CIS starting issues

[mrm930]

I have been reading a lot of different threads to get a better handle on this. Also to help my understanding of the CIS. My car is a 78 turbo with a 79 930 motor.

Okay, engine has started and idled. When I attempted to rev up a bit. It sputtered a bit and died. Tried starting it again, and nothing. Checked vacuum lines, etc., wouldnt fire again. Increased the air meter adjustment. Also increased the idle setting. After a methodical set of adjustments, the motor fired. Idled fine, I let it warm up a bit, and adjusted the idle. Turned the engine off and tried to restart, no luck. Since then it has started a few times but usually died after about 10 secs.

I reconnected the decal valve set-up, hoping to get it back to original hook ups may help. No difference. Inter cooler is hooked up

CHECKS:
-used an induction timing light and checked all 12 of the spark plug wires. (Twin plugged). All wires showed electrical flow.
-removed air cleaner and pushed down metering plate with ignition on. Both pumps fired up.
-rechecked vacuum and fuel lines.
-checked fuel flow coming out of the fuel distributor and all 6 had fuel flow
-disconnected fuel shut off switch at the rear of the fuel head. Turned on ignition and pumps run

With the fuel cutoff switch disconnected, the engine will try to start. Adjusting the fuel head mixture to enrich the fuel ratio, seems to help a bit. But still will not run.

What am I missing here? I can keep playing with the metering valve and idle, however that seems to be a bit half-way thru the issue.

Any suggestions would be great.

Thanks everyone
Mark

[mrm930]

The fuel head, WUR were all rebuilt by Chris at TurboKraft. So these are clean and new.

[mrm930]

The vacuum lines are connected per the California diagram (page 26-39) from the turbo worksho manual. With the exception of he egr valve, air pump and associated valve bodies connected with the anti smog setup

[Alan L]

You say the FD and WUR are new. Have you just fitted them?
Was the car running fine until........
Or has something been worked on before this happened?
Alan

[Bucketlist]

I see no mention of checking fuel pressures. Without knowing cold control pressure some of us would have a hard time figuring this out. Air fuel ratio numbers are also important as you get it running. Search cold control pressure and air fuel mixture. Also you should look through https://forums.pelicanparts.com/911-930-turbo-super-charging-forum/547032-sticky-common-answers-why-my-car-doesnt-start.html

[mrm930]

This 78 930 was a complete project car. I bought it when it was a roller and everything was in boxes. Ii came without a motor. Purchased a 79 motor, rebuilt by Henry Schmidt at supertec. Purchased a CIS pressure test kit, not here yet.

I will test pressures and get back to you all next week.

Just really odd how it fired up and idled up to temp. Then nothing. Complete restart has been more off than on.

Back to everyone soon

[mrm930]

First test: I have power to the WUR, rotte bypass valve and both thermal valves. I have power only with ignition on and the fuel head unplugged. Fuel pumps running. Reconnect the green plug and power shuts down to all.

I assume this is normal. These are only activated while starting the engine (I assume)

[T77911S]

correct

[356911930]

When you checked the spark plug wires did you check the timing?

Rahl

[mrm930]

Yes. It is a twi plug crank fire ignition set up. Everything aligns as per the instructions.

[mrm930]

Another issue I have noted is the nomenclature thrown out in some threads. Pulled the aux. air valve (AAV), to test it. More than a few threads noted the AAV and what should happen cold and what should happen hot. Wait, what t f? Reading in more depth, these guys were referring to the throttle bypass valve, calling it the AAV. I am new to testing the CIS, but very capable. I didn’t start and continue owning a high end custom fabrication company for 40 years without knowing what I am doing.

These mis-informed threads should be deleted. No help, just muddies up the waters for understanding.

My ***** of the day. Re-reading my factory workshopmanual again.

Back when I settle out the facts and pressures so that I am communicating to those in the know correctly.

Thanks,
Mark

[T77911S]

not sure what you are calling the "throttle bypass valve" unless you are referring to the aux air regulator. AAR.
the AAR bypasses the throttle body. its purpose is to raise the idle when cold. its not a true regulator. it is open when cold and closed when warm

the AAV is open when cranking only. it is like putting your foot on the gas while cranking but then lifting once it starts.

