CIS woes.

[car911914]

1976 911S Targa
Owned and driven weekend's for 30 years.

Please look at this 2 minute video explaining the problem:

https://youtu.be/2sDMSo3be1c

The fuel pressure and flow were checked and up to specification. The fuel distributor was professionally rebuilt ($630). Any ideas why I am not getting fuel pressure to the injectors?

[72911]

So the original issue was you installed your newly rebuilt fuel distributor and the car would not start and then you put your test rig on? I check my injector pattern by removing all the injectors and set them up to spray into 6 glass bottles with hols in their metal caps. You can try this and that should at least let you see if it is all the injectors. I have that same test rig and I don't remember if you should have flow to the injectors when testing control pressure. Control pressure is the counter acting pressure ABOVE the metering valve that adjusts full system fuel flow to the injectors depending on the current condition (cold, high vacuum, hot ect..). Move your test lever back to system pressure and raise the air valve. Be aware that all the injectors flow fuel and I only see one injector hose removed. You could be setting yourself up for hydraulic lock if you keep at it. There should be a slight squeal when the injectors are open and flowing.

[Bob Kontak]

Originally Posted by 72911

I have that same test rig and I don't remember if you should have flow to the injectors when testing control pressure.

With the control pressure test you are only introducing the pressure gauge into that part of the circuit.

What I see in the video is that car911914 is testing fuel flow from the open injector line and is assuming that control pressure (20-ish psi) is what is driving the injector line flow.

I think that is what he is saying.

System pressure drives the injectors opening. It's well over 45 psi. Control pressure allows the big fat dowel pin to moderate the quantity of fuel dispensed. Lower control pressure equals more fuel pissed out from the "high side" chamber. Higher control pressure equals less. But it all (the injector fuel) comes from the chamber apart from the control pressure chamber.

All that said, there appears to be a flow issue. This is what car911914 should focus on and talk to us about.

[Bob Kontak]

Originally Posted by 72911

You could be setting yourself up for hydraulic lock if you keep at it.

Google cylinder hydro-lock.

[72911]

Originally Posted by Bob Kontak

With the control pressure test you are only introducing the pressure gauge into that part of the circuit.

What I see in the video is that car911914 is testing fuel flow from the open injector line and is assuming that control pressure (20-ish psi) is what is driving the injector line flow.

All that said, there appears to be a flow issue. This is what car911914 should focus on and talk to us about.

I couldn't tell if the disconnected hose is from an injector or coming from the control pressure regulator. If you raise the air valve by hand and the pump is running you should have the injectors pulled out of the manifold or the hoses disconnected and running into a container(s). This is why I mentioned hydraulic lock, if fuel is being injected into the cylinders and the plugs are still installed. I agree more input is needed here, that is why I suggested the injector flow test into bottles. It lets you know a lot about your system quickly (all injectors working, enough fuel pressure, system pressure regulator functioning...ect). Let's see what car911914 has found.

[Bob Kontak]

Originally Posted by 72911

I couldn't tell if the disconnected hose is from an injector or coming from the control pressure regulator.

Fair enough. I would not bet my life it's an injector line but I think it is. However, it's coming from one of the two (control/system) and OP can clear that up for us.

I hydraulic locked my 81 in the way back playing around while starting to learn the system. Not a clue of what the problem was. Once found out, there was work involved. Pull plugs. Crank with assured lack of ignition source. Drop exhaust and drain. Change oil.

[car911914]

I don't think it would matter if the pressure test gauge was set to System or Control because it is connected to the WUR which tweeks things so the car runs richer or leaner. However, if you really watch my video closely I state (and show) I switch the system back to control pressure before demonstrating the poor flow. Since I am demonstrating with cold control pressure, if anything I should be getting extra fuel because it would be running rich at that time.

I also believed this is a fuel flow issue so today I checked the flow where the fuel line enters the fuel distributor (so this flow is taking into account resistance from the fuel lines, fuel accumulator and fuel filter). All fuel components are brand new. The Bosch fuel pump specification says it is suppose to perform at a minimum of 56 Gallons Per Hour (GPH) exiting the pump which is about .91 gallons per minute. I am getting about .7 gallons per minute at the fuel distributor which seems reasonable.

[car911914]

The first picture shows how I dumped the fuel going to the fuel distributor into a gallon jug.

The second picture is how full the gallon jug got with fuel after allowing the fuel pump to run for 60 seconds.

Also, believe me, I learned all about fuel block/lock the hard way. lol You can safely push the fuel meter plate up and listen for the "wine" of injectors functioning as long as you do this VERY conservatively. If I get concerned about fuel lock I use a little starting fuel to start the car to make sure excess fuel is burnt.

[boyt911sc]

Car911914,

Something is wrong with your fuel pressure test. Look very closely at your video when you measured the cold control fuel pressure and switched to system pressure. You clearly said both pressures were “perfect” (?). I don’t think so. Why? Go back and review the video.

What was the value of the CCP in psi./bar?
What was the value of the SP?
What was the value of the control pressure after switching the valve from system pressure? The second cold control pressure reading was much higher than the previous reading.

Either the pressure gauge is questionable or something wrong with your set-up. I suspect the fuel distributor plunger was not fully at rest (down) when you started the test. Keep us posted.

Tony

[LlamaMan]

Car911914,
I just went through rebuilding an entire K jetronic system and rebuilt and tested each component myself - and a few days ago the car finally runs fine now. Every component had problems and each time it seemed complex but it always ended up being something very clear and logical.
-It looks in your video that you have removed the hose from the injector and placed in a jar (so no injector is in the video, true ?). If you have 70psi as system pressure and you lift the plunger manually, then gas should definitely flow out that hose.

