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Join Date: May 2004
Location: Boulder, Colorado
Posts: 7,275
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Sorry to hear that a new fuel pump didn't solve all the problems. But it seems it solved a few of them? What are your system, control pressure cold and warm, and residual pressure readings? You have them from the old pump, so what do the ones from the new pump say?
For instance, if your cold control pressures are too high, that suggests a problem with the WUR. And there are ways of adjusting that. If your system pressures are still funky, maybe you need yet another, but real Bosch? pump? If that stuff seems OK, I would investigate how well the oxygen sensor/lambda system is working. When I transplanted an '82 3.0 into my 2.7, I decided not to install the electronics to control the frequency valve/oxygen sensor system. Who needs that, I'm not interested in fuel economy, just power and I can tune things. Well, I was wrong - the car was hard to start. As soon as I installed the rest of the stuff, even without the oxygen sensor (which required welding a bung onto my exhaust system), the car started like it should. That is the system which makes Targa80''s car work as he describes. The WUR sort of does also, but if it is within its control pressure specs (control pressure increases with temperature), then I'd look at how the frequency valve system is doing. |
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11-21-2020, 12:20 PM
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Hi Walt, thank you for the reply. Yep, peeling the onion of problems with the car. And the pump that I put on is a genuine Bosch unit. The one that was on is the cheap Chinese unit, looks exactly the same from the outside but it has a weird part number.
Anyways, I haven't tested pressures with this new pump yet but ill work on that tomorrow. |
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11-21-2020, 02:35 PM
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Pressure Testing Results
Hi everyone, finally I've managed to do my pressure testing. The results are very puzzling. I've attached pics so that you guys can correct me if I did anything wrong. Temperature was about 6-8 Celsius if that makes a difference. I followed the procedure in the below link:
https://www.pelicanparts.com/911/technical_specs/Testing_Bosch_CIS.htm This is the fuel pressure gauge I am using, I hope I bought the correct one: A. Engine cold, valve open- Slightly over 5 bar B. Engine warm, valve open- 5.2 bar C. Engine warm, valve closed- 5.2 bar D. Engine warm, rest pressure valve open, 0.25 bar. Pressure dropped to 0 in 1 minute 25 seconds. More tests E. Engine cold, valve closed, WUR connector disconnected- 5 bar F. Engine cold, valve open, WUR connector disconnected- 5 bar G. Engine cold, valve open, WUR connected- 5 bar Anyways, I figured that I have multiple system failures. Can someone kindly tell me what the system pressures should be for my car (1980 911 SC Targa US spec). Also, what should be my next steps in addressing my issue keeping in mind the fuel pump, check valve, and accumulator are new. Any help would be greatly appreciated as I am at a loss. Also, the last pic is my car.          
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11-29-2020, 09:54 AM
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Have you checked the resistance across warm up regulator should be approx. 20 ohms. If OK see if you have voltage supplied.
__________________
Walt 82SC 3.0 81SC 3.6 |
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11-29-2020, 12:45 PM
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Quote:
Landyman, All your above data are all WRONG! They don’t make sense. Allow me to give you hand in your CIS troubleshooting work and learn how to do it right. Send the FP, FD, and WUR to be for FREE test and evaluation. It would only take me a few mins. to test and evaluate these CIS components. Include a return shipping label and will ship them back to you the following day. I will include the test data like CCP, WCP, system pressure, and residual pressure. From these information you should be able to replicate these values. If not, there is something wrong with your pressure gauge. PM me if your are interested. Tony |
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11-29-2020, 12:47 PM
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Hi Walt, thank you for the reply. I am new to Porsches so excuse the dumb question. If I energize the WUR, should my fuel pressure vary? I have a feeling my WUR is jammed/ not getting power. Also , when should the WUR be energized? Only on cold startups?
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11-29-2020, 12:54 PM
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PM sent
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11-29-2020, 01:41 PM
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CIS troubleshooting........
Edric,
I did not realize you are from England. So sending the CIS components to me would not be ideal because of the shipping cost. Unless you know someone with an APO. I had received packages from Germany (US air base) that cost like local deliveries. We could overcome this problem by communicating via emails and you post the results in this thread. What you lack is test and verification. For example: You have not demonstrated that you could measure your control fuel pressure readings with confidence. Not even sure your pressure gauge kit is working correctly (?). And that was the reason I offered to do some testing for you to establish once and for all if the gauge is reliable. Anyway, we are back to square one. Why are you getting the same pressure readings for the control and system pressures? If this is real, there is flow restriction in the system for the control pressure to be the same as the system pressure. Or the pressure gauge is questionable. Tony |
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11-29-2020, 02:26 PM
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Email sent, hope it didn't go into your spam box.
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11-29-2020, 02:56 PM
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Join Date: May 2004
Location: Boulder, Colorado
Posts: 7,275
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Landy - The 5+ bar readings are within spec for system fuel pressure, which you get with the valve closed (took me a while to spot the red plastic handle and thus the valve).
