Stalls climbing overpasses - please advise

[dvallot]

My 72 Blazer has a 350 and the original fuel tank. It cuts out going uphill and often will not start when parked. I have had this/these problems with my Quadrajet as well as my Carter AFB carburetors. I have also changed the mechanical fuel pump and the inline filter. I wonder if a wire could be moving and shorting out the ignition? The only thing that makes me think that can't be it is that if sits a while, it will start. Any suggestions are welcome. I hope you all had a great Christmas and that you old trucks are running - Bubba

[Jimmy72custom]

When your blazer sits and won't start you need to see what you are missing, spark, fuel or compression. Once you find this out you can trouble shoot the suspect system.

[LUV2XCLR8]

WELCOME 2 THE BOARD FROM WEST 10-UH-C

[dvallot]

My Blazer has Compression, spark, and fuel. I drive it often. However, Something is causing an intermittent absence of either fuel or spark. Since it only happens intermittently, it is difficult to troubleshoot. I have new MSD sparkbox, coil, wires, and distributor.

[FRENCHBLUE72]

I would check to make sure all the electrical connections are good and have a corsion around em. Also sounds like it maybe a coil?????

[tim_and_bobbi_blazer]

dvallot, when I trouble shoot, I try to eliminate one thing at a time.

First thing I'd do if I had your problem is look for something broken or out of place. You mentioned wiring. Also, try it with a full tank of gas. Check the timing and that the distributor is tight. You know, normal maintenance.

I'd think it would be odd for your problem to be electric. Unless you can find a connection that's moving when you go up or down hills, sounds like it would be something else. You could look for overly stretched wires that could be pulling when the body moves around. I'd think that would be real easy to see though. While your looking around the distributor, you could check for a vacuum leak that may be messing with your vacuum advance.

Next, I'd check out the fuel system. Sounds like you have done a lot to it. I'd make sure it was something as simple as vapor lock or choke setting. Does the problem happen in only hot weather or cold weather??

Then I'd pull the in line filter and replace with a piece of hose. That would tell you if it was the filter clogged. Then it may be time to put that ole mechanical pump back on. That would tell you if the electric pump was bad.

It kind of sounds like it could be a sticking float/ needle valve in your carb. You'd have to pull it apart to find out. You could try an old Q-Jet if you have one laying around, as long as you know it's good, just to try.

Moral is just eleminate one thing at a time and you'll find it.

[crzngmychvy]

To me it sounds like a spark problem I had for awhile. I had to deal with a few bad modules in my HEI dist. Since you have an MSD setup it is not going to br exactly the same, but the symptoms sound very similar. I suggest you start there. Good luck!

[Huck]

Couple of other things to think about---the wire from the fuse box to your MSD distirbutor--is it heavy enough? Are you getting vacuum advance both mechanical and from you carb? Have you done a vacuum test? Ignition switch good?? Almost sounds like flooding out---how do the plugs look color wise? If engine doesn't want to start when cold, pull air filter and look down carb while pushing accelerator--getting a good squert? Where is the choke butterfly--open or closed when cold? Just some things i've seen cause similar problems---good luck---Huck