CIS Fuel Pressures Test Help - First Timer

[J-Gel]

I'm working on getting my 83 SC started up for the first time in decades, and have gotten to the point where its time to take my pressure readings..

In preparation, I've read through the " CIS Troubleshooting for Dummies" thread, along with the Bentley Manual, and watched the time capsule "Bosch K-Jetronic (CIS) explained" video to get myself acclimated with what I'm working with and trying to accomplish at the end of this test.

My question before I begin this test is... What is the purpose of the fuel pump relay bypass switch? I understand I want to be able to toggle the pump on and off at various points throughout the test, but if the pump turns on when the key is in the ON position prior to START, why is this switch assembly necessary? Is there a problem engaging the pump by simply turning the key to ON?

Now, I don't ask because I want to take a shortcut. I DID build this switch assembly as the threads instructed but got hung up with my bullet terminals that turned out to be too thick to fit into the female ends of the relay port. After driving to multiple different FLAPS, hardware stores, electrical supply, a hobby store, and even an electrical contractor office, I did not find any bullet terminals that would fit, which begs the question, do I truly need this switch? I imagine I do, I don't know why it would be part of the instructions otherwise.. but after checking everywhere and going home empty handed, I have to ask.

And of course, if the answer is "Yes, you n00b, you NEED this switch!", are there any suggestions where I can find these connections? Any dimension I need to search, find online anywhere?

- - Looking forward to getting past this seemingly silly hang-up and posting the real juice once I have my test results

[hughc]

I may be wrong but my understanding is that the fuel pump in a 83 sc will not turn on until you start to crank the engine, therefore the need for a manual switch.

as far as the bullet terminals not fitting the socket holes I slightly filed the terminals until they fit. Not the prettiest job but adequate to do the testing you want to do.

I'm sure there are nicer solutions but this has worked for me for a few years.

[walt]

Yes you need the switch as the fuel pump only turns on when the engine is cranked as described above. Maybe you could try a bit of solder on the bullet ends to get a tighter fit.

[SkiVT]

Are you saying your fuel pump comes on when the key is in the “on” position? If so you have a problem.

Fuel Pump Always Running

[boyt911sc]

J-Gel,

The FP for ‘76~’83 CIS cars should not RUN when the ignition switch @ ON position (not START). If it does, your ground contact for terminal #85 is missing or the relay is defective. Check if the AFS (air flow sensor) switch is attached. The AFS switch is located at the backside of the AFM (airflow meter) just below the “Pope” rubber boot.

I strongly recommend that you take time to read DKLever48’s post about FP relay troubleshooting tests and get a good understanding how the FP relay works. You need this relay by pass switch to start/stop the fuel pump specially when you are performing a fuel pressure test.

Tony

[Sub8]

Originally Posted by J-Gel

I'm working on getting my 83 SC started up for the first time in decades, and have gotten to the point where its time to take my pressure readings..

In preparation, I've read through the " CIS Troubleshooting for Dummies" thread, along with the Bentley Manual, and watched the time capsule "Bosch K-Jetronic (CIS) explained" video to get myself acclimated with what I'm working with and trying to accomplish at the end of this test.

My question before I begin this test is... What is the purpose of the fuel pump relay bypass switch? I understand I want to be able to toggle the pump on and off at various points throughout the test, but if the pump turns on when the key is in the ON position prior to START, why is this switch assembly necessary? Is there a problem engaging the pump by simply turning the key to ON?

Now, I don't ask because I want to take a shortcut. I DID build this switch assembly as the threads instructed but got hung up with my bullet terminals that turned out to be too thick to fit into the female ends of the relay port. After driving to multiple different FLAPS, hardware stores, electrical supply, a hobby store, and even an electrical contractor office, I did not find any bullet terminals that would fit, which begs the question, do I truly need this switch? I imagine I do, I don't know why it would be part of the instructions otherwise.. but after checking everywhere and going home empty handed, I have to ask.

And of course, if the answer is "Yes, you n00b, you NEED this switch!", are there any suggestions where I can find these connections? Any dimension I need to search, find online anywhere?

