TomEberlin

We are getting an ohm reading of 10.5 to 11 ohms on the WUR on my 81 911 SC. It makes no difference if the WUR is connected electrically or not. The car starts fine cold and starts fine warm. It however is not running like it should.

theiceman

resistance is measured disconnected as you are checking the resistance of the element, not the circuit. Although im not sure off the top of my head what it should be.

Sounds like you may need some cis gauges and go over the whole thing. What do you mean by not running right ?

TomEberlin

The reason I posted the question is because everything I read said the resistance should be between 15 and maybe up to 25? Obviously 11 ohms means it is not shorted out or open but there isn't much left to cause the erratic running of the car? I will get you the numbers from the CIS testing which according to the manual we have, and what we can find from Pelican Parts and others is in range? We do have an MSD ignition in it and have considered that may be a problem? When revving the car it will completely cut out at about 3500 RPM's even though the pill we have in it is for 6000 rpm. Yes we have tried different pills. If the car is warm and won't start I can take auxiliary air box cover off turn the key on push the plate up to force the injectors to pump fuel and it will start? It won't run great after but it will at least then start.

theiceman

okay I will keep an eye on the Pelican forum as I saw you posted there. pointless posting in both places. Tony over there knows CIS very very well.

if the car does not perform at operating temp I would think you can take the wur out of the equation. I have all my numbers somewhere when I baselines my CIS. I have a 78 so may be slightly different.

Hot start issues could be the accumulator ( not holding fuel pressure) as the accumulators job is to hold fuel pressure as you have no cold start enrichment when the car is warm. My first thing I would assume is that its not your MSD as you have proven its a fueling issue by lifting the plate, unless you have two issues.

What is the history of the engine ? new build ? sudden on set issue ?

also remember you need 1mm lift on the airplate when its at rest ( I think its 1mm but youd better double check )

cutting out may be fuel volume issue so you need to check fuel pump and check valve and filter obviously.

I think the CIS gauges are going to tell you a lot about where you are sitting.

TomEberlin

We took the WUR apart last night and found the one wire had all of it's insulation melted off. I replaced the fuel pump and fuel filter already. I have good pressure which sorry I am at work and don't have the numbers on me. That was the first thing we did was buy a pressure tester so we wouldn't be just throwing parts at it. We also replaced the injectors with new ones and new seals. The fuel volume was also tested. The insulation concerns us as to why it melted off? We are thinking maybe just age? I ordered a new WUR it will be here Monday or maybe hopefully Saturday. I do really appreciate your help. It's kind of like the old Rennlist from years ago when we belonged to it.

theiceman

Tom What year is the car ? what engine is it ? I know there are differences in WUR based on year / engine.

I don't know where you are from but I actually have a spare WUR somewhere.
The reason I am thinking it is not the WUR is because the heating ellent is to help it warm up . I am pretty sure with it being bolted to the runner it will get hot on its own eventually anyway and reflect the right reading. But you never know. if I find my wur I will record the resistance and post it here.

remember you are looking at different pressures with CIS .
There is system pressure ( put out by the pump )
Control pressure ( provided by the WUR )
residual pressure ( what is maintained after system shut down. )

I hope these are all in spec. I cant imagine a WUR is cheap by any stretch of the imagination.

TomEberlin

It's an 81 SC Targa. It uses the same WUR as the 82 or 83. I can't tell you if it was ever changed before and that is why it matches the 82 or 83 model Targa? I am in Pennsylvania 30 miles North of Williamsport in the middle of the mountains. Great place to own a Porsche. We have a couple of 914's and this 911 and buzzing on the mountain roads is pure joy. All the pressures measured good according to the manual we have and what we found on line. The only reason we thought maybe the WUR was bad is because of the resistance reading being that low? Now that we can see the insulation melted it obviously does have a problem.

TomEberlin

$275.00 for a used one in working condition with a 30 day guarantee. I talked to the people who are selling them and they seemed legit.

TomEberlin

Got the WUR today in the mail. The car runs like a new one. Thanks for your help it is greatly appreciated.

theiceman

What was the resistance of the new one ?

TomEberlin

7.5 ohms. The numbers I found on the internet make no sense at all. The numbers are supposed to be between 15 and 25? I am using a $600.00 Fluke so I am pretty sure of the accuracy. The car starts without touching the gas and levels out to a very smooth idle in just a minute or so. I am getting it inspected today so I will give it a nice run on Wednesday to warm it up real good. We did run it until the engine was warm and it started right off.

theiceman

Personally I think the resistance of the WUR element has little to do with its performance, but that is just my opinion. all it is is a heating element .

Really glad you got her sorted.

I just rebuilt my whole engine and I am having some trouble starting and running cold so I have a few things to check ( cold start valve, thermo timer , WUR ) .

I took the CIS off and put it in the corner and then put it back after the rebuild without touching it so I am hoping it is just a little varnish from the old gas that will clear out in time. the CIS ran flawlessly before the rebuild.

TomEberlin

It must have some significant importance, the heating element I mean because the old one after further inspection has a crack where the lead connects into the top of the element which would not let it warm up properly. We did a valve job about 6 years ago, replaced the clutch and flywheel while we had it apart. We did the same just pulled the CIS and sat it off to the side. We did upgrade to an MDS ignition at the same time. Put it back together and it ran flawlessly. Considering neither my son or myself are trained Porsche mechanics we feel pretty good about the CIS fix. I read in some of the European threads about the WUR and it is only called that here in North America? I think the Germans call it a fuel pressure regulator? I do have a degree in electronics so that helps in measuring and looking at things that are technical in nature. My son is just a natural born mechanic and he loves a challenge. When all the BAR readings were in tolerance and the gas volume was correct everything pointed to the WUR. I was 99.9 percent sure that is where my problem was and when we disassembled it and saw the melted insulation I was 100 percent sure. Next is run it for a while and then a valve job.

theiceman

I sure hope you mean a valve adjustment

TomEberlin

Right. lol The last one was expensive enough. I thing I only put maybe 100 to 200 miles on it since then.