theiceman

I would say the realy clicking on after it fires up is correct. There are two feeds to tthe pump if I remember correctly , Ater the car fires up the relay is fired and held on by a safety switch that requires throtle body vacuum to be maintained. If the engine stops , vacuum is lost and the relay de energizes the fuel pump. In order for this to work you need a secondary supply to the fuel pump in order to get the car started in the first place to generate the vacuum.

psychoideas

Ice, you are on the money there. I just had issues with my fuel pump relay and ended up fixing it.



Now I'm misunderstanding. From the above, do you mean that when you turn your ignition on but do not energize the starter motor, the fuel pump runs?

Or do you mean that the fuel pump runs only while you are cranking the engine to start it?


Because (like Ice said) if your fuel pump starts to run when you turn the ignition on, without cranking, your fuel pump relay is faulty.

This happened with mine. There is a diode between pins 85 and 86 inside the relay that was blown out on mine. I pulled a diode from inside an old computer mouse and replaced it. Pump only works now while the engine is turning.

[/QUOTE]I really need some time to work on this car. I just hope I don't break some undriven 14 year record! [/QUOTE]

If you can break my record with the car you have now, let me know and I'll come over with some good old Aussie beers to celebrate

psychoideas

Ice,

On my 76 it is the vacuum demanded that opens the switch. The contact for the switch is actually the 'stop' that the sensor plate sits on when the engine isn't running. Although it is the vacuum that raises the plate to start the pump there isn't a need to "build up" vacuum. The mere act of cranking creates vacuum to lift the sensor plate and thus start the pump and send fuel to the injectors.
A simple test is to remove the air cleaner, turn the ignition on (engine not running) and gently lift the sensor plate with your fingers. Once off the stop you should hear the pump start to run and as you raise it further you'll hear the injectors start to whistle.

Like I said, this is based on my 76 and newer cars may use a different system.

theiceman

Hi Frank mine is exactly the same ... but I did not realize just crankining would be enough to lift the plate and fire the pump ... hmmm...... back to the book ........

psychoideas

Ice,
Someone recently told me that, like you said, when the ignition is first turned on the pump will run for a preset time (10 seconds or so) then stop. After this it only runs when the sensor plate is lifted. Maybe this is true in your case.
When I looked into the operation of mine, it was not the case.

To see if that is what yours does, turn the ignition on from outside the car and have a listen.
It's easy for me to hear it at the moment because I have no "hood" or "windshield" on the car.

Cheers,

frank

theiceman

The person who would know for sure is Pete. I think our systems are identicle. I thought he explained the pump ran while being cranked, and then when you let off the satarter the relay took over. I will check my bently and see if it gives any info . This is all very informative stuff.

Houpty GT

I too thought the fuel pump would run for a few seconds when the ignition is first turned on. This is common on several other CIS systems. But Ice said that theses cars have an the additional circuit that runs during cranking. I will have to check into this.

I am considering this gauge. http://www.otctools.com/products/detail.php?id=1743
It appears to be american made and I have found it for about $130. I am suspicious of the JC Whitney gauge because I would assume it is a chinese product and I don't want to buy something that is going to break. I would also like to spend a little less than the $220 for the gauge from Performance Products. I think the best option for me would be to find someone with a gauge in South Carolina I can borrow.

rentadate

Hey Ice...long time no talking to. My SC motor just started doing this about a week ago...except it is after I drive it and turn it off wen it is "up to temp." I find it amusing watching the vallet think it is all HIS fault. I have a qwirk with mine tho. When I turn the key and I wait a few seconds with the buzzing sound of I think the fuel pump (which does not shut off by the way) and I crank it about 7 seconds or so after it buzzes. Fires right up. Trick for me is to catch it at the right second and crank.

The mechanic says it is something with the fuel system, and told me to do exactly like Peter said. I don't know how to fix it, but he is willing to look at it for free and adjust it if needed. Then again, I'm also dropping it off next week to have the valves adjusted brakes inspected/fixed and to find out what is causing it to overheat in the dead of winter.

-Nick (^_^)

theiceman

Hi Guys I did a bit of research as it is a slow day today ... I might post a bit of an article I was reading if I can scan it later . I did see on my schematic that pin 87 of the fuel pump relay comes from the ignition in the " start position" . Frank is yours the same ? not sure if this is powering the fuel pump or not but it is interesting all the same.

I also read as Frank stated that while cranking the firing pulse signal sent from the coil is enough to keep the relay active, because if it shuts off you will lose the fuel pump the air valve and I think the enrichment valve. It also stated that if it does not start after 15 seconds of cranking it shuts it all down to fear of flooding.... very interesting stuff.

Nick it sounds like your problem may be accumulator related, once the engine is up to temp no aids are given to starting and the system depends on the fuel pressure maintained by the accumulator. Most starting hot problems are related to this.
Could the buzz you are hearing be the CD unit in the back ( located at the rear driveers corner? ) if so I am pretty sure it should buzz any time the ignition is on .

The one thing I am struggling with is this ... on modern cars as soon as the ignition goes on the computer turns on the fuel pump to build up fuel system pressure and turns off . On our SCs they don't have a computer , how would it do this ? all time delays on our cars are done with bi metalic strips, and other such archaic technology. That is why I think it does not work this way ... but I am wrong more than I'm right but oh well.

