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Rough running at weird intervals-any thoughts?

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77MidgetMkIV

77MidgetMkIV

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Evening Campers!
Long time no post for me- I took the winter off from the car to pursue a new winter hobby, brewing beer, and also started my Master's Degree. Free time is a rare beast these days. Anywho, I rolled the Midget out last Saturday and cleaned it up, checked the fluids, etc etc, and turned it over. Started right up. Took it for a shakedown ride, and all was spiffing! Went for an extended ride (about 1/2 hour or so) and then stopped at the local to catch part of the Sox game. When I came out 1 hour later, the Midget would not run even-it was sputtering hard at low RPM with no power. Once I got it to higher RPM, it would drive ok, but it would continue to stall at lower RPM. This happened last fall, and I thought I licked the issue by cleaning the dizzy, plug wires, connections, etc. It seems that when the car gets hot, and then cools a little, the problem appears. when I let it cool down over night, it starts right up and is fine in the morning. If I run it a while, then let it set a bit, voila! problem appears again. New gas tank, newish fuel pump (electric aftermarket), clean filter, and clean lines. It appears to fire normally under a timing gun. BTW- the dizzy is the electronic type from a Datsun 510 (don't ask....)
I am stumped. Any thoughts?
 
Sounds like a heat sink issue with fuel/carb. This is a 1500, so I'm not as "conversant" as with a twin SU 1275 unit. What carb setup?

OOOH! Is there a "control box" for the iggy? If so, try cooling it with "canned air"... the stuff to blow crud outta computer keyboards or camera gear... when the problem manifests itself. If it runs right after the "blast" your problem is the "electronics".
 
It has the stock ZS carb. If by "control box", you mean an external component for the dizzy, then yeah, I got one. I will have to check that out. I have a Lucas dizzy that I am going to rebuild/convert to electronic ignition, but I have not been able to get around to it.
 
FYI, my car does something similar, except it idles very slowly, almost stalling, and can be hard to start after sitting for 10-15 minutes when the engine is hot. I have to keep giving it gas to keep it going, but usually within a minute of starting it again it idles fine, so I've chalked it up to hot air in the intake. I had posted a while back, and other 1500 owners have said they experience the same. I have a Pertronix installed, but since it's inside the distributor I'm thinking that if that's what is being affected, then it either won't run at all or it wouldn't "fix" itself that quickly after starting it. Still, try doc's suggestion of cooling the control box when it misbehaves, that could still be the culprit.

P.S.: Welcome to the beer brewing hobby. I've made a few myself, and just a few bottles of American amber ale left before I start another.
 
Thx Sparky-"nice" to know that there are others out there that are having simliar problems. I am going to pick up a can of air and drive it around the 'hood and try to recreate the issue to try that.

Nice on the homebrewing too! I have batches 9 and 10 in carboys right now. I will be bottling one this week, and moving the other to secondary this weekend. I am drinking a roasted red and a coffee cream stout. I have a Pale Ale and a Raspberry ale in carboys.
 
Cool! The coffee cream stout sounds interesting. My girlfriend would get a chuckle out of that since she knows I'm a confirmed coffeeholic /ubbthreads/images/graemlins/crazyeyes.gif. So did that come from a kit or was that your own creation? I think next time I'm getting ingredients I'll pick up a carboy and try a two-step fermentation.
 
My own creation. Additions of espresso and a caramel made from malt extract and brown sugar. Also, lactose is added as a non-fermentable sugar to give some sweetness and some body. It came out pretty good, albeit a little thicker than a traditional stout. Very tasty though.

Just talked to another buddy who also pointed me in the direction of the module possibly overheating. I will have to investimagate.
 
"Oh, ye of little faith!"

Kids! *sheesh* /ubbthreads/images/graemlins/jester.gif

EDIT: On reconsideration; I likely wouldn't entirely trust ME either. /ubbthreads/images/graemlins/hammer.gif /ubbthreads/images/graemlins/thirsty.gif
 
Not at all Doc-I was merely confirming what I had already read here. As for the fuel/carb component, I did not mention that I had exhausted that angle in the fall when this first popped up. New tank, cleaned lined, clean filter, clean jets, clean bowl, fully operational carb. No issues at all there. that is the first place I checked.
 
/ubbthreads/images/graemlins/wink.gif

...all in jest, Mark... well, mostly in jest.

I hope the thing lights off like an Atlas booster after the "chilling experience" and you can nail down the problem.
 
well, hopefully, though that then will most likely lead me on a Grailquest to find a new module for this specific dizzy. If that is in fact the problem, I think that I will be rebuilding the Lucas dizzy that I have as an electronic ignition dizzy and replace it. I'll let you all know.
 
Re: Rough running at weird intervals-GOT IT!!!!!!

I think I got it! Float and inlet valve issues appears to be the winner. After going through the dizzy yet another time and assuring myself that it was as it should be, I moved over to the fuel system. Poking around, I noticed that it actually ran better when I disconnected the fuel pump power, until it ran out of fuel, which took a while. This told me that the bowl was getting really full, and that the fuel pressure was flooding the engine. Thing is that I had already checked this area, and the valve was fine at that time. This time, I noticed that I could get it to stick open, and that the deflection on the actuator tab on the float was exaggerated, most likely from being pinned open. Anywho, I cleaned the valve out and test bent the tab a little and threw the carb back on temporarily. The change was instant and definite. Looks like the carb is getting a complete service this weekend- As I stated, I went down this avenue before and everything "looked" fine....Last time I trust myself!!! Hopefully I will be back on the road by the weekend!
 
Re: Rough running at weird intervals-GOT IT!!!!!!

Glad you found it Mark. How's the crow taste?...lol. Seriously, now I've a new possibility to check over once I get the engine back together.
JC
 
Re: Rough running at weird intervals-GOT IT!!!!!!

Yeah. Definitely one for the carb gremlins this time. Tonight is carb, beer, and Red Sox night!
 
Re: Rough running at weird intervals-GOT IT!!!!!!

Great plan. Glad it WASN'T the module. Had you TESTED the output pressure at carb supply? The aftermarket pumps can be all over the scale, the carb (float needle/seat) can't take much more than 4 PSI.
 
Re: Rough running at weird intervals-GOT IT!!!!!!

Aftermarket electric pump is rated at 2psi. Car had been running fine from the time I bought it (March 2000) until last fall (sept 2005). The issue I think was that the valve was not closing completely, and since the tab arm on the float was deflected down too much, the float would top out off room in the bowl, but the valve would still be open.
 
Re: Rough running at weird intervals-GOT IT!!!!!!

eeep. Good catch!
 
Re: Rough running at weird intervals-GOT IT!!!!!!

Worked on the carb last night. Runs much much much better now. I have to adjust my idle as well, but that was enough for one night. I am a little PO'd, though, as I dropped a screw that secures my manual choke cable, and I cannot find it. Also, I still need to get the rear/bottom nut on that secures the carb. Can't seem to get it back on this time, and my knuckles are skinless. Minor issues, though, and I should be driving tomorrow after I verify the timing.
 
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