Help Diagnosing CIS

[KMoore68]

Hi,

I am attempting to fix a cold-start issue and was hoping for assistance interpreting the results of my CIS pressure test.

I ran the test today and it was 18C outside, I wasn't able to measure the temperature of the WUR however it has been sitting in an enclosed insulated garage for a number of days.

The WUR is 0438140-033 and the engine is a 1977 2.7 with approx 188k miles on it.

The test results are:

System pressure : 5.5 bar
Cold Control pressure : 1.4 bar
Warm Conrol pressure : 3 bar at 5 minutes

[SkiVT]

- your system pressure looks high as should be around 5.0

- can you describe the cold start behavior you are trying to solve?

- can you add a picture of your vacuum hoses attached to the wur back to throttle body?

- knowing the air temperature inside the garage when you run the cold pressure test would help more accurately assess your result. My garage is 71 this morning and the outside air is 64, for example.

Have a read of this thread as well;

Confused : Double Vacuum on WUR 77 2.7 Weird Warm Control Pressure at Idle

[KMoore68]

The cold start issue is that the car seems to take a bit of cranking before it fires and then some blue smoke and a rough idle until the car warms up.

Here is a pic of the WUR that I can get, i'm not sure how else to get it as the view seems blocked.

Does the high system pressure mean my WUR needs to be rebuilt/new?

[SkiVT]

System pressure is controlled by the fuel distributor. There are some shims in a pressure valve that can raise/lower it. To better assess the wur, you really need to know the air temp inside your garage. The spec for the 033 looks very close assuming your ccp/wcp readings were done without vacuum and the air temp was around 21c in the garage. The insulated garage should have been warmer than the outside 18c.

To follow the vacuum hose off the top of the wur, you would need to remove the large heater hose. I believe the throttle vacuum is held off at start up when connected correctly to allow for a richer mixture. If incorrectly connected it could impact your cold start.

Have you verified you have now unmetered air? This is also a common problem.

There are three videos on the YouTube channel below you may want to watch as the mechanic explains most issues and it’s your engine, wur, etc

https://youtu.be/Ii5k773lwKs

[KMoore68]

Thanks for the tips, i'll investigate the vacuum hose and also watch the videos!

[SkiVT]

The one labeled with “diagnose” has a section on system pressure around the 21:30 mark

[Showdown]

These should help. The first pic is from the workshop manuals for 1976/1977. The second pic is the same graph but WITHOUT vacuum applied to the WUR. If you have a vacuum pump you can disregard the second pic but if not then you’ll want to reference the range outlined in black.

[David Inc.]

Originally Posted by SkiVT

- your system pressure looks high as should be around 5.0

- can you describe the cold start behavior you are trying to solve?

- can you add a picture of your vacuum hoses attached to the wur back to throttle body?

- knowing the air temperature inside the garage when you run the cold pressure test would help more accurately assess your result. My garage is 71 this morning and the outside air is 64, for example.

Have a read of this thread as well;

Confused : Double Vacuum on WUR 77 2.7 Weird Warm Control Pressure at Idle

I just recently found this video series and I have to say they do an excellent job explaining everything. They've been releasing videos fairly steadily, as well, so definitely a channel to subscribe to.