The Stovebolt Site Forums The Shop Area Engine Shop 57 3100 V8 283 Rochester 2 barrel stumbles warm

Sorry for the big post. Just trying to give you all the information.


OK I searched the Engine and Driveline forum for STUMBLE and got two hits. Anything else got 40 pages of unrelated stuff.

This one was good: https://www.stovebolt.com/ubbthread...;Words=stumble&Search=true#Post84259

"Gasping stumble out of idle" but it is not helping me much as it is a 6 cylinder but carbs are carbs right? I can try some of those things.



So here is the deal. I have a 57 3100 1/2 ton, was originally a V8 but I think the one in it now is a bit newer than 57 like maybe a 66 or so.

Use to have automatic choke on it when I got it 21 years ago. Has a Rochester with manual choke now that I put on 16 years ago and it has been fine for many years but recently, last 2 years it is giving me issues and lately the last 2 weeks it has been really bad.

Progressively getting worse.

It starts great when cold. revs fine and smooth. Drives under load OK but after 10 to 15 minutes when it gets warmed up (NOT HOT) still bottom 1/3 of temp range it will start to stumble under any load or accelecation attempt.

Worse than that. I idles OK and runs OK if you are very gentle. Then if you shut it off like at the dump for 5 minutes to unload it will not start. no pops or attempts, just turns over and over and no firing of any cylinders at all.

It has spark, and I can press the throttle and look down the carb and it squirts, I can squirt some Starting fluid in it from an arisol can and it will not even pop once. Like it has no spark at all but I can see it has spark with my tester. (a little thing you stick in place of the sparg plug and ground it and it flashes the same when COLD as when not starting)

If I pump the peddle it does nothing, does not seem to flood gas on engine either. no pop no attempt to start.

If I leave the peddle to the floor and crank and crank, stop and crank and crank, nothing. Doing this to try to clear it if it was flooded.

Then for no reason after 10 minutes of trying things, trying again with no throttle it will eventually start to pop, stumble and die then another try or two you can get it going and it is fine and will idle and drive. But it stumble when reving in nuetral or when driving.

At that point it will not drive well as and load or heavy acceleration makes it skip and stumble like h*ll.

If you get it home and at idle rev the engine it stumbles all over the place.

Let it sit 30 minutes or an hour and start it and it is great. starts instantly, revs beautifuly and pulls hard for about 10 minutes or so.

So once it is warmed up it sucks.

I tried pulling the vacuum advance hose off and it is a bit worse without it on.

I tried choking it a bit when running but that is worse too.

I checked the timing about 4 days ago and it was at 10 BTDC so I set it to 8 like the book says with the vacuum off. Maybe that is making it worse. Maybe I need 12 or 14? I may try that later.

Some other info. I have an old style Pertronics 1181 http://www.shopatron.com/product/part_number=1181/591.0.26484.26485.0.0.0

It has the ring on top that is a pain to gap as the distributor shaft rises under load some. I did the shim trip with a washed on the base of the distributor but that helped get the slop out some but there is still slop.

But when I have the issue the gap is real small. Paper thin as when cold but can be lifed to a gap of .050 or so I guess bigger than my guage of .044. They say limit should be .010 to .040

This may be some of my issues but it still sparks all the time I have these issues so I think it is not that.

But I have ordered a new version 71181
http://www.jegs.com/i/Pertronix/751/71181/10002/-1 that is lobe sensing, no ring and has other features. That is going in this week-end I hope.

But with the current one 1181 I have had it and used it for 8-10 years. 500 miles a year (very low useage on this truck) and it seems to always work other than these random will not start episodes.

Although today once it was warm it was really bad and would not start 3 times in a row. At the dump payment station, after unloading, at the grocery store! Each time it had spark and to 10 minutes to get it to go. Whell once it started just by keeping the peddle down but that did not work for the other two times.


I can try the carb clean or other things but what blows me away is it is great COLD.

Starts acting up when warm.

I use to think the starting issue was vabor lock or something. But if I can squirt gas in with the peddle like I can shouldn't it fire as long as I have good spark?

It has a new coil too, well 4 years old or so.

I can see fuel past/in the filter in front of the carburator.


So what are your thoughts?

Why is it fine COLD but suck when warm and why does it start great when COLD but has issues when warm (not HOT). much worse lately. getting worse as time goes by.

It will get HOT if I idle long so I know the difference. 10 minutes idleing and she starts to get hot. I need to get an electric pusher fan. My mechanical fan is 3/4 inch off the radiator (relatively new) and the fan is a 6 blade new style.

ideas?

Why does it stumble?

Why does it not start when warm?

Hmmm, I guess there is no one out there with a V8 that ever stumbled?

One other thing I forgot to mention. I do not know if this has value guides and stuff setup for unleaded gas. It might or might not. When I first got it 20 years ago i use to add the lead addative but for the last 12 years I have not done that. I have driven it maybe 2500 miles in the last 12 years.

