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87 930 Starts but will not run

Hi Guys
I have replaced the WUR on my 87 930 with a "digital" version from unwired tools. After replacing the car will start but only runs for a second. According to the software and my fuel pressure gauge the control pressures are correct. I should also mention that during the work I had the bypass valve off but I have checked all the hose and electrical connections and all seem correct. The only thing I have noticed is the wire to what I believe is the overboost sensor may be damaged but I am not sure how to check this. Any suggestions as to how to troubleshoot would be greatly appreciated.
Thanks

Old 11-29-2008, 12:21 PM
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Temporarily ground the brown wire going to the boost sensor switch to the chassis ground. If it's a defective over boost sensor switch, the engine should start.
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Last edited by WERK I; 11-29-2008 at 02:28 PM..
Old 11-29-2008, 12:59 PM
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Quote:
Originally Posted by darling930 View Post
Hi Guys
I have replaced the WUR on my 87 930 with a "digital" version from unwired tools. After replacing the car will start but only runs for a second.
Thanks
When it starts, can you quickly give it a bunch of throttle and keep it running albeit poorly? If so, probable huge air leak. Look to the work/stuff you did with the bypass valve. I once forgot to re-attach my AAR valve,(huge air leak) and my symptom of 'not running' mirrored your described symptom.
Old 11-29-2008, 01:57 PM
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It will not run either by depressing the throttle or by pushing down slightly on the air metering plate. If I am correct adding throttle would briefly increase air flow and compensate for a rich condition (before the air metering plate has a chance to catch up) and pushing down on the metering plate (without touching the throttle) should compensate for a lean condition.
Old 11-29-2008, 02:24 PM
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Quote:
Originally Posted by darling930 View Post
It will not run either by depressing the throttle or by pushing down slightly on the air metering plate. If I am correct adding throttle would briefly increase air flow and compensate for a rich condition (before the air metering plate has a chance to catch up) and pushing down on the metering plate (without touching the throttle) should compensate for a lean condition.
Adding throttle increases both air and fuel. Give it enough throttle, enough fuel will flow to overcome a huge leak (I know this as this is how I "discovered" the 3/4" ID AAR hose was disconnected.) And yes, moving metering plate will add fuel, no air.
When it starts to quit, adding throttle does nothing? Can you hear or verify that both pumps are running? If you hold the ignition key in the start position after it starts, does the engine still die in 1-second?
Do you have mechanical fuel pressure gage in the fuel head/WUR loop or just the pressure as reported by the Unwired software? Are you sure you are reading control pressure, not "target" pressure?
Try unplugging fuel pump cutoff switch connection, top/back of CIS body?
Old 11-29-2008, 02:59 PM
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Adding throttle does nothing. I am fairly sure the fuel pumps are running and I have tried it with the fuel pump cutoff switch unplugged with no difference. Leaving the key "cranking" the engine sputters a couple of times but still dies quickly. I have verified the control pressure with a mechanical gauge not just the software. Also since I have left off hoses in the past I have gone through all the hoses I can think of attached to the intake/bypass valve and cannot find any loose. I am stumped. The only other things I can think of are the overboost switch and the mixture. Although I would think that if it were the mixture there should be some effect by opening the throttle and/or moving the metering plate. Or I suppose something totally unrelated to fuel like an ignition snafu but then I do not think it would fire at all.
Old 11-29-2008, 03:25 PM
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Adding throttle does nothing. I am fairly sure the fuel pumps are running and I have tried it with the fuel pump cutoff switch unplugged with no difference. Leaving the key "cranking" the engine sputters a couple of times but still dies quickly. I have verified the control pressure with a mechanical gauge not just the software. Also since I have left off hoses in the past I have gone through all the hoses I can think of attached to the intake/bypass valve and cannot find any loose. I am stumped. The only other things I can think of are the overboost switch and the mixture. Although I would think that if it were the mixture there should be some effect by opening the throttle and/or moving the metering plate. Or I suppose something totally unrelated to fuel like an ignition snafu but then I do not think it would fire at all.
Ah, it sputters but never “catches” and “runs” for a second?
I don’t have an overboost switch. What do they do? Shut off fuel pumps or ignition to engine or both? Do they “let go of ground” to switch?
Since you have good fuel supply and control pressures, probably not an overboost switch or a pump issue.
Try “flooding” the engine (caution on amount of fuel fed) by pressing on sensor plate (1-2 second?) - ignition on.
(Sensor plate should have resistance and noise level in the fuel system should change.)
Attempt to start, being ready to add throttle if you sense that’s what’s needed to get it to catch.
If engine continues to sputter, never catches/starts, and you can smell raw fuel in the exhaust pipe, I’d rule out a fueling problem.
If it catches/runs for a second or two, then “shuts off,” the problem is too much air or a spark/timing issue. (Not likely unless you fussed with distributor or coil. Was the RPM input to the DWUR taken from the coil? If so, disconnect, see if engine starts, runs.)
I’m as stumped as you if you can’t get the engine to wake up.
Good luck, let us know where the Gremlin was.
Chris
Old 11-29-2008, 04:14 PM
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Actually it only sputters and tries to continue to run if I hold the key in start (only for a second or two). If I just flick the key like normal it starts strong then immediately dies and no amount of coaxing with the throttle or the metering plate will keep it running at all. The RPM input for the DWUR is taken from a coil induction around one of the spark plug wires. The installation instructions say it does not matter which one.