[flightlead404]

Originally Posted by mrm930

Another issue I have noted is the nomenclature thrown out in some threads. Pulled the aux. air valve (AAV), to test it. More than a few threads noted the AAV and what should happen cold and what should happen hot. Wait, what t f? Reading in more depth, these guys were referring to the throttle bypass valve, calling it the AAV. I am new to testing the CIS, but very capable. I didn’t start and continue owning a high end custom fabrication company for 40 years without knowing what I am doing.

These mis-informed threads should be deleted. No help, just muddies up the waters for understanding.

My ***** of the day. Re-reading my factory workshopmanual again.

Back when I settle out the facts and pressures so that I am communicating to those in the know correctly.

Thanks,
Mark

Part of the issue is multiple terms used by the factory materials, possibly due to translation. Then there are "traditional" terms probably created back in the day by old carb-heads who didn't grok what CIS components really do.

e.g. calling the "yellow relay" the "speed relay"

[mrm930]

Okay, Bosch fuel pressure tester finally arrived.

WUR hook-up first. Regulator no. 054. Reference the factory chart, the WUR spec’s out. At cold temp it was at 2.0 bar, heated it was at 3.5 bar.
However system pressure, maybe hit 3.0. Weird, since the WUR was higher. I thought that the gauge was off. Reverse the hookup with the valve on the fuel head side instead of the WUR. Same reading, system pressure was way down.

So how did this engine start and run for about 5 minutes a month ago, and now it won’t start. If the system pressure was that low before, it never would have started.

Hooked up direct to a fuel injector line to get a reading. 3.0 at best.

Other then shimming the fuel head and getting the pressure up, outdated I be looking at a faulty fuel pump? The rear is a Bosch 044 purchased from Chris at turbokraft. Do I by another one and replace the front pump? It is the original from 1979.

Background, when I had the car completely disassembled, I replaced the tunnel with 1/2” aluminum hardline. I never want to do that again! It was a *****! All the fuel lines are new SS braided with alcohol resistant poly liners. And they are larger diameter than the factory ones.

Suggestions? Fuel pump replacement first, or fuel head shims?

Thanks all

[mrm930]

History: the fuel head and WUR were rebuilt by Chris at turbokraft and modified to run more fuel. The fuel head was purchased from turbokraft when Dave was running it. It was for a V-8 racing Mercedes’ motor. Dave changed it for a 930 motor, plugging 2 outlets

[Alan L]

Last I heard, you had a leaking accumulator. Presumably fixed.
To verify the fuel pressure then I would look at hooking a gauge in at the delivery to the FD, briefly. That means no fuel will flow - so you don't want to do that too long. But just verify if the pumps are capable of delivering 6 bar. The gauge should shoot up,. Verify and switch off. You may have to hunt for some suitable fitting to cobble together. Doesn't have to be your CIS set up. Anything with a gauge. If you are not getting 6 bar, then which pump is faulty? To find that you hook a gauge in between the two pumps - in a T piece, at the intake fitting on the rear pump.
There is a differential pressure that tells you which is lazy. If the pressure is higher than spec, rear pump NG. If lower, the front pump NG. If you go that track I can find the spec, but from memory it is around 1.5 bar.
Alan

[mrm930]

Just was hooking pressure gauge before fuel head to check pumps. Nice to hear I was on the same page. Back with results

[Alan L]

Right - in case you have to verify the pumps integrity, the pressure differential between the two should be between 2-4 bar. If below 2 bar, front pump is weak, above 4 bar rear pump is lazy.
Alan

[mrm930]

Pressure test directly of off the fuel filter didn’t go well. 3.5 peak. Then you could here the rear pump struggle a bit. Pressure dropped to 3.0. I shut it down at that point, didn’t eWant to damage the reap pump. That’s the new 044 pump. Looks like one of the pumps is bad. I assume the front pump. I split the power feed for each pump, and no fuses popped. However the front pump did sound different from the rear.

Calling Chris Carroll on Monday and get a pump on order. Please feel free to to comment on this if you think I have a narrow focus on this and that I am overlooking another issue.

Pump must have gave up, while I was doing some start up/run tests.

Thanks for the help.

To be continued

[Alan L]

It could be either pump. Sounds like probably front, but not precise diagnosis.
Can you do that differential test - that will tell you.
Or alternatively you could get another 044 pump. I run one front and rear. So you can swap out whichever proves faulty. There is a slight mucking around to fit the 044 up front - fittings I think, maybe a wiring terminal adjustment. Or that may be the rear, can't remember.
The differential test will give you the exact answer.
Alan