930 Fuel Pressure, Advice Needed

[RarlyL8]

Quicky 930 swap update # 453

Stayed up late last night and tore into things deep. Here is where we are:

Problem - high idle, 2200 to 2400 RPM upon start up.

- No known vacuum leaks
- Timing presumed correct @ 5 ATDC
- Idle adjustment screw all the way closed
- Lincage free, throttle plate possition looks correct
- Fuel head piston has free travel
- Air metering plate firm and closed with fuel pumps on
- Idle does NOT change when WUR is removed (engine cold)

I have no way to check the fuel pressure. The CIS is dependant upon pressure to function, but in what range?
The front pump is stock SC ('78) the rear pump is stock 930 ('78). I have not been able to find any info on regulation of this system. Any input, as always, is appreciated.

(I promise to stop calling other people stupid for spending too much money on their cars).

[dean]

I have the same fuel pump arrangement as you. It works for me. It sounds like you are getting too much air into the motor. Do you have a decel valve? Check that out. Aux air reg. check that out. Bad vacume retard on dist.?
Did you ever set your total timing?

[RarlyL8]

I set the timing best I could under the circumstances. It was a tooth off.
The aux. air valve has been removed, the intercooler also has no provisions for one.
The dizzy is a ROW unit with only one vac port on the pot. This port doesn't seem to pull vac until the RPMs are up and the engine is warm. There is a thermol time switch in that vac line. I plan to bypass this switch as well.

Thanks for the tip on the decel valve, I have not looked at it yet.
All along I have thought a vac leak was causing my high idle, but I have not found one that changes anything.

Concerning the decel valve - did you eliminate the vac plumbing and plug it off or just tie it together after removing the valve?

[dean]

I took the decel valve out and plugged both lines. You can't tie them together. You would have a very high idle. I also have a ROW motor. My vacume retard it connected to the intake side of the throttle so I have vacume at idle to the pot.
I knew it was off a tooth. Mine did the same thing. What do you mean you timed it the best you could?

[RarlyL8]

I bumped the engine over to TDC line-up at the fan notch. Removed the dizzy and rotated it one tooth so that #1 lined up properly with the rotor. It was off just enough to not allow enough advance adjustment (movement).

I cannot check the timing at 950 RPM because the engine will not run that low. It is unnerving to start a freshly rebuilt motor and let it scream at 2200 - 2400 RPM, so I only start it after I have made changes. So far nothing I have done will pull the idle down except massively retarding the timing, and you know what happens when you shut down an engine that severely retarded. Not a good thing.

You say you have vacuum at idle to the pot. If I bypass the thermol time switch then my engine should also have vac at idle. Right now there is no vac at idle. The switch is keeping the vac from the pot until the engine warms, I have checked this a couple of times. If this pot is vacuum RETARD it would explain a few things. I have been lead to believe it was ADVANCE. This is why the thermol time switch was left in place.

I will try the decel valve bypass after I eliminate the TT switch. The timing light is left connected all the time in the event that the idle pulls down, or I have the opportunity to check it at varying RPMs.

I sure hate to get my hopes up again, but it looks like we may be on to something. Even if this doesn't work it is another piece to the puzzle.

[TurboRuf]

Rarly,

>If this pot is vacuum RETARD it would explain a few things. I >have been lead to believe it was ADVANCE. This is why the >thermo time switch was left in place.

You are correct, the TT is for advance.

Even with your advance line plugged (port open on distributor), you should be able to get it to idle way lower than 2000RPM.

I finally have my turbo timing dialed in after countless questions to the board (thanks to everyone for all the help). Since I have a ROW motor and a US distributor, opposite your setup, I ran the retard port straight to the lower left TB port and the advance to the thermo time switch. Then the thermo time switch goes to the upper right TB port.

Is your lower left TB port plugged?

[dean]

You can tell if your vacume pot it advancing or retarding by appling vacume to it while looking at the timing.

You have to check the timing with the centrifical adv. maxed out. Around 3000 rpm. It will not hurt your motor. Then you can see if the rest of the dist. is in spec.

I don't know anything about the themo time thingie. So I would eliminate the thing for now

[RarlyL8]

Lots of head scratching this weekend.

Any CIS component that contributes to a fast idle was eliminated. This includes:

- Thermo switch (between dizzy vac pot and throttle body) bypassed
- Vac Pot Bypass Valve (some call it the throttle bypass valve) bypassed.
- Throttle wired shut, cannot be moved 1mm.
- Idle adjustment screw fully shut.
- Warm up regulator disabled (vac removed and wiring pulled).
- Aux. air valve was removed long ago.
- All open vac ports and lines properly plugged.

Observed result:

Motor starts right up (bone cold) and idles at 1800RPM.

HOW IN THE HELL CAN THIS MOTOR RUN WITH THE THROTTLE PLATE WIRED SHUT?

When I pull the vac line off the dizzy pot (thermo switch bypassed) the engine jumps to 2400RPM. Put it back and engine settles back to 1800. This vac pot must be retard, and the thermo switch is apparently working properly. It is connected below the throttle body tward the rear of the car.

No other device that effects idle makes a difference at this point when re-established. Only the thermo switch.

Air MUST be getting in below the throttle body for this engine to run at all, let alone at 1800RPM. It does not run rich. You cannot see exhaust gasses at all, just hear the noise and feel the heat.

My throttle body only has five (5) ports.
- One port tward the rear of the car attaches the thermo switch.
- Two ports off the idle adjustment screw are plugged (smog crap).
- Two ports (T) near the idle adjustment screw for the WUR and Vac Bypass Valve.

It may be time to clean off the top of this engine and strart from scratch.

[TurboRuf]

Rarly,

This may be the problem...

>When I pull the vac line off the dizzy pot (thermo switch >bypassed) the engine jumps to 2400RPM. Put it back and >engine settles back to 1800. This vac pot must be retard, and >the thermo switch is apparently working properly. It is >connected below the throttle body tward the rear of the car.

This is the vac port that is used for retard (lower rear port on US distributors), not advance (front port). You should not connect this to the Thermo Time Switch.

You will need to attach your advance line to the right of the WUR port (upper right of TB). Then plug your lower rear TB port.

I can try to post a picture later.

[finadict]

Our 930 idle jumped up to 1800 over the course of about a month, we could adjust it down to 1000 or so. however the the hydrocarbons were extremly high. JW has the car but the phenolic injector blocks were cracked and warped allowing an excessive air leak, may not be your problem but they are a weak spot.... good luck

[RarlyL8]

Four out of six injector blocks were cracked and have been replaced.

My dizzy is an ROW unit, only one vac line to the pot. This line is connected correctly according to the diagram in the 930 shop manual.

I'm compiling a list of things to check after I tear the CIS completely down. Rechecking the injector blocks will be on the list. There isn't that much between the throttle and cylinders.

Another newby question. My throttle plate has ~1/8 hole in it cenered tward the bottom (rear of car). So far I have assumed this to be stock. Is it present in all 930s?