Question after replacing fuel filter and accumulator
 

After replacing the fuel filter and accumulator, is there any particular procedure that I need to follow? I presume just allow the fuel pump to run for a minute or two to bleed the system of air from the new units? I'm asking cuz I'm a wrench dummy. TIA

Remove the air filter from the intake. Turn on the ignition and gently press up on the plunger inside the intake. You will then hear the fuel pump run, and within a few seconds, a vibration/squeal of the injectors spewing fuel. As soon as you hear the injectors, release the plunger. Your system is now primed and ready for starting.

Pressure test.........
 

Running the FP for a minute or two after the removal of the fuel filter and accumulator is imperative. Not only getting the system pressurized but for checking for fuel leak/s before attempting to run the motor.

Tony

Thanks vm.

On my '79 911SC, I am of the impression that by turning the ignition one click, the fuel pump will run, regardless of whether I press up on the plunger ... am I wrong?

Yes, you are wrong--if your SC is operating correctly.

From '76 onward, the cars were fitted with a fuel pump relay which functioned as a safety precaution should the engine die. That set up, which you should have, only allows the pump to run when the plunger in the intake is raised from its stop, as when vacuum from the engine moves it upward. CIS engines prior to '76 did not have the relay and the pump would run as soon as the ignition was in the RUN position.

On your car, the pump should not run with the ignition switch in the "Run" position. If it does, either someone has disconnected the Air Flow Sensor switch in the engine compartment, or the relay/relay circuit is faulty.

Thanks L.J., I will check this week

Hi Tony: reviving this old thread. I completed my fuel filter replacement yesterday, so coming back here to this post that I bookmarked for procedures for fuel pressure/priming and leak detection.

If I follow the procedure described in the post above, and run the fuel pump as you describe below for a minute or two, where's all that fuel going -- flooding the cylinders? Is part of the procedure after running the FB for a minute or two, to wait it out for the fuel to evaporate? One ~ two min seems like a long time, with loads of fuel delivered? I must be missing something.

Would appreciate your further guidance here.

Thanks!

Hi; just throwing this out for consideration. I'm no CIS guru, but am inclined to think the CIS fueling architecture would be similar as my 3.3 turbo. There's a blue electrical plug on the back of fuel head that if disconnected will allow the pump (2 on my car one on yours) to run with the key in the run position, with the excess fuel returned to the tank. I unplug this when testing the WUR circuit, or fuel pressures, or when replacing and priming the fuel filter. Plug it back in and when you turn the key no fuel as per the guidance you are getting until the engine fires. I would be hesitant to play with the plunger for anything more than a few seconds for fear of locking up the engine with raw fuel. Tony knows his CIS stuff, and while I should not speak for him, I expect he assumed you were disconnecting this blue plug first.

My 2 cents.

Cheers....

CIS Troubleshooting..........
 

Jonathan,

Running the FP without running the motor will only deliver the fuel back to the tank. So you could run the FP for an extended period of time without worry flooding the cylinder/s provided the fuel distributor is not leaking. As long as the FD plunger is at rest (all the way down), fuel will NOT be delivered to the fuel injectors unless the FD is defective and leaking.

In your case, running the FP for a minute or 2 after working on your fuel line system is a prudent way to test for fuel leaks. You don’t want to run your motor with a fuel leak. The one-minute or 2 pressure test will allow you to inspect and look around for any fuel leak that you might have missed earlier.

I try to avoid or limit injecting raw fuel to the combustion chambers by lifting the FD plunger. But if you do, 1~2 sec. is more than enough time you need to purge the air in the fuel injector lines.

Tony

There is a good posting about a FP relay jumper you can leverage in your fuel charging efforts

Thanks for chiming in Daytona. Looks like your thoughts are correct, consistent w what Tony (the CIS guru) just mentioned in his reply to my post.

Thanks for your detailed response, Tony. Much appreciated. I will proceed slowly w caution make sure there are no fuel leaks.

FD Plunger - where/how?
 

