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So I have been saying for a few years I was going to swap out my fuel accumulator. Well I hate to say I am about to put the original one back. Don't let anyone tell you it is a fun job.
So the symptoms are common. Starts great when stone cold drives nicely has full power but when it gets hot and sits for a few hours it is difficult to start and needs a little gas to get her to idle normally taking a few min before settling in. It is embarrassing when leaving a show when the car doesn't fire up properly and in all honesty doesn't sound half as good as my C2. Another project for another day.
I made an assumption it was the accumulator but that is my own fault. After pulling half the engine apart and testing the accumulator I clearly wasted my time. I decided to test the new unit and the original unit to the car. I pulled a vacuum on both units and I see no loss of vacuum on either side of the diaphragm. They both respond to the test the same way.
So question? Would you reinstall the original 39k mile 30 year old accumulator or take a chance with the new one and hope it is better than most other products I am getting from Porsche new? Any advice would be appreciated. I hope to get this back together soon as we are about to resurrect the Blue Meanie project and I want to focus on that.
So I guess it is onto checking control pressures and the rest. I have to dust off my CIS test kit I haven't used it since I owned my SC's. Not looking forward to the time needed to do this. If everything looks good I will pull test and clean my injectors and check the fuel pumps but so far everything appears to be fine.
Not bad for 30 year old car. everything is soft an pliable and I don't see anything out of line. Hope it isn't the wur and something more simple like leaky injectors. It is just easier to remove everything so a good chance to clean as I go. I'm getting too old for this LOL.
I would install the new one.
your old one has low miles BUT is old and been subjected to Fuel with ethanol in it may have compromised the diaphragm, no telling if and/or when it might fail.
I would go with the NEW Porsche unit for sure , but i wouldn't hesitate to use your original. probably better than the new stuff. I doubt its the WUR or the injectors. don't go down the rabbit hole my friend. You're on the right track with the fuel accumulator.
i would stay with the old one. replaced mine about 8 years ago (as a test with symptoms similar to yours) with a new bosch unit which died this year. now i mounted the old one again (kept it) and i am fine for the moment.
fault in my case was the fuel head. one of the o-rings arround metering slits was done and fell off. so pressure went wrong way inside.
I am on the fence. I have had so many problems with new parts from Porsche and it is a royal PITA job. Although always good to inspect everything occasionally. I am leaning towards the new unit. Will report back when I am up and running. 🤞
I might pull the injectors and clean them while in there. I have access to the eq to do the job, I can have them cleaned and flow tested in less time than it takes to remove them. I have been working on so many N/A 964's as of late that I had forgotten how much more work it is to access things on these cars. I hope I don't have to get involved with the fuel head. I had issues with one of my SC's and I recall it being another fun job. Although my SC's were all 79's so they had the flexible fuel lines vs the rigid ones of the >80's and turbos. The rigid lines add to the difficulty.
The Blue Meanie should be on the dyno in another week so I need to clear the projects so I can focus on it and the **** Box for an upcoming Glen DE in August. I just missed our Summit Point event because of the Lime rock snafu. I can't miss another. I seem to get more track miles than street these days.
So after a bit of further investigation I decided against the injectors for the time being. I do plan to drop the engine in the future. It will be much easier to access all of them with the engine out of the car.
Interesting question for those still running the EGR system. How much of a hot start problem might stem from never changing the filter? In all honesty I had no idea it was buried down in there. I dropped the ball on that. I pulled the filter (another PITA) and it is clogged solid. Even after trying to blow some of the dirt out and there was a lot, I still can't see light or feel air flow when used on the filter. I know very little about these systems other than I removed mine from my SC's. Long shot but at a Min I guess I should replace this while everything is apart.
I've had a bunch of similar dilemmas and have generally erred towards installing the new part while the engine is out even if the old one seems okay and can be kept as a spare.
I would definitely replace that filter or delete the EGR system.
I'm with Peter,
You have the used one in stock. There's not much to that design. When problem solving always install used parts.
I'm replacing my new fuel pump sometime soon.
I think there's 3 sensors that control the timing, cold start injector and regulate the fuel pressure.
If you have a sensor that's sending a cold single to the Control unit then the car will run too rich.
Starving for fuel will barely run the engine. AUX injector is not big failure from what we read.
Ordered up the filter. I was planning on changing it but it wasn't on my radar so buried and hidden in the engine.