Nick sounds like you will be doing well after your work . After the valve adjustment he will ( or should ) check the CO levels and adjust anything that is needed.

I checked what Pete asked and it was all clean as a whistle, it also fired up after about 5 seconds of cranking too.. so nothing consistent..

Peter Zimmermann

Just got back from holiday... Ice, the reason that system priming, etc., is not necessary is that the SC stil uses a cold start injector. That went away in '84 when electric injectors came on the scene. The CIS car starts on the 7th injector, and while that happens the system charges. There is no timed device that allows the pump to run with the ignition, regardless of temperature. If it does run with ignition the normal cause is that the sensor plate stop switch on the forward side of the sensor plate housing is unplugged. The reason behind the engineering for that switch is that it's a safety switch that shuts off the fuel pump following an accident severe enough to stall the engine.

psychoideas

Unless of course you are upside down. In which case the sensor plate would fall off the stop and allow the fuel pump to run.
I'm sure the fire fueled at 1.7 litres per minute from the pump would ease the pain pretty quickly.

Houpty GT

I don't think I mentioned but my car only sounds like it backfires only on the drivers side of the exhaust. Here is some info on the fuel pump relay. I will need to check for the voltage from the starting circuit.

Fuel Pump relay:
Operation of the '76 and later relay:

The relay has two sets of contacts - Normally Open (NO) and Normally Closed (NC). In electrical lingo, "Normal" infers no power on the relay coil. On the basic Porsche round relay, pin 87 is NO, pin 87a is NC and pin 30 is the "arm" of the contact that switches between the two.

Relay Connections:
The fuel pump is connected to pin 30 of the relay socket. (Note that you can't jumper power to the fuel pump by jumpering +12 Volts to a fuse on the fuse panel. The fuse which protects the fuel pump is in the wiring that goes from the NC contact to the ignition switch). +12 Volts from the starter terminal of the ignition switch goes to the NO contact and +12 volts from the "Run" terminal goes to the "hot" end of the relay coil (pin 86) and to the NC contact. The "cold" end of the relay coil (pin 85) goes to the Safety Switch on the air flow sensor housing, and the other contact of the Safety Switch goes to ground. The switch is closed when the airflow sensor plate is at rest (engine not running).

Operational Sequence:
Ignition switch turned to "Run" (Not Start) - Relay energized. Relay contact pulled to the NO position.

Ignition switch turned to "Start" - Starter voltage goes to fuel pump through the NO contact. Fuel pump runs while engine is cranked.

Engine starts and ignition switch released from "Start" position - The Safety Switch opens as the air flow sensor plate rises off its stop. This de-energizes the relay coil, and the relay arm flips back to NC, sending voltage from the "Run" terminal of the ignition switch though the fuse and through the NC contact to the fuel pump. Engine is running, fuel pump is running.

Engine dies due to accident or other malfunction - Airflow sensor plate goes to its stop, closing the Safety Switch, and energizing the fuel pump relay (remember the ignition is still on). Relay pulls the contact back to the NO position. But since there is no voltage on this contact from the starter, fuel pump is disabled.

Key is turned off - +12 volts is removed from relay, fuel pump is now off for good.

Another function of the same circuit is overrev protection (unless overrev comes from downshifting problem). At the rev limit, speed sensor closes an internal switch, wired to the same terminal as the Safety Switch, energizing the fuel pump relay, shutting down the fuel pump.

http://members.rennlist.com/jimwms/CIS/CIShome.html

psychoideas

Houpty,

Where were you three weeks ago when I was pulling my hair out>

Houpty GT

I finally bought a fuel pressure tester from JC whitney. I am somewhat dissapointed because I was told that it was made in Brazil and the one I got was made in China and I fear it may have poor readings.

My system pressure was 80 psi so I removed the shims on the pressure relief and it dropped closer to the 65-75 sec. I then checked my controll pressure when it was 50 degrees out and there is little noticiable change in pressure. I removed the return line from the WUR and the system still held pressure. With the return line removed and the pump running and the gauge set to check control pressure, fuel was coming out of the return line and nothing noticable coming from the WUR. I believe this is backwards of what should happen.

What does the WUR use to maintain residual pressure? Does the return line go to the gas tank or does it go to the pressure relief valve first as shown in the Bosch K-jetronic manual?

It appears I am having a problem with the WUR because no fuel came out of it and I have a spare I need to try but I think I may have a clogged return line because fuel was coming the wrong way. I will try to look into this tonight but I wanted to get this out there for help incase I don't find anything.

Does the bimetallic spring in the WUR tend to fail?

Houpty GT

I switched the spare WUR out and the pressures seem to have been corrected though I would like it if they were 2-3 psi lower. Is there any way to lower the system pressure if I have already removed all the shims/washers?

I disassembled the old WUR and found that the fuel screen was clogged with dirt and rust particles. Makes me wonder if there are any other screens that need to be cleaned.

The WUR return line must go back to the system pressure regulator some how otherwise it would not be able to hold residual pressure.

I still need to start the car and see how it runs. I think it should be ready for the street now.