So, I got back into the engine bay this AM, and drained the engine oil. Only 1 QT drained from the side tank, and ~ 7QTS from the engine case --- total 8 QTS.

While waiting for the oil to drain, I removed the air filter to look for the FD plunger, and see how it moves/works --- up/down as Tony described.

FAILED!!! Don't know what I'm looking at, or what to look for. What does the plunger look like? I took some fotos. Can someone point me to it in these fotos? Much thanks!!!

http://forums.pelicanparts.com/uploa...1679859523.JPG
http://forums.pelicanparts.com/uploa...1679859523.JPG
http://forums.pelicanparts.com/uploa...1679859523.JPG

Also, while removing air filter, I noticed this piece was wobbling/loose. What is it, what does it do, and should I secure it?

http://forums.pelicanparts.com/uploa...1679859523.JPG

Is this the FD Plunger?
 

I returned to the engine bay, and re-inspected inside of the airbox. Found that this lever moves up/down. Default is down. I can push up, and loaded spring automatically pushes back down to normal state.

Is this the FD Plunger that Tony mentioned?
https://www.youtube.com/watch?v=lo7nS-wsxO0

See if this helps you visualize. The plunger is right next to the 5 and is not visible in the airbox, from memory. The arm you moved up and down in video goes up moving the plunger. Plunger up increases fuel. Sensor plate up increases air.

http://forums.pelicanparts.com/uploa...1679865218.jpg

This also helps visualize

https://youtu.be/a4fJAfXYxWk

Hi SkiVT - thanks for posting the video and the diagram/image. It does help me visualize where the FD Plunger sits. If I interpret correctly, the plunger sits pretty much in the center of the FD unit, and not visible inside the air box (view obstructed by the lever arm) --- is that correct?

Now, as I showed in the video I posted, I can only pull the lever down, but cannot push it up. So, then how do I execute procedure that ossible described in Post #2 above? I'm a bit confused about this --- this is really a big level up for me in terms of wrenching. So, appreciate the support and understanding here.


Post # 2 from Ossiblue above:
"Remove the air filter from the intake. Turn on the ignition and gently press up on the plunger inside the intake. You will then hear the fuel pump run, and within a few seconds, a vibration/squeal of the injectors spewing fuel. As soon as you hear the injectors, release the plunger. Your system is now primed and ready for starting."

I assume I am not pushing up on the actual plunger, but rather pushing up or pulling down on the lever?

Thanks!

You push the lever up from the same spot you pulled down. If it doesn’t go up you got problems. The plunger can get stuck but it’s not really common. When you push the lever up, you feel some slight smooth resistance then remove your hand and it should fall back to resting position. I didn’t see if your engine was running fine before and you were replacing parts or had some other problem. If the plunger is actually stuck, no way i can see an engine running.

Hi SkiVT--- really appreciate your follow ups here, particularly on a Sunday. I searched/watched a few more videos on YouTube, then dove back into engine bay.

This time, instead of pulling that lever down, I gently pushed it up using gradual increasing effort. It broke loose and went up. After that first time, the lever freely moves up w minimal, barely any effort, and drops down by gravity with no resistance. I think it did get somewhat gummed up, but was able to break free. I hope that doesn't indicate signs of gumming up elsewhere.

I wonder if there's a way to verify/validate if the FD plunger is also moving freely, without removing the FD?

Yeah, the car sat for 2 ~ 3 years. I've been doing little projects, getting it ready to start the engine, then take it to get smog'd (SoCal here) and then registered, and back on the road.

- installed new battery
- drained fuel tank, and installed new tank screen/filter
- installed new fuel filter
- changed the oil today

Next weekend, I'll add a 12oz bottle of Techron Complete Fuel Cleaner (Concentrate Plus) then a few gallons of fresh fuel. Then, run the fuel pump testing and fuel pressure priming, and leak detection procedures. If all goes well, the, will attempt to fire up the engine!!!

Pictures of the FD plunger/piston.......
 

