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fredmeister fredmeister is offline
Smart quod bastardus
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Join Date: Oct 2002
Location: Baltimore, MD, USA
Posts: 2,235
I wanted to update my original post with more details.

I have installed a Leask modded WUR and also the MSD programmable unit at the same time.

So far I have concentrated on getting a good timing curve programmed and I have been assuming the bad running right off idle is due to the timing not being right.

I have checked the rotor and all wires and they are good. I am running the non resistor rotor and the timing curve I have programmed is exactly the same as from the stock USA distributor curves from the factory manual. Idle timing is 2 degrees BTDC and the MSD unit is retarding total timing from 32 degrees BTDC 30 degrees at idle. Vacuum is 7 psi absolute and 1000rpm.

With the WUR set to 6.4 bar SP and warm control pressure at 3.4bar the idle AF ratio is 13.0 to 1 or so for the first minute or 2 of running. Then it starts to miss and idle speed fluctuates. As soon as I apply any throttle to rev the engine it starts to misfire and stall and backfire while the AF ratio bounces all over going very lean. Eventually the idle drops and the car stalls.

My theory is the front fuel pump is overheating as it runs so the first minute of operation it is fine cause its cool then it starts to heatup and the issue starts. Like I said the wiring in the fuse panel is stock and is very hot to the touch and the front pump seems noisier than I remember last season before it went in storage. I think I can rule out if the MSD unit is at fault now because it appears to be retarding timing according to the programmed curves and I monitor it on my laptop watching the manifold pressure, rpm, and amount of retard real time during this testing.

I have tested the system with the CIS gages installed and noticed the system pressure bounces every so often between 6.0 and 6.4 bar but it never drops to zero or anywhere close to indicate the front pump shutting down. Also the warm control pressure is rock steady during the time when the car is stalling and idle speed fluctuating. I would have suspected the warm control pressure to be fluctuating during this time to explain the AF ratio changes when this is happening. But dont see this.

Question: Can the MSD be misfiring within the distributor cap at idle because of the huge amount of retard at idle 30 degrees that has to be there for vacuum advance and low rpm operation? I read this on the MSD site somewhere and people mention filing the rotor tip to a point to prevent the spark from jumping to the next plug terminal over inside the cap which would fire the wrong cylinder during high retard. I think this is called spark lead or soemthing. Right now the rotor tip is stock and about 1/4 inch in circumference.

Or am I in need of a new front pump?.....I dont like the heat in the fuses and I am going to take voltage drops at the pump terminals today and look into modifying the wiring to the relays to break up the single power source thru fuse #6 into separate lines by adding another fuse block. Like Richard mentioned above. I hate this electrical crap. More mess in the trunk and more confusion.

I really want to rule out the MSD and isolate this to someting else. I dont think the WUR is at fault either but that was modded as well when this whole thing started. I think this might be coincidence as warm control pressure is in the ball park as mentioned and rock steady at 3.4bar.

Thanks for your ideas,
1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max
---"When you're racing it's life! Anything else either before or after, is just waiting"
Old 05-04-2013, 08:48 AM
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