My suspects in order of likelihood:
1)-Fuel Distributor bad. You said pro rebuild...was it CISFlowtech ? If so they will help you diagnose. Any other shop should have tested on their flow bench and have data for you and will test it again for you. a) You might try to check flow out of the return line, should be a decent gush not just a dribble. b) Check another line(s). Are none of them flowing ? c) If your rebuild shop won't help, you can split it open yourself and might find the problem.
2)-Injector hose mixed up, kinked, plugged.
3)-Air plate not actually lifting the plunger. Can you feel the plunger resistance and it's pushing back against you (with 40PSI), maybe the lift plate is not actually pushing up the plunger ?

Interesting problem. Last week I posted that I had control pressure = system pressure, after some academic discussion, turned out the previous owner had connected the pipes to the WUR backward. So check the basics !

Good luck, please let us know what you find.

[Bob Kontak]

Originally Posted by boyt911sc

You clearly said both pressures were “perfect” (?). I don’t think so. Why? Go back and review the video.

Based on a 76/77 control pressure graph (which I'm not sure is for this exact car) IF the ambient temps were 30C/86F, CCP at 40 psi (2.75 bar) is about right. If temps were 25C/77F would be around 33 psi (2.25 bar).

Odd thing was the switch back to CCP. It spiked at over 60psi.

This is my source data.

[72911]

I'd still like to hear the back story on this issue. Why was the fuel dist rebuilt? Was the car running and then had a start issue. If this was a routine rebuild how was the car running before?

[gomezoneill]

That jug looks like it's full of urine not fuel. How old is the fuel in the tank?

[car911914]

Here is an update on my CIS woes.

Yes, I took off the injector and put the hose in the jar so you could see how fast the fuel flowed. With the injector on you would see nothing because there is not enough pressure to cause the injector to squirt.

Yes, the fuel does look like urine. I always ad Sta-bil fuel stabilizer if I know the fuel might get old and that stuff is red. But the fuel could be water at this point because I can not get anything out the injectors. Short squirt of starter fluid and the car starts right up until the starter fluid is burnt.

I used parts-klassik to rebuild my fuel distributor. After a discussion with the technical guy (Larry) he felt my fuel flow was not sufficient. The specification says the engine needs 125 liters-per-hour(lph)@72psi so I upgrade to a 300 lph@72psi. After the upgrade I checked the pressure and flow at the fuel distributor, both were running at specification but that did not correct the problem.

I am going to remove the fuel distributor tomorrow and send it to parksklassik for them to figure out. I have to pay shipping both ways and $85 if they determine there is no problem with the fuel distributor. Two weeks to send the part there then two weeks to send the part back so I am looking at at least another month without my Porsche.

[boyt911sc]

Originally Posted by car911914

Here is an update on my CIS woes.

Yes, I took off the injector and put the hose in the jar so you could see how fast the fuel flowed. With the injector on you would see nothing because there is not enough pressure to cause the injector to squirt.

Yes, the fuel does look like urine. I always ad Sta-bil fuel stabilizer if I know the fuel might get old and that stuff is red. But the fuel could be water at this point because I can not get anything out the injectors. Short squirt of starter fluid and the car starts right up until the starter fluid is burnt.

I used parts-klassik to rebuild my fuel distributor. After a discussion with the technical guy (Larry) he felt my fuel flow was not sufficient. The specification says the engine needs 125 liters-per-hour(lph)@72psi so I upgrade to a 300 lph@72psi. After the upgrade I checked the pressure and flow at the fuel distributor, both were running at specification but that did not correct the problem.

I am going to remove the fuel distributor tomorrow and send it to parksklassik for them to figure out. I have to pay shipping both ways and $85 if they determine there is no problem with the fuel distributor. Two weeks to send the part there then two weeks to send the part back so I am looking at at least another month without my Porsche.

Dan,

Your video showed a system pressure of 70+psi. on the gauge. That is more than what a CIS injector would need to open and spray atomized fuel. A good working CIS fuel injector would have a cracking (opening) pressure between 36~52 psi.(spec.).

What was very strange in your video was the cold control pressure readings. The first reading was described “perfect” but the next reading was much higher than the “perfect” value. Have you noticed it?

The difference about these two (2) control pressure readings could be attributed to a defective WUR or pressure gauge fault (?). But a no flow from the fuel lines is a FD problem. Let’s hope the rebuilder does not put the blame on the customer. Keep your fingers crossed.

Tony

[car911914]

Problem solved! Robert at Fuel Injection Corporation in California helped me figure this out, he is a great guy! Turned out my Warm Up Regulator was working properly. My car is running like new now. Hurray!

[Funracer]

Originally Posted by car911914

Problem solved! Robert at Fuel Injection Corporation in California helped me figure this out, he is a great guy! Turned out my Warm Up Regulator was working properly. My car is running like new now. Hurray!

WUR is working properly. What was the problem then?

[pmax]

Congrats.

Curious about how you turned on the pump from the engine compartment and that flicker of the fuel pressure as measured by your gauge at 0.24 and that second value does appear high as others have observed given not much time has apparently passed between the first and second CCP measurements the other possibility being the video's edited for length, which, thinking more about it, I would say is actually the more likely scenario knowing now that the WUR is all good. On a side note, love those old school Craftsman, a thing of beauty both in design and looks.