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Engine stumble halp

Posted: Thu Jun 25, 2020 10:04 am
by acurtis
74 710M, rebuilt the carbs SSII. Engine starts on first try and idles fine but stumbles and backfires(into carbs) under any acceleration- without any load.

Re: Engine stumble halp

Posted: Thu Jun 25, 2020 10:13 am
by ChickenPinz
Years ago I had that same experience on a '72 Chevy V8 with HEI. Ran fine but would complain with any load. Turned out to be a failed (cracked?) distributor cap and it was thus getting weak spark. Not sure if it's the issue in your case, but the symptoms were the same as what you described.

Re: Engine stumble halp

Posted: Thu Jun 25, 2020 11:39 am
by Joeri
Backfiring in the intake or carbs means timing to early...in the exhaust...to late. Oh and dont forget that the timing numbers on the petrol pinzgauers are 1-2-4-3 and NOT 1-3-4-2 :mrgreen: :P

Re: Engine stumble halp

Posted: Thu Jun 25, 2020 12:11 pm
by acurtis
Makes sense-
I will try to retard the timing - and see what happens- not sure how far with the Solid State Ignition

Here is a link to a video I posted on a facebook group that shows it stumbling.


https://www.facebook.com/groups/43366129234

Re: Engine stumble halp

Posted: Thu Jun 25, 2020 12:13 pm
by acurtis

Re: Engine stumble halp

Posted: Thu Jun 25, 2020 3:43 pm
by whitesik
According to the description and the video, your pinz has the Pinz SSI. So it does not have a distributor cap per se, the timing is set by the red LED, and the cylinder sequence is very much different than the original as it fires on two cylinders at a time with the waste spark. Download the instructions for the Pinz SSI and set the timing.

Re: Engine stumble halp

Posted: Mon Jun 29, 2020 1:13 am
by boeing7873
I have the SSI and mine runs a little happier a touch advanced from red LED.
I drive it around, squeeze my hand in the engine compartment and adjust timing by feel. Got better results than with red light.
But, that is me the caveman, not me the engineer.
JC

Re: Engine stumble halp

Posted: Mon Jun 29, 2020 8:54 am
by pinzinator
Make sure that the c-clip is tight, that holds the module in place on the aluminum shaft. If it is loose vibration can change timing. Don't over tighten, and make sure the clip isn't upside-down.

Verify that the aluminum shaft is correctly inserted into the slots inside the engine. This can be done by trying to tighten the Phillips screw that holds the disc in place. If it feels tight it is in, but if it rotates the male dogs at the bottom of the shaft are riding on top of the shaft and are held in place by downward pressure only, like a clutch plate. There it no way to hold correct timing if this is the case, and the dog may be damaged. I can send a new one if this happened.

Make sure the pinch clamp is tight. Sometimes the clamp has to be filed slightly at the opening to allow more clamping force. Or replace the clamp with a better one, this is what I recommend- https://www.speedwaymotors.com/Distribu ... gLVhfD_BwE

Re: Engine stumble halp

Posted: Mon Jun 29, 2020 10:50 am
by newtopinz
How much advance?
I see from the PinzSSI website up to 1-2 mm, which I think is the distance from the mark to the pointer. Some speak in terms of degrees but I believe that does not apply to the SSI since it's optical? or something to the extend they have shielded wires?
Also, it seem that the light stays on for about 1-2 mm of such distance, so when advancing, if the light goes off right at TDC, is that more like 1 mm advance or 2 mm advance?

Re: Engine stumble halp

Posted: Mon Jun 29, 2020 2:55 pm
by pinzinator
From my experience the Pinz runs great if there's a mm or two of advance. Just don't allow timing after TDC.

Re: Engine stumble halp

Posted: Mon Jul 13, 2020 1:02 am
by boeing7873
Since your ignition is modern and has low chances of being a problem except for timing, I would start with making sure you have no vacuum leaks and your acceleration pumps are squirting well.
Vacuum leaks are easy to spot with a good smoke machine. Unless you find something obvious, you would be surprised how difficult to spot them are.
I dealt with acceleration stumbling for quite a while. Spraying engine start fluid over the entire engine did not reveal the problem. But the smoke... both choke plates were leaking.