'77 S WUR query

[Alan L]

Trying to sort a cold start issue on my friends 77S.
the WUR number is 0438.140.033 (correct WUR for the car).
But the thermo vac plumbing seems opposite to my SC. Just trying to check if this is plumbed right. The Thermo vac is connected to the top port on the WUR body. There is another line from the bottom port, leading to somewhere else.
is this correct?
Where do you buy bits for these? diaphragm and body O- ring.
Thanks
Alan

[Paulporsche]

Setup for US spec cars. Not sure about NZ but it may be helpful.

[kach22i]

Originally Posted by Alan L

Where do you buy bits for these? diaphragm and body O- ring.

Alan, use the search function to get information on the rebuild threads. One firm here in the USA charges around $350 to rebuild if memory serves, they use to advertise in the PCA Panorama magazine.

See the photo in post #12, be warned that I also encounter some starting problems and cannot verify that this is a healthy set-up.
1977 - trace small CIS vacuum line


Here is a modification to control the pressure:
Modified my WUR

I'd like to do this one day.

[Alan L]

Thanks Guys. paulPorsche, is #28 supposed to be the WUR, can't make much sense of that.
kach22i, that pic looks like how this one was hooked up. looks like Thermo valve hose goes to top of WUR and the lower throttle body point provides the vac.
I have made the mod to my SC WUR, as described - for setting Cold Pressure. I will do it to this one if it is off spec. But at the moment I can't get it to hold a vacuum. Just starting on the long trail to see why so hard to start. If I nail something, I'll post it here.
Thanks
Alan

[kach22i]

Originally Posted by Alan L

Just starting on the long trail to see why so hard to start.

After I changed my vac lines everything was out of whack air/fuel ratio wise and I had to re-adjust with a vengeance.

Did the owner of the car recently change a vac line or two? That will do it.

[Alan L]

It has been like this 2-3 yrs - since he bought it. We did a top end rebuild on it about a year ago - mainly to get rid of a heap of oil leaks. At the time we checked the obvious stuff - vacuum lines, CSV, intake runners etc. Found nothing obvious. On first crank after reassembly, believe it or not it fired up first turn. We thought we had unwittingly fixed it. Til we went to start it again.
Alan

[Alan L]

I think I have fixed it - will know better in the morning.
1) the WUR was incapable of holding vacuum- the seal was past use by date.
2) Cold pressure was 0.5 - 0.8 bar too high. Knocked the plug down while watching the pressure gauge. Only get one shot at that. If you overshoot, you go back to modifying it.
Alan

[HenrikL]

Originally Posted by Alan L

1) the WUR was incapable of holding vacuum- the seal was past use by date.

How did you diagnose this? I have a '77 that also behaves strange.

[boyt911sc]

Originally Posted by Alan L

I think I have fixed it - will know better in the morning.
1) the WUR was incapable of holding vacuum- the seal was past use by date.
2) Cold pressure was 0.5 - 0.8 bar too high. Knocked the plug down while watching the pressure gauge. Only get one shot at that. If you overshoot, you go back to modifying it.
Alan

Alan,

Knocking the plug down makes the cold control fuel pressure lower. Your current cold control fuel pressure has to go the opposite direction (higher pressure instead of going down)!!!!! You don't need the TTV (thermotime valve) to start the engine. The TTV comes into action after the engine has started. If the WUR is not holding vacuum it should not matter for cold start-up.

Not until you have pressure tested the system (engine) for air/vacuum leaks you are guessing!!!!! You may get lucky sometime but you cannot relay on LUCK all the time. Before you make any unnecessary tinkering of your WUR, test it without running the engine. This test has been discussed so many times in the forum and it sounded like a broken record.

Tony

[boyt911sc]

Originally Posted by kach22i

Alan, use the search function to get information on the rebuild threads. One firm here in the USA charges around $350 to rebuild if memory serves, they use to advertise in the PCA Panorama magazine.

See the photo in post #12, be warned that I also encounter some starting problems and cannot verify that this is a healthy set-up.
1977 - trace small CIS vacuum line


Here is a modification to control the pressure:
Modified my WUR

I'd like to do this one day.

Kachi,

The picture you have provided showing the vacuum line connections between the throttle body, TTV, and WUR has many discrepancies. Unless you are sure and have corrected these connections, posting this reference picture would only contribute or lead misinformation to people looking for a good reference.

Tony

[Alan L]

OK, I've got it starting well now, first kick.
In summary, the issues were;
Crappy seal on WUR body - vac leak, and not holding thermo valve vac.
Cold pressure too high - warped finger basically, as time does to them. Re set (knocking plug in).
Stiff diaphragm - only getting 0.3 bar instead of 0.7.
Have set pressures to compromise this a bit, since parts will take 2-3 weeks and it is now starting/running beautifully.
he had wired up a switch to the CSV to pump more fuel in on start - was the only way he could start it at cold. Have chucked all that out now, and first turn of key is enough.
Alan

[T77911S]

that diagram paul posted looks ike it is from an earlier car. the 77 does not have all that fuel enrichment crap on the side of the TB, plus there is no TTV.

the bottom port on the WUR is to atsmosphere.

the top port is vacuum.

the TTV is not needed but is nice to have if it works. it lowers the CCP for better starting.

[Alan L]

Just for clarification, in case it helps, yes the TTV helps starting enrichmnet. But the opposite way. When the TTV opens it allows vac to the WUR, which bumps the Control pressure up - ie leans it off. This is the normal operating position for the WUR and TTV - ie TTV leaned out.
For starting, effectively the TTV is disabled - allowing a 0.7 bar Control pressure drop.
Part of the problem with my friends WUR is that it only has half the normal TTV range. So the setting of the CP is a bit of a compromise. A new diaphragm would probably fix that - his is quite stiff - little flex.
The car has been like this since he bought it. I feel a bit bad now, I should have looked at it ages ago for him. We took the time to rebuild the top end (and check for leaks/hoses etc) since it was leaking so much oil, but I never had a chance to find the time to start on this one. It has made all the difference. He could have been running it like this for the last few years. :-(
I have seen quite a few postings on troublesome starting on the 77s. Apart from the fact they seem to have a complex plumbing system, it is possible many suffer from the ageing WUR issues this one had.
Alan

[kach22i]

Originally Posted by Alan L

...., it is possible many suffer from the ageing WUR issues this one had.
Alan

Alan, where did you source the replacement parts so quickly from?

[Alan L]

I didn't get any parts. Part s are an issue here, and I don't really want his car in my shed for 2-3 weeks (he has my SC). I had his engine in my w/shop for about 2 months once, and that was enough. Can't do any other jobs.
The WUR body gasket I managed to replace with an O ring I found in my 'don't throw this away bin'. From memory it belonged to a Honda motor bike I rebult about 20 yrs ago, but it could hardly have sized better. The length was pefect to the mm, the diameter, in a perfect world would have been 3 mm instead of 2.8.
Ideally the diaphragm should be replaced, and if he wants to track one down, we can do so and spend an hour fitting it, now we know where we are going. But since I didn't have one I have set the Cold pressures vac/no vac compromising the 0.4 bar range I am missing, ie the no vac CP is marginally higher than it should be, because when the TTV opens it only raises 0.3 bar and takes us into the warm up curve specs. I have set us at the low range of these specs to compensate. The car starts fine - 200% better than before, so whether he wants to order one, I don't know. he is coming to collect car tonight.
regards
Alan

[kach22i]

Cool, thank you for the reply.