Below are some pictures of the FD plunger/piston:

http://forums.pelicanparts.com/uploa...1679886345.jpg

http://forums.pelicanparts.com/uploa...1679886345.jpg

http://forums.pelicanparts.com/uploa...1679886345.jpg

http://forums.pelicanparts.com/uploa...1679886345.jpg

It is difficult to get a good look at the FD plunger with the fuel distributor installed on the AFM (air flow meter). You will need a remote camera to view the bottom section of the plunger if you have the PF installed on the AFM.

If you want to test the upward and downward movements of the plunger, use the lever arm and watch the plunger drops down to its rest point. Removing the FD from the AFM is so far the best method for inspecting a FD.

Tony

Thanks for the tips Tony! The lever arm is moving up/down freely, w/o resistance. I'm going to try to find a way to inspect the plunger while operating the lever, perhaps using mirror or camera.

Of course, Tony is correct, but I like quick and easy tests that allow me to kill off legs in the troubleshooting path and (hopefully) save time. Were you able to get the injectors to squeak (showing they are delivering fuel) by lifting the arm (as Ossiblue and Tony suggested) during your tests so far?


If so, then let me suggest this: with the car off, push up on the arm that holds the sensor plate. It will have very little resistance. Let it back down and push it up a few more times. It should feel about the same, and calibrate your factory-installed precision digital sensor (finger) for the amount of force it takes. Then turn on the fuel pump, and push up again and let it back down. It should take more force and you should feel it push the arm back down against your finger. That is the control pressure pushing down on the top of the plunger, and showing that the plunger moves. If in doubt, you can do this a few more times to be sure. Just be aware that when you do this you will squirt fuel through the injectors in to the intake ports (and you will hear them operating), so don't sit there holding the arm up. And then crank the engine to clear the excess fuel.


If that doesn't produce the desired results, then I think you need to remove the FD and squirt carb cleaner into it to free up the plunger. I had a stuck plunger on a car that sat for 20+ years, and a few squirts of carb cleaner, plus pressing on the plunger a few times, freed it up. You can also try putting a LITTLE air pressure into the control pressure port, but be VERY careful you do not shoot the plunger out of the FD and onto the floor, because it is a HIGH precision part, and if you scuff it up, it's damaged and you will need a new FD. Hold the FD in the palm of your hand to keep the plunger contained in the FD body. Proceed with caution.

Thanks for your suggestion PeteKz. SkiVT suggested this test procedure a few posts above; glad that you are reinforcing/corroborating. Great minds think alike.

I will go back into the engine bay and check the lever again and pay attention, and try to replicate what you and SkiVT and Tony prescribed. Yesterday, once I got the lever and sensor plate to move freely up/down, I didn't detect any resistance when pushing up. There could have been a tiny bit, so I will check again.

For sure, I'm all for quick and easy tests. Hopefully it will be all good, and won't have to remove anything to check.

NO FUEL DELIVERY --- what to do next?

So, I finally gave this a try. First added ~ 2.5 fresh Super Unleaded fuel, along w ~ 10 oz Chevron Techron. Is that enough fuel to get engine started? The tank was completely drained/empty before.

- removed air filter
- checked the FD / air lever --- it moves up/down freely
- turned key to run position
- lifted the lever inside the airbox

I was waiting for some noise to come in, and signs of fuel delivery; nothing happened. No noise of injectors activating, no fuel running spraying anywhere, even with the FD lever lifted up. I tried this a few times, even lifting the lever up for 5 ~ 6 seconds. Nothing happened.

Shut ignition, removed key. Inspected the fuel filter connections --- no leaks, probably no fuel flowed.

Should next step be inspecting/diagnosing the fuel pump? Does it run? Does it get proper voltage/current? Then go downstream towards accumulator?

I reinstalled the air filter. Then tried to start the car. The starter turns, engine is turning, oil pressure gauge indicates pressure is trying to build up, but doesn't start.

Would appreciate suggestions/recommendations.

Thanks!

I just quickly re-scanned the thread. I don't think you have verified that your fuel pump runs.

Do this: Jumper the FP relay as described above. Turn on the key to Ignition. You should hear the fuel pump running. If not, that is where you focus next. Report back your findings.

