's in there. I'll just keep the used bits for spares. I (for some reason) just don't think the problem is in the tank, unless it's the "short hose" but, would that result in the pressure readings I'm getting?
If I go in, I'll be replacing everything that's in there. I'll just keep the used bits for spares. I (for some reason) just don't think the problem is in the tank, unless it's the "short hose" but, would that result in the pressure readings I'm getting?
05-10-2011, 10:31 PM
#56
Rennlist Member
Thread Starter
05-10-2011, 11:00 PM
#57
Race Car
Very interesting. This would be the first time I've ever heard of an FPR causing such an issue. That, or there is a blockage somewhere in the fuel circuit. Since the filter is right after the main pump, it is very unlikely to be beyond that. Maybe a very large chunk of rubber came off and is causing a large flow restriction before the main pump, but is too large to actually get into it to jam it? Was the external pump loud when it was running (I know that's relative)?
Dan
'91 928GT S/C 475hp/460lb.ft
Dan
'91 928GT S/C
475hp/460lb.ft
05-10-2011, 11:18 PM
#58
Rennlist Member
Thread Starter
Hey Dan,
No, the pumps were relatively quiet and regular. What I would expect to hear from an electric fuel pump. Didn't sound like anything was amiss.
Is there any known way to reverse polarity on the system (in place) for a few pulses to check the potential for a transient blockage?
Is there any known way to reverse polarity on the system (in place) for a few pulses to check the potential for a transient blockage?
Very interesting. This would be the first time I've ever heard of an FPR causing such an issue. That, or there is a blockage somewhere in the fuel circuit. Since the filter is right after the main pump, it is very unlikely to be beyond that. Maybe a very large chunk of rubber came off and is causing a large flow restriction before the main pump, but is too large to actually get into it to jam it? Was the external pump loud when it was running (I know that's relative)?
Dan
'91 928GT S/C 475hp/460lb.ft
Dan
'91 928GT S/C
475hp/460lb.ft
05-10-2011, 11:26 PM
#59
Race Car
No, the pumps were relatively quiet and regular. What I would expect to hear from an electric fuel pump. Didn't sound like anything was amiss.
Is there any known way to reverse polarity on the system (in place) for a few pulses to check the potential for a transient blockage?
Is there any known way to reverse polarity on the system (in place) for a few pulses to check the potential for a transient blockage?
Dan
'91 928GT S/C
475hp/460lb.ft
05-10-2011, 11:31 PM
#60
Rennlist Member
any troubleshooting should check each potential failure point..
just because they sound fine does not mean that they ARE fine.. a blockage would not affect thier sound.
since they are getting correct voltage there area only a few possibilities.. one is that the fpr is bad.. if you are sure your test proved it is go back to the next point...
I would remove the flexable fuel line from where it enters the engine compartment... get some brass fittings from the hardware store and adapt to get to a standard pressure gauge...
turn on fuel pump and see if there is pressure there... that will tell you if fuel is getting htere..
next test at the output of the pump the same way, some flex tube, brass fittings and a pressure gauge.... this will eliminate any clogged lines and everything from there forward....
then remove pump, bench test and see if it will build pressure....
keep working back to the tank until you find the culprit....there are only a few failure points in the pump and plumbing.
just because they sound fine does not mean that they ARE fine.. a blockage would not affect thier sound.
since they are getting correct voltage there area only a few possibilities.. one is that the fpr is bad.. if you are sure your test proved it is go back to the next point...
I would remove the flexable fuel line from where it enters the engine compartment... get some brass fittings from the hardware store and adapt to get to a standard pressure gauge...
turn on fuel pump and see if there is pressure there... that will tell you if fuel is getting htere..
next test at the output of the pump the same way, some flex tube, brass fittings and a pressure gauge.... this will eliminate any clogged lines and everything from there forward....
then remove pump, bench test and see if it will build pressure....
keep working back to the tank until you find the culprit....there are only a few failure points in the pump and plumbing.