Ive took the car to two mechanics and left with nothing but diagnostic bills. This problem must be fixed, the car will start I'll let it warm and it can sit still for 10 minutes no issues. I start to drive and for some reason when I have to stop (press the brake) it will just shut down. And when it shuts down, it wont start again. It will turn over sometimes, not always, but then it will just cut back off again. It has now done this to me in the middle of the street, an intersection, and a highway exit.

Im not sure, but the only things they have in common is that each time I was using my brakes. Ive been fortunate that it happend at tiems with no traffic, but this is my daily driver so I got to get this thing on the road and have it be safe. Any ideas, Im thinking it has to be somewhere in the ignition so here are the specs.

MSD distributer, MSD cap and rotor, MSD Blaster coil, and a MSD 6a Box. Accel shorty plugs, Accel 8.8 spiral wires. Also if it in the carb, I noticed some gas on my intake the other day its a Demon 650 DP. Any help is appreciated.

Thanks ahead of time.

 

It's not you're ignition. With the car in gear.... hold the brake firmly with you're left foot, then mash the gas with you're right foot real hard, then immediately let go. Did the car stall?

I'm guessing it did, which means you have a vacuum leak.

Again, with the car in idle (but now in park).... spray some Carb cleaner by the intake bolts, and the Carb base. If the engine 'revs' up at any given point, then there's you're leak.

Most importantly.... double check the connection from the brake booster to the engine. Where is it hooked up, on the Carb, or on the intake? Make sure it's not leaky, because not only will it give you vacuum issues.... if it gets any worse, then the next time you stall, you might not be able to stop.

 

BTW.... how did you tune the Carb? Did you use a vacuum gauge? If you did, what was the highest reading that you were able to maintain (and did you get the reading in gear)? Where did you notice the fuel on the intake?

If you didn't use a vacuum gauge, then you need to get one fast...

 

Might want to use wd-40. that carb cleaner is highly flamable and you don't want to get the spray in your eyes, I've done that and it hurts bad! wd-40 will make the idle drop insted of rev up Ok? :nono:

 

If you want to go this route, you can also get an empty windex bottle, fill it with water.... and get the same effect (the engine will sputter, and want to die).

But I'm against this, as the last thing you want in those combustion chambers is something non-flammable. Carb cleaner will be fine.... just keep it about a foot away from the engine, and an arm length away from you're face (you should also wear safety goggles if this is a concern)....

 

3 things are required for an engine to run: fuel in reasonable amounts, spark at the right time, and compression. A no-start condition is one of the easiest car failures to diagnose; since you can be fairly certain that you have exactly one and only one problem causing this symptom, all you have to do is narrow it down to which of the magic 3 ingredients is missing, and then figure out why.

I think you can eliminate compression right away. It doesn't go away so bad that the engine won't even run at all one minute, then return to normal the next.

A vacuum leak won't cause a no-start. A run-terrible, yes; a stall-in-the-middle-of-the-street, yes; a no-start, no. Don't chase this red herring until you get the engine to start every time and run reliably.

So it's either fuel or spark. In the case of fuel, it could be either too much, or too little. Gas on the intake is a clue. Check the float level sometime when the car is running, make sure it's in specs; then when the car won't run, look down in the intake and see if everything is wet with fuel. If so, see if you can get it to start by flooring the gas and cranking it. If so, you definitely have a carb problem, or your fuel pressure is simply set too high (if you are using a FI pump and a regulator).

If it's not fuel, it's spark. Try a different HEI, just a known good stock vacuum advance one. Disconnect every piece of aftermarket anything; especially the MSD box, but also noise suppression, or any other part you have that's not stock. If the car runs then you know it's ignition related.

 

Very true, RB....

But he indicates that he can get it to run for 10 minutes (idling) while in Park. He then states that once it's in gear, it'll stall (especially when pressing the brake).

It's gotta be vacuum, no?

 

Yes, it could indeed; he might have a bad brake booster or something, as well as a leaky gasket or broken hose. And he'll definitely need to look into that, once he gets the more serious issue handled, if it's still doing it. But... That's something else, and whatever it is, fixing it might even cure the vacuum-leak-like (say that 10 times as fast as you can!) behavior as well.

It's more a question of troubleshooting logic, than pure technical accuracy, or right and wrong; "triage" you might say. Restore breathing first, then stop the bleeding, then work on the sore throat.

 

I had a similar problem awhile back, as the engine would run, then die.... then wouldn't start back up until it was cooler (my choke was stuck closed).

It 'could' very well be that his choke is also stuck in the closed position when he tries to re-start it (but it's very true though.... when you get right down to it, it's all trial and error).