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How to connect & operate the Hoffman CIS Test Kit
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ideola  



Joined: 01 Oct 2004
Posts: 15318
Location: Woodstock IL

PostPosted: Wed Sep 28, 2011 6:51 am    Post subject: How to connect & operate the Hoffman CIS Test Kit Reply with quote

The below text is adapted from an instruction sheet that was inserted into a used copy I acquired some time ago of Bosch Fuel Injection & Engine Management (ISBN 0-8376-0300-5) by Charles O. Probst. I have slightly adapted to the text to be consistent with 924 parlance but accept no responsibility for the accuracy or efficacy of the text itself. At the end of this post is a link to a photograph of the original text.

Instructions for Continuous Injection System (C.I.S.)
Bosch K-Jetronic Fuel Injection
WARNINGS
  1. Do not loosen fuel line fittings until you have placed a cloth around them. Fuel may be under pressure in the sytem, and could spray out and result in a fire hazard and possible personal injury. Dispose of cloth properly.
  2. Do not allow dirt to enter the system as it might clog fuel injectors.
  3. Use new o-rings when making connections after tests have been completed. Order these from where you purchased the tester.

PROCEDURE
Before checking the fuel injection system, make a complete ignition check first, including coil, spark plug wires, and valves to make sure the problem is not in these components.

Then, check for vacuum leaks at:
  • Brake booster vaccum lines
  • Evaporative canniseter
  • Cold start injector
  • Air sensor boot
  • Vacuum limiter
  • A/C door actuator
  • Intake manifold
  • EGR valve
  • Air ducts
The continuous injection system has a primary circuit with pressure regulated at the fuel distributor. This is called the supply pressure, system pressure, primary pressure, or line pressure. The other circuit is the control circuit, with pressure regulated by a control pressure regulator, also called the warm-up regulator (WUR).

The connecting hose without the valve should be connected to the center of the fuel distributor and the hose on the valve side should be connected to the hose removed from the fuel distributor (which is the feed line to the WUR).

WARNING: Hand tighten the o-ring end of the adapter into the fuel distributor. Do NOT wrench tighten.

Consult factory manual or dealer for proper test sequence and test pressures. A general procedure is such:
VALVE CLOSED = system pressure
VALVE OPEN, WUR & AAV disconnected = cold control pressure
VALVE OPEN, WUR & AAV connected = warm control pressure
VALVE CLOSED + 1 HOUR = system leakdown

WARNING: When pressure checks are finished, cover the relief valve that is located on the test kit just below the gauge with a cloth before depressing the valve to relieve fuel pressure. Fuel may be under pressure and unless cloth is used, it WILL spray out and could result in a fire hazard and possible personal injury. Disconnect the connecting hoses from the fuel system, reconnect the fuel lines, and check for fuel leakage.

ADAPTERS for 1973-Current Porsche applications
(see diagram below)
Fuel Distributor: R14I40 + o-ring R14K
WUR Hose: R14I41 + bolt and copper crush washers from fuel distributor


And here is a photo of the Hoffman CIS Tester with the two referenced adapters, and my notations on the tester itself indicating which line should be attached where. The glare from the flash might make it a little hard to see, but if you look carefully, you can see that the line that comes out of the LEFT side of the gauge has no valve and is labeled FD. The line that comes out of the RIGHT side of the gauge has the valve and is labeled WUR. You can see the fittings for the appropriate connections laid out at the end of each hose, which correspond to the part numbers in the diagram above.


Here are links to photographs of the rest of the document, which is generic, i.e. not specific to the 924.



from the Porsche 924 Technical Specifications Booklet
1976-1984 Porsche 924 NA Fuel System Specifications
(all markets except as noted below)
Electric fuel pump Delivery rate: Min. 750 cm3/30 s
System pressure test value: 4.5...5.2 bar
Adjust, value: 4.7...4.9 bar
Control pressure cold (approx. 20 C): 1.3...1.7 bar
Control pressure warm: 3.4...3.8 bar
Leak test
Min. pressure after 10 min.: 1.7 bar
Min. pressure after 20 min.: 1.5 bar
Opening pressure of inject valves: 2.5...3.6 bar

1980-1982 US, Canada, Japan 924 NA
All the same as above EXCEPT for:
Control pressure cold (approx. 20 C): 1.7...2.1 bar