But would any sort of engine ware associated with not using leaded gas have this type of effect of not running well when warm or not starting well hen warm?

Or is this more likely a bad coil or ignition parts?

unleaded gas won't be an issue, especially with that little mileage

I'd suspect the pertronix first off, seems to me everything points to that - "have spark" doesn't mean you have enough spark or at the right times, like under acceleration or load - gas doesn't sound like an issue, but there couldn't be any harm doing the carb, years take their toll on gaskets and rubber bits, more so with ethanol if that's a CA thing, float bowl might not be filling

you're likely not getting responses cuz us other 283 runners haven't had anything like that happen, mine tends to stumble and complain until it gets well warmed up then goes like a goosed rabbit but I have a stock [points] dist, never have to use the choke except in the dead of winter

Bill

Right, I do not have to use the choke here in california either.
I originaly changed from points to pertronixs years ago because every time I went to use
the truck, which was usually months between runs it would have rusty, pitted points and not start
without cleaning and re-gapping. It got too repetitive the pertronix fixed that.
But has always had a bit of high end stumble since installing the old pertronix 1181. Nothing as bad as it is now though.
Hope I get my new parts soon. I got this next week off to work on it.

I agree it's probably the petronics module although it possibly could be the coil. I never liked that Petronics unit for that particular dist. I used to use the Crane unit that used the dist. cam lobe. They have gone out of business & Summit didn't have any left so I wound up with the Petronics. I'm glad to hear there is another one available that uses the dist. cam for a reluctor. I'm betting when you get that new unit on it will solve it.

Just an update. I got my new Pertronix flamethrower coil and 71181 - Pertronix Ignitor III installed.

Almost easy. They say no modification required. But you have to route the wires out somehow. They show you having a hole in the bottom of the distributor that you stick a gromet in and wires thru. I did not have that. Not that I could see anyways. And I did not want to drill one in there so I bought a cheap distributer cap and drilled a hole in the lower side of it and ran it out there. I am hoping the distributor cap does no crack as a result. I may have to do a hole in the distributor if it does.

The old Pertronix had the wires positioned where you could go right out the corner of the sliding door in the front. But the new one has the wires coming off the far back end of the device. YOu choice is to go out the rear drivers side of the cap (closest exit if you drill a hole) or loop it around the inside of the cap and go out the vacuum slot but that worried me that it would get caught up in the mechanical advance or rotor.

Anyways I got it in there. Started it right up. had to retime it as it had moved from 10 degrees to negative 4 with the swap of the parts. This one is lope sensing and has a rev limiter and built in resister.

So I retimed it to 10 or 12. Can't reember now. Book says 4 BTDC in specs and 8 BUDC in page about timing.

Along the way I noted that the coil wire on the coil side was pretty loose. THe rubber cap was really tight on it but the metal connection was loose. So maybe that was part of it.

I bent the tangs out a bit and stuck it in and assured a tighter fit. I have another set of wires to put on later but I was trying to see what was the cause of the issue one thing at a time.


ANother note. The installation instructions tells you to remove the 3-4 inch white resister on the firewall that has the connections from the ignition key on one side and the wire to the coil on the other. They say to splice all the wires together and throw out the resister. They say you may have a resister or a resister wire but to remove either one.

When I tried that by just puting all the wires on one end of the resister(I was lazy) it would not run. It would start with the key in start position but as soon as I released the key to ON it would stall out every time immediately. I tried about 10 times. No go.

Then I put the resister back in place (put the wires in the old positions) and it started right up and ran fine.

So I think something is different. THis does not work like they said. They said the igniter would service that function of the resistor for starting and for best performance to remove the resister. But for me it seems to need the resister. Any ideas?



So the real test....off the to dump.
Did ok all the way there but that is normal. Then it heats up siting to pay at the both and then I turn it off and open hood while unloading.

Once we are ready to go I close hood and pray. Typically it is hard starting then. Usually no gar pedal is best at that point and have to try a few times it catches stumbles and runs smmooth. This time it just started up smooth! GOOD sign.

Then we got it out on the road and it accelerated smoothly in the gears. Normally with the problem it would not take gas and you had to really eas into it or it would stumble all over.

SO it appears to be fixed!

It does have a minor stumble if I am going 20-30 in 3rd and floor it. I think that is just it not being able to take all the pumped gas as the engine can not turn over that fast.

It also had a couple minor stumbles while accelerating hard but it accellerated a and was pretty smooth. I think the rest of this is just getting the timing correct.

It has never run this good since back when I had points in it. But they were a pain as they would pit and corroad and get wet as I do not use the truck often enough.

So it appears that the new Pertronix Igniter or Coil or coil wire was the issue.

I do not think it was the wire as when it would not start I had spark to the plugs. But it is hard to say. The old pertronix was prone to having issues with the need to gap betwwen a magnetic ring and a sensor. The new one has no ring or any gapping. It just senses the lobe. So it does not matter that the distributor rides up as it gets hot or as you accelerate hard. The new one still just sense the lobe. The old one would have issues with the gap widening.

