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-   -   85 Euro 930 turbo problem (http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/987261-85-euro-930-turbo-problem.html)

solarispete 02-11-2018 07:46 AM

85 Euro 930 turbo problem
 
Hi all,
I am having problems with my 1985 Euro 930 wondering if anyone can help.

The car seems to run ok when cold, when warmed up, when the turbo comes on, it hesitates and literally lags, almost cut out... It doesn't stall the car. I noticed when this happens, car idles higher than usual (around 1300 rpm). Sometimes, if I turn off the engine, wait a few minutes and start it up again, seems to run ok for a while.

Finally took it to my local Porsche mechanic. He suspected the WUR and sent to some shop in California to have it rebuilt... They told me the "diaphragm" was bad... Anyway, he put the rebuilt unit on and he tested it was good and then it went bad again. He's still diagnosing but can't seem to find the issue... Loss of fuel pressure when turbo is engaged. So far, he checked and replaced the following but still doesn't help...
1) vaccum lines (found no leaks)
2) replaced the two red fuel relays in front fuse box
3) replaced the black enrichment relay in the back fuse box
4) the fuel pumps were replaced about 6 years ago so there should be ok
5) replaced fuel accumulator

still runs poorly... if anything it's worse... he says sometimes he has problems starting... running too rich?

Any advice?

One thing he keeps insisting is that I am not using the right fuel. I use the Chevron 91 high Octane, which says that there could be 10% ethanol. He wants me to use Chevron 94 which does not contain ethanol. For one, it's $1.70/L in Canada and not all stations carry it. He insists that the ethanol is bad for classic Porsches. Any thoughts on this? I have friends who have 86 911 Carreras and Octane with ethanol caused no problems. BUT my mechanic believes the 96 Carreras have different fuel systems than the 930, so I don't know. Thoughts?

h20cooled7 02-22-2018 05:17 PM

I had a shorted cold start injector on my 80, gave me fits. engine was running on 7 injectors really.
repaired wires and adjusted mixture and ran fine. I run ethonal fuel and I don't have issues , but I don't let it sit to long either. Mya want to check advance on dist also. Good Luck

RarlyL8 02-22-2018 06:06 PM

How much boost are you running?
WUR diaphragm is good to 1.0bar, any more and it may rupture. Where did you have the WUR rebuilt? Not many out there doing this correctly or with the OEM parts anymore.
There are a few things that can cause the symptoms you describe.
First is an air/boost leak. Double check everything from the turbo outlet to the throttle body.
Verify fuel pumps both are functioning 100% at 12V minimum when running.
Verify cold, warm, and system fuel pressures. How is loss of fuel pressure being determined under boost?

Speedy Squirrel 02-22-2018 07:30 PM

“Anyway, he put the rebuilt unit on and he tested it was good and then it went bad again.” Was it fixed again? This does sound a lot like the fuel enrichment diaphragm.

Alan L 02-22-2018 07:53 PM

Yes I am at a loss to as to how to diagnose loss of fuel pressure under boost - unless a gauge is specifically set up for road test.
It really seems like a massive fuel dump on boost - or an air leak - or both.
The best way to test air leak is pressurise the system and find where it is leaking from - you may be surprised. What does the WP drop to on boost? You can test this in the w/shop. Presumably he has if he is checking the WUR out.
Alan

flightlead404 02-23-2018 02:59 AM

Quote:

Originally Posted by solarispete (Post 9922501)
Hi all,
I am having problems with my 1985 Euro 930 wondering if anyone can help.

The car seems to run ok when cold, when warmed up, when the turbo comes on, it hesitates and literally lags, almost cut out... It doesn't stall the car. I noticed when this happens, car idles higher than usual (around 1300 rpm). Sometimes, if I turn off the engine, wait a few minutes and start it up again, seems to run ok for a while.

Finally took it to my local Porsche mechanic. He suspected the WUR and sent to some shop in California to have it rebuilt... They told me the "diaphragm" was bad... Anyway, he put the rebuilt unit on and he tested it was good and then it went bad again. He's still diagnosing but can't seem to find the issue... Loss of fuel pressure when turbo is engaged. So far, he checked and replaced the following but still doesn't help...
1) vaccum lines (found no leaks)
2) replaced the two red fuel relays in front fuse box
3) replaced the black enrichment relay in the back fuse box
4) the fuel pumps were replaced about 6 years ago so there should be ok
5) replaced fuel accumulator

still runs poorly... if anything it's worse... he says sometimes he has problems starting... running too rich?