Old 11-29-2008, 07:26 PM
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Quote:
Originally Posted by darling930 View Post
Actually it only sputters and tries to continue to run if I hold the key in start (only for a second or two). If I just flick the key like normal it starts strong then immediately dies and no amount of coaxing with the throttle or the metering plate will keep it running at all. The RPM input for the DWUR is taken from a coil induction around one of the spark plug wires. . . .
Starts strong with the normal flick, then immediate death - now sounds like a fueling issue. Re-install the stock WUR, attempt start again.
If your DWUR has inductive pickup for RPM, it's a very early version.
Old 11-30-2008, 06:19 AM
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Quote:
Originally Posted by 356-930 View Post
Starts strong with the normal flick, then immediate death - now sounds like a fueling issue. Re-install the stock WUR, attempt start again.
If your DWUR has inductive pickup for RPM, it's a very early version.
I agree with 356,, it sounds to me like your warm up cycle in the DWUR might be off,, the smartest thing is to take a step back and eliminate the DWUR as a possible culprit.
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Old 11-30-2008, 07:58 AM
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My car did the same thing after I foolishly played with the idle mixture enrichment during a period of extended car downtime. It was too lean.
Sounds like your mixture is too lean also.
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Old 11-30-2008, 11:02 AM
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Problem is I do not have a functional stock WUR as I bought the Unwired tools version after the car had "eaten" several WUR's. It gets expensive replacing them on a regular basis. A bit more to the saga: I discovered this morning that one of the O rings on the intercooler had disintegrated. I am thinking Halelulea that must be the leak in the system. After replacing the O ring however the car will start and run sometimes but only with a lot of throttle. It is blowing out a lot of white smoke however will not run if I let off the throttle. I think it is very rich and obviously I had adjusted the mixture to compensate for an unknown air leak. However if I adjust the mixture leaner it will not start at all. I suspect that you guys maybe correct in that the warm up cycle is off however it is still set from the factory settings from unwired tools. They assure me that the warm up cycle is acceptable.
Old 11-30-2008, 11:15 AM
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If I can get it to start and at least run some the plan is to adjust the mixture once the car is warmed up
Old 11-30-2008, 11:16 AM
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Here's what I would do. Change your warm up cycle to richen up the mixture.. If you can't get it started with the key on, push down on the mixture adjust stem and you can here the pumps running, that should prime the system enough to start it..
Also if you may need to pull the power to the WUR and apply 12V to get it to communicate to your laptop for the download as the circuit that powers it up doesn't come on until the pumps are running ( when the car is running or the ignitition switches the car on)..
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Old 11-30-2008, 11:26 AM
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Quote:
Originally Posted by darling930 View Post
. . . I discovered this morning that one of the O rings on the intercooler had disintegrated. . . . After replacing the O ring however the car will start and run sometimes but only with a lot of throttle. It is blowing out a lot of white smoke however will not run if I let off the throttle. I think it is very rich and obviously I had adjusted the mixture to compensate for an unknown air leak. However if I adjust the mixture leaner it will not start at all. . . .
White smoke is either vaporized unburned fuel or oil. If too rich and burning, black smoke.
Smell the "white smoke." does it smell like fuel or oil?
You note, "if I adjust the mixture leaner, it will not start at all." Sure sign the engine is already too lean.
Again, suggest flooding the engine, attempt to start. If it starts,runs then dies, mixture is too lean.
According to my Bosch ref info, WUR CP on yr. 86+ 930's cold is 1.4-1.8 bar (@25C/75F. Warm is 3.75+/- 0.2 bar.
Old 11-30-2008, 01:15 PM
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Thanks for the suggestions. I think the white smoke is unburned fuel. I agree with the CP at the beginning of the warm up cycle (I have a set of curves from the porsche shop manual) and I am reading a pressure of 1.6 bar on the gauge. I believe that you are both correct as I can get it to start by running the fuel pumps manually for a second then cranking it. I am hoping to play with it some after work this week but it maybe a couple of days before I get to try again. Again thanks for the suggestions and I will repost when I get to play some more.
Old 11-30-2008, 06:49 PM
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Quote:
Originally Posted by darling930 View Post
Problem is I do not have a functional stock WUR as I bought the Unwired tools version after the car had "eaten" several WUR's. It gets expensive replacing them on a regular basis. A bit more to the saga: I discovered this morning that one of the O rings on the intercooler had disintegrated. I am thinking Halelulea that must be the leak in the system. After replacing the O ring however the car will start and run sometimes but only with a lot of throttle. It is blowing out a lot of white smoke however will not run if I let off the throttle. I think it is very rich and obviously I had adjusted the mixture to compensate for an unknown air leak. However if I adjust the mixture leaner it will not start at all. I suspect that you guys maybe correct in that the warm up cycle is off however it is still set from the factory settings from unwired tools. They assure me that the warm up cycle is acceptable.
OMG, be careful. I sent mine back for warranty replacement and have not received anything back other than 36 email promises and one bogus UPS tracking number that has yet to be tracked past the front door of Unwired Tools. This has gone on for seven months.

Old 06-05-2012, 01:56 PM
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