TOPIC: Fuel supply 1982

Hi All
I am sure this have been discussed earlier, but...
I have a 1982 that fires and has recently been running like 6 month ago.
Today i found a dead fuel pump in the rear. As it is a EU model i dont know if there are more fuel pumps. The hose i took off the fuelpump seam to come straight from the tank. I drained the tank for old and ugly fuel. As it ran freely out of the tank i do not think thee is a pump in the tank.

Does anyone have any experience with this on a 1982 Euro model ??
Will i look for one more fuel pump ??

If you have a 1982 928S then you have a pump in the tank as well

HI and thanks for answer.
I guess i have to take the tank out to get to it ??
I can not hear it run when i put 12 volt on the cables from the external pump. I will assume they run together ??
When i drained the tank yesterday the old gas was running out like nothing stopped it in the tank.That is why i did not think there is a pump in there.

Jan, my '79 US had both internal and external pumps. Assuming that your '82 is the same, you don't have to take the tank out to get to the internal pump. The internal pump is immediately inside of where the fuel comes out of bottom of the tank. If there is an internal pump, it should be connected to electrical connections that should be visible from the outside of the tank at the same location. You get to the internal pump or the screen filter by taking out that connection. A pump is shown as #1 in this drawing, www.autoatlanta.com/porsche-parts/hardpa...78-82§ion=201-05 .
Be forewarned that a new internal fuel pump is expensive. I replaced mine with just a fuel strainer, shown as #2 in the drawing. I found that a new external pump and a clean fuel filter would meet the flow rate and pressure requirements for my CIS system. Also, first ( I know you know this, but) be very careful with all that gas! Great ventilation, no ignition sources close by and all that. Second, if you are going to remove the pump or strainer, that connection can be brittle. Be gentle and patient so that you don't crack the fuel tank accidentally.

If you are not hearing the external fuel pump run when you turn the ignition on and turn the key to the crank position, then something is not right, either electrically or with the external pump. You might want to diagnose the external pump issues first. You can take the fuel pump relay out and put a jumper between the appropriate slots to turn the fuel pump(s) on without needing a key or the engine running. It's been a while since I had to do that, but if you need guidance on doing that I can look it up for you or provide a reference.

I hope that this helps!

Hi and Thanks for good reply.
I am quite sure there is no pump in the tank as there are no wires what so ever to any pump in the tank. I am quite sure i just have a filter there. On the after part of the tank is a fuel pump and a filter. I have dismantled that and drained the tank. Uh ugly gas... The pump was exposed to 12 volt direct and does not run. So i have ordered a new pump, filter, copper rings and what ever needed. I have changed the relay, fusebox, and do not have 12 volt at the pump terminals when i turn the key to ignition. I do not know if the pump will run after start up or before start. There must be some regulation after the check valve that give signal not to give power to the pump. I cant seem to open the links sent to me so I am hoping for some result after i get my new pump. The car ran last fall and at that point a new pump and filter was installed. The car sat empty of fuel all winter in the frost so that has most likely a big impact on this issue. Besides that i came far with all the electrical parts as i am much better at that part. The things we do for love...

You sure seem to be on the right track! If 12 volts does not energize the pump, it’s dead! There is a safety system that shuts off power to the pump when the engine is not running. On start up, the pump has power when you are cranking the engine over and for about a second after you stop cranking. If the car started, then the pump stays on. So if the car is not starting, unless you are able to see the voltage when you are cranking, you may be getting voltage at the pump for just the short time that you crank. I’m with you, a new pump is probably the answer. Since you have identified the pump relay, I've attached a picture of the terminals to jump so that you can send voltage to the pump without having to crank. I found that jumping these terminals was very useful when diagnosing fuel delivery problems like you have.
I’m sorry that the link didn’t work. It’s a good site to use to see parts and to get part numbers. See if you can type in just through the /porsche-parts/ part of the address.

The black wires form my jumper in the fuel relay socket. I used a switch for this one, but the switch is not necessary.

HI again
Again thanks for explanation of the power supply.
I hope to see the pump soon and will give it some external 12 volt. I have rigged up so i can see voltage when cranking and will monitor that. jumping the relay is a good option as well. This one needs a lot of love, but getting it running so not too much is stuck and corroded is first step.