One more question. Like I said it has been a while since I worked on CIS. I know there are 11 compression springs that hold the top of the flapper plate air chamber to the bottom. I am not sure if all of these get springs or not.
Mine has 2 that I can see that have no springs. I have to assume this was the way it came unless someone did something years before my ownership. I have had the car for half its miles but doesn't seem like something someone would do with 20k or less miles. No signs of it being tampered with. Prior to my ownership the car was mostly serviced by ANDIAL.
I'm with Peter,
You have the used one in stock. There's not much to that design. When problem solving always install used parts.
I'm replacing my new fuel pump sometime soon.
I think there's 3 sensors that control the timing, cold start injector and regulate the fuel pressure.
If you have a sensor that's sending a cold single to the Control unit then the car will run too rich.
Starving for fuel will barely run the engine. AUX injector is not big failure from what we read.
I don't have a rich hot start issue. If anything it is quite lean until I can get it to idle properly then it becomes stoic until under load and then slightly rich. Once she settles out she runs fine. Solid idle and AFR's
- I would continue to use the old pressure accumulator for quality reasons.
- Droping the engine makes a lot of things easier, but I would first carry out systematic troubleshooting:
- - Exclude false air (preferable with a fog machine)
- - Check system pressure and control pressure at the WUR
- - Check fuel pressure loss due to leaking injectors
- - Check termo time switch
- The air filter for the SAI has no influence on your problem. The SAI should remain installed, the oxygen injection into the manifold causes after burning and improves the response of the turbo.
- The fuel ditributor is initially not suspicious; i would check it if all other tests provide no evidence of the failure.
- The injectors (density and fuel quantities) can be checked relatively easily if the rigid lines are replaced with hoses. I replaced recently all injectors for several reasons, they weren't easy to get for the 3.6.
- I would continue to use the old pressure accumulator for quality reasons.
- Droping the engine makes a lot of things easier, but I would first carry out systematic troubleshooting:
- - Exclude false air (preferable with a fog machine)
- - Check system pressure and control pressure at the WUR
- - Check fuel pressure loss due to leaking injectors
- - Check termo time switch
- The air filter for the SAI has no influence on your problem. The SAI should remain installed, the oxygen injection into the manifold causes after burning and improves the response of the turbo.
- The fuel ditributor is initially not suspicious; i would check it if all other tests provide no evidence of the failure.
- The injectors (density and fuel quantities) can be checked relatively easily if the rigid lines are replaced with hoses. I replaced recently all injectors for several reasons, they weren't easy to get for the 3.6.
Fritz
I am concerned over the quality as well. I am very displeased with both price and quality as the price goes up the quality seems to go down. I do plan to drop the engine this winter. My other projects are almost complete so I will have the time for a change. For now I just had a change in my personal plans so I have no choice but to button things up. I hate doing things twice. I already installed the new accumulator but have the original and another used spare which also checks out fine. I will consider what i do when the engine is dropped. I also need to do the valve lash. Much easier to address everything then.
I didn't remember much about the air pump although I do recall this wording on my SC pump before removing it. They are joking right? Who wants to check anything this difficult to get to daily. They probably could have found a better location if it was that important.
It is a PITA but after tackling the job again after so many years the next time will be much easier. I will check the control pressure tomorrow but have no time for the injectors. I was just informed the filter is 2 weeks out which I don't have time to wait for so I cleaned the old one for now as best I could. Wishful thinking things will have improved but at least i know what to order and what to address next time.
Once I get the oil situation cleaned up on the **** Box project and the Blue Meanie done i will revisit. I will report back if there are any significant findings tomorrow.
thx
BTW I have access to a nice little machine. Although I like your bottle method. I did that with my 79 SC. Gives you a better idea about how the system is working vs just the injectors.
This is a great little toy. I also have a smoke machine which I will test tomorrow. I should have a better idea tomorrow.
Well, maybe the instructions are written for Dubai and due to warranty reasons, in any case not much desert sand should be blown into and through the turbo.......
The test bench is nice, but better suited for electromagnetically controlled injectors. The purely mechanical ones of the K-Jetronic cannot realy be cleaned either because the sealing cones and nozzles are only accessible via the opening pressure, so while injecting.
07-09-2024, 05:21 PM
Fuel accumulator advice?
I hate doing things twice. I already installed the new accumulator but have the original and another used spare which also checks out fine. I will consider what i do when the engine is dropped. I also need to do the valve lash. Much easier to address everything then.