Porsche 931 Series 1 (M31.01 & M31.02) Fuel System Specifications
Electric fuel pump Delivery rate: min. 1050cm3/30s
System pressure test value: 5.8...6.5 bar
Adjust, value: 6.0...6.3 bar
Control pressure cold (approx. 20 C): 2.0...2.4 bar
Control pressure warm: 3.45...3.85 bar
Leak test
Min. pressure after 10 min.: 2.0 bar
Min. pressure after 20 min.: 1.7 bar
Opening pressure of injection valves: 2.7...3.8 bar

Porsche 931 Series 2 (M31.03 & M31.04) Fuel System Specifications
All the same as above EXCEPT for:
Control pressure cold (approx. 20 C): 2.4...2.8 bar
_________________
15 981 GTS | 04 955 Turbo | 88 924S SE | 82 931 (x2) | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod (x2) | 78 Poli-Form | 78 Limited Edition | 77 Martini
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ideola  



Joined: 01 Oct 2004
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Location: Woodstock IL

PostPosted: Wed Sep 28, 2011 6:54 am    Post subject: Reply with quote



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15 981 GTS | 04 955 Turbo | 88 924S SE | 82 931 (x2) | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod (x2) | 78 Poli-Form | 78 Limited Edition | 77 Martini


Last edited by ideola on Tue Jan 03, 2017 5:20 am; edited 1 time in total
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ideola  



Joined: 01 Oct 2004
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Location: Woodstock IL

PostPosted: Wed Sep 28, 2011 7:00 am    Post subject: Reply with quote

From the Probst book:

SYSTEM PRESSURE
MEASUREMENT
With the gauge valve closed to read system pressure, bridge the fuel pump safety circuit and run the pump. The gauge should read within the limits given in your shop manual (see tech specs cited above). What if system pressure is not in specification? If you've tested fuel pump delivery and it's OK, then you should adjust system pressure as described below.
ADJUSTMENT
If the pressure is not in specification, you can adjust it by adding or subtracting shims in the system pressure regulator (in the case of the 924/931, this regulator is integral to the fuel distributor). Each 0.1mm shim changes system pressure by 0.15 bar (2.2 psi). Use new o-rings and copper gasket when you reinstall the piston.
NOTE
If system pressure cannot be adjusted to specification, or if you drop the piston, you'll have to replace the entire fuel distributor assembly because these parts are mated for the necessary fine tolerances.
_________________
15 981 GTS | 04 955 Turbo | 88 924S SE | 82 931 (x2) | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod (x2) | 78 Poli-Form | 78 Limited Edition | 77 Martini
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ideola  



Joined: 01 Oct 2004
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PostPosted: Wed Sep 28, 2011 7:09 am    Post subject: Reply with quote

From the Probst book:

CONTROL PRESSURE
COLD
Control pressure is related to temperature. If the regulator is cool enough for you hand to touch, it's cool enough to test. You can't fool K-basic and K-lambda by disconnecting the coolant temperature sensor because they don't have one.

Control pressure goes up when temperature goes up. Higher control pressure reduces slit size and reduces enrichment. If you study a typical control pressure specification graph (such as the one linked to in the O.P.), you can see that when the control pressure regulator is at ambient (or surrounding) temperature in the shop, probably about 70F (20C), cold control pressure for the car being checked should be between 1.4 and 1.8 bar (20-26 psi). [editor's note: compare against the cold control pressure cited from the tech specs booklet posted in the O.P.]

With the fuel pump running, open the pressure gauge valve so that fuel no flows through the control pressure regulator. The gauge should show a drop from system pressure to control pressure. Typical cold control pressure is about 1.5 bar (22 psi). The control pressure regulator is reducing the pressure; that will give the engine the richer mixture needed for cold operation.

WARM
For the warm control pressure test, reconnect the wiring connector to heat up the regulator [editor's note: the Probst book neglects to mention in the "cold" section that the electrical connectors to BOTH the WUR and the AAV should be disconnected for the cold test]. With the pump running, the pressure should slowly rise to a typical specification of between 3.4 and 3.8 bar (49-55 psi). [editor's note: as above, compare against the warm control pressure cited from the tech specs booklet posted in the O.P.] Starting from ordinary shop temperatures, it should take one to two minutes for the pressure to rise from cold control to warm control, so don't get impatient.

