| View previous topic :: View next topic |
| Author |
Message |
dgKnecht
Joined: 17 Nov 2002
Posts: 42
Location: Palatka, FL
|
 Posted: Wed Oct 10, 2007 8:49 am Post subject: fuel pressure |
 |
|
about a week ago, after i had changed the fuel filter and flushed the tank, the motor started missing pretty bad, mostly at lower rpm. i checked the recently installed
plugs and #1 seemed unusually fresh, so i pulled the injectors and #1 wasn't spraying
at all, and #2 was kinda weak, #3 and #4 were sprayin real good.
so i think i have plugged/bad injectors and buy some new ones.
they come in today and i install #1 and check it, still no spray, so i think maybe the
fuel dizzy is plugged on that port and i swapped it with #3.....problem stayed with the #1
line and injector.
i can blow air through the line, but i'm wondering if maybe there is so little fuel pressure
from the pump that it can only really open two injectors at a time or maybe those two that are spraying good have really weak springs in them?
should i go ahead and change all four then retest?
_________________
78 924
--all of us have been through some bad times.....i once had a job where i had to drive a Chevette  |
|
| Back to top |
|
 |
mgatlag
Joined: 02 Aug 2007
Posts: 647
Location: Avon, IN
|
| Posted: Thu Oct 11, 2007 12:08 am Post subject: |
|
|
have you done a fuel test off the fuel distributor yet? You may want to start there and see how much you have flowing. IIRC you need to have 750ml in one minute's time.
_________________
Michael
'77 1/2 924 N/A- 5 speed Audi box
'04 Ford Taurus - gone!!
'92 Jeep Cherokee Laredo - gone!!
Porsche... better than tea with Miss McGill
(Slap Shot) |
|
| Back to top |
|
|
dgKnecht
Joined: 17 Nov 2002
Posts: 42
Location: Palatka, FL
|
| Posted: Fri Oct 12, 2007 12:41 am Post subject: |
|
|
i haven't done the timed test yet, but i did replace all of the injectors, now none will spray. The fuel pump is pretty loud and the car had sit for a couple years. When i first tried to start the car the fuel pump wouldn't run and i squeezed the input hose and it started runing. i guess i was hoping that by just cleaning out the tank and putting some techron in there i could salvage the pump.
_________________
78 924
--all of us have been through some bad times.....i once had a job where i had to drive a Chevette |
|
| Back to top |
|
|
Smoothie
Joined: 01 Jan 2003
Posts: 8032
Location: DE (the one near MD, PA, NJ)
|
| Posted: Fri Oct 12, 2007 1:05 am Post subject: |
|
|
| dgKnecht wrote: | | the fuel pump wouldn't run and i squeezed the input hose and it started runing. |
This suggests there was some junk in the line. -And if it wasn't removed, it's probably clogging the pump. Though it's also possible that while messing with the hose, the wire connections got wiggled and you actually fixed an electrical problem.
Otherwise -
You are lifting up on the air metering plate to do your testing, correct?
If yes, then do the pump volume output test.
If that's good, then you'll need to get a CIS pressure tester or go the more expensive hit and miss parts replacement route. -But the parts kit to repair the fuel pressure regulator is very cheap, so you could start there (shot o-rings in the fp regulator could be returning too much fuel to the tank and causing low system pressure).
_________________
"..it's made in Germany. You know the Germans always make good stuff."
'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox |
|
| Back to top |
|
|
dgKnecht
Joined: 17 Nov 2002
Posts: 42
Location: Palatka, FL
|
| Posted: Fri Oct 12, 2007 2:38 am Post subject: |
|
|
THANKS for the advice there Smoothie, looking at the tech section
on how to do the flow test i see,
| Quote: |
To accomplish this test, clamp the return line at the tank, disconnect it at the fuel distributor, and let it flow out of the return line into a measuring container.
|
then i see on my fuel distributor that there are two lines going into one
banjo bolt on the air filter side of the distributor, and another two lines going into one banjo bolt on the side closer to the radiator.
The Haynes picture 31.5 says the two on the air filter side are the input/return, but on my car they are input, (output of fuel filter) and the feed to CSV.
is this where i'm supposed to disconnect the line?
_________________
78 924
--all of us have been through some bad times.....i once had a job where i had to drive a Chevette |
|
| Back to top |
|
|
RC
Joined: 25 Mar 2007
Posts: 2637
Location: Australia
|
| Posted: Fri Oct 12, 2007 7:26 am Post subject: |
|
|
Personally I find the easiest is just to undo the line at the cold start valve and place it in a clean bottle. This will test the pump, lines and filter flow but not the flow through the metering unit return valve.
BTW the haynes spec is 750cc in 30 seconds.
Probably a good idea to check for crap by again removing the filter and drain the inlet side into a glass and observe. This will give a good indication of what is in your lines and tank. Hopefully it will all be clean. Always clean and flush all crap out before you put a new filter on.
Roger |
|
| Back to top |
|
|
dgKnecht
Joined: 17 Nov 2002
Posts: 42
Location: Palatka, FL
|
| Posted: Sat Oct 13, 2007 8:54 am Post subject: |
|
|
| Quote: |
Personally I find the easiest is just to undo the line at the cold start valve and place it in a clean bottle. This will test the pump, lines and filter flow but not the flow through the metering unit return valve. |
so do i need to remove and plug the return line at the tank??
_________________
78 924
--all of us have been through some bad times.....i once had a job where i had to drive a Chevette |
|
| Back to top |
|
|
RC
Joined: 25 Mar 2007
Posts: 2637
Location: Australia
|
| Posted: Sat Oct 13, 2007 11:01 am Post subject: |
|
|
No need to as there will be no return pressure or flow with the supply line to the CSV disconnected. This is just a quick test for the pump and filter. If they are OK you will probably get a litre in 30 secs, less than 750cc indicates a problem.
Roger |
|
| Back to top |
|
|
dgKnecht
Joined: 17 Nov 2002
Posts: 42
Location: Palatka, FL
|
| Posted: Mon Oct 15, 2007 10:06 pm Post subject: |
|
|
ok there was only about 250ml at the cold start valve, so i then disconnected the input to the filter and tested, same - about 250 ml........i pulled the fuel
pump and it really looks laquered up on the input, i also notice a leaking accumulator.
| Quote: |
NOTE: Porsche 924's of 1976-76 manufacture have an early-style fuel distributor. This is not compatible with accumulators available as replacement parts. Bosch code 0438 100 039 (old number) Bosch code 0438 100 005 (new number) Only the 005 fuel distributor is now available. Replacing the accum- ulator requires that the 039 distributor be replaced with the 005 unit as well as new lines Conversely, replacing the fuel distributor necessitates the replacement of the accumulator in all pre-1979 models
|
my fuel distributor says 047 133 353 C ??? which is niether number quoted above.
_________________
78 924
--all of us have been through some bad times.....i once had a job where i had to drive a Chevette |
|
| Back to top |
|
|
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
924 FAQ (Technical)
