924Board.org

[AznDrgn]

This is a continuation of my previous problem but I've decided to start a new thread that wasn't so cluttered. If you need background on the problem here's the link, http://www.924board.org/viewtopic.php?t=8479

Right now the car starts up very easily and runs fine for about 30 seconds. If I give it any gas and hold at a a faster speed than idle it'll rev up hold there and then slow down and start sputtering and die. If I let it sit at idle it'll eventually do that as well. Now I suspected the control pressure regulator so I got the gauges and hooked them up. Yesterday morning it seemed fine, system pressure was 70psi (valve closed) and control pressure was ~30psi (valve open), I tried 3 WUR's all of which functioned the same and one was a definate known good one. Yesterday afternoon I ran the same test again since I found that I had mixed up two of my wires (thermo time switch and WUR power) I switched them back and now I have no change in pressure, I just show system pressure all the time no matter if the valve is open or closed. It was doing the same thing before I swapped them back too so I am very confused. The only thing I can figure is a have a lack of volume, my pressure stays the same even when the engine is sputtering and starting to die. I'm about to run the fuel volume tests so we'll see what that yields. In the mean time if anyone has any ideas of what else to look into please let me know.

Thanks
Danny
_________________
-'87 Jeep Cherokee 4.0L 6" of lift 33" Super Swampers

-'83 Callaway 944 2.5L turbo, 300HP, 1 of 42 ever made

[dpw928]

Danny,

What was the engine temperature when you tested it? If the engine was cold, what was the outside air temp? If it was around 80F your cold pressures are good. As the engine warms up, your control pressure should go up to 38 or above. If it stays low, plug the electrical connector into the WUR and check it again. If it still doesn't go up, check the connector to make sure you are getting 12 volts. Have you checked to see if your cold start valve is cutting off? If it continues to inject fuel, it could cause your engine to stumble after the initial start. Did you do a leakdown test when you had the gauges hooked up? If your system doesn't hold control pressure above 27 psi after 10 minutes you have a leakdown problem. Check your injectors, pressure relief valve (on side of distributor) and the case under the distributor for signs of leakage.

Dennis
_________________
81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black

[John Brown]

Danny. You gotta approach this stuff in a stepwise systematic way.

The guage doesn't lie. Even with the electric leads off the fuel regulator the control pressure should be at the cold reading and the sytem pressure should be good. All contained on Haynes Chapter 3, Section 4. The only thing I would suggest differently is that it is easier to check the system by jumpering the fuel pump relay so you do not need to run the engine.

System pressure 70psi +/-5. Cold control pressure at around 80F around 30psi. Warm control pressure 52psi +/-5.

Start with engine cold, electric to the WUR disconnected, and jumper the fuel pump. System pressure should be 70. Then check control pressure at 30ish. Now hook up power to the WUR. You can then watch as the control pressure rises to 52. It should take 5 minutes or less. Note that while you are doing all of this NO fuel should be passing to the injectors as the metering plate is not off the stop.

If system pressure is not good (too low) the at this point then start working backwards from the distributor looking for restictions. If no restrictions then a bad pump. Or gunk in the screen inside the tank. By the way, the intank pump will not show up as a low pressure unless it and/or the screen are clogged. The system pressure is made by the main pump.

If the control pressures are holding at system pressure loosen the OUTLET fitting on the WUR. (The one on the bottom). Let fuel leak from this fitting. If control pressure falls to correct value then there is a restriction in the fuel return line; If control pressure stays way high (typically at system pressure) then the WUR is bad.

I have had absolutely no success repairing these gems. The one on the little 924 would hold for a few seconds to a minute and the 'snap' closed forcing control pressure to system pressure. So I have observed first hand that when they go bad they may not be static. Which surprised me. But I repeated the 'experiment' several times with the same results. Who knows. These things apparently are PFM as we say in the trade.

No matter what else is wrong, if the control pressure is not correct the car will NOT run correctly and this needs to be fixed before moving on to the next problem.

The last configuration you describe, control pressure at system pressure, will cause the mixture to be very lean. Which generally matches your description.

If the sytsem pressure drops after some period I would strongly suspect the fuel pump. Since they cost lots I would check for debris in the lines, replace the filter, pull the intank pump and check the screen and the intank pump and clean out the 'big chunks' from the tank. Also monitor voltage at the pump to see if voltage is staying up. But after all that it's a good bet that low system pressure is a pump.

Call me if you wish.

