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Ready to shoot the thing! Long story please help!

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Damon

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OK, had the '78 Midget w/ 1500 at the local High School auto shop (wife works for the district) and had "choice" student working on car with teacher oversight. Student has placed twice in the top three in the country in the Skills USA competition for automotive diagnosis and repair, so we (and his teacher) felt he was competent to work on the car. Teacher does not allow just any student to work on teacher cars, and especially THIS car!
He adjusted the timing for our altitude--WY vs CA, replaced a frost plug that had pushed out, a couple cooling system hoses and changed distributer cap and rotor.
Car has Pertronix ignition and PO hooked up electronic fuel pump under hood.
After performing the work the student took the car out for a test drive, several miles up several steep hills, and noted with satisfaction the increase in power (no more bogging down) and speed. They then ran it several times in the shop while doing minor work.
We picked up the car a week ago, and I got about four blocks from the school and after stopping for a stop sign, the car hesitated, lost power, surged and died. I rolled to the shoulder and tried restarting it. Cranked with no luck several times. Finally got it going, and made it almost back to the shop when it lost power and died again. Luckily this time a couple HS kids were near and helped push it up to shop. Teacher was puzzled as he knew it was running well for long periods in the shop and said HE would work on the car this time.
Went to pick it up Friday after teacher said it should be OK now, though he never told me what he did with it.
Got about two blocks and repeat of previous. Finally got restarted and got back to school. Teacher and I played with it, checked for fuel delivery (fine) and adjusted idle. Car would start and run, but if we tried turning off and restarting, it would not start for at least half hour or so, if it did.
Teacher was convinced it was fuel delivery problem (acted like had plugged fuel filter to me) but we could find no problems. Teacher was still scratching his head when I left with the car on a trailer, saying fuel delivery but could not figure it out. And of course Friday was last day of school so we couldn't let him play with it any more.
I thought possibly vapor lock, but after trailering home and later trying to start several times with cold engine, no luck.
It would start on occasion, with rough cold idle and a warm idle at about 8-900 rpm. However, when we try to give it gas to test drive, it surges and bumps, then dies, only to not restart for at least a half hour. It can sit and idle with the hood closed for more than an hour or so with no problems...
Electronic fuel pump does make a loud ticking sound and does get hot, but fuel delivery when disconnected from carb is fine and constant.
Could the fuel pump be dieing and not produce enough volume to run the car under load or heating excessivly and causing vapor lock from it to the carb?

Its extremely frustrating because I have not had the car here to tinker with for the last four weeks while its been at the school, and on top of the electrical gremlins I mentioned in previous posts, plus new carpet and top etc we want to install but haven't been able to w/o the car here, now this.
Any ideas or suggestions, other than to shoot it? Well, thats not really an option, because even with its many frustrations my wife loves the car, so she would wrestle the gun from me and shoot me if I harmed her "baby"!
 
oh boy, just what we need - a car that's been given up on by the school shop teacher... :laugh: J/K

Is everything but the fuel pump and dizzy stock and meant for this car?

Is the fuel pump delivering too much pressure?

Do you have (or can you get) a pressure regulator? There's one on my 64 Sprite that has a dial for 1, 2, 3 + pounds of fuel pressure. It will act like you describe with too much pressure.

That's my 'off the top of the head' first guess.
 
Not sure what your fix is, but does the carb have a heat shield between it and the exhaust manifold?
Rik
 
Since you now have seen this problem with a cold engine as well as hot, my suspicion is that you have a fuel delivery problem. I know you said the pump appears to move a lot of fuel (even when hot), but it could be that you have a blockage at (or a stuck) float valve and that fuel is never reaching the jet.

I assume that your '78 would have the ZS Stromberg on it. That will make checking the float bowl a little difficult, but next time the car will not start when cold, switch off the ignition and carefully drop the float bowl to see what (if anything) is inside.
 
I would check the coil maybe it's giving up the ghost? Ballast resistor?

Check voltage to the pertronix unit if you have a so so connection it maybe enough when warmed up to drop the voltage low enough to drop out the unit, some stop working at I think 10 volts?
 
Thanks for the ideas and suggestions. What stumped us both (shop teacher and me) was that it was running fine, albeit losing umph on the hills due to incorrect timing for this altitude, and now its not. I was wondering if too much adjustment of the timing may play into the problems.
I don't think its too much pressure from the fuel pump, because nothing was touched with the pump and it was fine before. I guess maybe a blockage could have been dislodged and now the pump is delivering its full and too much pressure. I can get a hold of a pressure regulator so we can check it. I did some reading back in the forums and got some ideas from there as well...
I work the next four days leaving the house at 3:30 AM and getting home at 9 PM, so next Friday or Saturday I'll get a chance to try these things and see if any of them helps. I'll post my results! Thanks again!
 
I agree that the first thing that I would try is a new coil and go from there.

Before doing that,check that there is fire at the plugs when it won't start (hook up a loose plug to one of the spark wires and crank the engine- if there is fire THEN play with the fuel system.
BillM
 
Looking back at your description.

to recap

1. fuel is flowing to the carb.
2. timing is correct
3. car was running before albeit not quite right for altitude.

what is different?
1. not fuel pump
2. not carb
3. cap & rotor

which would be my first guess.
second guess - student bumped a wire - check & tighten every spark related wire.

then replace coil

I'm betting electrical here especially as problem is sporadic - which is either a wire that isn't connected right - or a wire that is cracked but I'm guessing former.
 
It seems to me that, since it misbehaves more or less reliably, you should be able to determine if it's fuel or electrical. When it won't start, just see if you have voltage at the plugs, in the usual manner (see if a spark will jump from the plug connector to the body of the engine, or use one of them newfangled spark testers). That will either show that it's spark or rule it out.

You might want to look at my story of a less extreme but similar problem; it's at https://www.nonlintec.com/sprite/fuel/. Not exactly classical vapor locking, but similar. The fact that you can't restart the car for some time, then can, makes me think it might be something like this.
 
Who wired the Pertronix ignition? Connecting an after market ignition in to a 1500 can be a bit challenging as the stock ignition system offer quite a few power wires to choose from.

If you do not have an internally ballasted coil, make sure that your coil is powered by the white wire with the green stripe. This lead has a "resistance wire" wired into it's circuit that acts as a coil ballast. I have never wired a Pertronix system, but I assume that it requires a full, unballasted 12V. I believe that there is either a pure white wire, or perhaps a white/blue wire that provides ignition switched 12V. I can't remember which one it is, but a quick look at the wiring diagram in the Haynes manual should provide an answer.

Also, as RickB mentioned, too MUCH fuel pressure is a very common problem with after market fuel pumps. If you have too much fuel pressure, it can overpower your float valve causing your car to flood. This could cause the symptoms that you describe.
 
The earlier Sprites and Midgets had a screen type permanent fuel filter inside the gas tank at the fuel hose outlet which can clog. I don't know if the later models have this or not. Anyway, someone told me a story one time about their car exhibiting similar symptoms and the fix was blowing compressed air back through the fuel line to blow the clog out. I guess it made a loud "pop" and shot gas out of the fill neck(now that I think about it, it's a good thing that gas cap was off)but it fixed the problem for good. Honestly though, I'm going with ignition problem.
Hope this helps!
Mark
 
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