Dennis Wilson

The control pressure appears to be too low at 10 psi. It should vary from 15 to 50 psi dependent upon temperature. Have you cleaned the inlet and outlet ports of the WUR. Also, since the air sensor place is still sluggish, the cylinder and piston in the fuel distributor is probably slugged. Suggest you remove the fuel distributor, remove and clean the piston and cylinder with injector cleaner.

Dennis

jpitman2

The 75 system is correct. The control pressure cold is dependent on ambient temp - I suspect that in FL the 10psi is low. Some coughing is an improvement over nothing. Control pressure is not really adjustable - its mostly a dismantle the WUR and move either the main regulator part (round cast iron part) in or out with tapping (not easy), or move the post that carries the bimetallic strip in (tapping from outside) or out (tapping from inside). I forget if the injectors have been tested or not ? If not , that might be next step, checking that they all open and fire a good spray. Sames goes for cold start injector. Can you find a way to spray some gas into the airplate inlet while its cranking ? If the cold start injector is not firing, some extra gas might be all it needs.
jp 83 Euro S AT 55k

NordicSaab

Thank you for the feedback. All of the fuel injectors are new... I replaced them with the Mercedes model as suggested by the forum. I have read about the wur and adjusting control pressure by drilling the copper cover on the back of the unit and adjusting using the "hidden" allen screw.

Would the control pressure being too low prevent the car from starting?

Sent from my iPad using Rennlist

jpitman2

Low control shouldnt prevent starting, but it will go rich and maybe die in minutes unless control comes up as it warms. You have checked for sparks - all that side is good? Were you pressing airplate in a little while cranking? Have you verified that injectors fire with airplate pressed in (with pump running)? Apparently firing injectors are audible in the engine bay. The fuel pump relay relies on signals from the spark box to keep the pump running, so maybe try cranking with the relay jumpered to ensure there is no problem there.
jp 83 Euro S AT 55k

LT Texan

Does the control pressure rise over time with the WUR heater wire hooked up? It should! Does it go up to 30, 40, 45psi?

What is the temp outside? I think the lowest control pressure should be around 15-20psi when it is COLD outside. (It is not cold outside!)

Did you do a flow test with those new injectors attached? I was able to confirm they all had consistent volume delivery.

Question for the crowd, can you mess with the A/F adjustment screw enough to where she won't run?

jpitman2

Yes, the control should rise with the heater connected - easy to check with the gauge fitted, connect the heater, turn key to Run position.
Yes you can mess with main mixture control till it wont run - anti clock lean should do it. I have seen notes that say, with pump relay jumpered, turn mixture to rich (clockwise) until you can hear the injectors fire, then back until they just stop - mixture should then be enough to start.
Have you tested that all injector pipes will supply fuel ? ie removes pipes from injectors, put ends into containers, run pump, press airplate, all should show flow.
hp 83 Euro S AT 55k

NordicSaab

I did press the airplate in while cranking and I can hear the injectors firing. I have also attached a spare injector and have a mist of fuel with the fuel pump on just like other forums have suggested.

When I have been trying to start the car I have been doing so with a toggle on a long lead to jump the fuel relay as desired and a momentary trigger setup to jump the starter relay. This way I can observe and modify the engine while actively cranking. I do all of this with the ignition on, of course.

So, At one point I backed out the mixture adjustment screw (counterclockwise) to its last few threads. I never went back and reset it. I will use the method you describe here and see If I can reset it to the proper height.

As far as the lines to the injects. each one was cleaned individually, blown out, and when I had them on the car I can fuel for a moment to make sure each was receiving fuel. The injectors are new. I really believe I have a setting out of whack.

The spark seems strong. It is a nice blue pulse. Before it was somewhat weak with the Blue coil. The Silver coil really livened it up. All the Coils have been resistance tested. At this point I do not suspect the ignition system being the issue.

jpitman2

Well, you seem to have covered all the bases here, so if you can hear the injectors firing, it ought to run, or at least fire some. Try turning the mixture screw in until they fire, then back till they stop, then crank. If ignition timing was off, you would at least get a backfire (NOT good on CIS!). Have you thought to check for fuel smell at the exhaust after a bit of cranking? Is there any chance the idle screw has been closed in too far?
jp 83 Euro S AT 55k.

Luis_M

Hi, I have the same year and engine ROW model. My engine came fitted with a damper and a CIS hot start valve in-line between the FD and the WUR, attached between the intake manifold legs for Cylinders 3 and 4. When the engine is hot, this HSV (p/n 928.605.103.00) is supposed to bypass the WUR and send the fuel from the FD outlet straight back to the return line through an additional fuel line that wraps around the back of the engine. This is done to lower control pressure to assist in hot starts. This valve is only supposed to be open while cranking. If it is stuck open or leaking, it could explain your low control pressures. Bad unmolested WURs tend to give abnormally HIGH control pressures (from gunked up inlet screens, etc.). The WSM has instructions on how to test this HSV for leaks if you have one. They seem to be pretty rare so please let me know if you happen to have one installed...

Also, let us know what happens to control pressure over time as this speaks to the health of the WUR. When I jumper my fuel pump relay, I get power to the heater element at the WUR and have a gradual increase in control pressure over a few minutes. This is the expected behaviour.

@jpitman, btw during normal operation, my fuel pump runs for a few seconds then stops when I turn the key to ON, before I crank the engine.

Luis
1981 Euro S 5sp

jpitman2

Luis, my 83 fuel pump has NEVER run at key ON, only while cranking, and I have always had correct relay (AFAIK anyway). The pressure lowering valve you speak of is on my car, and it failed the opposite way to that you refer to - the temp sensor would close , but with a resistance of 20 Ohms, which is high enough to prevent the solenoid from firing. I replaced it with a 924 version, and all is now good.
jp 83 Euro S AT 55k

NordicSaab

Alright... still no start. Took a step back and reviewed all my work from the WSM (Get a set if you don't have them!) and I came across the section on distributor re-installation.

In that moment I realized that I didn't time the distributor when I put it back in. I set the engine to top dead center and pulled off the cap and sure enough I was 90 degrees retarded.

I will reset this evening and hopefully start the car for the first time in many months. I believe this thread may be coming to an end (Thank God)