Good Luck! Please let us know how it turns out!

Yes I will follow up with progress and pictures for the next guy

Hi again
will try to see if i can get a picture attached from the fuel pump, filter, hose thing.

I am not able to upload pictures here. PLease let me know what i am doing wrong.
I chose a picture under Add File and insert, but nothing comes up.

I found that I had to either decrease the resolution of the pictures or make them smaller to post

HI again
Now i received the aftermarked fuel pump that is a bit smaller that the original Bosch that was in there.
New check valve, copper rings, filter and gas. Car starts but dies right after it has started. I can start it a few times and then it does not start. If i then wait some minutes it will start again, but it will not continue to run.
So is it the fuel pump that is not giving sufficient pressure to run, or is it feed back from engine ??
I can hear the pump run after the car stalles until i turn the key off.
Any advice ??

Jan,
I'm only familiar with my '79 KJET CIS system. Is your '82 this system too? Somewhere it went to LJET, but I'm not sure when.
If it is KJET, then it is all pressure controlled.
I think that your '82 is a KJET CIS (continuous flow) like mine. Anyway, here are some specs for '82's from the Workshop Manual.
The easiest spec to check is the fuel delivery flow rate. This specs assumes that the fuel filter is good and no that there are no flow obstructions.
The fuel filter is, of course, another potential problem source.


Don't know what brand pump you got, but I went with Bosch when I refurbished my system.

Here's another reference that you might find useful.

drive.google.com/file/d/1uuj9bm0UfVWtrbxPVGRfaoASQRbQftl3/view

BTW, if you don't have a copy of the 928 Workshop Manuel (WSM), I got my copy from Roger at 928sRus. It is indispensable!
As you have found, keeping these classics running is both challenging and rewarding!

there are so many things that can be causing this problem. First of all disconnect the fuel line, squirt some gas into the intake manifold and hit the starter.
when the engine starts take note if gas is flowing from the line at that time and if it keeps flowing when the engine shuts down. If gas is constantly flowing then the pump is functioning properly. If gas is constantly there then the next step would be to make sure your new check valve is not stuck in the closed position.

Hi and thanks for answers.
New fuel pump, original, installed and same problem. The car starts right up and dies. Fuel pump is running a second after it dies to build up pressure. So fuel supply to engine is good.
Then today we started up several times. I opened to one of the injectors to see if any fuel was actually coming that far, and it was. I read about the k jetronic system and found out the reason for starting up is the extra fuel valve that gives extra fuel into the air-filter and the mix comes in that way when the engine is cold. That means it dies not use the injectors to start up when cold.
Started several times and the engine started to run rough for a few seconds. Then we did this a few times and found the engine is running the 10-15 seconds and that must be via injectors. It is like it needs some exersize as it has been sitting for a while empty of gas. I also looked at the filter in the warm up valve and it is nice and clean. I guess next step is to find out what pressure there is on the warm up valve. I am learning about this, but again have to leave the project some days for work.
If you have any suggestions now I am this far it would be appreciated.
Cant get the pictures uploaded

OK . I am now assuming your check valve is not stuck in the closed position so you not have to check if your damper is working.
Better yet for quick results just replace it and see what happens. You might be pleasantly surprised.

Jan,
That’s good news that it’s showing signs of life!

I found the fuel system to be the most difficult aspect of my car to understand.
It’s beautiful in concept, but hell if it gets out of wack.

I reread all of your posts and have some questions, just so we are all on the same page.
Your car is a K Jetronic system, correct? It is a “simple” CIS system, right?

You said that it stopped running 6 months ago.
Was it running well? It it just abruptly quit?

While you are on a work break, I think that you are probably right that you are probably headed to measuring the system and control pressures, so you might order a CIS fuel pressure test set with lots of adapters. You will not know what’s happening with the system without Knowing the pressures.

Another thing that you could do is to run some sort of cleaner through the system, particularly because it’s been idle for some time. I use Techron, but many other swear by other products. You can circulate the fuel and cleaner by jumping the fuel pump relay.

