need opinion on pressures

niner11 · 05-23-2004, 05:51 PM

Well, got an 82sc with CIS and have been fighting a hard warm start problem for a little while. First replaced the fuel accumulator then the fuel check valve with no improvement. Now, obviously I should have bought the CIS gauges first but I'm a little slow.

Put the new gauges on the car and measured some pressures both hot and cold.
system pressure: 68psi
control pressure: 50psi cold
50psi warm
Residual pressure: @10mins 25psi
:@ 20mins 23psi
WUR gets 12v as soon as engine starts
Fuel pump operates while cranking motor

The odd thing is that I have a warm start problem but its my cold pressures that are off. They are 50 and should probably be in the 30's to low 40's. The car always starts but when its hot and has been sitting for a while is when I have the prob. Any advice would be appreciated.

yelcab1 · 05-23-2004, 07:53 PM

It is not odd, it is right.

Your cold control pressure is too high, making the CIS system run too lean while warming up, that is why you have the problem. I know this, because I have the same issue that I just fixed. Your WUR is bad (mine too). $400 for a new one, or adjust the cold pressure by knocking in the pin on the WUR with a couple of taps of a hammer. Then, adjust your CO to be within spec, and your problem will go away.

niner11 · 05-23-2004, 08:03 PM

Thanks for the reply. Ok, I agree that the cold pressures are too high making the car run too lean on start up but looking at the chart in the bently book, the warm pressures are right on the money. When the car is cold it starts and runs fine

vash · vash's Garage

i always do it in this order:
cold control press (car cold)
flip valve closed and not system press
start car note warm press
and then shut off car, and not at rest press.

i think all you need is a good pin knocking session.

vash · vash's Garage

damn, you sure it isnt ignition related? my old spark plug wires would crap out when warm. your pressures are not bad, except the cold press.

my book says the other causes are loss of at rest press.
mis adjusted air sensor plate, sticky plunger in FD, leaky injectors, leaking CSV, and incorrect control pressure.

niner11 · 05-24-2004, 06:18 AM

Residual pressures seem ok but I guess anything is possible. When the car finally starts hot it almost seems like its flooded. Not sure but its unlikely that more than one injector would be leaking.
If I jumper the fuel pump so that it comes on with the ignition the car will start right up. I suppose that is the same thing as lifting the air sensor plate for a few seconds. Any more ideas?

yelcab1 · 05-24-2004, 06:31 AM

I suggest knocking the pin in to achieve the correct cold pressure, then start from there.

niner11 · 05-31-2004, 07:00 PM

still working on this same problem from the begining of the thread.
Not going to mess with the dowel pin on the WUR yet since the warm pressures are on the money and I have a warm start problem.
Lifting the sensor plate causes the car to start as if it has no warm start problem. To me this indicates that residual pressure is low but the gauges say it is not. Am I missing something here? I thought that possibly the cold start valve or an injector was leaking but if the car starts hot with the fuel pump jumpered then it is not flooded. looking for more ideas before I take apart the WUR. Car runs perfect when cold and hot, just prob with warm start. Thanks

niner11 · 06-03-2004, 10:46 AM

bump?

yelcab1 · 06-03-2004, 11:36 AM

niner11,

I see your line of reasonsing for not believing the cold pressure to be the issue. But, ... it seems you are out of options. In my very humble, but very recently proven correct, opinion, it is your cold control pressure that is screwing up your warm start.

1. Replace your WUR, or
2. make it adjsutable for cold control pressure, and adjust it to the right place.

Then adjust your idle mix, your idle speed and enjoy.

I will stop my pontification now. Good luck.

MotoSook · 06-03-2004, 12:04 PM

Does the car start easily in the morning?

Sounds like the cold pressure may not have been taken when the car is totally cold.

And if it's a very warm day, the cold pressure should be higher, follow the chart.

The car has a hot start problem. 50 psig control pressure (or even the 50 psig cold pressure) should not cause that. I've been able to start my car with higher control pressures than that, cold!

When the car is hot, the cold start system should not be a factor.

I wonder if the idle mixture is just not right. When you get it started, does it run w/o problems? Does your oil temperature climb higher than usual?

Have you done anything to the car prior to this or after this, other than take pressures?

niner11 · 06-03-2004, 05:25 PM

Thanks for the replies. The car runs great after it is started and the oil temp is a bit warmer than I would like. Nothing higher than 230F. The motor has recently been rebuilt (1800miles ago) so I could have several things going on.
Souk, car starts with about 1second of cranking regardless of ambient temp. Are you thinking that the oil temp could be related to a lean condition?

yelcab1 · 06-03-2004, 07:11 PM

For me, there are 3 phases WUR temperature:

1. Stone cold, in the morning, 65 degrees in Cal.
2. Burn my hands hot, after the car has been running for 30 minutes.
3. and Warm, when the hot car has been sitting there cooling down for about 30 minutes or an hour.

Cold control pressure is at its lowest (25psi) when stone cold,
Hot control pressure is at 55 psi when hot hot.
And, warm control pressure is anywhere between 25psi and 55psi when warm. If it is always 55psi when warm, the car starts but runs lean, has a hard time trying to idle, and wants to die unless you keep your foot in the gas and feather it. By feathering the gas, you are correcting the lean problem by giving it gas.

Your WUR is bad, either replace it or adjust it. Then adjust your mixture and idle speed. Anything you do now may just cover up the symptoms of a bad WUR, which you already know to be bad.

niner11 · 08-20-2004, 12:38 PM

Researched how to make my WUR adjustable and then put my cis gauges on the car to take some readings. For grins I replaced the vac line going to the WUR even though it looked fine. Earlier in this thread I had the same control pressures both hot and cold so I was getting ready to knock the pin in a little and lower my cold pressure (in order to make the car run richer when cold-I think). Well, once the vac line was changed the cold pressures went from 50 to 25. Pretty close to where my 82 should be. Car starts and drives fine now.

Anyway, for the archives I would suggest changing the vac line on the WUR before making any changes to the WUR itself. Obviously visually inspecting vacuum lines doesnt work. YMMV, Chuck