If control pressure did not rise properly, check for restriction in the return line. Also measure the supply voltage to the heater of the control pressure regulator (a.k.a. WUR). It should be at least 11.5 volts power supply. If return line is clear and the voltage checks out OK, replace the control pressure regulator (a.k.a. WUR).
_________________
15 981 GTS | 04 955 Turbo | 88 924S SE | 82 931 (x2) | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod (x2) | 78 Poli-Form | 78 Limited Edition | 77 Martini
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ideola  



Joined: 01 Oct 2004
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PostPosted: Wed Sep 28, 2011 7:18 am    Post subject: Reply with quote

From the Probst book:

RESIDUAL PRESSURE
The residual pressure test measures the amount of system pressure leakage. When you turn off the pump after your warm control pressure test, system leakage should be small enough so that pressure stays at a specified pressure for a specified time: usually 3 bar (43.5 psi) for 10-20 minutes.

If residual pressure falls below the minimums with the gauge valve open, the leak is probably in the control pressure circuit, at the push valve o-rings. If it is an older system without a push valve, the leak is probably at the control pressure regulator.

Rerun the leakage test with the valve closed to shut off any possible leakage through the control pressure regulator. If you still observe low pressure on the gauge, the regulator is OK, but there is system pressure leakage.

In the system pressure circuit, the cold start injector or port injectors could be leaking, or it could be the system pressure regulator o-ring (i.e within the fuel distributor for the 924/931 units), or it could be the fuel pump check valve, or ti could be other components and connections (i.e. other components could include the accumulator(s)). Check the check valve as described below. Run the pump to build pressure in the system and look closely for fuel leaks at fuel line unions. To quick-check the fuel accumulator, remove the screw from the end of the accumulator. If fuel leaks out, the accumulator diaphragm is faulty and the accumulator should be replaced.

FUEL PUMP CHECK VALVE
The fuel pump check valve is part of the outlet fitting on the pump, but early models may vary, so check your shop manual. To check the valve, disconnect the fuel supply line to the fuel distributor and attach the pressure gauge. Make sure that the gauge valve is closed. Run the fuel pump until pressure reaches 5 bar (78 psi) and shut off the pump. If residual pressure falls below specification, replace the pump check valve. Before you remove the fitting remove the gas tank cap, clamp the pump inlet hose so no fuel will escape, and clean the fittings. Install a new seal and check valve and torque to specification. Check all connections with the pump running and redo the leakage test.

Remove the gauge and reconnect the fuel lines when fisnished. With the gauge, you've checked K-basic and K-lambda system pressure, and warm and cold control pressure, as well as residual pressure
_________________
15 981 GTS | 04 955 Turbo | 88 924S SE | 82 931 (x2) | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod (x2) | 78 Poli-Form | 78 Limited Edition | 77 Martini
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ideola  



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PostPosted: Wed Sep 28, 2011 7:24 am    Post subject: Reply with quote

My notes:
  • In order to run these test, you need to have a fuel pump relay jumper. This is a short piece of wire with a male spade terminal on each end. Remove the fuel pump relay and install the jumper on the 30 and 87 pins on the fuse block. The fuel pump should run.
  • I strongly recommend removing the injectors from the head and inserting them into glass jars or bottles while doing these tests. If you have a bad injector, or if you have one or more bad ports on the fuel distributor, you will flood those cylinders with fuel, and it WILL cause hydrolock on the engine, as well as contaminating your engine oil. Do yourself a favor and go the extra step to pull the injectors. You can test their spray pattern while you're at it.
  • Haynes has some additional pointers that the Probst book doesn't mention. One is to be sure to hang the gauge so that it is always at the highest point while doing tests, as well as opening and closing the valve several times when you first connect it to allow system pressure to properly build...otherwise, you may not be getting accurate readings. Not going to copy all of the Haynes text...get your own copy and refer to it...

_________________
15 981 GTS | 04 955 Turbo | 88 924S SE | 82 931 (x2) | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod (x2) | 78 Poli-Form | 78 Limited Edition | 77 Martini


Last edited by ideola on Tue Oct 04, 2011 1:25 am; edited 1 time in total
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leadfoot  



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PostPosted: Fri Sep 30, 2011 6:08 pm    Post subject: Reply with quote

there's a bleed valve on the side, again the manual doesn't say it pisses out fuel from this when bleeding so use a rag here too...
thanks Dan good writeup
Stu
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ideola  



Joined: 01 Oct 2004
Posts: 15318
Location: Woodstock IL

PostPosted: Fri Sep 30, 2011 8:14 pm    Post subject: Reply with quote

leadfoot wrote:
there's a bleed valve on the side, again the manual doesn't say it pisses out fuel from this when bleeding so use a rag here too...
thanks Dan good writeup
Stu

Thanks Stu...