Here are a few more references that you may find useful.

forums.pelicanparts.com/porsche-911-tech...hooting-dummies.html

forums.pelicanparts.com/porsche-911-tech...jetronic-issues.html

rennlist.com/forums/928-forum/807102-cis...nal-reflections.html

Hopefully, you will not need these, but here are some places to check the injectors, WUR, and fuel distribution, if needed. CIS injectors can not be rebuilt. Roger At 928sRUs can get You Bosch or Mercedes, should you need them.

WUR and fuel distributor testing and rebuild:
www.cisflowtech.com/

Injector testing:
www.witchhunter.com/

Good luck!

HI again and Thanks for answer.
The car drove up from Fl to New England without any problems after a big service in Florida before the trip. Previous owner then emptied it
for gas, ran it empty as it was going to sit for the winter in the cold. Then in the summer here he sold it to me or rather we did some swopping. I came there with a new battery and some fresh fuel and we expected the car to run. So it did run fine earlier.
The fuel system is a CIS k jetronic system as on older 78-79 928's. It is from Europe and has a /11 engine in it = 300 hp but same fuel system as all older ones. I have earlier used Tectron with good results.
I got a original fuel pump from Roger 928srus which did not change anything. But it was worth a try. So I have a fuel pump for sale...
The car starts up and limps and dies after a little while, but it comes more and more. Now it is sitting for a while as i am out on an assignment.
I will get to it when home again. I have been researching a lot on the internet and a Belgium webpage har a lot of good info, in french, which is not a problem for me, but i have not come to try it yet. We will get there. If not i guess i have to go to a garage who can fix it, but that is too easy (and expensive) Sometimes it pays to be stubborn.

Jan, thanks for the added details! I have been thinking about what you are facing. It seems like there is good reason to hold out hope that whatever is happening is minor to correct. It’s possible that in the 6 months of sitting around that some of those small passages in the fuel distributor have gotten clogged or a few of the injectors are stuck or not spraying well. One thing to try, while your are waiting for CIS fuel gages, is while running the pump, press the air flow plate down by hand. That will allow some fuel to flow through the fuel distributor and the injectors, hopefully helping to free them up. Alternatively, I believe that some people advocate pulling the injectors out and forcing something like WD40 through them. I haven’t tried that myself.

I admire your stubbornness! I’m the same way. I think that’s how we really get to understand these fascinating machines.

Jan, I found this link in my bookmarks for a Baseline Fuel Tuning Procedure. You may need to adjust your air-fuel mixture.
928classics.com/bosch-kjetronic-cis-fuel/

joejabq wrote:

Jan, I think that I might have just experienced what you have. My '79 was running well after having the fuel distributor rebuilt at CISFlowtech. I stopped driving the car and started working on the interior. After not driving the car for ~5 months, it wouldn't start without adjusting the air fuel mixture each time and in fact, it barely ran, finally dying in my driveway. I used the 928classics fuel tuning procedure to try to diagnose the issues. I found that the system pressure was at an inconsistent 60 psi ( it was 75 psi after the fuel distributor was reinstalled and it should be between 65- 75 psi). I pulled the System Pressure value and found that plunger O-ring and the outer sealing O-ring were both broken, In fact, the plunger O-ring was missing pieces. I talked to CISFlowtech, and they suspect that ethanol gasoline combined with sitting, caused the O-ring to first swell and then fall apart. They sent me new O-rings. I installed them and the car is back up running. I'm going to try to swear off using gasoline with ethanol to see if I can keep this from happening again. Luckily, there are a few gas stations not too far from my house that sells ethanol free gas.
I just wanted to pass this along if you haven't found your issues. I'm just wondering if ethanol (combined with sitting idle) could be the root cause culprit for your fuel pump dying and the no start?

HI again and thanks for info
Been at work...Now starting to think about this project again.
I found that if it gets going a bit it wants to start and we are looking into the fuel distributer now next. Found a mechanic who used to work on these systems, and he will come down to my garage with some knowledge and rusty memory, but we have before got impossible things up and running. He also suspect something in the direction of what you are saying. He thinks the fuel plunger is stuck due to a drop of water when the car was run empty and a bit of moisture came into the system from the bottom of the tank. I will let everyone know what we find, but have patience as work is calling this time of year.