HELP! 2.7L runs only when gas poured in.

[mark944T]

Novice here.

I have a 1974 911 that has been sitting for a number of years. Cleaned fuel tank and lines but it will only run when I pour some gas in the Throttle Body and stop after several seconds when the gas runs out. Let me say I know nothing about these systems.

It is getting gas to the Fuel Distributer and gas is going to the part in the picture below. Im guessing that is the Cold Start Valve? (I have a service manual but the picture is different) The line going into it is from the center of the Fuel Distributer and gas comes out of that. The arrow in the photo points to a line that looks like it is going back to the Throttle Body. When I pull that line it is dry. Any help is greatly appreciated!

[Walter_Middie]

Mark,

The part you are looking at is called the Warm Up Regulator (WUR). This in not a good name, as this device regulates fuel pressure at all times (not just during warm up). There are threads on how to take apart and even to modify it so that you can adjust the pressure yourself. These are pretty easy to remove from the car and take apart - not much to them.

Modified my WUR

[mark944T]

Originally Posted by Walter_Middie

Mark,

The part you are looking at is called the Warm Up Regulator (WUR). This in not a good name, as this device regulates fuel pressure at all times (not just during warm up). There are threads on how to take apart and even to modify it so that you can adjust the pressure yourself. These are pretty easy to remove from the car and take apart - not much to them.

Modified my WUR

So you think that’s the problem since the line I’m pointing to is dry?

[gomezoneill]

Originally Posted by mark944T

So you think that’s the problem since the line I’m pointing to is dry?

WOW, a guy that admits he knows nothing questions a guy who knows a lot!

[Walter_Middie]

I wasn't suggesting that you need to modify your WUR - I was just pointing to a good thread with pictures - such as this one:



If you're getting fuel into the WUR and not out, there must be something hanging up in there - or you're not developing enough fuel pressure to operate the WUR. You may need to get some pressure testing tools - I'd still pull the WUR and see if it looks OK inside it.

[mark944T]

Originally Posted by gomezoneill

WOW, a guy that admits he knows nothing questions a guy who knows a lot!

Ok, it’s my WUR in the picture but I asked if the one line that is dry is an indication of it being at fault for not drawing fuel. His link is to modify a WUR. Can it be rebuilt? How do I know if it is at fault? Do I test the connection? I need more info if possible. I just want to get the car running and not start modifying things.

[mark944T]

Originally Posted by Walter_Middie

I wasn't suggesting that you need to modify your WUR - I was just pointing to a good thread with pictures - such as this one:



If you're getting fuel into the WUR and not out, there must be something hanging up in there - or you're not developing enough fuel pressure to operate the WUR. You may need to get some pressure testing tools - I'd still pull the WUR and see if it looks OK inside it.

Thanks. I guess I’ll look for something. I’m an old school V8 guy. Porsche stuff new to me. No Holley there.

[Walter_Middie]

I just want to get the car running and not start modifying things.

Patience. Take the time to get it right, and it will run great for years.

[nomore]

Mark, good job on getting a 74. I have one also that was only a little better running than yours 2years ago. I just got back from a 100 mile loop. You can get it to run properly with patience and reading; starting with the "CIS for dummies" thread. CIS is basically a system of parts that have
to work together to perform well. The 74 is the most "basic" fuel injection system with the least amount of components. Start by identifying all the components and their function. CIS sitting is the worst thing. some thing is most likely gummed up. Lots of good info on this forum to help you.
I too am a carb guy, surprised you got the car to do anything dumping fuel in throttle body.

[mark944T]

Everything looks ok inside. Is there a test for the wiring?

[mark944T]

Originally Posted by mark944T

Everything looks ok inside. Is there a test for the wiring?

[Walter_Middie]

Is there a test for the wiring?

18 to 22 ohms resistance between the contacts. Also, make sure there is 12 volts all the time to the WUR.

[mark944T]

Originally Posted by Walter_Middie

18 to 22 ohms resistance between the contacts. Also, make sure there is 12 volts all the time to the WUR.

Getting 36 ohms between contacts in WUR.

[Walter_Middie]

If the WUR looks OK, and you don't have a fuel pressure tester, I'd also check the fuel pump delivery. It should be at least 850 cc in 30 seconds. This can be tested from the output of the fuel pump, output of the fuel filter, and the return line to the tank.

You may be able to borrow a fuel pressure tester from a local auto parts store.

[Walter_Middie]

Getting 36 ohms between contacts in WUR.

Mine was as high as 30 ohms - yours may be tired, but it was not an open contact. It should still work.

[mark944T]

Originally Posted by Walter_Middie

Mine was as high as 30 ohms - yours may be tired, but it was not an open contact. It should still work.

Ok I’ll need to check fuel pressure. Might take a few days.

[al lkosmal]

I'm not a CIS expert, but I believe that the hose you have the yellow arrow pointing to is the vacuum hose and should be dry. The fuel lines are the other two in the pic.



https://jimsbasementworkshop.com/CIS/CIShome.html

regards,
al

[nomore]

Can you blow compressed air through the WUR ports.

[mark944T]

Originally Posted by al lkosmal

I'm not a CIS expert, but I believe that the hose you have the yellow arrow pointing to is the vacuum hose and should be dry. The fuel lines are the other two in the pic.



https://jimsbasementworkshop.com/CIS/CIShome.html

regards,
al

The line you point to had fuel in it. The small one with the hose clamp appears to go to the return fuel line. The one with the yellow arrow could be a vacuum line since there was no clamp on it.
I could be attacking this all wrong.

[fanaudical]

I'll confirm that - Line with yellow arrow is vacuum and should be dry.

Here's a link to help with CIS troubleshooting:

https://jimsbasementworkshop.com/CIS/