- - Looking forward to getting past this seemingly silly hang-up and posting the real juice once I have my test results

A 2 inch length of thick wire is perfectly adequate......

[1Bad86]

From my understanding the relay prevents the fuel pumps from running in the event of an accident. On my car simply unplugging the switch from the back of the flapper box will allow my pumps to run making this test easy.

[J-Gel]

Thank you all.

Yes, my FP runs with ignition @ ON (not START). I see that's clearly where the confusion arose as that is apparently not correct operating procedure..

Thank you SkiVT and Boyt for those references, they appear to be very helpful. The DKLever thread is exactly what I need, as the terminal breakdown and test procedures are definitely a great resource. I will use those threads as much as possible to avoid beginning a new saga as that one sounded to be (at least it concluded with a happy ending! It turned out to be pretty engaging reading). I do believe DK struggled to keep his FP running while I contrarily seem to have mine always on, but I will still conduct the same tests as Boyt outlined (with Test 3 revised) and post results to hopefully identify the issue..

In the meantime, is there harm in running my fuel pressure tests first as it currently stands, before fixing this FP issue, since my ignition is apparently working as a simple FP toggle anyway?

[boyt911sc]

J-Gel,

Go ahead and do your fuel pressure tests. You could fix the problem later. Most important is for you to understand how the FP relay works and your investigation would be much easier. Keep us posted.

Tony

[J-Gel]

Ok, the day is finally here, gauges arrived and time to get pressurized!

Now, again forgive me if this is a basic hardware question, but I hooked up my gauge according to all instruction, On/Off valve on the WUR side, and started my fuel pump to take my first System Pressure reading and found fuel leaking fairly rapidly out of the swivel end of the gauge hoses, on the FD side before reaching the gauge itself. The fuel was coming from the joint circled in blue.





This is beyond my adapter connections from the FD line, so I know it wasn't loose fittings on my end since the fuel made it past those, but rather from the swivel end of the gauge hose itself before it could travel over and up to the gauge. Should I be installing a washer somewhere? I tried using one of the only black rubber washers that came with the kit but it still leaked just as much when engaging the pump again. The white plastic washers are all too large to fit inside.



I guess the good news is I at least have confirmation that I'm getting fuel into the engine compartment at all after installing new fuel lines from the tank... Can't wait to solve this hiccup and post my results

[J-Gel]

OK after visiting a few hardware stores I found some rubber o-rings that managed to hold off the leaking, after securing all connections very tight..

I'm hoping these results make sense, I believe I followed tirwin step by step pretty closely.

1. Year of engine:1983
2. US or RoW (Rest of World):ROW
3. WUR model number:089
4. Ambient temperature at time of test (in degrees C):31 C
5. WUR Resistance (in Ohms):30.8 Ohm
6. System Pressure (in bars):4.4 bar
7. Cold Control Pressure (in bars):2.1 bar
8. Warm Control Pressure (in bars):3 bar
9. Time delta for Cold -> Warm Control Pressure (in minutes & seconds):1:15 (Expected to wait 3-5min however it seemed to clearly level off at 3 bar for another 30 seconds after I clocked it
10. Residual Pressure @ 5 min (in bars):1.6 bar***
11. Residual Pressure @ 15 min (in bars):1.4 bar
12. Residual Pressure @ 30 min (in bars):1.25 bar
13. Residual Pressure @ 60 min (in bars):1.2 bar


*** Note: Upon turned off fuel pump, pressure immediately dropped from 3.0 (warm control) to 2.2 bar. This measurement would be answer (9.5) as it was the first residual pressure however no time elapsed

Any feedback on these results GREATLY appreciated

[SkiVT]

The 089 wur is euro/ROW with specs attached for 81 a 83 cars I believe.

[SkiVT]

Notice the graph values are with vacuum applied to the wur. Your numbers will be .6 or so lower than the graph if you did not apply vacuum to the wur.