John

[CMXXXI]

This is my contribution: Here's the pages from the factory manual that cover testing with the CIS gauges. Note that the control pressure is ambient temperature dependent, and in a fairly narrow tolerance band.
._.._.._.
._.._.
Click on the images for larger pictures.
_________________
'79 Eurospec 931

[AznDrgn]

ok so problems solved, sorta. Bad idle was because of bad injector spray patterns at low pressure so I cleaned those up and replaced one or two of them. Then the pressure problem was due to a bad control pressure regulator. I have one that reads 20.0ohms and one that reads 18.9 ohms but neither one reduces the pressure at all. I have voltage at the lead so I know that isn't the problem. Is it possible that they are just clogged? Is there any way to clean them out? I have it open but I don't know what to do with it now, don't see much else to take apart.

Temporarily I have a WUR from a 2.7L 911 engine. Configuration is pretty close to if not the same as for the 931 WUR, it has two vaccuum line connections on it which I plugged. So now I have a WUR that works, at warm idle I get 70psi system pressure and 42-45 psi control pressure which is about right. Car runs great, idles nice, starts up easily, revs until I load it. I tried driving it and it's a bit sluggish so I figured there must be something still off with the mix. I tinkered with it and set it to between 1.5%CO and 2.0%CO as it says to in the Haynes manual. It's still sluggish to rev and when it gets up I max out around 4000rpm and I get some poping in the exhaust which is normally means it's too rich. I leaned out to 1.0% CO and ran again same result. Leaned out to .5% CO and acceleration was worse and still same result. I can't seem to get past 4000rpm, I lack power and I don't know why, the car used to pull hard right up to red line. Tomorrow I am going to go back and look at the engine that the WUR came from and I'm going to try and connect the vaccum lines and see if that makes a difference. Then I guess the next step is to get a proper working WUR for the car. Any other suggestions are greatly appreciated.
_________________
-'87 Jeep Cherokee 4.0L 6" of lift 33" Super Swampers

-'83 Callaway 944 2.5L turbo, 300HP, 1 of 42 ever made

[Roger]

Where is the control pressure regulator? I didnt think our cars had one. Also the poping noise can be due to a lean mixture.
_________________
1981 924 NA

Some people are like Slinkies. Not really good for anything, but you
still can't help but smile when you see one tumble down the stairs.

[AznDrgn]

The control pressure regulator, AKA the warm up regulator is located on the back of the intake manifold. All Bosch CIS injection engines have one and unless your car is very special you have one as well.
_________________
-'87 Jeep Cherokee 4.0L 6" of lift 33" Super Swampers

-'83 Callaway 944 2.5L turbo, 300HP, 1 of 42 ever made

[CMXXXI]

Drgn: You've double and triple checked to make sure you don't have any intake and/or vacuum leaks? It really sounds like the WUR is toast, and I've got a feeling that the car really needs one that is designed for it instead of substituting one from another motor.

Roger: This photo has a lot of stuff stripped off the top of the motor, but the WUR is outlined, and is the device on the back-side of the intake manifold having two fuel lines running to it.

Here's what they look like removed. N/A foreground left, the other two fit the 931.

Click photos for larger images
_________________
'79 Eurospec 931

[AznDrgn]

CMXXXI I thought it was that too but it wasn't, I checked the vaccum lines with soapy water 3 times and then went over each one by hand and redid them and then ran soapy water again and still nothing. I intend to get a WUR for the car ASAP in fact I just sent off my money to 924martinirosi for the one he's got.

You'll never guess why I was topping out at 4000rpm, it was the most idiotic thing in the world. The jacobs ignition I have installed has a built in rev limiter built into it and for some reason it was set at 4000rpm. I reset it to 6000rpm and it works fine now.
_________________
-'87 Jeep Cherokee 4.0L 6" of lift 33" Super Swampers

-'83 Callaway 944 2.5L turbo, 300HP, 1 of 42 ever made

[78porsche924]

hahaha, always the little things you over look. i do that type of stuff all the time. my car wouldn't start before and i was freaking out. then i remembered that the spark plug wires were disconnected.
_________________
90 944 S2
78 924 NA <---now sold and killed by new owner
snailshell trans
Bae turbo kit
to check out my 944 S2 http://www.cardomain.com/member_pages/view_page.pl?page_id=388139

[CMXXXI]

[Roger]

Ok WUR=control pressure regulator
_________________
1981 924 NA

Some people are like Slinkies. Not really good for anything, but you
still can't help but smile when you see one tumble down the stairs.