weird problem with engine

[yodabiri]

So my buddy has a 65 mustang (it has a 200 with the original 1100 autolite and DUI ignition, and t5 trans).He isnt very much into computers, hence I am posting the question. Anyways we worked on tuning it with getting the right timing and adjusting the idle not too long ago and it was running like a dream for almost 2 weeks now, until a couple of days ago. So we were cruising and came to a red light, and all of a sudden the car just died, but not comletely. It started trying to come back to life and made this horrible backfiring noise over and over as it died and started, died and started, and it didnt stop doing that until the key was taken out of the igintion. When we got the car off the road, and opened the hood, white/grey smoke started pouring out of the carburetor throat. We tried to start the car, but it would only rev up and would completely refuse to idle down, and once it stalled, it started that backfiring sound crap again. We could rev it up and keep it there at ~3000rpm with some effort, but it would not idle at all. I am thoroughly baffled by this. The timing is fine and the carburetor seems fine (he took it apart and cleaned it). Does anybody have any idea what can be causing this? Could it be caused by a clogged fuel line, or worse by the ignition?

Thanks in advance, I hope somebody knows something about this.

 

[JackFish]

Check for vacuum leaks. Since the carb was rebuilt we can assume it's OK. Or can we?

 

[rbohm]

8) sounds like there are two problems here, one is that the carb is flooding due to fuel boil. too much heat boils the fuel in the bowl and you get that dumping down into the engine. the second problem sounds like you might have a timing chain that has stretched.

 

[69.5Mav]

I would suggest looking into the float/needle seat. If the needle seat is not shutting off the fuel the carb will fload and raw fuel will dump into the engine. Is there black smoke coming out the tail pipe? How do the plugs look?

 

[Marine05]

Had the same problem with mine awhile back and it was a vacuum leak. Check every inch of your hoses and connectors for splits and breaks. Drove me crazy for months and decided to replumb all the hoses and havent had any problems since.

 

[jahearne]

Sounds like a jumped timing chain.

 

[yodabiri]

We will definitely check on all of the easily accessible issues. Would a timing chain really cause these symptoms all of a sudden with no warning? Thanks for the info and suggestions, I will get back to you guys with the result.

 

[fordconvert]

How do you know timing is ok? My first thought was the distributor is just loose and it drifted out of time. Isnt there issues with some of the hold downs and the dui? Just grab it and try to turn it to rule that out. A timing light even at cranking speeds should tell you if the chain skipped. Also pull the cap and make sure everything looks ok in there. I have seen people put the center contact in wrong so it burns the crap out everything. I have seen the rotor not screwed on properly so it got loose but still somehow still runs. With the cap off rock the engine back and fourth using the crank pulley and see if there is a delay in the response of the rotor when you change direction. This will tell you if the chain is really bad.

All thats easy to check. if thats all good then I would be back to fuel problem.

 

[Frankenstang]

When we got the car off the road, and opened the hood, white/grey smoke started pouring out of the carburetor throat. We tried to start the car, but it would only rev up and would completely refuse to idle down, and once it stalled, it started that backfiring sound crap again. We could rev it up and keep it there at ~3000rpm with some effort, but it would not idle at all.

I'd tend to agree with other posts that this would appear to be fuel related on the surface...specifically the "white/grey smoke pouring out of the carburetor throat" would seem to suggest it's flooding, which could be caused by crud in lines or tank getting into the carb and preventing the float/needle/seat from sealing, as mentioned. I'd also look for fuel flowing outside the carb (ie around the fuel vent rod, bowl gasket, throttle/base areas). The stock inline 1100 fuel filter does not have a very fine filtering element at all, I'd be sure I had a secondary generic inline filter (like fram g2) to prevent smaller curd from getting in the carb.

Although the difficulty in diagnosing something like this is because improper timing could cause this condition as well, especially if you're having to deliver alot of fuel to keep it running (ie idling at ~3000rpm to keep it running). At that point you may be pushing so much fuel that if it stalls some 'white/grey' smoke is not surprising (especially if its not running smoothly at that idle...ie not burning all the fuel your delivering). As far as timing goes, I'd start with verifying TDC via the spark plug hole on #1. I'd also be sure to check for a vacuum leak on the advance mechanism or a faulty mech advance (I'm not real familiar with the dui, so don't know if you have combo mech/vacuum advance..but either way would check that all the advance mechanisms are functioning correctly). I like fordconvert's idea of checking for slop in timing chain by rotating crank back and forth and looking for lag in rotor changing rotation directions...will tell you condition/wear on the timing chain. I'd think you'd have much more trouble even getting it to run if it jumped time.

Always tough when an engine spontaneously/suddenly starts running poorly, but that usually leads me to think fuel first (particularly with older fuel systems), although sudden failure in the ignition/timing system is also possible. Your friends particular situation where it's running "running like a dream"..."came to a light", stalled then ran like crap, seems to have been described many times and generally was fuel related...going from a high flow (fuel) running condition, to a low flow running condition where crap has a chance to settle/move/clog during the transition from decreased to increased fuel demand.

 

[69.5Mav]

yodabiri

Any progress

 

[dmsmith55]

Try changing out the module inside the DUI distributor. I had a similar problem that was cured by a new module from the parts store.

 

[falcon fanatic]

Ditto on the module. Sudden onset of problem suggests this. $14 at autozone if you want to test this theory by throwing a little money at it. Went crazy for a week trying to get my car to run. Rebuilt the carb, fussed with all the vacuum lines and gaskets, etc, etc. In the end it was a 5 minute fix.

Not to say it isn't a fuel problem or vacuum leak.

Jumped timing chain? With all due respect, give me a break. That would have to be one old, stretched, worn out timing chain to jump a tooth on a car with a 4500 rpm redline.

 

[yodabiri]

Thanks for all the responses. I have been out of town and away from the internet for a while. My friend has been busy with work and hasnt had time to work on the car. I will let him know about all the suggested things. Also what is the part number for the module, that may be the first thing to try?

Thanks again!

 

[dmsmith55]

I work out of town and will not be back home till 9-4 weekend. I don't remember a part number and whether I had one or just asked for a module. I think all the HEI modules were the same. I will try to post next weekend. Meantime Falcon Fanatic might have a part number.

 

[fordconvert]

Most of the GM modules were the same 78-80 so you are safe asking for one in that era. Just pick something common like a 77 C10 truck with a 350v8. Or put on your cowboy had and wax up your mustache and say you have a 77 trans am with the 400. Most stores also have a 'performance' version from MSD or Acel or someone like that. I would personally stay away from the $14 store brands. Get a big name brand or GM one. They tend to be more in the $30-40 range.

With the HEI style I often see people but the center contact in wrong. The contact goes in first then the rubber washer under the coil. Only the little spring sticks through the washer and touches the bottom of the coil. The contact should slightly stick out of the cap. The washer and contact come with a replacement cap. Also be sure to connect the ground wire to one of the mounting screws and remember to transfer over the ground wire or bar that goes to the connector.

 

[yodabiri]

So we finally got the problem solved, it was indeed the module in the DUI.
The car fired right up after getting that changed.
Thanks for all of your suggestions and help, without that, we wouldnt have gotten the car to work.