Car stops when hot

Smilen65 · Mar 11, 2004

I’m running a 289 with Throttle body injection and an electric fan.

I’m pulling my hair out. Here’s the problem, when my 65 gets completely warm after a drive for instance it begins to intermittently idle very rough at a decreased rpm and sometimes stop. When driving even on the freeway this has happened I couldn’t get the car past 40 mph. Keep in mind this problem does not always occur when the car is warmed up, only sometimes. Sometimes idle is fine and it runs great. When the problem is occurring and I rev it up it sounds much deeper than normal and becomes gutless. The alternator is keeping the battery charged even at extended idle with the electric fan running. I even tried a direct connect from the battery to the coil while problem was occurring but this didn’t help.

I tried sealing off all possible vacuum leaks by capping them at the TBI including the pcv and brake booster and the vacuum advance. Since the problem occurs at idle only when very warm I was thinking vacuum leak, but this didn’t solve the problem it would run fine for about 25 min at idle, then bad again. It appears there is no leak. So my next thought was ignition, I removed the Igniter and went back to points and condenser, problem still occurs. I tested my coil and it appears to be within specs. Cap and rotor look fine, plugs are new. I think the key is it only happens when hot. I’m not overheating by the way. With the TBI I had to run some more fuel lines any thought on the possibility of vapor lock? The fuel lines get pretty hot. Maybe plug wires?

crushnut · Mar 11, 2004

Smilen65 said:
With the TBI I had to run some more fuel lines any thought on the possibility of vapor lock? The fuel lines get pretty hot. Maybe plug wires?

Vapor lock is a possibility, boiling gas is not a good thing and could be causing the problems you are having. Anyone else?

mp67 · Mar 11, 2004

crushnut said:
Vapor lock is a possibility, boiling gas is not a good thing and could be causing the problems you are having. Anyone else?

I would say its a fuel problem. Hook an inline fuel pressure gage after the fuel pump and before the carb. When it starts running rough, check to see if the pressure is as high as when it is running good. Mechanical pumps can act like that if the pump is weak. Are you running electric? I went through a couple of pumps on a car before acting the same way before I figured out the pump was mounted too close to the exhaust.

rbohm · Mar 11, 2004

vapor lock is a possibility, but also check your fuel lines, especiall the return line, for obstructions. it sounds like two cfi cars i have had that actually ran too rich.

6Stang7 · Mar 11, 2004

Can vapor lock effect TBI????? I didn't think fuel could be forced out of an injector; however, I can see the lines getting too hot, causing the gas to boil and him get gas vapor or not enough gas out. Why are you running TBI btw???

-Shaun

65 project · Mar 11, 2004

You might try wrapping the fuel lines to see if that makes any difference. If that does stop the problem, I would take another look at the coil. If the coil is bad, they don't usually break down until they get hot. After they cool down, they will usually checkout ok. Since they're not that expensive, I would probably replace it.

Ozsum67 · Mar 11, 2004

It may be fuel related, but it probably isn't vapor lock this time of year where you live.

rbohm · Mar 11, 2004

6Stang7 said:
Can vapor lock effect TBI????? I didn't think fuel could be forced out of an injector; however, I can see the lines getting too hot, causing the gas to boil and him get gas vapor or not enough gas out. Why are you running TBI btw???

-Shaun

you just described vapor lock, and i think you are getting fuel boiling mixed up with vapor lock. two thing occur to me;
1: if the pump is in the tank, you cannot get vapor lock, and
2: since your problem happens when the car is hot it is very possible that the tfi module needs replacing.

6Stang7 · Mar 11, 2004

I though vapor lock was gas boiling in the bowls, and the pressure that is created from this forces the gas out the jets; flooding the engine.

-Shaun

pabear89 · Mar 11, 2004

6Stang7 said:
I though vapor lock was gas boiling in the bowls, and the pressure that is created from this forces the gas out the jets; flooding the engine.

-Shaun

Would not the same thing happen in the fuel lines if their subjected to high heat source?

Pb

Ozsum67 · Mar 12, 2004

pabear89 said:
Would not the same thing happen in the fuel lines if their subjected to high heat source?

Pb

Yes, but for it to happen this time of year, the fuel line may have to be actually making contact with the exhaust manifold.

6Stang7 · Mar 12, 2004

pabear89 said:
Would not the same thing happen in the fuel lines if their subjected to high heat source?

Pb

I wouldn't think so, since an injector is basically an electronically controlled valve that makes a complete seal when not in use. With a carb, there are no valves the prevent or totaly block off passage from the float bowls to the jets. With an injector; however, they use an electromagnet, that when energized, causes the opening of a valve and allow the fuel to be forced out a tiny nozzle. These injectors are able to handle the pressure that is created by the fuel pump, so they are making a good seal. I would think that becuase of this, fuel can only come out when the ECU opens the injector; therefore, you couldn't have any flooding of the engine created by excess pressure from boiling gas. Smilen65, when you start to have these problem again, look at the injectors spraying while the car is running. What does it look like?

-Shaun

Smilen65 · Mar 12, 2004

20hrs of labor and I figure out Im an Idiot

Man I must be a moron. It turns out the problem was power to the unit. I recently changed the positive terminal on the battery. The new terminal is coated red, the controller power for the tbi is hooked to the terminal at the bolt but the inside of the hole that the bolt goes through is coated red as well. So I had intermittent power. I have no idea how it was running at all. When I checked the voltage it was at 0.9. We have had some pretty hot days lately so I figured it must be heat related, maybe the lower humidity stopped the power from arcing. Well at least all my fuel lines are insulated now... They were getting too hot, so hot you could hardly touch them, it turns out they were just too close to the exhaust manifold.

Smilen65 · Mar 12, 2004

By the Way, just say no to TBI

Ive had the holley 650 tbi unit installed for about 2 monthes and it works good in general but not to much better than my stock autolite carb. The system lacks many features that make fuel injection superior. For instance an O2 sensor (optional). Its eaiser to tune but thats about all. The amount of labor involved in the install coupled with the cost(800.00), I wish I would of left it alone. Milage is only slightly better as well. Oh and if you want your temp gauge to work you cant use the eletric choke unless you can fugure out how to jam two sensors into one hole. Not to mention fuel delivery is determained by throttle position only If the TPS is slightly off you end up with a messed up fuel delivery curve.

Thanks again for all the help guys.

crushnut · Mar 12, 2004

Glad you got it all figured out Gees, i thought fuel injection was suppose to be better

6Stang7 · Mar 12, 2004

TBI is basically an electric carb. All it did was make carbs A LOT more complex then they already are. Horriable idea, that's all I got to say.

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