Hi Pete - I'll try anything at this point. Thank! I have a Bentley manual, and it has foto showing: jump "30 to 87a" --- see foto below. It shows a fancy jumper wire w a fuse and switch. Do I really need all that? Where to buy?

I searched and found another thread here, and it simplifies the process into:

- Take out your Fuel pump relay and jump (with a chunk of wire) across terminals 87A and 30.
- Turn the key to the on position.
- You should hear the pump running.

Is that all there is to it? Find a piece of wire and bridge the two terminals 87a and 30?

http://forums.pelicanparts.com/uploa...1680405567.JPG

Jonathan,

If you are willing to gamble burning your wiring harness during your investigations, you could use jumper wires without a fuse. But I would NOT recommend doing it specially for someone like you.

To play safe, using a set of wire jumpers with fused installed is a prudent course of action. If you have not read DKLever48’s post about testing the FP Relay Socket terminals (87A, 87, 86, 85, & 30), please spend a few minutes reading it.

Install a pressure gauge and find out if your FP is operating when terminal #30 is energized.

Tony

Hi Tony - thanks for pointing out the risk. Makes sense to add a fuse. I'm going to Home Depot and O Reilly tomorrow to pick up the parts and build my own fancy jumper wire.

- toggle switch on/off from Home Depot
- fuse holder and 15 or 20 amp fuse from O Reilly auto parts; my Bentley manual lists FP fuse #16 rated at 25 amps; so will go w 15 or 20 to be safe
- bullet style crimp connector from HD
- 14 gauge or thicker wire from HD

I spent more than a few minutes --- over 1 hr reading the entire DKLever48 thread on FP troubleshooting. Great thread, lots of very detailed explanations for the less experienced like myself. Thanks for pointing that out Tony.

Since Tony replied, I'll defer.

Tony & PeteKz --- Reporting back. I put together a proper jump wire w a 20 amp fuse and on/off toggle switch. See foto below.

The result : FP not running; I stuck my head under the car, and hand touching the belly pan where the FP would be just above. Did not hear anything; did not feel any vibration, or any signs of a moving mechanism down there.

Here's what I did, exactly:

FIRST TEST:
- removed red FP relay
- inserted one jump wire (JW) test lead (TL) into slot # 30 (6 o'clock)
- inserted the other JW TL into slot # 87a (11 o'clock)
- toggle switch in JW is "OFF"
-inserted car key, move to "ON" position
- flipped JW toggle switch to "ON
- CDI buzzing goes on
- I crawl under car to listen, put hand on belly pan near the FP position --- nothing moving, no sound down there. FP not turning on.

SECOND TEST:
- one jump wire (JW) test lead (TL) into slot # 30 (6 o'clock)
- other JW TL into slot # 87a (11 o'clock)
- toggle switch in JW is "ON"
-inserted car key, move to "ON" position
- CDI buzzing goes on
- I crawl under car to listen, put hand on belly pan near the FP position --- nothing moving, no sound down there. FP not turning on. Same result.

What's next? Connect battery power directly to FP? What is the procedure? What equipment do I need?

Thanks!

Adding foto of my jump wire set-up for the FP relay jump test

testhttp://forums.pelicanparts.com/uploa...1680473577.JPG

Did you check for 12 volts at the hot pin in the relay socket? Turn the key back on and check that you have voltage to the socket. If you do, then try jumping from the battery directly to the fuel pump pin in the relay socket (through your fuse setup). If it works, then you have to trace back to the fuse block to find what is broken or disconnected. Double check that FP fuse is good.

If it still does not run, then you will have to jack up the car and take off the splash cover and run a wire from the battery directly to the fuel pump. Measure the ohms to ground from the FP to make sure that's not causing the problem (should be zero ohms). If the FP runs, then you have to find where the wire to the FP is broken, or a corroded connection. If the FP does not run with 12 volts directly to it, then it is bad.

Troubleshooting FP Relay Socket Terminals.......
 