To test what your control pressure (the WUR is better named the control pressure regulator), you open the valve (which is what your setup looks like. Ball park figures for cold CP might be 2 bar, hot pressures maybe 3.4. The cold pressures vary with temperature, being lower at low temps so you have a richer mixture, and gradually increasing as the WUR warms up. The warm CP is fixed - when you engine is warm enough, the WUR still sets the CP, but only at a fixed level. The WUR does its thing in two ways - there is a heating coil inside the WUR. And engine heat eventually gets the whole WUR warm. If the heating coil fails, you would still eventually, if driving, get the control pressure up to the leaner warm running end of the spectrum. None of your control pressures are what they should be at all - they seem to be at system pressure, which typically means the WUR is clogged (happened to me) or otherwise stuck closed, or there is a pinched or clogged line on the discharge side of the WUR. The WUR can be disassembled reasonable easily to check how it is operating mechanically. 5 bar control pressures are not a result of the heater/CP warm up control system inside the WUR being bad - they may be, but when they fail they keep the CP too low, not too high. When you say engine warm, rest pressure valve open, you mean the fuel pump is not running and you are checking the residual pressure drop by having the single manual valve in your system open? Residual pressure is checked with the valve closed - you pressurize the system to 5+ bar, and turn the fuel pump off. If that's what you did, and it dropped as you indicate, it isn't in spec for sure. Leaks can occur at the pressure retention valve on the fuel pump (first thing a guy thinks of), or from a leaking injector, or issues with the pressure valve in the FD - which has one or two small O ring seals, depending on model of car/FD. Or a leak at a fitting, but you'd have seen/smelled that. Tony can walk you through this in the methodical system he uses, and help you identify why you apparently have bad control pressures. Bad leak down times (too short) don't usually affect driving much - they make hot starting difficult and frustrating, and need to be fixed. But are perhaps a lesser order of problem. A leaking injector can lead to a cylinder running rich, and gasoline getting into the oil, which isn't good. There are ways to check for a leaking injector - the simplest is to pull them all out with heir supply lines attached, and pressurize (but don't try to start) the system, and look to see if fuel dribbles out of one or more. The simplest way to fix that is new injectors, though one can try to fix them by running cleaning fluids through them and then retesting. |
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11-30-2020, 03:34 PM
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Hello everyone. Thanks so much for your help. Turns out I had multiple system failures. My WUR was stuck hence my control pressures were always 5.2. Took it apart, cleaned it. Put the block in acetone as per Tony's suggestion and got my control pressures way down. Sadly that WUR never really worked properly as it would constantly get jammed giving the system random control pressures. I got a WUR on eBay from a Escort/Jetta part number: 0438140 073. I had to add a nipple for the vent tube and while I was modifying it I made it adjustable.
  This WUR has slightly lower ohms on its bimetallic strip (18 ohms vs 24) but it still gives me really close to stock control pressures. Starts first try hot or cold so I think i will leave my FrankenWUR alone. The other problem i had was no residual pressure, that was the easiest and cheapest fix. I bought the below kit from eBay and now it starts first crank when hot because it actually maintains fuel pressure. Anyways, I hope this helps somebody fix their car. Now I have an idle problem but I will start another post. Special thanks to Tony, he's a top man. |
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01-31-2021, 11:09 AM
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Control fuel pressures........
Edric,
Do this test for me. Connect your CIS pressure gauge and monitor the cold control pressure readings versus time. Do this test with a completely cold motor. Start........This would be the initial pressure gauge reading when the motor starts. After 1 min. After 2 min. After 3 min. Etc. Wait until the CCP (cold control pressure) becomes WCP (warm control pressure) and has stabilized (steady pressure reading). End of test. Please share your data with us. Thanks. Tony |
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01-31-2021, 01:03 PM
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Having had this issue on my 914/6. The seat of the pants check for a hot start problem is a shot of ether into the intake. If it starts it’s the check valve. Cheap part back in the day. Located in the fuel pump neck.
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01-31-2021, 03:33 PM
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Join Date: Aug 2011
Location: Bend, OR
Posts: 80
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Reviving a bit of an older thread here as I am working through a hot start problem on my 1980 911SC. I've just ordered a set of CIS gauges and hope to dig into the testing this weekend. However, prior to doing that, I ordered a new fuel pump check valve, thinking that would be an inexpensive shot at fixing the problem. However, my fuel pump ended up being the internal valve variant, to which I replaced. Problem remains. I've removed the primary pressure relief valve from the fuel distributor and have attached a pic in the hopes that the experts here can either give me a thumbs up or down on the condition of the o-rings. The look and feel fine to me. However, I'm more than willing to replace them, but am having difficulty finding the correct size or part number. Any help would be appreciated.
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06-23-2023, 09:45 AM
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Primary Pressure Valve……….
Quote:
There is a small hidden o-ring in your PPV. Take a look at pictures below:   There are 2 o-rings shown in your picture. The 3rd. o-ring is hidden inside the threaded section of the PPV where that tiny hole is located. It is not easy to replace this tiny o-ring and Bosch recommends replacing the whole unit. And a new unit is very expensive. Tony |
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06-23-2023, 11:38 AM
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Location: Bend, OR
Posts: 80
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Thanks, Tony! I was curious why the valve included a provision for an allen wrench. Now I know. �� I’ll have to pull mine apart and investigate further. Is that internal o-ring typically “more” responsible for a loss in residual pressure than the one on the piston? To be fair, I’m not 100% how the residual pressure is behaving without measuring, but I’m just trying to take a preliminary look at possibilities.
I've read that the PPR o-ring kit from Delorean Industries (see link below) may work. Any history with this kit? https://deloreanindustries.com/online-store/fuel-emissions/2-2-0-fuel-injection-system-kjet/1-2-ppr-o-ring-kit-fuel-distributor/ Last edited by oregon87; 06-23-2023 at 01:37 PM.. |
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06-23-2023, 12:27 PM
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Da cab
