Doug_B_928

Good idea. There are two outlets. So, should I plug one and pump air into the other one, or leave the second one with the line attached to it?

LT Texan

The one on top is to atmosphere. The bottom side one is for vacuum.

Doug_B_928

When I was playing with it the other day, the one on top was making a slight difference to the hunting idle during warm up. If it's venting to atmosphere in the TB does that observation tell us anything?

LT Texan

I wouldn't think so. The hose connects before the throttle plate.

Maybe it means the gasket in the WUR for the vacuum enrichment is shot?

Doug_B_928

I put 10psi on both ports of the WUR and they both held vacuum. Then I plugged the WUR ports and the lines going to the TB. The car started fine. So I guess the improved starting wasn't via sucking additional air through the vacuum line. I have to wait a few days between tests to replicate the cold start symptoms. The next one will be with the WUR ports open and the lines to the TB closed, just to see if that makes a difference.

Guy

Doug,

As you know, the WUR vacuum is an enrichment circuit. When car is at WOT, the vacuum decreases which lowers control pressure and richens the mixture in doing so.

The vacuum causes the fuel pressure to increase at idle. Your car running and starting better without the enrichment circuit sounds to me to be indicative of the car running too lean. The vac leans it out even further making starting difficult.

Even with this condition, there are other reasons why your car could have a rich smelling exhaust (rings, valve seals etc).

Double check your pressures, make the checks with vac connected and car running. If within spec, I would start to look towards enriching your mixture slightly. You don't want to eliminate the WUR vacuum, you would lean out too much under heavy throttle.

I have mine 98% correct, I am logging miles before a final tweak, I have learned first hand how sensitive these adjustments are.

Doug_B_928

Great explanation, thanks Guy. I'll do the check you suggest and report back.

checkmate1996

Amen to that!

Doug_B_928

It seems that having the test gauge attached is lucky. I've tried every combination (with vacuum attached, detached, etc.) and it always starts great with the gauge attached. I didn't have time to re-do the cold control pressure etc., but will check that tomorrow night.Here's a video of a cold start with the gauge attached.

checkmate1996

Doug,

I'm a bit concerned...here's why. If you have a 'cold' engine, and you have hooked up the CIS gauges, bled the lines, check system pressure real quick prior to starting your engine, it should read somewhere between 1 & 2 bar (depending on temp) right off the bat PRIOR to you starting the engine - NOT ZERO!!. Also, your next step is to make sure the WUR has 12v/plugged in and wait 5 minutes to see if rises to 3.4 ,....

Doug_B_928

Hey Brad,

I didn't check the other pressures because I wanted to see what happens from a normal cold start when the car has been sitting for several days (with zero pressure in the system). I have tested for power to the WUR in the past and it is getting power. I've done all the pressure tests in the past and the only one that is a bit out of spec is a slightly low cold control pressure.

checkmate1996

Doug,

Let's clarify a few things to make sure we are on the same page:
Cold Start Pressure = Refers to checking fuel pressure when Engine temp is below 37 degrees C IIRC (I'm really going off memory here)
System Pressure - refers to pressure when fuel pump and/or engine is engaged/turned over
Warm Pressure - After five minutes of the WUR being plugged in, the engine and the bi-metallic strip heat up to adjust cold pressure richness to lean it out.

That being said, even if you hook the CIS gauges right off the bat with out checking system etc, it SHOULD READ between 1 & 2 bar depending on temp. IT SHOULD NOT START AT ZERO BAR.

Also, have you created a switch that you can connect to your fuel pump relay to do all of your tests? this is a must ... this enables you to continually check cold start without turning the engine over...

Doug_B_928

I'm typing on my phone, so apologies for any mistakes. We are on the same page, but I refer to cold control as being measured when the engine is really cold from having not been run for at least a day.

I have a switch for the fuel pump. Didn't use it in the test in the video because I wanted to see what actually happens when starting the car normally.

If there is pressure in the system after more than one day of not running, and with the key in the off position (BTW my fuel pump does not start running even when the key is turned to the first position) wouldn't there be a lot of fuel spilled when connecting the gauges? Or, for example, when changing the fuel lines in the engine compartment?

checkmate1996

Doug you technically don't have to wait a day (in reality you just need to wait long enough for the bi-metallic strip to cool down. 3-5 hours if run hard, less if you just started and shut it off). You have a temp switch that gauges engine 'coldness'. This is what's kick's off the cold start valve to add extra fuel upon cold start up.

Most likely, your system rest pressure after one day will be close to zero if not zero. You shouldn't too much with a lot of fuel pouring out of the wur when you disconnect it to hook up CIS gauge. To that end, even if you do have pressure in the system, there are safe ways to reduce some of the pressure. One is to open the gas tank lid. Second, take a vacuum pump and place on top of the WUR and force pressure back into the system. You will get some fuel leakage, just have a towel handy if not wrapped around the wur to catch any fuel. Always have fire extinguisher handy when working with fuel...

Doug_B_928

Good info, Brad, thanks. Yeah, I was leaving it that long because I'm trying to replicate the symptoms I'm experiencing. If the car has been started on a given day, usually it will start fine again that day. Makes me think that the problem has something to do with fuel pressure because the problem appears when it's starting from a zero pressure state. When I watch the gauge in the video I notice that it comes up slowly over the first 10-12 seconds. In the video I took of the tach when it's actually exhibiting the symptoms, the problem occurs during this period (see here: ). I was hoping to see a rough start with the gauge on to see if the needle on the psi gauge behaved the same as it does when the car starts well, but no joy. But, given that needle seems to come up slowly and, as the video shows, the car starts fine, I guess that indicates that perhaps the problem is not pressure related. Since I've done starts with various combinations of the vacuum hoses on/off, and electrical connections to WUR and AAV on and off, as ridiculous as it sounds, it seems like having the gauge on solves the problem. Makes no sense to me but the result is consistent.