Loss of power and backfire: help!

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hatzlibutzli
Germany
Posts: 31
Joined: Mon Dec 28, 2015 11:47 pm

Re: Loss of power and backfire: help!

Post by hatzlibutzli »

@Pinzcat: as far as i know the SSI does not have an ignition breaker ...

@one2many: you are quite right in generally, but the reported symptoms "running worse when warm" suggest to much petrol ...

@JohnL: idle speed should be 800-900 rpm ... a cold start @ temperatures lower than 10 °C (50° Fahrenheit) should need the choke ... if it starts without choke your mixture is too fat

Good luck!

Simon
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Haf-e
United States of America
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Location: Mount Vernon WA USA

Re: Loss of power and backfire: help!

Post by Haf-e »

Tight valve clearance often only show up once warm and can also not affect a compression test.

Worth checking...
Haf-e

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Pinzcat
France
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Joined: Sat Jan 24, 2015 4:53 am
Location: France, Evian

Re: Loss of power and backfire: help!

Post by Pinzcat »

Sorry, i confused SSI with fuel injection :roll:
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John L
United States of America
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Joined: Thu Sep 15, 2011 7:48 am
Location: Covington, Louisiana

Re: Loss of power and backfire: help!

Post by John L »

"Before you muck around too much with your carbs if you haven't already done so you need to check your valve clearances, overly tight clearances will definitely cause your symptoms and they need to be done routinely on air cooled engines IMO.

You did say that your compression and leak down tests "seemed fine" , I'm curious about what was the percentage of leak down across all cylinders?

It's true that good compression and acceptable leak down results will rule out valve clearances as the culprit but if you have any doubt then check your clearances, it's good measure in any case."

Great point. The carbs have to be somewhat OK since it starts and idles perfect. I'll check the clearances first. What should the valve clearances be? I know I so a post on this earlier.

As for the compression and leak down... I recall the lowest compression was 140 plus and the highest was 155. If I remember, Cylinder #1 was 150, #2 was 155, #3 was 150 and #4 was 140. As for the percentage leak down across all cylinders, I don't recall. I'll retest it this weekend. I'll spend some quality time with her on Christmas Eve. :D

Pinzinator, I think you are referring to the 4500 RPM Limiter? Someone else mentioned that as well. After I check the valve clearances, confirm that I'm happy with the carb tuning, and if I still have a problem I'll see about jumping that to see if it solves the problem. Thanks for the input.

I wish I was closer to Andre or Jim... If all else fails Andre I'll tow her to you and let you work some magic on her.

Merry Christmas and Happy Holidays everyone!
Texas710
United States of America
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Joined: Thu Jan 22, 2015 4:00 pm
Location: San Antonio, TX

Re: Loss of power and backfire: help!

Post by Texas710 »

I had an issue with my 4500 rpm limiter. But symptoms were a little different, essentially a loss of power up in the higher rpms. When you pushed the truck, you could tell it wasn't giving its all. That and my tach would bounce around.

It is one of the easiest things to do if you can crimp 2 flat blades on about 6" of wire. I jumped mine and have not had the same issue and feel the truck starts better. If you don't like it, just replug the thing back together.

Have you pulled the plugs to see what they look like?
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edzz
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Location: Coeur d'Alene, ID

Re: Loss of power and backfire: help!

Post by edzz »

You said you have new carbs, have you checked to insure that all the jets are correct? Not knowing where you sourced the new carbs I would question if they are set up for a Pinz or a???
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one2many
Australia
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Joined: Sun Dec 22, 2013 5:53 pm
Location: Melbourne Australia

Re: Loss of power and backfire: help!

Post by one2many »

John.L....valve clearance is 0.2mm for both inlet and exhaust and they are set with engine cold. This info is in the manual, section A engine, technical data page 1 and again on page 12 same section.

It's handy to have new rocker cover gaskets when you do your valve clearances but home made from gasket paper will work fine in a pinch if parts suppliers are closed over Xmas period, just be sure to use Permatex no.3 aviation sealant.

Merry Xmas
1985 pinzgauer 712K factory 2.7lt civilian (RHD, 4 door K)
1979 Volvo tgb 1314a (under construction to om606 diesel/722.6 trans. Dual cab/tray)
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