I like it so far.

the thing with the resistor > what happened is the exact symptoms of a bad resistor [open circuit], it starts, but dies when you let off starter - I'd think you must have done a poor job of putting the wires on 1 terminal, because that should be the same as attaching them all together, thus bypassing the resistor - the other thing you could do is just put a jumper wire across the resistor terminals, but if they say to not use it, you should not use it

also note that the 283 is an engine that likes revs [one of its finer points!], stumbling at lower rpm when you try to accelerate isn't suprising, especially if your accelerator pump isn't 100% .... and yes, that loose coil wire could have caused misfiring, at start or running, a bad connection can increase resistance, decrease voltage

Bill

Red58,

And of course you are RIGHT about the "poor job of putting the wires on 1 terminal"!

I just tried it with a jumper wire pulling one off the resister and jumpering to the other one and it also died in the ON state. Then I tried with both in place on the resister (on separate ends, normal) and it worked. Then I jumpered accross the resister and it worked. Now wait that should have failed like the first test? Then I pulled one end off again and jumpered from it to the other wire (cutting out the resister and it worked! (Just like you and Pertronix said it should!)

What do you expect from 52 year old wiring and a 54 year old wirer? ;-)

So I spliced them together, well I screwed them all to one terminal of the resister. And I cut a yellow wire out of the mix which is a cheapo arfter market lights ON detecter (for when the lights are on and the key is OFF). I cut that out and put on the other end of the resister. Seems to work better there as now it does not give a false positive when it is idling and the generator is low on power. Before it would faintly beep in that case. So I will try it like that for a while. Maybe I will get even better performance with the resister out of the ignition circuit.


So the old wiring got me. It is a bit dirty and stiff and very old. Have been hoping it would not short out and catch fire. I carry a fire extinguisher with me.

But that is next on my list, well very close to the top, to put in a new wiring harness. I want the old style so I think I am going with this one from ClassicParts : Wiring Harness-Generator 55-59

Is that a good one for an original V8 with deluxe cab and heater or does it not matter?

I think I will get a new ignition switch too as I tried to replace it once from them and it would not fit my old wiring. Mine is more like the 5000 series switch. Maybe cause it shows a V8 like mine. The 3000 4000 Series wiring diagram in the Assembly manual only shows 6 cyclinders since the V8 was a future at that time when it was made.

I also need to find out if that wiring harness has the headlight, tail lights, turnsignals and heater harness and optional original stylt fuse box harness betweeen the ignition, fuse box and lightswitch.

And I need to get the firewall gromets and probably some other things I am forgetting....

cleaning connections is worthwhile, critical even, all it takes is a bit of road grunge and there can be a bad connection - could have been the extra non-original wire doing something too

yes that harness should have all the correct stuff you need, and all the suppliers are about the same price ... remember that the assembly manual was done in 55, when the V8 was primarily available in big trucks - the 6 had the foot start, so a 2 position switch, the V8 had solenoid start, so a 3 position switch - later [and aftermarket] switches had the ACC position as well, so 4 .... some wiring has individual connectors for the switch, some had a single plug with all the wires, any for a V8 [with 'start' position] can be made to work fine

Bill

I need to check on that V8 versus 6 ignition switch stuff. I know I saw one site that differentiated them. ClassicParts does not seem to do that.
OK, I see Truckers has one for a V8 Generator that looks like it would work for me: V8 generator wiring harness COMPLETE WIRE HANRESS KITS 1957 CHEVY V8 WITH GENERATOR

American Classic is a forum sponser, notice the banner up in the corner here about 10% off - HAR-009, 55-59 harness, for generator, complete ... and EL-887, Ignition switch without lock cylinder, V8 - most ign sws now are the solenoid start type, which is V8, they can also easily be used with the foot start

Bill

nice price on that harness. It does not say harness is for V8 though.

there's a difference? cast about your mind and see if you can come up with some wiring a V8 has that a 6 doesn't .... 2 spark plug wires?

the only electrical parts you might buy that need to be specified 6 or V8 is that ignition switch, and that's a matter of having the solenoid start position, which actually could be on a 6 as well .... if you're expecting to find a harness that has the identical connector[s] as yours on the ign sw, forget it, originally some trucks had one large plastic plug that all the wires went to, some had one plug with about 4 wires + a few single ones, some had all individual connections, doesn't seem to be any pattern I've seen, certainly not engine size .... both the 6 and 8 wiring has the same number of connections possible and the diagram in the 57 shop manual will cover it as well as the instructions with the new harness

Bill

So if I get a switch and wires from same place think they will work together?


By the way it is running really nice now. I put the converted Oil Bath to K&N filter on and it does not gasp on full throttle and winds up smoothly. It starts well and has not had any hard starting hot mishaps since the new lobe sensing Pertronixs parts were added and the rewire around the Resister.

It is actually fun to drive when you do not have to worry about it starting!

I just need to do something for the "can not idle long of she gets hot problem".