...actually, the loose leaf paper instructions that I transcribed do include this warning...
Quote:
WARNING: When pressure checks are finished, cover the relief valve that is located on the test kit just below the gauge with a cloth before depressing the valve to relieve fuel pressure. Fuel may be under pressure and unless cloth is used, it WILL spray out and could result in a fire hazard and possible personal injury. Disconnect the connecting hoses from the fuel system, reconnect the fuel lines, and check for fuel leakage.

...but it's not mentioned in either Haynes or the Probst book, so it does bear repeating!!!!!
_________________
15 981 GTS | 04 955 Turbo | 88 924S SE | 82 931 (x2) | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod (x2) | 78 Poli-Form | 78 Limited Edition | 77 Martini
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tuf-924  



Joined: 05 Nov 2009
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Location: wollongong

PostPosted: Mon Oct 03, 2011 10:45 am    Post subject: Reply with quote

Hey are you able to upload pictures of teater plugged in the vehicle ready to be used as cannot figure out how it has to be connected, I have the official Porsche part VAG 1318 I have no idea where to hook it in to
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dpw928  



Joined: 02 Nov 2002
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Location: owasso, ok 74055

PostPosted: Mon Oct 03, 2011 10:56 pm    Post subject: Reply with quote

Ideola,

Great posting, but just one question about jumping the fuel pump relay. On my 931 the 15 feed wire is a 16 or 18 gauge whereas the feed wire on my 928 is a larger 12 gauge. I have always thought that bypassing the 924/931 at the 15 connection could overheat the feed wire. I would love to hear that I'm wrong in my thinking. Have you or anyone else actually used the 15 connection and did it work out OK?

Dennis
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ideola  



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Location: Woodstock IL

PostPosted: Tue Oct 04, 2011 12:22 am    Post subject: Reply with quote

The 15-to-87 connection is from memory...pretty sure it's correct, but should verify against FSM/Haynes.

When I've used the jumper, I've never had an issue with the wiring...but I don't like leaving the pump running for any longer than absolutely necessary...maybe a few minutes at most while checking the various settings on the tester. I certainly wouldn't operate the car this way...!
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15 981 GTS | 04 955 Turbo | 88 924S SE | 82 931 (x2) | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod (x2) | 78 Poli-Form | 78 Limited Edition | 77 Martini
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dpw928  



Joined: 02 Nov 2002
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PostPosted: Tue Oct 04, 2011 1:06 am    Post subject: Reply with quote

Thanks. I know it works OK on the 928 as my 78 5 speed was bypassed with a fused splice when I bought it. I didn't notice for 2 months. Never tried it on the 924/931 as the 15 lead appears to be much smaller. Think the WSM says to jump the 30 and 87 on both.

Dennis
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ideola  



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PostPosted: Tue Oct 04, 2011 1:24 am    Post subject: Reply with quote

You are correct, FSM says to jumper pins 30 & 87. Will edit above.

I'm guessing the difference is that 30-to-87 cause the pump to run without the key in the on position, while 15-to-87 requires the key...I've gotten into the habit of doing the latter so I can switch the key on and off to turn the pump on and off...maybe it's not a good idea due to the wire gauge issue that you mentioned...
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15 981 GTS | 04 955 Turbo | 88 924S SE | 82 931 (x2) | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod (x2) | 78 Poli-Form | 78 Limited Edition | 77 Martini
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dpw928  



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PostPosted: Tue Oct 04, 2011 1:33 am    Post subject: Reply with quote

I also like the option to use the key (15 and 87) but that is because I'm an old f@rt. Just wondering if anyone has used this bypass on a 924/931 for any lenght of time.

Dennis
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TheBib  



Joined: 21 Aug 2011
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PostPosted: Fri Oct 07, 2011 12:42 am    Post subject: Reply with quote

I jumpered 30 and 87 and yes indeed the pump came on with the key in the off position. Haynes manual says that you need to turn on the ignition to get the pump to operate, i think they are incorrect. I thought i had an issue, sounds like not.

my first question: Specifically regarding the warm control pressure, I am assuming that the car is not running, and that the reason the WUR, warms up, is because by jumpering the fuel pump, this also provides power to the WUR circut.

my second question: you mention about dropping the piston in the process of changing the shims. You mean like physically dropping it and damaging it when it hits the ground or another object correct?
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