Sudden poor performance

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tgreening
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Sudden poor performance

Post by tgreening » Thu Jan 10, 2019 9:15 pm

As in running great, downshift (fairly high resulting rpm), running bad. Just that quick. It "feels" like she's missing or maybe running on less than 4 cylinders now. She pops a bit sitting and idling, but when I stab the throttle (parked in neutral) there is a very very slight bog but it takes right off with no apparent issues. It only seems to be a problem while moving and under load.

Just looking for some ideas/pointers while sitting here in my chair thinking about it and dreading working on it in 20-ish degree weather we're having here at the moment. No, it wont fit in my garage.

Appears to have a civilian ignition conversion. Not sure if it's a full Pertronix or not. Electric fuel pump, can't remember brand sitting here, but do remember recognizing the brand.

First thought is to check plug wire connections at each end, pop the distributor cap and have a look-see. Not sure where to go from there. Pull the plugs next, or something else electrical/vacuum/fuel related to check first?

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pcolette
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Re: Sudden poor performance

Post by pcolette » Thu Jan 10, 2019 10:36 pm

Agree that you should check all wires, plugs, dist. cap, etc. Be sure to check the timing. Distributor may have loosened and rotated just enough to cause some issues.
Paul C.
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'73 Swiss 710M
'89 Puch 230GE
2002 MB G500 (For Sale)

Texas710
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Re: Sudden poor performance

Post by Texas710 » Fri Jan 11, 2019 8:29 am

Not sure if you have disabled the 4500 limiter? I had a stumbling problem that would come and go, this fixed the issue. But for sure, check all connections, the molex connector, fuel filters/lines.

Merrick
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Re: Sudden poor performance

Post by Merrick » Fri Jan 11, 2019 10:08 am

I would pull the distributor cap and check it for moisture. I have this issue with my 712 and again with my 710 a few weeks ago after a temp drop... and some river crossings. Everything looked and felt tight but there was enough water in there to cause issues. Hopefully just a little WD40 will fix your issue.
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waterdog
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Re: Sudden poor performance

Post by waterdog » Fri Jan 11, 2019 12:58 pm

get yourself a new set of accelerator pumps for the carburetors..... fixed mine with that bog under load
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tgreening
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Re: Sudden poor performance

Post by tgreening » Sat Jan 12, 2019 7:24 pm

waterdog wrote:
Fri Jan 11, 2019 12:58 pm
get yourself a new set of accelerator pumps for the carburetors..... fixed mine with that bog under load

The bog is very very slight, barely there. I may do the carb rebuild thing but right now I’d rather entertain the idea of a FI setup.

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edzz
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Re: Sudden poor performance

Post by edzz » Sat Jan 12, 2019 9:40 pm

Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt.

tgreening
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Re: Sudden poor performance

Post by tgreening » Sun Jan 13, 2019 7:11 pm

edzz wrote:
Sat Jan 12, 2019 9:40 pm
look here may help
viewtopic.php?f=12&t=6311&p=44335&hilit ... all#p44335
Thanks. More info is always better.

boeing7873
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Re: Sudden poor performance

Post by boeing7873 » Mon Jan 14, 2019 3:56 am

Make sure all jets are clean. And carb acceleration pumps can be checked with engine stopped, with flashlight. Just make sure all four are squirting a nice stream of gas when you move the throttles to open.
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tgreening
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Re: Sudden poor performance

Post by tgreening » Wed Jan 16, 2019 7:00 pm

Success! Sort of?

I decided to dig into this a bit more today. Checked the fuel shutoff solenoids and all had 24-ish volts and all made nice clicky noises when reconnecting. Plug wires all seemed secure and in good condition, at both ends. Coil had about 23-ish volts when cranking and 18 volts running at idle. The dizzy cap is sealed with silicone and I didn’t mess with it at this point. My rpm module, based on its blinking light when key on and the voltage measurements I got is supposedly good. I jumpered it anyway and went for a ride. Ran like a scalded dog. Well as good as a weak-kneed 4-cylinder scalded dog can run.

Now, was that module bad in spite of it checking good, or did my fat-fingered fumbling around with the electricy bits solve a bad connection somewhere? I know I can just reconnect the module and go for a ride, but I’m done for the day so I’m just doing some arm-chair quarterbacking at the moment.

Oh yeah, pic for attention which seems to be the stupid habit on Facebook these days.....

4E018155-8981-4AEE-AC6D-3FF0F19CA5ED.jpeg
4E018155-8981-4AEE-AC6D-3FF0F19CA5ED.jpeg (700.51 KiB) Viewed 641 times
Dizzy Pic

Texas710
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Re: Sudden poor performance

Post by Texas710 » Thu Jan 17, 2019 11:34 am

I took out the 4500 limiter a few years ago, I would wager that most on the forum have, and I have not missed it once. Never had that particular issue come back. My issue would come and go, I think as the module ages, it starts to fail but not all at once.

BTW - some people have had problems with the flamethrower coil, might be something to look into

tgreening
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Re: Sudden poor performance

Post by tgreening » Fri Jan 18, 2019 11:25 pm

I’m wondering if someone far. More knowledgeable than I might take a closer look at this last photo I posted. Obviously there’s the distributor and coil, and on the other side of the engine plug wires with normal rubber boots on the ends vs what EI sells with their kits. I’m assuming this one came from SAV. But....


It was my understanding that the civilian Pertronix kit used either the original points/condenser or the Pertronix “igniter”. Now....

If you look at the photo to the left you see what looks like a brown wire or tube. What this is is a vacuum line that runs from the drivers side of the engine and pretty sure it’s going to the distributor. I’ll have to pop the engine cover to verify exactly where it does terminate because I didn’t pay much attention to it until researching the ignition system tonight, which got me to wondering. Is there some form of the Pertronix kit that used vacuum advance? Is this even a Pertronix system?

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pcolette
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Re: Sudden poor performance

Post by pcolette » Sat Jan 19, 2019 3:04 am

The brown plastic tube is a vacuum line that runs from a fitting on the driver's side of the engine to a fitting on the underside of the distributor. It is not a vacuum advance. It’s purpose was to pull any buildup of moisture out of the distributor.

The civilian kits came from 3 or more sources and evolved over the years. Some came with the Pertronix igniter and some did not. When you pull the distributor cap, you'll have a better understanding of what you have.
Paul C.
_________
'73 Swiss 710M
'89 Puch 230GE
2002 MB G500 (For Sale)

tgreening
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Re: Sudden poor performance

Post by tgreening » Sat Jan 19, 2019 9:34 am

pcolette wrote:
Sat Jan 19, 2019 3:04 am
The brown plastic tube is a vacuum line that runs from a fitting on the driver's side of the engine to a fitting on the underside of the distributor. It is not a vacuum advance. It’s purpose was to pull any buildup of moisture out of the distributor.

The civilian kits came from 3 or more sources and evolved over the years. Some came with the Pertronix igniter and some did not. When you pull the distributor cap, you'll have a better understanding of what you have.


Thanks a bunch. I remember the tube attaching pretty low on the dizzy. Right now it’s running well, and I have a number of things I want to address, so prioritizing is difficult. I have a brand new Tuff River top sitting in my garage I need to get on, I think my shocks could stand being replaced but it seems neither SAV or EI is stocking those Doetsch replacements (though I’ve not asked them either), I have a heater I need to install, and a slew of little things to check into.

And it’s snowing and friggin cold and no space in the garage. :)

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TechMOGogy
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Re: Sudden poor performance

Post by TechMOGogy » Mon Jan 21, 2019 8:46 pm

See here re your shock question
viewtopic.php?f=15&t=7959&start=45#p87512
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