Jonathan,

You could easily identify your electrical problem/s by replicating or doing DKLever48’s Tests. Follow the test procedures and post your test RESULTS. A simple way to test your FP is to:

• Apply 12 volts directly to terminal #30 (relay socket) @ 6 O’clock.
• Or apply 12 volts directly to the positive (+) terminal of the FP.

If the FP is bad or defective, pull it out and test it on the bench. There is a small chance the ground contact is missing. Keep us posted.

Tony

Pete/Tony --- thanks both for replying w next steps.

Pete --- No, I did not check voltage at all. I'd like to try that next. And, it sounds like you and Tony both are suggesting the same.

So, using my jump wire, insert one pin into #30 (as Tony mentioned), and the other pin to the +positive lead on the battery?

Then, for direct battery to FP test --- battery positive terminal to FP positive terminal?

Yes, we are suggesting the same thing. But we are looking at it as a step by step process to troubleshoot from the relay socket to the FP. As Tony recommended, slow down for a few minutes, think this through, and re-read DKLever48 post. Do One thing at at time.

First, do you have 12v at the socket when you turn on the key? Report you result.

Tony & PeteKz - I believe I've confirmed I have 12V @ FP socket.

I've completed the tests outlined by Tony for Dklever48. I used my multimeter. Here are my results (also in my notes/foto below):

Here is the basic test for the FP and relay circuitry:
1). Pull out the FP relay and do the test (ignition switch @ OFF position) for the individual terminal at the socket: A simple 12-volt self-powered test light will work well for this test or a regular non-powered test light, or a volt meter.

87...........no power
87a.........no power
86...........no power (87a 86 are bridged)
85...........no power (should be grounded at this point)
30...........no power (has ground contact?)

MY RESULTS: no power on all ports on the socket; checks with Tony's expected results.

2). Turn ignition switch @ ON position (not start):

87............no power
87a..........has power
86...........has power
85...........no power, presence of ground contact
30...........no power, presence of ground contact

MY RESULTS: no power @ 87 / 85 / 30 ; 12.2 V @ 87a and 86; checks with Tony's expected results.

3). Next, insert the FP relay into the socket and turn the ignition SW @ ON position (not start):

87...........has power
87a.........no power
86...........no power
85...........should have ground contact
30...........no power but exhibit ground contact.

QUESTION: Is this next step? How do I do this test if the relay is inserted into the socket? Or, do we already know enough to go to the FP itself?

ADDITIONAL TEST: I also tested the fuse that supports the FP, Fuse #16 per Bentley manual. Key @ ON position. I got 12.2 V ; 14.4 ohms resistance (is this too high?) IGNORE THIS TEST RESULT - I didn't measure correctly

http://forums.pelicanparts.com/uploa...1680561583.jpg

http://forums.pelicanparts.com/uploa...1680561583.jpg

I don't recall: Did you have a spare relay that you substituted to make sure it wasn't the relay? Maybe that was someone else. Also check to see if the relay clicks when you turn on the key (with the arm/metering plate on the engine propped open).

Anyway, I think it's time to go under the car and see if you have +12v at the FP positive terminal, when you put the jumper into the relay socket. And check that the ground from the fuel pump is good.

If you have 12v volts at the pump and the ground is good, and it doesn't run, then the fuel pump is bad.

No that was another discussion thread or another member at this Forum.
Agree, need to test for 12V at the FP itself, and confirm it is grounded properly.

Test #3 has several errors......
 

Jonathan,

The section you quoted (Test #3) was corrected. See post #28 of the above thread. And continue to read after post #28 for more information. Ignore “Test #3 Results” until to read post #28 up to several posts later.

SUMMARY:
I made several “typo” in the test #3 posting and nobody noticed the mistakes until I noticed them. In short, continue reading further down the thread until you read the correction I posted.

Tony

Jonathan: I'll anticipate that you will go under the car and check for 12 volts and ground at the fuel pump terminals. If those test correctly, then your fuel pump is bad, but here is one other thing to try while you are down there: Whack the fuel pump with a small mallet or block of wood. It may start running again. If it does, it may continue to run long enough (weeks? Months?) to get the rest of your work done.