[wgirardot]

Originally Posted by J-Gel

I'm working on getting my 83 SC started up for the first time in decades, and have gotten to the point where its time to take my pressure readings..

In preparation, I've read through the " CIS Troubleshooting for Dummies" thread, along with the Bentley Manual, and watched the time capsule "Bosch K-Jetronic (CIS) explained" video to get myself acclimated with what I'm working with and trying to accomplish at the end of this test.

My question before I begin this test is... What is the purpose of the fuel pump relay bypass switch? I understand I want to be able to toggle the pump on and off at various points throughout the test, but if the pump turns on when the key is in the ON position prior to START, why is this switch assembly necessary? Is there a problem engaging the pump by simply turning the key to ON?

Now, I don't ask because I want to take a shortcut. I DID build this switch assembly as the threads instructed but got hung up with my bullet terminals that turned out to be too thick to fit into the female ends of the relay port. After driving to multiple different FLAPS, hardware stores, electrical supply, a hobby store, and even an electrical contractor office, I did not find any bullet terminals that would fit, which begs the question, do I truly need this switch? I imagine I do, I don't know why it would be part of the instructions otherwise.. but after checking everywhere and going home empty handed, I have to ask.

And of course, if the answer is "Yes, you n00b, you NEED this switch!", are there any suggestions where I can find these connections? Any dimension I need to search, find online anywhere?

- - Looking forward to getting past this seemingly silly hang-up and posting the real juice once I have my test results

How about a simple jumper with small alligator clips on both ends. Works for me

Bill

[J-Gel]

Originally Posted by wgirardot

How about a simple jumper with small alligator clips on both ends. Works for me

Bill

Thanks Bill, turns out I don't need a jumper switch since my pump runs with the key @ ON position. Will correct that in time, but wanted to solve fuel issues first so went ahead with the test

[J-Gel]

Originally Posted by SkiVT

The 089 wur is euro/ROW with specs attached for 81 a 83 cars I believe.

Wow, thanks for pointing that out. After further investigation of my vin, turns out I do have a ROW model... Good to know lol... Updating this info in my results listing in post 11**

I certainly did not apply a vacuum to the WUR, so adjusting the graph by the 0.6bar that would seem to put my range somewhere around 1.6-2.0bar according to my ambient temperature.
What is that range referring to, if the specific ranges below the chart for the various readings are listed as well?

As for what I can make out of my results, system pressure seems to be a little low, warm control pressure and leak test seemingly looking good falling between the atmospheric pressure range listed, if Im not mistaken? Not sure where I compare my cold control pressure, or if my low system pressure is low enough to be a problem?

I'm unable to get my engine started, and am hoping this test locates the problem!

[SkiVT]

You should post some pictures of the wur area to confirm Vacuum lines, ttv, decel valve, etc (see pic). Your sys pressure is a touch low and ccp high, which means lean at startup, which is not a good thing.



Does the engine start and then stall/stop or not start at all? No start at all can include a csv problem but wur ccp issues are more tied to the engine not running well, after starting, for the first 30 seconds to several minutes.

[J-Gel]

My engine doesn't start at all. This car has been garaged for the last 20 years. Background info and, more importantly, recently completed progress so far, can be found in my intro post here.

'83 911SC Targa - Inheritance Story 20 Years in the Making

Since then, I've also replaced ignition items such as spark plugs, wire, distributor cap and rotor, and restored spark to my system.






Please let me know if these photos are what you had in mind?

Another thought, my CDI box doesn't whir or make any sound with the ignition @ ON. Just pointing out if that might have any impact for my startup issue, as I understand I should probably be hearing something from it.

[boyt911sc]

J-Gel,

Your fuel pressure readings look good except for the system pressure @ 4.4 bar. But this will not prevent the engine from starting. Check the following:

• Ignition (CDI, Ignition coil, spark plugs, timing)
• Fuel delivery (CSV, fuel injectors, fuel distributor)
• Hook up an inductive timing light to check for ignition signal.
• Air or vacuum leak (use a smoke generator to locate hard to find leak sources.)
• Others

Keep us posted.

Tony