Any advice?

One thing he keeps insisting is that I am not using the right fuel. I use the Chevron 91 high Octane, which says that there could be 10% ethanol. He wants me to use Chevron 94 which does not contain ethanol. For one, it's $1.70/L in Canada and not all stations carry it. He insists that the ethanol is bad for classic Porsches. Any thoughts on this? I have friends who have 86 911 Carreras and Octane with ethanol caused no problems. BUT my mechanic believes the 96 Carreras have different fuel systems than the 930, so I don't know. Thoughts?

My first thought is your mechanic is randomly replacing parts trying to diagnose the problem by throwing darts at it rather than taking a considered methodical approach.

Second, I have experienced the same behaviour and it was due to a bad seal between the boost pipe and the intercooler.

Do you have a wideband? Do you actually know what is happening with your AFR? Are you going lean or pig rich?

flightlead404 02-23-2018 03:02 AM

Quote:

Originally Posted by Alan L (Post 9937648)
Yes I am at a loss to as to how to diagnose loss of fuel pressure under boost - unless a gauge is specifically set up for road test.
It really seems like a massive fuel dump on boost - or an air leak - or both.
The best way to test air leak is pressurise the system and find where it is leaking from - you may be surprised. What does the WP drop to on boost? You can test this in the w/shop. Presumably he has if he is checking the WUR out.
Alan

I concur. I don't see what mechanism could cause a sudden and significant drop in fuel pressure at boost onset.

And are you talking about system pressure or control pressure?

How was the "drop in fuel pressure" diagnosed? What actual instrumentation was used? Or is the mechanic just guessing?

Alan L 02-23-2018 09:45 AM

I agree - it seems like a bit of a random approach. You can tell/check whether the fuel relays are working etc. We are missing a lot of useful information to make a considered attempt at identifying the issue. The WUR would be one suspect and he seems to have checked that? But it would be useful to have the numbers that he must have checked, rather than 'OK'. Did he do a boost dump WP test? I am wondering if that is what he is referring to with 'loss of fuel pressure on boost'. This can be rectified if the issue - but we need to know what the data is. Has he hooked an AFR gauge in - that would tell us/him a lot. You say it is leak free. Maybe, maybe not.
The number of people who have posted here saying they don't think they have any leaks, then.........
It may even be an IC seal lifting on boost, and 'sealing' when not on boost. The way I check these for sure, is to pressurise the whole system, from the intake elbow by the airplate. To 5 psi. You will be surprised where the air finds its way out.
We really need some solid info to follow a solid track to isolate the issue. There are a multitude of places to throw darts at. It has all been done before. Just need a systematic approach where we can confidently eliminate possibilities.
Regards
Alan

flightlead404 02-24-2018 08:02 AM

Quote:

Originally Posted by Alan L (Post 9938281)
I agree - it seems like a bit of a random approach. You can tell/check whether the fuel relays are working etc. We are missing a lot of useful information to make a considered attempt at identifying the issue. The WUR would be one suspect and he seems to have checked that? But it would be useful to have the numbers that he must have checked, rather than 'OK'. Did he do a boost dump WP test? I am wondering if that is what he is referring to with 'loss of fuel pressure on boost'. This can be rectified if the issue - but we need to know what the data is. Has he hooked an AFR gauge in - that would tell us/him a lot. You say it is leak free. Maybe, maybe not.
The number of people who have posted here saying they don't think they have any leaks, then.........
It may even be an IC seal lifting on boost, and 'sealing' when not on boost. The way I check these for sure, is to pressurise the whole system, from the intake elbow by the airplate. To 5 psi. You will be surprised where the air finds its way out.
We really need some solid info to follow a solid track to isolate the issue. There are a multitude of places to throw darts at. It has all been done before. Just need a systematic approach where we can confidently eliminate possibilities.
Regards
Alan

I concur. Based on what I see here I don't think the "mechanic" knows anything about these cars. Were the basic CIS fuel pressure checks done? Fuel delivery rate tested?

When boost comes on with a US 1986 turbo WUR the control pressure is supposed to drop ~0.85bar, idk if the WUR in the 85 Euro does the same but I expect so. A drop in control pressure richens mixture, I wonder if that is what the mechanic is seeing that makes him think there is a loss of fuel pressure on boost.


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